This is an excerpt from Knowledge-Domain Interoperability and an Open Hyperdocument System by Douglas Engelbart.

It makes a handy measuring stick for collaborative systems.

See a paper on the topic: An Evaluation of the World Wide Web as a Platform for Electronic Commerce

Essential Elements of an Open Hyperdocument System

Mixed Object Documents
to provide for an arbitrary mix of text, diagrams, equasions, tables, raster-scan images (single frames, or even live video), spread sheets, recorded sound, etc. -- all bundled within a common "envelope" to be stored, transmitted, read (played) and printed as a coherent entity called a "document."
Explicitly Structured Documents
where the objects comprising a document are arranged in an explicit hierarchical structure, and compund-object substructures may be explicitly addressed for access or manipulation of the structural relationships.
View Control of Object's Form, Sequence, and Content
where a structured, mixed-object document may be displayed in a window according to a flexible choice of viewing options -- especially by selective level clipping (outline for viewing), but also by filtering on content, by truncation or some algorithmic view that provides a more useful view of structure and/or object content (including new sequences or groupings of objects that actually reside in other documents). Editing on structure or object content from such special views would be allowed whenever appropriate.
The Basic "Hyperdocument"
where embedded objects called "links" can point to any arbitrary object within the document, or within another document in a specified domain of documents -- and the link can be actuated by a user or an automatic process to "go see what is at the other end," or "bring the other-end object to this location," or "execute the process identified a the other end." (These executable processes may control peripheral devices such as CD ROM, video-disk players, etc.)
Hyperdocument "Back-Link" Capability
when reading a hyperdocument online, a worker can utilize information about links from other objects within this or other hyperdocuments that point to this hyperdocument -- or to designated objects or passages of interest in this hyperdocument.
The Hyperdocument "Library System"
where hyperdocuments can be submitted to a library-like service that catalogs them and guarantees access when referenced by its catalog number, or "jumped to" with an appropriate link. Links within newly submitted hyperdocuments can cite any passages within any of the prior documents, and the back-link service lets the online reader of a document detect and "go examine" any passage of a subsequent document that has a link citing that passage.
Hyperdocument Mail
where an integrated, general-purpose mail service enables a hyperdocument of any size to be mailed. Any embedded links are also faithfully trasmitted -- and any recipient can then follow those links to their designated targets in other mail items, in common-access files, or in "library" items.
Personal Signature Encryption
where a user can affix his personal signature to a document, or a specified segment within the document, using the private signature key. Users can verify that the signature is authentic and that no bit of the signed document or document segment has been altered since it was signed.
Access Control
Hyperdocuments in personal, group, and library files can have access restrictions down to the object level.
Link Addresses That Are Readable and Interpretable by Humans
one of the "viewing options" for displaying/printing a link object should provide a human-readable description of the "address path" leading to the cited object; AND, that the human must be able to read the path description, interpret it, and follow it (find the destination "by hand" so to speak).
Every Object Addressable
in principal, every object that someone might validly want/need to cite should have an unambiguous address (capable of being protrayed in a manner as to be human readable and interpretable). (E.g. not acceptable to be unable to link to an object within a "frame" or "card.")
Hard-Copy Print Options to Show Address of Objects and Address Specification of Links
so that, besides online workers being able to follow a link-citation path (manually, or via an automatic link jump), people working with associated hard copy can read and interpret the link-citation, and follow the indicated path to the cited object in the designated hard-copy document.

Also, suppose that a hard-copy worker wants to have a link to a given object established in the online file. By visual inspection of the hard copy, he should be able to determine a valid address path to that object and for instance hand-write an appropriate link specification for later online entry, or dicatate it over a phone to a colleage

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