----- Original Message ----- From: "Joseph Kesselman" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, June 19, 2003 5:52 AM Subject: Re: registering schema locations ... > What's wrong with having the document explicitly declare which schemas it > needs? It has to declare the namespaces, and if anyone knows the mapping > from one to the other it should be no harder to build that into the > document than to try to imply it afterward... and if it's in the document > you avoid having to blaze a path into uncharted and (at least for now) > nonportable terratory.
Reasons (presumably known to the XML Schema specifiers and the Xerces crew): 1. The application reading the document uses schema validation to ensure that any validated document meets certain preconditions (thus eliminating many possible error conditions it might have to defend against). But this only works if the schema used for validation is the one which corresponds to the application code. If the document can specify the schema itself, and a different schema is used, a schema-valid document may not meet the expected preconditions. A different schema might be specified in the document for varying reasons, ranging from inadvertent version skew to fraudulent intent. 2. The schema specified in the document may be inaccessible to the processing application, or for performance reasons, the application may wish to use a local copy of the schema. If that application must then use an entity resolver, it might as well ignore the schema specified in the document, as the schema spec and Xerces allow. The originator of this thread asked for other mechanisms (beside the external-schema-location property on the parser) to bind namespaces to schemas. The recent Oasis Catalog mechanism should probably be mentioned. (Sorry, I don't have a reference.) Jeff --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
