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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Should xlink:arcrole or xlink:role be the primary way todispatchon r
 Thomas B. Passin wrote: > Jonathan Borden says - > > > > > Using Ron's analysis, the arrow or arc connecting the document to its > > related resources is named by the attribute xlink:arcrole. The xlink:role > > defines another arrow between the related resource and its type. > > > > To me it seems most natural to have the most important, or primary way > > to name a related resource as an arc from the RDDL document to the related > > resource and that the xlink:arcrole be the name of this arc. > > > This isn't hard to sort out. Any link on any diagram ***should*** be labeled > as to its purpose unless there is a clear convention for its use. This simple > rule is often violated, so that people tend to ***think*** that they know what > a link or arrow means when they often don't. We just have to get clear on > what the label should be. > > Now, if you draw an arrow representing an xlink from one node to another, it > should be labeled, even if you omit the label in practice for "simplicity". > Whatever that label would be, that's the arcrole. What could be simpler? > > Jonathan said that the xlink:role could be represented by another arc. That's > just going to be confusing. We don't want two arcs for one xlink, I don't > think. If "arcrole" is the label at the middle of the arc, then "role" can be > the label for the far end of the arc. right. this is a better way to describe it. > > According to section 5.5 of the xlink rec, role and arcrole are supposed to be > absolute URIs, and the title attribute is there to provide for a > human-readable description of the "the meaning of a link or resource". This > could be ambiguous - do we title the purpose of the link or the nature of the > resource pointed to? I say, title the purpose of the link, since that's the > whole reason for having the xlink in the first place. ok. > > This leaves the role. What should "xlink:role" be used for? What's left? > The nature or purpose of the resource pointed to. > > Now for some examples, without syntax. I hope I've got the right idea here. > Let's say that your document is supposed to import two schema fragments, have > a main schema that imports the fragments, and finally be transformed using an > xslt stylesheet. The stylesheet itself includes another stylesheet. You > decide to point to all these resources using an rddl document. > > For the main schema: > title='Main Schema' > arcrole='urn:rddl:linkrole:xml-main-schema' > role='urn:rddl:resourcetype:xsd-schema' (or use the > schema namespace) Let me also answer Jason's question about why ever have xl:role=xl:arcrole: In some specific situations, the purpose and nature of a resource are the same, for example the main XML Schema: Its purpose is to be an "XML Schema" and it *is* an "XML Schema" so in this particular situation: xlink:title="XML Schema" xlink:arcrole="http://www.w3.org/2000/10/XMLSchema xlink:role="http://www.w3.org/2000/10/XMLSchema but below the purpose is an "Imported Schema", but the nature is "XML Schema" > For the two schema fragments: > title = 'Imported Schema' > arcrole='urn:rddl:linkrole:import-schema' > role='urn:rddl:resourcetype:xsd-schema' (or use the > schema namespace) xl:arcrole="http://www.rddl.org/arcrole#imported-schema xl:role="http://www.w3.org/2000/10/XMLSchema (for us, we do specifically intend to place some documentation of these terms at the arcrole URI, so we'd actually prefer that its a URL :-) > > This approach covers it all. The purpose of each xlink is given in human and > machine form, the nature of the resource itself is indicated by the role > attribute. In this example, we can clearly distinguish between the purpose > and the nature of each resource, even when the same kind of resource is used > for different purposes. This is nice language. > > Can you see how nicely this would lend itself to an authoring tool? The tool > presents you with a list of known titles. You pick one, and the rddl > generator inserts the appropriate arcrole and role attributes (or maybe gives > you a choice of allowable resource types, such as RELAX or xml-schema). > Sweet! > one of the ideas behind basing RDDL on (X)HTML is that an HTML authoring tool might provide for tag specific extensions. -Jonathan 
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