This file states the problem of showing a deep tree of text to a reader, then the names research and practice give it, and the sub-questions the review answers.
The problem in one sentence
A body of writing is stored as a tree of units nested to any depth. Decide how it is shown, so the reader keeps the top levels in view and can still reach any leaf.
Terms used in every file of this folder
| node |
one unit of the tree: a heading or summary that stands for it, and a body that may hold child nodes |
| depth in storage |
the number of levels the stored tree has |
| depth in view |
the number of levels a reader sees open at one time |
| folded |
a node shown by its heading or summary only, its children hidden until the reader opens it |
| focus |
the node the reader is reading now |
| context |
what is shown around the focus: its ancestors, siblings, or an overview of the whole |
What the field calls it
| stretchtext |
text that expands and contracts in place, so the surrounding text stays as context |
Wikipedia 2026c: defined in print in 1970, described in an unpublished note by Nelson in 1967 |
| adaptive presentation, canned-text adaptation |
a system chooses which fragments of a page to show or stretch for this reader |
Brusilovsky 2001 |
| focus plus context (focus+context, F+C) |
focus and context fused in one view, often by eliding or shrinking the far parts |
Cockburn 2009 |
| fisheye view, degree of interest (DOI) |
show a node when its importance minus its distance from the focus passes a threshold |
Furnas 1986 |
| overview plus detail (O+D) |
a separate overview pane beside the detail view |
Cockburn 2009 |
| zooming, zoomable user interface (ZUI), semantic zoom |
one view at a time, moved in scale; semantic zoom changes content, not only size |
Bederson 1994; Hornbæk 2002 |
| expand/contract table of contents |
a contents tree opened one level at a time |
Chimera 1994 |
| hypertext structure: hierarchical, network, mixed |
how the links between nodes are arranged |
Mohageg 1992; McDonald 1998 |
| disorientation, "lost in hyperspace", cognitive overhead |
the reader not knowing where they are or how to go on |
Conklin 1987 |
| layered notice |
a short first layer with the full text one step away |
McDonald 2009 |
| recursive summarization, tree-organized retrieval |
a model summarizes chunks, then summaries, into a tree it reads or searches |
Wu 2021; Sarthi 2024 |
| progressive disclosure for agents |
an agent loads a short description first and the body on demand |
He 2026 |
What practitioners call it
| accordion, collapsible section, expander, "show more" |
stretchtext; folded node |
details and summary (HTML), disclosure widget |
stretchtext with one level (WHATWG 2026) |
| tree view, outline view, sidebar navigation |
expand/contract contents; fisheye of a tree |
| progressive disclosure, staged disclosure |
disclosure of function, later of content (Nielsen 2006b; Carroll 1984) |
code folding, #region |
manual fisheye of program text (Cockburn 2009) |
| outliner, block editor, zoom into a bullet ("hoist") |
outline processor; zooming on a subtree |
| breadcrumbs |
the ancestral line of the focus, the zero-order fisheye of Furnas 1986 |
| table of contents beside the text, minimap |
overview plus detail |
| skills, llms.txt, "load on demand" |
progressive disclosure of context (He 2026; linked review below) |
Sub-questions
| Q1 |
Does showing a unit with its children folded change comprehension, search time or recall? |
| Q2 |
Hierarchical against networked hypertext, beyond what the linked reviews hold |
| Q3 |
Focus plus context, fisheye and zoomable views of documents and outlines |
| Q4 |
How many levels a reader handles in one view, and whether depth in storage matters once depth in view is capped |
| Q5 |
Outliners and block editors in practice, with adoption numbers |
| Q6 |
Trees of summaries for models as readers, measured on benchmarks |
| Q7 |
Hidden content left unread, disorientation, deep nesting |
Search terms tried, three ways
- Academic: stretchtext, expandable text, collapsible outline, progressive disclosure, focus plus context, fisheye view, overview plus detail, zoomable user interface, hypertext structure, disorientation, layered notice, recursive summarization, tree-organized retrieval.
- Acronym: F+C, O+D, ZUI, DOI, RAG, RAPTOR.
- Author: Nelson, Furnas, Bederson, Cockburn, Hornbæk, Shneiderman, Chimera, Egan, McDonald, Rada, Brusilovsky, Höök, Sarthi, Wu.
- The word "outliner" could not be searched: both engines returned unrelated millions or tens of thousands, so outliners are covered through practice (protocol section 4).
Not reviewed here, linked instead
- Recall of the top levels of a text, the levels effect: psycholinguistics.
- Depth against breadth of menus and folders: file-structure.
- General before detail, advance organizers, zoom-lens sequencing: reading-order.
- Hypertext cognitive load, signaling, segmenting: learning-science.
- Collapsed content missed, as one company article: typography-and-layout.
- Progressive disclosure of context to agents, instruction files: llm-readers.
- Hierarchical proofs, Lamport's steps and levels: mathematical-writing.
- Slide builds as progressive disclosure: presentations.
- Storing the tree, reuse and validation: topic document-model of this repository; unit types: topic information-typing.