ISSUE closed: what is the root node

[Benoit Bezaire <benoit@itedo.com>]

Hi,

  There's been discussions on what the root node should be; the Picture
  or the Metafile. We need a root node for two things: the inheritance
  model, and the XCF.

  In this email I'm making a proposal for the WebCGMPicture to be the
  root node. Here's why:

  i) To me, the WebCGMMetafile is a simple placeholder for generic
  information about the file such as VDC extent, metafile version,
  profile edition, VDC type etc... and this, in my opinion, doesn't
  need to be a WebCGMNode.

  ii) I think the inheritance 'root' and the XCF 'root' should be the
  same; and for this reason, I think WebCGMPicture is a better choice
  (please see below).

  iii) Most of our style properties either apply to single APS' or the
  entire Picture, we've never discussion Metafile-wide style
  attributes.

  iv) WebCGM doesn't support multiple pictures per file, but some
  other profiles do; and if they 'extend' our model, I think it's best
  if the root is the Picture, here's why:

    - a DOM implementation supporting multiple pictures would likely
    iterate between pictures via:

    var meta = objectId.getWebCGMMetafile();
    var pic  = meta.firstPicture;
    while( pic.nextSibling )
    {
      ...
      pic = pic.nextSibling;
    }

    - this would allow each picture to be styled differently or in the
    same way (depending on the use case).

    - it would also allow to call applyCompanionFile per Picture (just
    replace the '...' above with the call. Again, a different XCF for
    each Picture could be applied, or the same to all pictures (the
    user has the option).

  v) Having the WebCGMPicture as the root element makes our profile
  easier to extend for other profiles, and I think that's what we
  want.

  vi) I understand that it seems natural to have WebCGMMetafile derive
  from WebCGMNode (I for one, agree), but I think we're blocking
  extensibility of the profile if we do that.

  Unless there are objections, I'm in favor of WebCGMPicture being the
  root element, okay?

-- 
 Benoit                 mailto:benoit@itedo.com