ISSUE: should DOM have an executeFragment() method?

[Lofton Henderson <lofton@rockynet.com>]

[This issue arose during today's telecon, while talking about pan/zoom.  I 
took the AI to briefly encapsulated and start a discussion.  Without a 
recommendation...]

ISSUE:  Should WebCGM 2.1 DOM have a method to execute the navigation 
specifications of a WebCGM URI fragment?

DISCUSSION:  While discussing the form of the new zoom/pan DOM 
functionality, the telecon identified that there are several bits in WebCGM 
2.0, and projected additions for WebCGM 2.1, that are related to the view 
within a picture.  These include:

1.) The fragment syntax of chapter 3, and particularly the object behaviors 
of 3.2.1.4;
2.) The viewcontext ApsAttr that is used in conjunction with #1;
3.) The (deprecated) viewport <param> and the VDC-extent-fitting <param>s 
of 3.4;
4.) The user pan/zoom that viewers are required to offer by 3.2.1.5;
5.) The projected getObjectExtents and pan/zoom methods of WebCGM 2.1;

[1] 
http://docs.oasis-open.org/webcgm/v2.0/OS/webcgm-v2.0-index.html#webcgm_3_1_2_4
[2] 
http://docs.oasis-open.org/webcgm/v2.0/OS/webcgm-v2.0-index.html#webcgm_3_1_2_5

The WebCGM 2.1 spec needs to look at all of these and sort them out -- 
priorities and interactions.  For example, we discussed and concluded that 
there is potential conflict between #4 and #5, but that user should be 
warned against doing ill-defined things (e.g., executing #4 user pan-zoom 
while a script is modifying the view #5 is a bad idea, and that the result 
is not standardized.)

Also for example, there was some thought of further deprecating the 
<param>s -- though they might fill some important niche in HTML 
integration, on the other hand it is unclear whether anyone has implemented 
them (a confidential survey is pending).

"Cleaning house" aside, a substantive question was identified.  While #2 
allows to set the 'viewcontext' attribute on an object, that setting is 
only realized if a link to that object is executed.  I.e., only by 
executing a 'linkuri'.  And the pre-packaged behaviors of #1 are only 
available by executing a linkuri to an object.

We discussed that the capabilities of #1 and #2 could be simulated in 
script by a sequence of steps using getObjectExtents and pan/zoom.

The question arose:  why not have, in addition to DOM pan/zoom method, a 
convenience method that enables execution of WebCGM fragments that address 
an object (by apsid) or objects (by name) and apply the dozen pre-packaged 
object behaviors of 3.2.1.4?

Some thought it would be handy.  There was not much discussion of the 
implementation burden, nor was there careful development of the use cases 
and requirements.

OPTIONS:
1.) YES, add such an executeFragment() method in addition to the new pan/zoom;
2.) NO, just add the capabilities of the new getObjectExtents and pan/zoom;

RECOMMENDATION:  None yet.
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