Do we need link-catalogs for schemas?

Bill la Forge b.laforge at
Fri Oct 9 19:18:13 BST 1998

Two concerns here:

        1. There should be a way to cascade whole Bind documents,
            not just individual entries, as well as adopting a
            entry rule. This would allow one Bind to override another,
            dropping inappropriate items under an entry.

        2. Binding an entry to a class should be accomplished without
            recourse to a link. This would allow for light-weight bindings.

From: Murray Maloney <murray at>

>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.
>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
>>I tried to push the idea that having just a simple "src" attribute in the
>>PI tied restricted it arbitrarily, and had the bad effect of hardwiring a
>>vendor's schema.
>>So instead I pushed a catalog idea, and in particular that the namespace
>>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,
>>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
>>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
>>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
>>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
>>using a fixed attribute) *but* we need to actually do it;
>>4) XLL proposal allows extended links, with which we can implement a
>>system, *but* we need to actually do it.
>>So I would propose that XML-DEV should design an element set for catalog
>>it should cascade or be able to link with other catalogues. It might be a
>>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 -->
>>    <entry id="lc1" GI="p" namespace="" >
>>        <description>Links for HTMLs P element type</description>
>>       <!-- links to schemas -->
>>        <a href=""
>>            role="-// XML DTD//EN" />
>>        <a href=""
>>            role="-// XSchema//EN" />
>>        <a href=""
>>            role="-// DCD//EN" />
>>        <a href=""
>>            role="-// RDF Schema//EN" />
>>        <!-- links to documentation -->
>>        <a href=""
>>            role="-//XML-DEV//NOTATION Virtual Hyper Glossary//EN" />
>>        <a href=""
>>            role="-//XML-DEV//TEXT English Documentation//EN"/>
>>        <a href="
>>            role="-//XML-DEV//TEXT Deusche Erklaerung//DE"/>
>>        <!-- links to further catalogs -->
>>        <a
>>            role="-//XML-DEV//SGML Link Catalog/EN"/>
>>    </entry>
>>In this example there is a single entry. The description field indicates
>>catalog entry relates to HTML paragraphs.  The first lot of links link to
>>definitions for HTML paragraphs, given in various notations (DTD, XSchema,
>>Schema). Then comes documentation for it in various ways (VHG, English,
>>Finally comes a link to another link-catalog, which allows cascading or a
web of
>>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
>>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
>>efforts to define a new single schema definition language are, to some
>>misguided and out-of-sequence in that it would be better to first set up
>>infrastructure by which schemas and documentation can be located.  I am
>>convinced that having multitudes of schema definition languages is a bad
>>perhaps it is better to let companies compete and just provide an
>>which allows them to provide good product without hijacking documents.
>>Rick Jelliffe

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