Am 26.01.2007 um 01:39 schrieb Braden McDaniel: > [...] > Why isn't this a job for a metadata spec? It seems to me that this > kind > of semantic information is too application-specific to encode in the > structure of the file format itself. > I could say as well, 3D appearance information is too application specific to encode in the structure of the file format itself. See also my previous post, its basically a matter of preferrence for outward or inner beauty :-)
Also, physics information already *IS* application specific semantic information... why not go all the way? > Note that you can attach metadata to any node in X3D. I don't know > what > the case is with COLLADA; however, you could also transmit such > metadata > out-of-band. > If there is a way to refer to the scene elements from outside, yes, certainly you can. You know VRML, the only way to do this is referring to DEF names, but DEF names are not required by the specification. Especially exported/generated VRML usually omits them, so the nodes remain anonymous, and you cannot refer to them from outside. VOS fortunately has vobject URIs for this purpose, phew! So an external semantic description may be the way to go if we really want to keep them separate. However, VOS is not a syntactic file format, but an object system. The object code already represents a form of semantics! Also, there is some overlap in semantic and geometric information, particularly object positions and bounds. So why keep them separate? > The out-of-band solution has a couple of interesting qualities: > * It readily supports a notion of allowing the same scene to > mean > different things to different clients. > * You could potentially define mappings from the semantic > metadata > file format to multiple different geometry file formats. So > the > same semantic data could be meaningful regardless of > whether the > geometry was expressed in X3D, COLLADA, or whatever. > > Anyone who's ever used HTML and CSS should be seeing an analogy here. > Precisely. That is one of my reasons for wanting the emphasis on the semantic part, not on any particular 3D file format. The semantic part is usually less bulky than geometry (no textures!), and by its very nature provides an excellent base for deciding which geometry parts to load. Leave geometry loading to file format plug-ins... > Whether the semantic metadata lives out-of-band or in the scene, > coupling the nature of its specification to that of the geometry seems > like the Wrong Way. > I am not quite sure wheter I agree or disagree, or even understand the sentence at all.. could you elaborate? Regards, Karsten Otto (kao) _______________________________________________ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
