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Subject: ISSUE closed: what is the root node
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
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