Engelbart defined view specs as different views defined by a developer to see the same document. It reminds me of the Model-View architecture.

Feed or Navigation Components

A Document with Viewspecs: outline viewspec (show only headings) + truncation viewspec (show only x first characters) is enough to build our Navigation Component. As our Navigation Component will automatically Truncatate Headings to x characters, the users will make the effort to reduce the Title/Headings size themsleves. (as in twitter people stick to the 260characters truncations) (edited)

Navigation Component

This Navigation component in the sidebar comes from the Navigation document below. The navigation Component applies Truncated Outline Viewspec to the document.

This is the navigation document.