Re: locating schemas via public ids

[Paul Grosso <pgrosso@arbortext.com>]

During its telcon last Thursday, the XML Schema WG voted to
turn down our request to address this issue in XML Schemas 1.0.

While they open the possibility of addressing this a future 
version, my reading of the discussion is that they don't have
an understanding of the issue that matches ours, so I see no
reason they would add it later.  (And who knows what "later"
is in Schema terms.)

So this may affect some things we may want to do in our work.

paul  

At 11:45 2001 01 25 -0600, Paul Grosso wrote:
>During this week's telcon of the OASIS Entity Resolution Technical 
>Committee (OERTC) [1], we discussed what is recorded in our issues
>document [2] as "Issue 13 - Public identifiers for schema locations",
>and I was tasked [3] with sending our comment to the XML Schema group
>and the XML CG.  (Since OASIS is both a liaison group to the W3C as
>well as a W3C member, we figured it would be safest to include the 
>XML CG in this loop.)  Our comment follows.
>
>----------------------------------------------------------------
>The OASIS Entity Resolution Technical Committee (OERTC) [1] is
>chartered to develop an entity resolution catalog format in XML
>(XML Catalog or xmlcat).  The purpose and functionality of this 
>catalog format is to cover that which the SGML Open/OASIS TR9401 [4] 
>Entity Management Catalog did, but using XML instance syntax and 
>tailored for use with XML.
>
>Many implementors and users have found public ids and entity
>management catalogs to be very useful in practical situations
>ranging from individual use to major production environments, and
>there is a desire to be able to use such techniques for accessing 
>XML resources, especially "public" resources such as published
>DTDs and Schemas.  The OERTC has the support of several implementors,
>and its work has received interest from the xml-dev community.
>
>During our work, we realized that the current Schema Structures
>draft appears to make it impossible to provide schema-locating
>hints using anything other than URIs.  Specifically, public
>identifiers [5] could not be used as the spec is currently written.
>
>In Structures, 6.3.2 How schema definitions are located on the Web [6], 
>it says:
>  [xsi:schemaLocation] records the author's warrant with pairs of
>  URI references (one for the namespace URI, and one for a hint as
>  to the location of a schema document defining names for that
>  namespace URI). [xsi:noNamespaceSchemaLocation] similarly provides
>  a URI reference as a hint as to the location of a schema document
>  with no targetNamespace.
>
>The problem is that each member of schemaLocation and the value of
>noNamespaceSchemaLocation is required to be a URI.  Furthermore,
>the members are undelimited and separated by spaces, and public
>identifiers can contain spaces.
>
>The XML Catalog (as did TR9401 before it) would allow a user
>to locate a resource using all the information that might be 
>known about it (name, system id, public id), and certainly schema 
>resources will be given public ids (several have already [7]).  But 
>this only works if there is some way to include that information in 
>schemaLocation.  Specifically, the second "member" of each "pair"
>in schemaLocation--and the value of noNamespaceSchemaLocation--should 
>be able to contain all the external identifier information representable 
>in XML 1.0 production 75 [8], not just the information in the first half 
>of that production as is currently the case.
>
>Therefore, the OERTC asks that the XML Schema WG make allowances
>in schemaLocation for specifying both public and system ids.  
>Though we realize that XML Schemas is nearly ready to go to PR, 
>we feel this is a crucial need that should be addressed in 
>the 1.0 version of XML Schemas, and we hope that the WG can find 
>some way to add this capability.
>
>Paul Grosso for 
> Lauren Wood, chair of the OASIS Entity Resolution Technical Committee,
> Laura Walker, OASIS AC representative, and
> the OASIS Entity Resolution Technical Committee
>
>[1] http://www.oasis-open.org/committees/entity/
>[2] http://www.oasis-open.org/committees/entity/issues.html
>[3] http://lists.oasis-open.org/archives/entity-resolution/200101/msg00024.html
>    (Issue 8 in the minutes)
>[4] http://www.oasis-open.org/committees/entity/9401.html
>[5] http://www.w3.org/TR/REC-xml#NT-PubidLiteral
>[6] http://www.w3.org/TR/2000/CR-xmlschema-1-20001024/#schema-loc
>[7] http://www.oasis-open.org/committees/entity/ident.html#schema
>[8] http://www.w3.org/TR/REC-xml#NT-ExternalID
>
>