Outliner

View of very basic outline with graphics. Notepad view in Ecco Pro.

An outliner is a computer program that allows one to organize text into discrete sections that are related in a tree structure or hierarchy. Text may be collapsed into a node, or expanded and edited.

Outliners are typically used for computer programming, collecting or organizing ideas, as Personal information management or for project management. It is generally acknowledged that Doug Engelbart was the first to see the advantages of the expandable-outline user interface paradigm in software. Mind Mappers and Wikis are related types of software.

Design

The principal attribute of outline editors is that they support or enforce the use of a hierarchy. For example:

• Editing: Sound parent-child relationships are enforced when the user modifies the document structure. For example:
  • Promoting, demoting, copying, or deleting a parent has the same effect on the children.
  • Every item entry must be within one level of its predecessor, such that each item must be a sibling or child of the preceding item (thus, no item can be a grandchild of the preceding item).
• Viewing: The tool enables the user to affect the display by level. For example:
  • Applying styles by outline level (e.g., bold all 1st level items)
  • Displaying selected levels (e.g., show all 1st and 2nd level items, but none deeper).
  • Hoisting an item hides all parent and sibling items; thereby focusing, or zooming in, on a particular branch. De-hoisting again reveals the full outline.
• Search: The tool retrieves all items that contain the query terms plus the ancestors (parent, grandparent...) that give them context.
• File import / export: Both the content and structure of outlines are conveyed when files are imported or exported (e.g., from and to tab-indented files).

Layout

File:OmniOutliner screenshot.png

Composing a Wikipedia article in OmniOutliner.

There are two basic types of outliners - one pane or intrinsic and two pane or extrinsic, each with its strengths and weaknesses. A one pane outliner is also known as an intrinsic outliner because the text itself is organized into an outline format - you can collapse or expand individual sections (such as paragraphs) of text, while keeping others in view. Everything is displayed within a single area, hence the term one pane.

One of the strengths of one pane outliners is that, because the text itself is what's structured and because you can see several nodes of text at once you can typically edit across sections more easily. The drawback is that because the structure isn't always visible, you don't have as strong an overview of the whole or ability to quickly navigate between sections as with a two-pane outliner. Some word processors, such as Microsoft Word have an Outline Mode to help with structuring documents.

A two pane outliner separates structure from content - the structure is extrinsic to the text. A tree structure with node titles is presented in one pane, and the text is shown in another. Since the structure is always clearly shown at all times separately from content, this format allowing for a quick overview of the structure and easy navigation. The drawback is that since only one node's worth of text is shown at one time and navigation has the additional step of crossing panes, the structure is more rigid, making editing across nodes more difficult. This view is similar to many file browsers and email programs (which can be thought of as three-pane outliners). This type of structure is useful also as a document management tool where the second pane is a document in place of textual information.

File:MagicView Inside ECCO.png

Ecco Pro with EccoMV pane.

A one and two pane outliner may be combined as a hybrid. This allows multiple notes' text and graphics to be shown at the same time. The organizational power of outline in hybrid is in the partent outline structure, not in the second pane text. Thus, a very effective structure for topical organization. One additional advantage of hybrid is that single pane can be used as single pane outliner with second pane used for notes or reference tracking.

File formats

Several file formats support an outline structure natively or encourage the use/creation of outline structures.

• XML - XML's purpose is to aid information systems in sharing structured data
• HTML/XHTML - outlines relatively trivial thanks to nested markup
• OPML - simple XML-based format designed for outlines, but also used for syndication feedlists
• OML - alternative to OPML
• RDF - (various formats) has web-oriented node & arc graph model, can be used for outline subset
• XOXO - dedicated HTML-based microformat for outlines
• CHM - standard Windows format for help, books, etc.

Desktop outliners

Name	Operating system	Notes
Acta	Mac OS 9	Free to download
ActionOutline	Windows
Bonsai (Desktop Edition)	Windows
Circus Ponies NoteBook	Mac OS X
Code Browser	Windows/Linux	folding text editor, can outline source code
Ecco Pro	Windows	Freeware outliner. EccoMV add-on for RTF pane.
GJots
Jreepad	Platform independent	Compatible with Treepad. Written in Java.
KeepNote	Windows/Linux/MacOS	Notes saved in HTML. Written in Python.
KeyNote	Windows	Mozilla Public License. No longer supported.
KeyNoteNF	Windows	Mozilla Public License. Evolution of KeyNote.
KJots
MORE	Mac OS 7/8/9
Leo	Windows/Linux/MacOS	Python application (use Tk for the UI)
Neomem
NoteCase		No longer supported.
NoteCase Pro
NoteKeeper
Noteliner	Windows	Lightweight freeware outliner with todo capabilites & tagging
OmniOutliner	Mac OS X
Opal	Mac OS X
OPML Editor	Mac/Windows	GPL
OrgMode	cross-platform	Emacs outlining mode
Sain Outliner	Windows	Low cost
SEO Note
The Guide	Windows
Tkoutline	Platform independent	Written in Tcl/Tk
ToDoList	Windows	Free (Eclipse Public License). Portable. Large number of node attributes. French and Spanish versions.
Tombo	Windows, Windows CE, Windows Mobile	Minimalistic. Regex search. GPLv2.
Total Text Container
Treeline outliner	Windows/Linux
Treepad	Windows/Linux
TuxCards
The Vim Outliner	cross-platform	Vim plugin
UV Outliner	Windows
Vim Outliner	cross-platform	Vim plugin
VOoM	cross-platform	Vim plugin, emulates two-pane outliner. Requires Python and Vim compiled with Python interface.
WhizFolders	Windows
WikidPad	cross-platform	Wiki-like outliner.

Online outliners

This table shows a list of online, browser-based outliners categorised by the functionality they provide (see 'Design' above).

Name	Promote/demote	Copy	Styling	Expose/hide levels	Hoist	Search	Import OPML	Export OPML	Export other	Collaboration	Files
ActionManager	No	No	No	Yes	No	No	No	No	No	No	No
Checkvist	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	No
Knowcase	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	No
Loosestitch	Yes	No	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes
Lucid	Yes	No	No	No	No	No	No	No	No	No	No
The Outliner of Giants	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	No	Yes
Tidylines	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Limited users	No
Thinklinkr	Yes	Yes	No	Yes	No	No	Yes	Yes	Yes	Yes	No
Treedolist	No	No	Yes	Yes	No	Yes	No	No	No	Yes	No

See also

• Code folding
• Folding editor
• Personal information manager
• List of personal information managers
• Mind map
• Desktop Wiki
• Notetaking, Comparison of notetaking software

External links

• Comparison of desktop outliners
• Comparison of online outliners
• Overview of Windows outlining programs (at least 4 years old)
• Expanding Brain Outliner Wiki
• Outlines: The Do Everything Tool
• OutlinerSoftware.com, Discussion of Outliners