xml-dev - Re: Do we need link-catalogs for schemas?

[Murray Maloney <murray@muzmo.com>]

I think that it is definitely worth looking at Rick's proposal.
I can imagine how SOX could use and benefit from this kind
of binding mechanism for every element, attribute, datatype,
entity, notation, and even PIs and namespaces themselves.

I would hope that such a binding mechanism would allow one
to associate XML objects with various flavors of semantics:
behaviour (IDL, Java, etc.), meaning (prose, images, etc.),
style sheets (CSS, XSL, etc.), equivalences (UML, XSchema, etc.),
and other relationships.

Regards,

Murray

At 09:51 AM 10/9/98 -0400, Rick Jelliffe wrote:
>
>Perhaps it is time to (attempt to) ressuscitate XML-Bind. This was a project of
>mine which I put forward during the Namespaces debate. The thrust of this was that
>the then namespace draft conflated two things:
>    * some way to *bind* GIs into public identififiers (URL+GI or whatever) {this
>is what the current namespace has limited itself to}
>    * some way to *link* this identifier to all sorts of interesting information.
>I tried to push the idea that having just a simple "src" attribute in the namespace
>PI tied restricted it arbitrarily, and had the bad effect of hardwiring a single
>vendor's schema.
>
>So instead I pushed a catalog idea, and in particular that the namespace proposal
>actually reflected a need for a new kind of link: linking from element types rather
>than from instances on elements. One wants to name them because one wants to link
>to or from them. I would like to raise this link-catalog idea again.
>
>The link-catalog idea was that potentially every stakeholder (end-user, document
>creator, browser-maker, DTD/schema creator) may want to use these type-links (for
>documentation, schema distribution, etc).  It would be best if this were explicitly
>marked up using XLL extended links. A document should be able to have a web of
>type-related resources linked to/from it.
>
>Now the great thing about using instance syntax for new schemas (e.g. XSchema) is
>that
>no new linking declaration system needs to be invented: we can define any kind of
>link we need and markup the element in the Xschema instance. That way we get
>type-links.
>
>So now we are at the stage:
>
>1) namespace proposal binds GI names to public identifiers
>2) XSchmema proposal (and its ilk) can allow links from GIs to a catalog (e.g.
>using a fixed attribute) *but* we need to actually do it;
>4) XLL proposal allows extended links, with which we can implement a catalog
>system, *but* we need to actually do it.
>
>So I would propose that XML-DEV should design an element set for catalog entries,
>it should cascade or be able to link with other catalogues. It might be a valuable
>enhancement to XSchema, and indicate to the W3C schema people the direction that
>people would like to go. (In particular, that there are many possible schemas, and
>even natrual language documents are valuable for defined document types.)
>
>The kind of thing I am thinking of is this:
>
><!-- example of a link-catalog -->
><XML-DEV:link-catalog>
>    <entry id="lc1" GI="p" namespace="urn:www.w3.org/html4#p" >
>        <description>Links for HTMLs P element type</description>
>       <!-- links to schemas -->
>        <a href="www.w3.org/html4.dtd#p"
>            role="-//www.w3.org/NOTATION XML DTD//EN" />
>        <a href="www.schema.net/Xschema/html4.xml#p"
>            role="-//www.w3.org/NOTATION XSchema//EN" />
>        <a href="www.ms.com/html4.txt#p"
>            role="-//www.ms.com/NOTATION DCD//EN" />
>        <a href="www.netscape.com/html4.htm+p"
>            role="-//www.w3.org//NOTATION RDF Schema//EN" />
>        <!-- links to documentation -->
>        <a href="www.vhg.org/html4/p"
>            role="-//XML-DEV//NOTATION Virtual Hyper Glossary//EN" />
>        <a href="www.schema.net/documentation/EN/html-paragraphs.htm"
>            role="-//XML-DEV//TEXT English Documentation//EN"/>
>        <a href="www.schema.net/documentation/DE/html-paragraphs.htm
>            role="-//XML-DEV//TEXT Deusche Erklaerung//DE"/>
>        <!-- links to further catalogs -->
>        <a href="www.schema.net/link-catalogs/html/p/link-catalog.xml#lc26"
>            role="-//XML-DEV//SGML Link Catalog/EN"/>
>    </entry>
></XML:DEV:catalog>
>
>In this example there is a single entry. The description field indicates the
>catalog entry relates to HTML paragraphs.  The first lot of links link to schema
>definitions for HTML paragraphs, given in various notations (DTD, XSchema, DCD, RDF
>Schema). Then comes documentation for it in various ways (VHG, English, German).
>Finally comes a link to another link-catalog, which allows cascading or a web of
>links.
>
>In each entry, I have used an XLL href (a URL) and used an SGML FPI (Formal Public
>Identifier) for the role atribute.  Anyone who wants to define a new role would
>make up a new FPI for that role. XML-DEV would create a good starting set of FPIs
>for the catalog:
>    DTD
>    XSchema
>    English Documentation  (.. and so on for every language)
>    link-catalog
>
>After that, there should be some kind of new attibute in Xschema, available on all
>elements, called perhaps  "link-catalog-href". This contains a URL pointing to an
>XML-Dev link-catalog
>
>IMHO this kind of thing would be a major addition to the power of XML: the W3C
>efforts to define a new single schema definition language are, to some extent,
>misguided and out-of-sequence in that it would be better to first set up an
>infrastructure by which schemas and documentation can be located.  I am not
>convinced that having multitudes of schema definition languages is a bad thing:
>perhaps it is better to let companies compete and just provide an infrastructure
>which allows them to provide good product without hijacking documents.
>
>Cheers.
>
>Rick Jelliffe
>
>
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