Re: Figure overlays in HTML+

Dave_Raggett (
Wed, 14 Jul 93 11:08:00 BST

Overlays and Annotatations with HTML+

Jay comments:

> We are interested in doing annotations as overlays (i.e. the user can
> draw arrows pointing to sections of text and make notes "on top" of
> the base document). This would be used on top of "regular" HTML+ text
> as well as FIGs. So, we would like to see FIGT permissible anywhere in
> the body of a document, not just within a FIG. We know that the
> position of text is not fixed in an HTML(+) document but are still
> interested in this type of annotation (cf. discussion on "annotations
> to changing documents").

FIGT as it stands is inappropriate outside a figure, since the attachment
mechanism is defined as an offset on the figure itself. Perhaps the PANEL
element is what you need. This is attached by an id reference, and would seem
ideal for your needs. For online use it could be rendered as an icon of a
thumbtack/drawing pin at the appropriate place. Clicking on taht would show
a popup panel with the arrow back to that point. The panel should have
buttons for next/previous when there are several annotations attached
to the same point (also show a number/cue indicating how many there are).

> Also, we would like to have multiple annotations as separate overlays
> (e.g. so different people's comments could be in different layers).
> There is a comment in the spec that "Figures shouldn't be nested" that
> would seem to rule that out. We'ld prefer to have the reverse:
> "overlays can be stacked".

The restriction forbidding nesting of tables, forms and figures is there
to help browsers and authors avoid overly complex documents. When a lot of
comments are made on a document, this presents choices to the reader:

a) To read all comments by a given person,
and then to go onto the next person and so on
b) To read all comments attached to a given point
regardless of author and then go on to the next point

Both of these would could be implemented by getting the server to send the
annotations separately from the original document. A neat solution is to use
the MIME multipart capability to segregrate annotations according to author
(itself passed in an RFC 822 header). The browser is then responsible to
merging them with this document, as appropriate to user preferences.

In any case the current HTML+ format seems adequate. Although it may be worth
adding a ROLE attribute to the PANEL tag, e.g. role="annotation".

What do you think?

Dave Raggett