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Emacs: introduction to Denote (simple note-taking)

UPDATE 2022-06-13 08:16 +0300: Rewrote the record to reflect the current state of the project. We are getting closer to version 0.1.0. Though better read the comprehensive manual, as I will not be updating this entry any more: https://protesilaos.com/emacs/denote.


On 2020-10-08 I wrote about My simple note-taking system for Emacs (without Org). Most of that entry described the methodology I have been using to organise my notes; a methodology that is Emacs-agnostic.

At the time, I wrote a toy package called “Unassuming Sidenotes of Little Significance” (USLS—also pronounced as “useless”) which helped me experiment with the workflow without having to rely on awkward shell scripts. Bringing everything into Emacs allowed me to standardise things and offered an opportunity to tinker with Elisp.

Fast-forward to present time: I have already written a few packages for Emacs and am better with Elisp. USLS was never meant to be anything other than useless for others, but its core idea remains interesting and fecund. I thus spent the last few days writing denote: the successor to USLS which is created with the express purpose of becoming a package on GNU ELPA.

The following elaborates on the specifics.


Overview

NOTE THAT WE ARE ACTIVELY WORKING TOWARDS VERSION 0.1.0 AND MIGHT STILL INTRODUCE BREAKING, BACKWARD-INCOMPATIBLE CHANGES. This is particularly true for the linking facility. Everything else is in a stable state.

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 (read “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 (read “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. Do not introduce dependencies on specific libraries. While Org is a killer app for Emacs and the default file type for new notes, Denote does not depend on org.el nor its extensions and does allow notes to be created in a variety of formats (read “Notes in multiple file types”). The author of Denote (Protesilaos, aka “Prot”) writes ordinary notes in plain text (.txt), switching to an Org file only when its expanded set of functionality is required for the task at hand (read “Points of entry”).

  • Portability: Notes are plain text and should remain portable. The way Denote writes file names, the front matter it include 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. It is up to the user to apply the requisite rigor in pursuit of their preferred workflow.

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.

The file-naming scheme

Notes are stored as a flat list in the denote-directory (i.e. no subdirectories). The default path is ~/Documents/notes.

Every note produced by Denote follows this pattern (read “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 (read “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).

Read “Extending Denote”.

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.

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 only in the note’s contents (read “Front matter”).

  • Keywords should not have spaces or other delimiters. If they do, they are converted into hyphens. Keywords are always downcased.

Points of entry

There are two ways to write a note with Denote: invoke the denote command or leverage the org-capture-templates by setting up a template which calls the function denote-org-capture.

In the first case, all that is needed is to run denote. It will first prompt for a title. Once it is supplied, the command will ask for keywords. The resulting note will have a file name as already explained (read “The file naming scheme”).

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.

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. ]

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. After that, the process is the same as with invoking denote directly, namely: a prompt for a title followed by a prompt for keywords.

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, 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.

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 (read “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 (read “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.

Front matter

Notes have their own “front matter”. This is a block of data at the top of the file, 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 (denote-file-type is nil):

#+title:      This is a sample note
#+date:       2022-06-10
#+filetags:   denote  testing
#+identifier: 20220610T202537

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

---
title:      "This is a sample note"
date:       2022-06-10
tags:       denote  testing
identifier: "20220610T202021"
---

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

+++
title      = "This is a sample note"
date       = 2022-06-10
tags       = ["denote", "testing"]
identifier = "20220610T201510"
+++

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

title:      This is a sample note
date:       2022-06-10
tags:       denote  testing
identifier: 20220610T202232
---------------------------

The format of the date in the front matter is controlled by the user option denote-front-matter-date-format:

  • When the value is nil (the default), the date uses a plain YEAR-MONTH-DAY notation, like 2022-06-08 (the ISO 8601 standard).

  • When the value is the org-timestamp symbol, the date is recorded as an inactive Org timestamp, such as [2022-06-08 Wed 06:19].

  • An arbitrary string value is interpreted as the argument for the function format-time-string. This gives the user maximum control over how time is represented in the front matter.

When denote-file-type specifies one of the Markdown flavors, we ignore this user option in order to enforce the RFC3339 specification (Markdown is typically employed in static site generators as source code for Web pages). However, when denote-front-matter-date-format has a string value, this rule is suspended: we use whatever the user wants.

Tweaking the front matter

What follows is for advanced users. When in doubt, only configure variables we describe as a “user option”: they are declared in the source code with the defcustom keyword.

Denote’s code base is designed in a composable way, which lets the user make precise interventions to affect the output of the relevant commands. One such case is to configure the front matter, such as by changing the order the keys appear in, renaming them, or adding new elements.

Some examples are in order, starting with the Org file type. This is what we have in denote.el:

(defvar denote-org-front-matter
  "#+title:      %s
#+date:       %s
#+filetags:   %s
#+identifier: %s
\n"
  "Org front matter value for `format'.
The order of the arguments is TITLE, DATE, KEYWORDS, ID.  If you
are an avdanced user who wants to edit this variable to affect
how front matter is produced, consider using something like %2$s
to control where Nth argument is placed.")

The default front matter is:

#+title:      This is a sample note
#+date:       2022-06-10
#+filetags:   denote  testing
#+identifier: 20220610T202537

We can add a PROPERTIES drawer to it, with something like this:

(setq denote-org-front-matter
      ":PROPERTIES:
:ID: %4$s
:END:
#+title:      %1$s
#+date:       %2$s
#+filetags:   %3$s
#+identifier: %4$s
\n")

The output is now formatted thus:

:PROPERTIES:
:ID: 20220611T092444
:END:
#+title:      This is a sample note
#+date:       2022-06-11
#+filetags:   denote  testing
#+identifier: 20220611T092444

Notice how we can pass a number to the %s specifier. This is what allows us to change the placement of the provided arguments.

For another example, we will use the plain text variant, as it differs a bit from the above. By default it is formatted this way:

title:      This is a sample note
date:       2022-06-10
tags:       denote  testing
identifier: 20220610T202232
---------------------------

The line with the hyphens is the product of the fifth format specifier, as documented in denote-text-front-matter. Its value is stored in denote-text-front-matter-delimiter. Say we want to have a delimiter both at the top and bottom:

(setq denote-text-front-matter
      "%5$s
title:      %1$s
date:       %2$s
tags:       %3$s
identifier: %4$s
%5$s\n\n")

Which gives us:

---------------------------
title:      This is a sample note
date:       2022-06-11
tags:       denote  testing
identifier: 20220611T093252
---------------------------

Or we would rather use another character instead of hyphens, such as the equals sign:

(setq denote-text-front-matter-delimiter (make-string 27 ?=))

Remember that this is for advanced users. If you want to see changes done on this front, you are welcome to share your thoughts and/or participate in the development of Denote.

Linking notes

Denote has a basic linking facility to quickly establish connections between notes. The command denote-link prompts for a file name in the denote-directory (only regular files are considered, not directories). It then retrieves the path of the given note, inserts it at point using the appropriate link notation, and creates a backlink entry in the target file (again using the appropriate notation).

What constitutes “appropriate link notation” depends on the file type of the given entry per denote-file-type (read “The file naming scheme”). For example when linking from an Org file to a Markdown file, the link in the former will follow Org syntax while the backlink in the latter will use that of Markdown. Org links use [[file:TARGET][DESCRIPTION]], those of Markdown are [DESCRIPTION](file:TARGET), while for plain text we implement our own scheme of <TYPE: TARGET> [DESCRIPTION], where TYPE is either LINK or BACKLINK (capitalization in the latter two is literal, because plain text lacks other means of emphasis).

Plain text links can benefit from Emacs’ notion of “future history”, else its ability to read the thing at point for relevant commands. With point over the TARGET, M-x find-file followed by M-n will fill the path to that file (this also works with point over just the identifier of a note).

Backlinks are optionally recorded at the end of a note under the heading with the title Denote backlinks. This is an opt-in feature that has to be set up by adding denote-link-backlinks to the special hook denote-link-insert-functions.

The reason backlinks are off by default is because we might still make breaking changes on how they are implemented. For the time being, Denote expects that users do not edit the section with the backlinks: it is controlled by Denote, such as to delete duplicate links (in the future it might also handle stuff like alphabetic sorting). Suggestions to improve backlinking are most welcome!

The section with the backlinks is formatted according to the note’s file type.

Backlinks that no longer point to available notes can be removed from the current buffer with the command denote-link-clear-stale-backlinks.

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-dired-field-date
  • denote-dired-field-delimiter
  • denote-dired-field-extension
  • denote-dired-field-keywords
  • denote-dired-field-time
  • denote-dired-field-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 (read “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).

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)

Notes in multiple file types

As noted before, Denote does not have a particular preference on the workflow the user wishes to follow nor does it expect a specific file type. It is entirely possible to store notes in a variety of formats across multiple directories and Denote will still be able to work with them, provided they follow the file-naming scheme and have an identifier in their front matter (where relevant). Here we show how to create new notes that deviate from the default value of denote-file-type and specify their own denote-directory.

Suppose you want to conform with the default of creating notes with the .org extension but, for whatever reason, wish to have a way to quickly produce a file with the .md extension and TOML-compliant front matter.

(setq denote-file-type nil)

(defun my-denote-markdown-toml ()
  (interactive)
  (let ((denote-file-type 'markdown-toml))
    (call-interactively #'denote)))

With the above, M-x my-denote-markdown-toml produces Markdown+TOML notes while M-x denote uses Org.

This principle can be taken a step further by let binding a second directory for those alternative notes. Maybe your standard notes are located in ~/Documents/notes/ but you plan to store the other ones in ~/blog/ (read “Fontification in Dired”).

(setq denote-file-type nil)
(setq denote-directory (expand-file-name "~/Documents/notes/"))

(defun my-denote-markdown-toml ()
  (interactive)
  (let ((denote-file-type 'markdown-toml)
        (denote-directory "~/blog/"))
    (call-interactively #'denote)))

Given Denote’s composable code, you can tweak the output however you like, including the contents of the file (read “Tweaking the front matter”).

If you do place different types of notes in their own directories, consider introducing directory-local variables to keep things working seamlessly. An obvious candidate for such a local variable is the denote-directory: you want notes in ~/blog/ to treat their directory as the canonical one; while those in ~/Documents/notes/ to do the same for that path. Write a .dir-locals.el file with the following contents and place it in each of those directories:

;;; Directory Local Variables
;;; For more information see (info "(emacs) Directory Variables")

((nil . ((denote-directory . (expand-file-name default-directory)))))

This will allow things to work smoothly (e.g. denote-infer-keywords).

Have more ideas? Something does not work quite right? Areas you wish were more abstract in the code? Please participate in the development process.

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.

  • To search through notes, use M-x grep, M-x find-name-dired, M-x consult-find, M-x consult-grep, and so on (the latter two are provided by the consult package).

  • To quickly jump to the denote-directory, visit it with M-x find-file and then make a bookmark with M-x bookmark-set. Access bookmarks with M-x bookmark-jump, M-x consult-buffer (from consult), and the like.

  • Control the versioning of notes by turning the denote-directory into a Git project. Consider the built-in project.el or the projectile package, as well as the built-in VC framework and/or the magit package.

  • It is possible to narrow the list of notes in Dired using a regular expression or literal string. Do M-x dired-mark-files-regexp RET type-regexp-here RET t k. The t will toggle the match so that it marks all files that do not match the regexp and k will remove them from the buffer (restore them by reverting the buffer).

  • A narrowed list of files can also be produced through the minibuffer, with the help of the embark package. For example, M-x find-file RET path/to/denote-directory RET regexp embark-act embark-export. The final two commands, embark-act and embark-export, are normally bound to keys. The whole sequence will thus look like C-x C-f path RET regexp C-. E.