Are GML Documents Hypermedia?
XLink is part of GML, but I've never seen a WFS return GML that links to other resources. Does anybody use GML like this, and what client would they use?
XLink is part of GML, but I've never seen a WFS return GML that links to other resources. Does anybody use GML like this, and what client would they use?
Comments
Re: Are GML Documents Hypermedia?
Author: Paul Ramsey
"what client would they use" is the ur-question that everyone ignores despite it's hyper-significance. Why do neogeographers build using JSON or RSS? Because there's a client that can consume them, the web browser. Why is KML relevant? Because there's a client that can consume it! Format relevance is 100% tied to the installed base of products capable of consuming the format -- shape files are still more relevant than GML, because of the huge installed base. If OGC wants GML to be relevant, they should be building and giving away (BSD license) good GML read/write libraries because doing so would drastically up the odds of products integrating GML support.Re: Are GML Documents Hypermedia?
Author: Sean
Paul, parsing GML to graphically render features is one thing, and that's being done in the browser already. What I'm asking is what clients exist for traversing a web of xlinked GML? In my opinion, without hypermedia links, the "GeoWeb" is just hot air.Re: Are GML Documents Hypermedia?
Author: Paul Ramsey
In my opinion, without a client, the "GeoWeb" is just hot air... which is saying much the same as you are. Note that KML includes the notion of hypermedia links and there is a KML client that can traverse them. So perhaps the GeoWeb is not hot air, just the GML-GeoWeb.Re: Are GML Documents Hypermedia?
Author: Bill Thorp
Definitely an interesting question. The Xlink spec says "The hyperlink's effect on windows, frames, go-back lists, style sheets in use, and so on is determined by user agents, not by the hyperlink itself." GML's vision of Xlink seems to be only for defining properties in a non-inline way. EG: [gml:location xlink:href="http://www.ga.gov.au/bin/gazm01?placename=leederville&placetype=R&state=WA+"/]. In my brief look, I found no other use cases. I don't think they imagined user-interactive "hyper" links at all, simply machine readable distributed data fetching. Building a client that treats Xlinks as a user-controlled "hyper" links would involve delayed xlink parsing, which is probably contrary to most Xlink-aware XML APIs out there.Re: Are GML Documents Hypermedia?
Author: Allan
I don't think the hyperlinking envisioned by GML was ever meant to be browsed with a browser without some intervening process like an XSLT engine to style things. But I do think it was originally meant to go beyond simply defining non-local properties. The way I understood that part of the vision was that eventually GML data could be stitched together using xlinks.