Denote (denote.el)

Simple notes for Emacs with an efficient file-naming scheme

The source code is available on SourceHut. The mailing list is also on SourceHut. Mirrors of the git source are also available on GitHub and GitLab. The official manual is right below.


This manual, written by Protesilaos Stavrou, describes the customization options for the Emacs package called denote (or denote.el), and provides every other piece of information pertinent to it.

The documentation furnished herein corresponds to stable version 0.2.0, released on 2022-07-04. Any reference to a newer feature which does not yet form part of the latest tagged commit, is explicitly marked as such.

Current development target is 0.3.0-dev.

If you are viewing the README.org version of this file, please note that the GNU ELPA machinery automatically generates an Info manual out of it.

Table of Contents

1. COPYING

Copyright (C) 2022 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

2. Overview

Denote aims to be a simple-to-use, focused-in-scope, and effective note-taking tool for Emacs. It is based on the following core design principles:

Predictability
File names must follow a consistent and descriptive naming convention (The file-naming scheme). The file name alone should offer a clear indication of what the contents are, without reference to any other metadatum. This convention is not specific to note-taking, as it is pertinent to any form of file that is part of the user’s long-term storage (Renaming files).
Composability
Be a good Emacs citizen, by integrating with other packages or built-in functionality instead of re-inventing functions such as for filtering or greping. The author of Denote (Protesilaos, aka “Prot”) writes ordinary notes in plain text (.txt), switching on demand to an Org file only when its expanded set of functionality is required for the task at hand (Points of entry).
Portability
Notes are plain text and should remain portable. The way Denote writes file names, the front matter it includes in the note’s header, and the links it establishes must all be adequately usable with standard Unix tools. No need for a database or some specialised software. As Denote develops and this manual is fully fleshed out, there will be concrete examples on how to do the Denote-equivalent on the command-line.
Flexibility
Do not assume the user’s preference for a note-taking methodology. Denote is conceptually similar to the Zettelkasten Method, which you can learn more about in this detailed introduction: https://zettelkasten.de/introduction/. Notes are atomic (one file per note) and have a unique identifier. However, Denote does not enforce a particular methodology for knowledge management, such as a restricted vocabulary or mutually exclusive sets of keywords. Denote also does not check if the user writes thematically atomic notes. It is up to the user to apply the requisite rigor and/or creativity in pursuit of their preferred workflow (Writing metanotes).
Hackability
Denote’s code base consists of small and reusable functions. They all have documentation strings. The idea is to make it easier for users of varying levels of expertise to understand what is going on and make surgical interventions where necessary (e.g. to tweak some formatting). In this manual, we provide concrete examples on such user-level configurations (Keep a journal or diary).

Now the important part… “Denote” is the familiar word, though it also is a play on the “note” concept. Plus, we can come up with acronyms, recursive or otherwise, of increasingly dubious utility like:

  • Don’t Ever Note Only The Epiphenomenal
  • Denote Everything Neatly; Omit The Excesses

But we’ll let you get back to work. Don’t Eschew or Neglect your Obligations, Tasks, and Engagements.

3. Points of entry

There are five ways to write a note with Denote: invoke the denote, denote-type, denote-date, denote-subdirectory commands, or leverage the org-capture-templates by setting up a template which calls the function denote-org-capture. We explain all those in the subsequent sections.

3.1. Standard note creation

The denote command will prompt for a title. Once that is supplied, it will ask for keywords. The resulting note will have a file name as already explained: The file naming scheme

The file type of the new note is determined by the user option denote-file-type (Front matter).

The keyword prompt supports minibuffer completion. Available candidates are those defined in the user option denote-known-keywords. More candidates can be inferred from the names of existing notes, by setting denote-infer-keywords to non-nil (which is the case by default).

Multiple keywords can be inserted by separating them with a comma (or whatever the value of the crm-indicator is—which should be a comma). When the user option denote-sort-keywords is non-nil (the default), keywords are sorted alphabetically (technically, the sorting is done with string-lessp).

The denote command can also be called from Lisp, in which case it expects the TITLE and KEYWORDS arguments. The former is a string, the latter a list of strings.

In the interest of discoverability, denote is also available under the alias denote-create-note.

3.2. Create note by specifying file type

The denote-type command is like denote except it also prompts for a file type to use as an ad-hoc value for denote-file-type. In practical terms, this lets you produce, say, a note in Markdown even though you normally write in Org (Standard note creation).

The denote-create-note-using-type is an alias of denote-type.

3.3. Create note using a date

Normally, Denote reads the current date and time to derive the identifier of a new note (Standard note creation). Sometimes, however, the user needs to set an explicit date+time value.

This is where the denote-date command comes in. It accepts the familiar TITLE and KEYWORDS arguments, though it starts by asking for a date. The input for the DATE argument is like 2022-06-16 or 2022-06-16 14:30. When the time is omitted, it is interpreted as 00:00.

Since the ability to insert a date may result in duplicate identifiers, Denote takes care to abort the operation if such an identity is established (e.g. when you use denote-date with 2022-06-16 twice, it will generate the same identifier of 20220616T000000). The user must thus call the denote-date command again and provide a unique date or date+time value.

The denote-create-note-using-date is an alias of denote-date.

3.4. Create note in a specific directory

The denote-subdirectory command is like denote except it prompts for a directory to place the new note in (Standard note creation). Candidates are the value of the user option denote-directory and any subdirectory inside of it. Denote does not create subdirectories.

The denote-create-note-in-subdirectory is a more descriptive alias of denote-subdirectory.

3.5. Create note using Org capture

For integration with org-capture, the user must first add the relevant template. Such as:

(with-eval-after-load 'org-capture
  (require 'denote-org-capture)
  (add-to-list 'org-capture-templates
               '("n" "New note (with Denote)" plain
                 (file denote-last-path)
                 #'denote-org-capture
                 :no-save t
                 :immediate-finish nil
                 :kill-buffer t
                 :jump-to-captured t)))

[ In the future, we might develop Denote in ways which do not require such manual intervention. More user feedback is required to identify the relevant workflows. ]

Once the template is added, it is accessed from the specified key. If, for instance, org-capture is bound to C-c c, then the note creation is initiated with C-c c n, per the above snippet. After that, the process is the same as with invoking denote directly, namely: a prompt for a title followed by a prompt for keywords (Standard note creation).

Users may prefer to leverage org-capture in order to extend file creation with the specifiers described in the org-capture-templates documentation (such as to capture the active region and/or create a hyperlink pointing to the given context). Due to the particular file-naming scheme of Denote, which is derived dynamically, such specifiers cannot be written directly in the template. Instead, they have to be assigned to the user option denote-org-capture-specifiers, which is interpreted by the function denote-org-capture. Example with our default value:

(setq denote-org-capture-specifiers "%l\n%i\n%?")

Note that denote-org-capture ignores the denote-file-type: it always sets the Org file extension for the created note to ensure that the capture process works as intended, especially for the desired output of the denote-org-capture-specifiers.

4. Renaming files

Denote’s file-naming scheme is not specific to notes or text files: it is useful for all sorts of files, such as multimedia and PDFs that form part of the user’s longer-term storage (The file-naming scheme). While Denote does not manage such files, it already has all the mechanisms to facilitate the task of renaming them.

To this end, we provide the denote-dired-rename-file command. It has a two-fold purpose: (i) to change the name of an existing file while retaining its identifier and (ii) to write a Denote-compliant file name for an item that was not created by denote or related commands (such as an image or PDF).

The denote-dired-rename-file command will target the file at point if it finds one in the current Dired buffer. Otherwise it prompts with minibuffer completion for a file name. It then uses the familiar prompts for a TITLE and KEYWORDS the same way the denote command does (Points of entry). As a final step, it asks for confirmation before renaming the file at point, showing a message like:

Rename sample.pdf to 20220612T052900--my-sample-title__testing.pdf? (y or n)

However, if the user option denote-dired-rename-expert is non-nil, conduct the renaming operation outright—no questions asked.

When operating on a file that has no identifier, such as sample.pdf, Denote reads the file properties to retrieve its last modification time. If the file was from a past date like 2000-11-31 it will get an identifier starting with 20001131 followed by the time component (per our file-naming scheme).

The file type extension (e.g. .pdf) is read from the underlying file and is preserved through the renaming process. Files that have no extension are simply left without one.

Renaming only occurs relative to the current directory. Files are not moved between directories.

The final step of the denote-dired-rename-file command is to call the special hook denote-dired-post-rename-functions. Functions added to that hook must accept three arguments, as explained in its doc string. For the time being, the only function we define is the one which updates the underlying note’s front matter to match the new file name: denote-dired-rewrite-front-matter. The function takes care to only operate on an actual note, instead of arbitrary files.

DEVELOPMENT NOTE: the denote-dired-rewrite-front-matter needs to be tested thoroughly. It rewrites file contents so we have to be sure it does the right thing. To avoid any trouble, it always asks for confirmation before performing the replacement. This confirmation ignores denote-dired-rename-expert for the time being, though we might want to lift that restriction once everything works as intended.

5. The file-naming scheme

Notes are stored the denote-directory. The default path is ~/Documents/notes. The denote-directory can be a flat listing, meaning that it has no subdirectories, or it can be a directory tree. Either way, Denote takes care to only consider “notes” as valid candidates in the relevant operations and will omit other files or directories.

Every note produced by Denote follows this pattern (Points of entry):

DATE--TITLE__KEYWORDS.EXTENSION

The DATE field represents the date in year-month-day format followed by the capital letter T (for “time”) and the current time in hour-minute-second notation. The presentation is compact: 20220531T091625. The DATE serves as the unique identifier of each note.

The TITLE field is the title of the note, as provided by the user. It automatically gets downcased and hyphenated. An entry about “Economics in the Euro Area” produces an economics-in-the-euro-area string for the TITLE of the file name.

The KEYWORDS field consists of one or more entries demarcated by an underscore (the separator is inserted automatically). Each keyword is a string provided by the user at the relevant prompt which broadly describes the contents of the entry. Keywords that need to be more than one-word-long must be written with hyphens: any other character, such as spaces or the plus sign is automatically converted into a hyphen. So when emacs_library appears in a file name, it is interpreted as two distinct keywords, whereas emacs-library is one keyword. This is reflected in how the keywords are recorded in the note (Front matter). While Denote supports multi-word keywords by default, the user option denote-allow-multi-word-keywords can be set to nil to forcibly join all words into one, meaning that an input of word1 word2 will be written as word1word2.

The EXTENSION is the file type. By default, it is .org (org-mode) though the user option denote-file-type provides support for Markdown with YAML or TOML variants (.md which runs markdown-mode) and plain text (.txt via text-mode). Consult its doc string for the minutia. While files end in the .org extension by default, the Denote code base does not actually depend on org.el and/or its accoutrements.

Examples:

20220610T043241--initial-thoughts-on-the-zettelkasten-method__notetaking.org
20220610T062201--define-custom-org-hyperlink-type__denote_emacs_package.md
20220610T162327--on-hierarchy-and-taxis__notetaking_philosophy.txt

The different field separators, namely -- and __ introduce an efficient way to anchor searches (such as with Emacs commands like isearch or from the command-line with find and related). A query for _word always matches a keyword, while a regexp in the form of, say, "\\([0-9T]+?\\)--\\(.*?\\)_" captures the date in group \1 and the title in \2 (test any regular expression in the current buffer by invoking M-x re-builder).

Features of the file-naming scheme for searching or filtering.

While Denote is an Emacs package, notes should work long-term and not depend on the functionality of a specific program. The file-naming scheme we apply guarantees that a listing is readable in a variety of contexts.

5.1. Sluggified title and keywords

Denote has to be highly opinionated about which characters can be used in file names and the file’s front matter in order to enforce its file-naming scheme. The private variable denote--punctuation-regexp holds the relevant value. In simple terms:

  • What we count as “illegal characters” are converted into hyphens.
  • Input for a file title is hyphenated and downcased. The original value is preserved in the note’s contents (Front matter).
  • Keywords should not have spaces or other delimiters. If they do, they are converted into hyphens. Keywords are always downcased.

5.2. Features of the file-naming scheme for searching or filtering

File names have three fields and two sets of field delimiters between them:

DATE--TITLE__KEYWORDS.EXTENSION

The first field delimiter is the double hyphen, while the second is the double underscore. These practically serve as anchors for easier searching. Consider this example:

20220621T062327--introduction-to-denote__denote_emacs.txt

You will notice that there are two matches for the word denote: one in the title field and another in the keywords’ field. Because of the distinct field delimiters, if we search for -denote we only match the first instance while _denote targets the second one. When sorting through your notes, this kind of specificity is invaluable—and you get it for free from the file names alone!

Users can get a lot of value out of this simple arrangement, even if they have no knowledge of regular expressions. One thing to consider, for maximum effect, is to avoid using multi-word keywords as those get hyphenated like the title and will thus interfere with the above: either set the user option denote-allow-multi-word-keywords to nil or simply insert single words at the relevant prompts.

6. Front matter

Notes have their own “front matter”. This is a block of data at the top of the file, with no empty lines between the entries, which is automatically generated at the creation of a new note. The front matter includes the title and keywords (aka “tags” or “filetags”, depending on the file type) which the user specified at the relevant prompt, as well as the date and unique identifier, which are derived automatically.

This is how it looks for Org mode (when denote-file-type is nil):

#+title:      This is a sample note
#+date:       [2022-06-30 Thu 16:09]
#+filetags:   denote  testing
#+identifier: 20220630T160934

For Markdown with YAML (denote-file-type has the markdown-yaml value), the front matter looks like this:

---
title:      "This is a sample note"
date:       2022-06-30T16:09:58+03:00
tags:       denote  testing
identifier: "20220630T160958"
---

For Markdown with TOML (denote-file-type has the markdown-toml value), it is:

+++
title      = "This is a sample note"
date       = 2022-06-30T16:10:13+03:00
tags       = ["denote", "testing"]
identifier = "20220630T161013"
+++

And for plain text (denote-file-type has the text value), we have the following:

title:      This is a sample note
date:       2022-06-30
tags:       denote  testing
identifier: 20220630T161028
---------------------------

The format of the date in the front matter is controlled by the user option denote-date-format. When nil, Denote uses a file-type-specific format:

  • For Org, an inactive timestamp is used, such as [2022-06-30 Wed 15:31].
  • For Markdown, the RFC3339 standard is applied: 2022-06-30T15:48:00+03:00.
  • For plain text, the format is that of ISO 8601: 2022-06-30.

If the value is a string, ignore the above and use it instead. The string must include format specifiers for the date. These are described in the doc string of format-time-string..

7. Linking notes

The denote-link command inserts a link at point to an entry specified at the minibuffer prompt. Links are formatted depending on the file type of current note. In Org and plain text buffers, links are formatted thus: [[denote:IDENTIFIER][TITLE]]. While in Markdown they are expressed as [TITLE](denote:IDENTIFIER).

When denote-link is called with a prefix argument (C-u by default), it formats links like [[denote:IDENTIFIER]]. The user might prefer its simplicity.

Inserted links are automatically buttonized and remain active for as long as the buffer is available. In Org this is handled by the major mode: the denote: hyperlink type works exactly like the standard file:. In Markdown and plain text, Denote performs the buttonization of those links. To buttonize links in existing files while visiting them, the user must add this snippet to their setup (it already excludes Org):

(add-hook 'find-file-hook #'denote-link-buttonize-buffer)

Denote has a major-mode-agnostic mechanism to collect all linked file references in the current buffer and return them as an appropriately formatted list. This list can then be used in interactive commands. The denote-link-find-file is such a command. It uses minibuffer completion to visit a file that is linked to from the current note. The candidates have the correct metadata, which is ideal for integration with other standards-compliant tools (Extending Denote). For instance, a package such as marginalia will display accurate annotations, while the embark package will be able to work its magic such as in exporting the list into a filtered Dired buffer (i.e. a familiar Dired listing with only the files of the current minibuffer session).

The command denote-link-backlinks produces a bespoke buffer which displays the file name of all notes linking to the current one. Each file name appears on its own line and is buttonized so that it performs the action of visiting the referenced file. The backlinks’ buffer looks like this:

Backlinks to "On being honest" (20220614T130812)
------------------------------------------------

20220614T145606--let-this-glance-become-a-stare__journal.txt
20220616T182958--not-feeling-butterflies-in-your-stomach__journal.txt

The backlinks’ buffer is fontified by default, though the user has access to the denote-link-fontify-backlinks option to disable this effect by setting its value to nil.

The placement of the backlinks’ buffer is subject to the user option denote-link-backlinks-display-buffer-action. Due to the nature of the underlying display-buffer mechanism, this inevitably is a relatively advanced feature. By default, the backlinks’ buffer is displayed below the current window. The doc string of our user option includes a sample configuration that places the buffer in a left side window instead. Reproducing it here for the sake of convenience:

(setq denote-link-backlinks-display-buffer-action
      '((display-buffer-reuse-window
         display-buffer-in-side-window)
        (side . left)
        (slot . 99)
        (window-width . 0.3)))

The command denote-link-add-links adds links at point matching a regular expression or plain string. The links are inserted as a typographic list, such as:

- link1
- link2
- link3

Each link is formatted according to the file type of the current note, as explained further above about the denote-link command. The current note is excluded from the matching entries (adding a link to itself is pointless).

When called with a prefix argument (C-u) denote-link-add-links will format all links as [[denote:IDENTIFIER]], hence a typographic list:

- [[denote:IDENTIFIER-1]]
- [[denote:IDENTIFIER-2]]
- [[denote:IDENTIFIER-3]]

Same examples of a regular expression that can be used with this command:

  • journal match all files which include journal anywhere in their name.
  • _journal match all files which include journal as a keyword.
  • ^2022.*_journal match all file names starting with 2022 and including the keyword journal.
  • \.txt match all files including .txt. In practical terms, this only applies to the file extension, as Denote automatically removes dots (and other characters) from the base file name.

If files are created with denote-sort-keywords as non-nil (the default), then it is easy to write a regexp that includes multiple keywords in alphabetic order:

  • _denote.*_package match all files that include both the denote and package keywords, in this order.
  • \(.*denote.*package.*\)\|\(.*package.*denote.*\) is the same as above, but out-of-order.

Remember that regexp constructs only need to be escaped once (like \|) when done interactively but twice when called from Lisp. What we show above is for interactive usage.

For convenience, the denote-link command has an alias called denote-link-insert-link. The denote-link-backlinks can also be used as denote-link-show-backlinks-buffer. While denote-link-add-links is aliased denote-link-insert-links-matching-regexp. The purpose of these aliases is to offer alternative, more descriptive names of select commands.

7.1. Writing metanotes

A “metanote” is an entry that describes other entries who have something in common. Writing metanotes can be part of a workflow where the user periodically reviews their work in search of patterns and deeper insights. For example, you might want to read your journal entries from the past year to reflect on your experiences, evolution as a person, and the like.

The command denote-link-add-links, which we covered extensively in the previous section, is suited for this task (Linking notes). You will create your metanote the way you use Denote ordinarily (metanotes may have the metanote keyword), write an introduction or however you want to go about it, invoke denote-link-add-links to cite the notes that match the given regexp, and continue writing.

Metanotes can serve as entry points to groupings of individual notes. They are not the same as a filtered list of files, i.e. what you would do in Dired or the minibuffer where you narrow the list of notes to a given query. Metanotes contain the filtered list plus your thoughts about it. The act of purposefully grouping notes together and contemplating on their shared patterns is what adds value.

Your future self will appreciate metanotes for the function they serve in encapsulating knowledge, while current you will be equipped with the knowledge derived from the deliberate self-reflection.

8. Fontification in Dired

One of the upsides of Denote’s file-naming scheme is the predictable pattern it establishes, which appears as a near-tabular presentation in a listing of notes (i.e. in Dired). The denote-dired-mode can help enhance this impression, by fontifying the components of the file name to make the date (identifier) and keywords stand out.

There are two ways to set the mode. Either use it for all directories, which probably is not needed:

(require 'denote-dired)
(add-hook 'dired-mode-hook #'denote-dired-mode)

Or configure the user option denote-dired-directories and then set up the function denote-dired-mode-in-directories:

(require 'denote-dired)

;; We use different ways to specify a path for demo purposes.
(setq denote-dired-directories
      (list denote-directory
            (thread-last denote-directory (expand-file-name "attachments"))
            (expand-file-name "~/Documents/vlog")))

(add-hook 'dired-mode-hook #'denote-dired-mode-in-directories)

The faces we define are:

  • denote-faces-date
  • denote-faces-delimiter
  • denote-faces-extension
  • denote-faces-keywords
  • denote-faces-subdirectory
  • denote-faces-time
  • denote-faces-title

For the time being, the diredfl package is not compatible with this facility.

The denote-dired-mode does not only fontify note files that were created by Denote: it covers every file name that follows our naming conventions (The file-naming scheme). This is particularly useful for scenaria where, say, one wants to organise their collection of PDFs and multimedia in a systematic way (and, perhaps, use them as attachments for the notes Denote produces).

9. Minibuffer histories

Denote has a dedicated minibuffer history for each one of its prompts. This practically means that using M-p (previous-history-element) and M-n (next-history-element) will only cycle through the relevant record of inputs, such as your latest titles in the TITLE prompt, and keywords in the KEYWORDS prompt.

The built-in savehist library saves minibuffer histories. Sample configuration:

(require 'savehist)
(setq savehist-file (locate-user-emacs-file "savehist"))
(setq history-length 10000)
(setq history-delete-duplicates t)
(setq savehist-save-minibuffer-history t)
(add-hook 'after-init-hook #'savehist-mode)

10. Extending Denote

Denote is a tool with a narrow scope: create notes and link between them, based on the aforementioned file-naming scheme. For other common operations the user is advised to rely on standard Emacs facilities or specialised third-party packages. This section covers the details.

10.1. Keep a journal or diary

While there are subtle technical differences between a journal and a diary, we will consider those equivalent in the interest of brevity: they both describe a personal space that holds a record of your thoughts about your experiences and/or view of events in the world.

Suppose you are committed to writing an entry every day. Unlike what we demonstrated before, your writing will follow a regular naming pattern. You know that the title of the new note must always look like Tuesday 14 June 2022 and the keyword has to be journal or diary. As such, you want to automate the task instead of being prompted each time, as is the norm with denote and the relevant commands (Points of entry). This is easy to accomplish because denote can be called from Lisp and given the required arguments of TITLE and KEYWORDS directly. All you need is a simple wrapper function:

(defun my-denote-journal ()
  "Create an entry tagged 'journal' with the date as its title."
  (interactive)
  (denote
   (format-time-string "%A %e %B %Y") ; format like Tuesday 14 June 2022
   "journal")) ; multiple keywords are a list of strings: '("one" "two")

By invoking my-denote-journal you will go straight into the newly created note and commit to your writing outright.

Of course, you can always set up the function so that it asks for a TITLE but still automatically applies the journal tag:

(defun denote-journal-with-title ()
  "Create an entry tagged 'journal', while prompting for a title."
  (interactive)
  (denote
   (denote--title-prompt) ; ask for title, instead of using human-readable date
   "journal"))

Sometimes journaling is done with the intent to hone one’s writing skills. Perhaps you are learning a new language or wish to communicate your ideas with greater clarity and precision. As with everything that requires a degree of sophistication, you have to work for it—write, write, write!

One way to test your progress is to set a timer. It helps you gauge your output and its quality. To use a timer with Emacs, consider the tmr package:

(defun my-denote-journal-with-tmr ()
  "Like `my-denote-journal', but also set a 10-minute timer.
The `tmr' command is part of the `tmr' package."
  (interactive)
  (denote
   (format-time-string "%A %e %B %Y")
   "journal")
  (tmr 10 "Practice writing in my journal")) ; set 10 minute timer with a description

Once the timer elapses, stop writing and review your performance. Practice makes perfect!

[ As Denote matures, we may add hooks to control what happens before or after the creation of a new note. We shall also document more examples of tasks that can be accomplished with this package. ]

Sources for tmr:

10.2. Narrow the list of files in Dired

Emacs’ standard file manager (or directory editor) can read a regular expression to mark the matching files. This is the command dired-mark-files-regexp, which is bound to % m by default. For example, % m _denote will match all files that have the denote keyword (Features of the file-naming scheme for searching or filtering).

Once the files are matched, the user has to options: (i) narrow the list to the matching items or (ii) exclude the matching items from the list.

For the former, we want to toggle the marks by typing t (calls the command dired-toggle-marks by default) and then hit the letter k (for dired-do-kill-lines). The remaining files are those that match the regexp that was provided earlier.

For the latter approach of filtering out the matching items, simply involves the use of the k command (dired-do-kill-lines) to omit the marked files from the list.

These sequences can be combined to incrementally narrow the list. Note that dired-do-kill-lines does not delete files: it simply hides them from the current view.

Revert to the original listing with g (revert-buffer).

For a convenient wrapper, consider this example:

(defvar prot-dired--limit-hist '()
  "Minibuffer history for `prot-dired-limit-regexp'.")

;;;###autoload
(defun prot-dired-limit-regexp (regexp omit)
  "Limit Dired to keep files matching REGEXP.

With optional OMIT argument as a prefix (\\[universal-argument]),
exclude files matching REGEXP.

Restore the buffer with \\<dired-mode-map>`\\[revert-buffer]'."
  (interactive
   (list
    (read-regexp
     (concat "Files "
             (when current-prefix-arg
               (propertize "NOT " 'face 'warning))
             "matching PATTERN: ")
     nil 'prot-dired--limit-hist)
    current-prefix-arg))
  (dired-mark-files-regexp regexp)
  (unless omit (dired-toggle-marks))
  (dired-do-kill-lines))

10.3. Use Embark to collect minibuffer candidates

embark is a remarkable package that lets you perform relevant, context-dependent actions using a prefix key (simplifying in the interest of brevity).

For our purposes, Embark can be used to produce a Dired listing directly from the minibuffer. Suppose the current note has links to three other notes. You might use the denote-link-find-file command to pick one via the minibuffer. But why not turn those three links into their own Dired listing? While in the minibuffer, invoke embark-act which you may have already bound to C-. and then follow it up with E (for the embark-export command).

This pattern can be repeated with any list of candidates, meaning that you can narrow the list by providing some input before eventually exporting the results with Embark.

Overall, this is very powerful and you might prefer it over doing the same thing directly in Dired, since you also benefit from all the power of the minibuffer (Narrow the list of files in Dired).

10.4. Search file contents

Emacs provides built-in commands which are wrappers of standard Unix tools: M-x grep lets the user input the flags of a grep call and pass a regular expression to the -e flag.

The author of Denote uses this thin wrapper instead:

(defvar prot-search--grep-hist '()
  "Input history of grep searches.")

;;;###autoload
(defun prot-search-grep (regexp &optional recursive)
  "Run grep for REGEXP.

Search in the current directory using `lgrep'.  With optional
prefix argument (\\[universal-argument]) for RECURSIVE, run a
search starting from the current directory with `rgrep'."
  (interactive
   (list
    (read-from-minibuffer (concat (if current-prefix-arg
                                      (propertize "Recursive" 'face 'warning)
                                    "Local")
                                  " grep for PATTERN: ")
                          nil nil nil 'prot-search--grep-hist)
    current-prefix-arg))
  (unless grep-command
    (grep-compute-defaults))
  (if recursive
      (rgrep regexp "*" default-directory)
    (lgrep regexp "*" default-directory)))

Rather than maintain custom code, consider using the excellent consult package: it provides commands such as consult-grep and consult-find which provide live results and are generally easier to use than the built-in commands.

10.5. Bookmark the directory with the notes

Part of the reason Denote does not reinvent existing functionality is to encourage you to learn more about Emacs. You do not need a bespoke “jump to my notes” directory because such commands do not scale well. Will you have a “jump to my downloads” then another for multimedia and so on? No.

Emacs has a built-in framework for recording persistent markers to locations. Visit the denote-directory (or any dir/file for that matter) and invoke the bookmark-set command (bound to C-x r m by default). It lets you create a bookmark.

The list of bookmarks can be reviewed with the bookmark-bmenu-list command (bound to C-x r l by default). A minibuffer interface is available with bookmark-jump (C-x r b).

If you use the consult package, its default consult-buffer command has the means to group together buffers, recent files, and bookmarks. Each of those types can be narrowed to with a prefix key. The package consult-dir is an extension to consult which provides useful extras for working with directories, including bookmarks.

10.6. Use the consult-notes package

If you are already using consult (which is a brilliant package), you will probably like its consult-notes extension. It uses the familiar mechanisms of Consult to filter searches via a prefix key. For example:

(setq consult-notes-data-dirs
      `(("Notes"  ?n ,denote-directory)
        ("Books"  ?b "~/Documents/books")))

With the above, M-x consult-notes will list the files in those two directories. If you type n and space, it narrows the list to just the notes, while b does the same for books.

Note that consult-notes is in its early stages of development. Expect improvements in the near future (written on 2022-06-22 16:48 +0300).

10.7. Treat your notes as a project

Emacs a built-in library for treating a directory tree as a “project”. This means that the contents of this tree are seen as part of the same set, so commands like project-switch-to-buffer (C-x p b by default) will only consider buffers in the current project (e.g. three notes that are currently being visited).

Normally, a “project” is a directory tree whose root is under version control. For our purposes, all you need is to navigate to the denote-directory (for the shell or via Dired) and use the command-line to run this (requires the git executable):

git init

From Dired, you can type M-! which invokes dired-smart-shell-command and then run the git call there.

The project can then be registered by invoking any project-related command inside of it, such as project-find-file (C-x p f).

It is a good idea to keep your notes under version control, as that gives you a history of changes for each file. We shall not delve into the technicalities here, though suffice to note that Emacs’ built-in version control framework or the exceptionally well-crafted magit package will get the job done (VC can work with other backends besides Git).

11. Installation

11.1. GNU ELPA package

The package is available as denote. Simply do:

M-x package-refresh-contents
M-x package-install

And search for it.

GNU ELPA provides the latest stable release. Those who prefer to follow the development process in order to report bugs or suggest changes, can use the version of the package from the GNU-devel ELPA archive. Read: https://protesilaos.com/codelog/2022-05-13-emacs-elpa-devel/.

11.2. Manual installation

Assuming your Emacs files are found in ~/.emacs.d/, execute the following commands in a shell prompt:

cd ~/.emacs.d

# Create a directory for manually-installed packages
mkdir manual-packages

# Go to the new directory
cd manual-packages

# Clone this repo, naming it "denote"
git clone https://git.sr.ht/~protesilaos/denote denote

Finally, in your init.el (or equivalent) evaluate this:

;; Make Elisp files in that directory available to the user.
(add-to-list 'load-path "~/.emacs.d/manual-packages/denote")

Everything is in place to set up the package.

12. Sample configuration

(require 'denote)

;; Remember to check the doc strings of those variables.
(setq denote-directory (expand-file-name "~/Documents/notes/"))
(setq denote-known-keywords
      '("emacs" "philosophy" "politics" "economics"))
(setq denote-infer-keywords t)
(setq denote-sort-keywords t)
(setq denote-file-type nil) ; Org is the default, set others here

;; We allow multi-word keywords by default.  The author's personal
;; preference is for single-word keywords for a more rigid workflow.
(setq denote-allow-multi-word-keywords t)

(setq denote-date-format nil) ; read doc string

;; You will not need to `require' all those individually once the
;; package is available.
(require 'denote-retrieve)
(require 'denote-link)

;; By default, we fontify backlinks in their bespoke buffer.
(setq denote-link-fontify-backlinks t)

;; Also see `denote-link-backlinks-display-buffer-action' which is a bit
;; advanced.

;; If you use Markdown or plain text files (Org renders links as buttons
;; right away)
(add-hook 'find-file-hook #'denote-link-buttonize-buffer)

(require 'denote-dired)
(setq denote-dired-rename-expert nil)

;; We use different ways to specify a path for demo purposes.
(setq denote-dired-directories
      (list denote-directory
            (thread-last denote-directory (expand-file-name "attachments"))
            (expand-file-name "~/Documents/books")))

;; Generic (great if you rename files Denote-style in lots of places):
;; (add-hook 'dired-mode-hook #'denote-dired-mode)
;;
;; OR if only want it in `denote-dired-directories':
(add-hook 'dired-mode-hook #'denote-dired-mode-in-directories)

;; Here is a custom, user-level command from one of the examples we
;; showed in this manual.  We define it here and add it to a key binding
;; below.
(defun my-denote-journal ()
  "Create an entry tagged 'journal', while prompting for a title."
  (interactive)
  (denote
   (denote--title-prompt)
   "journal"))

;; Denote does not define any key bindings.  This is for the user to
;; decide.  For example:
(let ((map global-map))
  (define-key map (kbd "C-c n j") #'my-denote-journal) ; our custom command
  (define-key map (kbd "C-c n n") #'denote)
  (define-key map (kbd "C-c n N") #'denote-type)
  (define-key map (kbd "C-c n d") #'denote-date)
  (define-key map (kbd "C-c n s") #'denote-subdirectory)
  ;; If you intend to use Denote with a variety of file types, it is
  ;; easier to bind the link-related commands to the `global-map', as
  ;; shown here.  Otherwise follow the same pattern for `org-mode-map',
  ;; `markdown-mode-map', and/or `text-mode-map'.
  (define-key map (kbd "C-c n i") #'denote-link) ; "insert" mnemonic
  (define-key map (kbd "C-c n I") #'denote-link-add-links)
  (define-key map (kbd "C-c n l") #'denote-link-find-file) ; "list" links
  (define-key map (kbd "C-c n b") #'denote-link-backlinks)
  ;; Note that `denote-dired-rename-file' can work from any context, not
  ;; just Dired bufffers.  That is why we bind it here to the
  ;; `global-map'.
  (define-key map (kbd "C-c n r") #'denote-dired-rename-file))

(with-eval-after-load 'org-capture
  (require 'denote-org-capture)
  (setq denote-org-capture-specifiers "%l\n%i\n%?")
  (add-to-list 'org-capture-templates
               '("n" "New note (with denote.el)" plain
                 (file denote-last-path)
                 #'denote-org-capture
                 :no-save t
                 :immediate-finish nil
                 :kill-buffer t
                 :jump-to-captured t)))

13. Contributing

Denote is a GNU ELPA package. As such, any significant change to the code requires copyright assignment to the Free Software Foundation (more below).

You do not need to be a programmer to contribute to this package. Sharing an idea or describing a workflow is equally helpful, as it teaches us something we may not know and might be able to cover either by extending Denote or expanding this manual (Things to do). If you prefer to write a blog post, make sure you share it with us: we can add a section herein referencing all such articles. Everyone gets acknowledged (Acknowledgements). There is no such thing as an “insignificant contribution”—they all matter.

If our public media are not suitable, you are welcome to contact me (Protesilaos) in private: https://protesilaos.com/contact.

Copyright assignment is a prerequisite to sharing code. It is a simple process. Check the request form below (please adapt it accordingly). You must write an email to the address mentioned in the form and then wait for the FSF to send you a legal agreement. Sign the document and file it back to them. This could all happen via email and take about a week. You are encouraged to go through this process. You only need to do it once. It will allow you to make contributions to Emacs in general.

Please email the following information to assign@gnu.org, and we
will send you the assignment form for your past and future changes.

Please use your full legal name (in ASCII characters) as the subject
line of the message.

REQUEST: SEND FORM FOR PAST AND FUTURE CHANGES

[What is the name of the program or package you're contributing to?]

GNU Emacs

[Did you copy any files or text written by someone else in these changes?
Even if that material is free software, we need to know about it.]

Copied a few snippets from the same files I edited.  Their author,
Protesilaos Stavrou, has already assigned copyright to the Free Software
Foundation.

[Do you have an employer who might have a basis to claim to own
your changes?  Do you attend a school which might make such a claim?]


[For the copyright registration, what country are you a citizen of?]


[What year were you born?]


[Please write your email address here.]


[Please write your postal address here.]





[Which files have you changed so far, and which new files have you written
so far?]

14. Things to do

Denote should work well for what is described in this manual. Though we can always do better. These are some of the tasks that are planned for the future and which you might want to help with (Contributing).

This is a non-exhaustive list and you are always welcome to either report or work on something else.

  • [ ] Ensure integration between denote: links and Embark.
  • [ ] Add command that expands the identifier in links to a full name.
  • [ ] Add command that rewrites full names in links, if they are invalid.
  • [ ] Consider completion-at-point after denote: links.
  • [ ] Support mutually-exclusive sets of tags.

These are just ideas. We need to consider the pros and cons in each case and act accordingly.

15. Alternatives to Denote

What follows is a list of Emacs packages for note-taking. I (Protesilaos) have not used any of them, as I was manually applying my file-naming scheme beforehand and by the time those packages were available I was already hacking on the predecessor of Denote as a means of learning Emacs Lisp (a package which I called “Unassuming Sidenotes of Little Significance”, aka “USLS” which is pronounced as “U-S-L-S” or “useless”). As such, I cannot comment at length on the differences between Denote and each of those packages, beside what I gather from their documentation.

org-roam
The de facto standard in the Emacs milieu—and rightly so! It has a massive community, is featureful, and should be an excellent companion to anyone who is invested in the Org ecosystem and/or knows what “Roam” is (I don’t). It has been explained to me that Org Roam uses a database to store a cache about your notes. It otherwise uses standard Org files. The cache helps refer to the same node through aliases which can provide lots of options. Personally, I follow a single-topic-per-note approach, so anything beyond that is overkill. If the database is only for a cache, then maybe that has no downside, though I am careful with any kind of specialised program as it creates a dependency. If you ask me about database software in particular, I have no idea how to use one, let alone debug it or retrieve data from it if something goes awry (I could learn, but that is beside the point).
zk (or zk.el)
Reading its documentation makes me think that this is Denote’s sibling—the two projects have a lot of things in common, including the preference to rely on plain files and standard tools. The core difference is that Denote has a strict file-naming scheme. Other differences in available features are, in principle, matters of style or circumstance: both packages can have them. As its initials imply, ZK enables a zettelkasten-like workflow. It does not enforce it though, letting the user adapt the method to their needs and requirements.
zettelkasten
This is another one of Denote’s relatives, at least insofar as the goal of simplicity is concerned. The major difference is that according to its documentation “the name of the file that is created is just a unique ID”. This is not consistent with our file-naming scheme which is all about making sense of your files by their name alone and being able to visually parse a listing of them without any kind of specialised tool (e.g. ls -l or ls -C on the command-line from inside the denote-directory give you a human-readable set of files names, while find * -maxdepth 0 -type f is another approach).
zetteldeft
This is a zettelkasten note-taking system built on top of the deft package. Deft provides a search interface to a directory, in this case the one holding the user’s zetteldeft notes. Denote has no such dependency and is not opinionated about how the user prefers to search/access their notes: use Dired, Grep, the consult package, or whatever else you already have set up for all things Emacs, not just your notes.

Searching through M-x list-packages for “zettel” brings up more matches. zetteldesk is an extension to Org Roam and, as such, I cannot possibly know what Org Roam truly misses and what the added-value of this package is. neuron-mode builds on top of an external program called neuron, which I have never used.

Searching for “note” gives us a few more results. notes-mode has precious little documentation and I cannot tell what it actually does (as I said in my presentation for LibrePlanet 2022, inadequate docs are a bug). side-notes differs from what we try to do with Denote, as it basically gives you the means to record your thoughts about some other project you are working on and keep them on the side: so it and Denote should not be mutually exclusive.

If I missed something, please let me know.

15.1. Alternative ideas wih Emacs and further reading

This section covers blog posts from the Emacs community on the matter of note-taking. They may reference some of the packages covered in the previous section or provide their custom code (Alternatives to Denote). The list is unsorted.

[ Development note: help expand this list. ]

16. Frequently Asked Questions

I (Protesilaos) answer some questions I have received or might get. It is assumed that you have read the rest of this manual: I will not go into the specifics of how Denote works.

16.1. Why develop Denote when PACKAGE already exists?

I wrote Denote because I was using a variant of Denote’s file-naming scheme before I was even an Emacs user (I switched to Emacs from Tmux+Vim+CLI in the summer of 2019). I was originally inspired by Jekyll, the static site generator, which I started using for my website in 2016 (was on WordPress before). Jekyll’s files follow the YYYY-MM-DD-TITLE.md pattern. I liked its efficiency relative to the unstructured mess I had before. Eventually, I started using that scheme outside the confines of my website’s source code. Over time I refined it and here we are.

Note-taking is something I take very seriously, as I am a prolific writer (just check my website, which only reveals the tip of the iceberg). As such, I need a program that does exactly what I want and which I know how to extend. I originally tried to use Org capture templates to create new files with a Denote-style file-naming scheme but never managed to achieve it. Maybe because org-capture has some hard-coded assumptions or I simply am not competent enough to hack on core Org facilities. Whatever the case, an alternative was in order.

The existence of PACKAGE is never a good reason for me not to conduct my own experiments for recreational, educational, or practical purposes. When the question arises of “why not contribute to PACKAGE instead?” the answer is that without me experimenting in the first place, I would lack the skills for such a task. Furthermore, contributing to another package does not guarantee I get what I want in terms of workflow.

Whether you should use Denote or not is another matter altogether: choose whatever you want.

16.2. Why not rely exclusively on Org?

I think Org is one of Emacs’ killer apps. I also believe it is not the right tool for every job. When I write notes, I want to focus on writing. Nothing more. I thus have no need for stuff like org-babel, scheduling to-do items, clocking time, and so on. The more “mental dependencies” you add to your workflow, the heavier the burden you carry and the less focused you are on the task at hand: there is always that temptation to tweak the markup, tinker with some syntactic construct, obsess about what ought to be irrelevant to writing as such.

In technical terms, I also am not fond of Org’s code base (I understand why it is the way it is—just commenting on the fact). Ever tried to read it? You will routinely find functions that are tens-to-hundreds of lines long and have all sorts of special casing. As I am not a programmer and only learnt to write Elisp through trial and error, I have no confidence in my ability to make Org do what I want at that level, hence denote instead of org-denote or something.

Perhaps the master programmer is one who can deal with complexity and keep adding to it. I am of the opposite view, as language—code included—is at its communicative best when it is clear and accessible.

Make no mistake: I use Org for the agenda and also to write technical documentation that needs to be exported to various formats, including this very manual.

16.3. Why care about Unix tools when you use Emacs?

My notes form part of my longer-term storage. I do not want to have to rely on a special program to be able to read them or filter them. Unix is universal, at least as far as I am concerned.

Denote streamlines some tasks and makes things easier in general, which is consistent with how Emacs provides a layer of interactivity on top of Unix. Still, Denote’s utilities can, in principle, be implemented as POSIX shell scripts (minus the Emacs-specific parts like fontification in Dired or the buttonization of links).

Portability matters. For example, in the future I might own a smartphone, so I prefer not to require Emacs, Org, or some other executable to access my files on the go.

Furthermore, I might want to share those files with someone. If I make Emacs a requirement, I am limiting my circle to a handful of relatively advanced users.

Please don’t misinterpret this: I am using Emacs full-time for my computing and maintain a growing list of packages for it. This is just me thinking long-term.

16.4. Why many small files instead of few large ones?

I have read that Org favours the latter method. If true, I strongly disagree with it because of the implicit dependency it introduces and the way it favours machine-friendliness over human-readability in terms of accessing information. Notes are long-term storage. I might want to access them on (i) some device with limited features, (ii) print on paper, (iii) share with another person who is not a tech wizard.

There are good arguments for few large files, but all either prioritize machine-friendliness or presuppose the use of sophisticated tools like Emacs+Org.

Good luck using less on a generic TTY to read a file with a zillion words, headings, sub-headings, sub-sub-headings, property drawers, and other constructs! You will not get the otherwise wonderful folding of headings the way you do in Emacs—do not take such features for granted.

My point is that notes should be atomic to help the user—and potentially the user’s family, friends, acquaintances—make sense of them in a wide range of scenaria. The more program-agnostic your file is, the better for you and/or everyone else you might share your writings with.

Human-readability means that we optimize for what matters to us. If (a) you are the only one who will ever read your notes, (b) always have access to good software like Emacs+Org, (c) do not care about printing on paper, then Denote’s model is not for you. Maybe you need to tweak some org-capture template to append a new entry to one mega file (I do that for my Org agenda, by the way, as I explained before about using the right tool for the job).

16.5. I add TODOs to my files; will the many files slow down the Org agenda?

I have not tested it, but assume that yes, many files will slow down the agenda. Consider looking into one of Denote’s alternatives, with org-roam being the obvious choice (Alternatives to Denote).

Or, if you want my opinion, decouple your longer-term storage from your ephemeral to-do list: Denote (and others) can be used for the former, while you let standard Org work splendidly for the latter—that is what I do, anyway.

16.6. I want to sort by last modified, why won’t Denote let me?

Denote does not sort files and will not reinvent tools that handle such functionality. This is the job of the file manager or command-line executable that lists files.

I encourage you to read the manpage of the ls executable. It will help you in general, while it applies to Emacs as well via Dired. The gist is that you can update the ls flags that Dired uses on-the-fly: type C-u M-x dired-sort-toggle-or-edit (C-u s by default) and append --sort=time at the prompt. To reverse the order, add the -r flag. The user option dired-listing-switches sets your default preference.

16.7. How do you handle the last modified case?

Denote does not insert any meta data or heading pertaining to edits in the file. I am of the view that these either do not scale well or are not descriptive enough. Suppose you use a “lastmod” heading with a timestamp: which lines where edited and what did the change amount to?

This is where an external program can be helpful. Use a Version Control System, such as Git, to keep track of all your notes. Every time you add a new file, record the addition. Same for post-creation edits. Your VCS will let you review the history of those changes. For instance, Emacs’ built-in version control framework has a command that produces a log of changes for the current file: M-x vc-print-log, bound to C-x v l by default. From there one can access the corresponding diff output (use M-x describe-mode (C-h m) in an unfamiliar buffer to learn more about it). With Git in particular, Emacs users have the option of the all-round excellent magit package.

In short: let Denote (or equivalent) create notes and link between them, the file manager organise and provide access to files, search programs deal with searching and narrowing, and version control software handle the tracking of changes.

17. Acknowledgements

Denote is meant to be a collective effort. Every bit of help matters.

Author/maintainer
Protesilaos Stavrou.
Contributions to code or the manual
Damien Cassou, Jack Baty, Jean-Philippe Gagné Guay, Kaushal Modi, Stefan Monnier.
Ideas and/or user feedback
Benjamin Kästner, Colin McLear, Damien Cassou, Frank Ehmsen, Jack Baty, Kaushal Modi, M. Hadi Timachi, Peter Prevos, Shreyas Ragavan, Sven Seebeck, Ypot.

Special thanks to Peter Povinec who helped refine the file-naming scheme, which is the cornerstone of this project.

18. GNU Free Documentation License


                GNU Free Documentation License
                 Version 1.3, 3 November 2008


 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

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This License is a kind of "copyleft", which means that derivative
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We have designed this License in order to use it for manuals for free
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preceding the beginning of the body of the text.

The "publisher" means any person or entity that distributes copies of
the Document to the public.

A section "Entitled XYZ" means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language.  (Here XYZ stands for a
specific section name mentioned below, such as "Acknowledgements",
"Dedications", "Endorsements", or "History".)  To "Preserve the Title"
of such a section when you modify the Document means that it remains a
section "Entitled XYZ" according to this definition.

The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document.  These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no
other conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and
you may publicly display copies.


3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify
you as the publisher of these copies.  The front cover must present
the full title with all words of the title equally prominent and
visible.  You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.

If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.

It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to
give them a chance to provide you with an updated version of the
Document.


4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it.  In addition, you must do these things in the Modified Version:

A. Use in the Title Page (and on the covers, if any) a title distinct
   from that of the Document, and from those of previous versions
   (which should, if there were any, be listed in the History section
   of the Document).  You may use the same title as a previous version
   if the original publisher of that version gives permission.
B. List on the Title Page, as authors, one or more persons or entities
   responsible for authorship of the modifications in the Modified
   Version, together with at least five of the principal authors of the
   Document (all of its principal authors, if it has fewer than five),
   unless they release you from this requirement.
C. State on the Title page the name of the publisher of the
   Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
   adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license notice
   giving the public permission to use the Modified Version under the
   terms of this License, in the form shown in the Addendum below.
G. Preserve in that license notice the full lists of Invariant Sections
   and required Cover Texts given in the Document's license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title, and add
   to it an item stating at least the title, year, new authors, and
   publisher of the Modified Version as given on the Title Page.  If
   there is no section Entitled "History" in the Document, create one
   stating the title, year, authors, and publisher of the Document as
   given on its Title Page, then add an item describing the Modified
   Version as stated in the previous sentence.
J. Preserve the network location, if any, given in the Document for
   public access to a Transparent copy of the Document, and likewise
   the network locations given in the Document for previous versions
   it was based on.  These may be placed in the "History" section.
   You may omit a network location for a work that was published at
   least four years before the Document itself, or if the original
   publisher of the version it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
   Preserve the Title of the section, and preserve in the section all
   the substance and tone of each of the contributor acknowledgements
   and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
   unaltered in their text and in their titles.  Section numbers
   or the equivalent are not considered part of the section titles.
M. Delete any section Entitled "Endorsements".  Such a section
   may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled "Endorsements"
   or to conflict in title with any Invariant Section.
O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.

You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity.  If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.


5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History"
in the various original documents, forming one section Entitled
"History"; likewise combine any sections Entitled "Acknowledgements",
and any sections Entitled "Dedications".  You must delete all sections
Entitled "Endorsements".


6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the rules
of this License for verbatim copying of each of the documents in all
other respects.

You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert a
copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.


7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.


8. TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections.  You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.


9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.

Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.

Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License.  If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.


10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the
GNU Free Documentation License from time to time.  Such new versions
will be similar in spirit to the present version, but may differ in
detail to address new problems or concerns.  See
https://www.gnu.org/licenses/.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.  If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy's public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.

11. RELICENSING

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works.  A
public wiki that anybody can edit is an example of such a server.  A
"Massive Multiauthor Collaboration" (or "MMC") contained in the site
means any set of copyrightable works thus published on the MMC site.

"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.

"Incorporate" means to publish or republish a Document, in whole or in
part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole or
in part into the MMC, (1) had no cover texts or invariant sections, and
(2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.


ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:

    Copyright (c)  YEAR  YOUR NAME.
    Permission is granted to copy, distribute and/or modify this document
    under the terms of the GNU Free Documentation License, Version 1.3
    or any later version published by the Free Software Foundation;
    with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
    A copy of the license is included in the section entitled "GNU
    Free Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this:

    with the Invariant Sections being LIST THEIR TITLES, with the
    Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.