import versus include schema

["Burcham, Bill" <Bill_Burcham@stercomm.com>]

Title: Message

To Chee-Kai's issue #16 from today's discussion.  To the first note:

 

<!--  Note: it is not non-compliant with XML Schema spec to import the same schema more than once, provided the semantic treatment result in exactly the same as if the schema had been loaded the first time.  But we should rule this more lenient (but not incorrect) spec out in UBL. -->

 

It's true that the UBL rule is more restrictive than the XSD one.  It is supposed to be.  The reason is this: UBL is comprised of components.  Each component is directly usable (by a user external to UBL) by import of a root schema for that component.  The component (root schema) itself includes any necessary (internal) schemas -- and also imports other root schemas it requires.  This frees the end-user from having to know the internal structure and dependencies of the component.

 

If two such root schemas (namespaces) are interdependent then they are not really usable in isolation.  Therefore they essentially comprise one component.  So if two components are interdependent UBL says they should be combined into a single component.  This is simply for design cleanliness, and clarity.

 

To the second point:

 

<!--  Note 2: The two-level import restriction has turned out to be too restrictive for implementation.  It needs to be relaxed.  An example wording is proposed above.  -->

 

We agreed on the call today to ask Chee-Kai for specifics here.  I don't know what the real issue is here.

 

-Bill