Compatible Evolution

XML is a YASDF*:

• add optional stuff
• don't delete stuff
• don't change the meaning of stuff
• communicate breaks in compatibility

* yet another self describing format

WSDL Last Call Issue - LC124

• Evolution an big issue for Web services
• WSDL WG failed to engage XML Schema WG
• LC124 - versioning last stand
• Concrete^W Cement Proposal

XML Schema 1.0 for Description

1. description of content constructed by a sender
2. description of content available for a receiver
3. validating the format of a message

Versioning and XML 1.0

• got to get it right in schema version 0
• UPA and greedy xs:any make writing extensible schemas tricky
• Have resort to dumb schema tricks

Validate Twice

Henry Thompson's technique:

1. Validate document
2. Prune PSVI elements marked "*[pe:validity()='notKnown']"
3. Validate pruned document

Annotation, Extension, Mandatory

• make ignoreUnknowns mandatory
• make ignoreUnknowns optional
  • <xs:schema wsdlx:mustIgnore='true' ...
  • <xs:element wsdlx:mustIgnore='true' ...
  • <xs:import wsdlx:mustIgnore='true' ...
  • <wsdl:types wsdlx:mustIgnore='true' ...
  • lots more ..

LC124 - Questions

• Does ignoreUnknowns impact data mapping?
• Is this a tractable problem?
• Should WSDL define this?