Re: [ubl] Discussion of substitution groups

["Stephen Green" <stephen_green@seventhproject.co.uk>]

>Exactly what is gained by using type derivation rather
>than just defining a new type that replaces the old in our schema?

>Mark

1. control of extension and restriction 
    using the XSD derivation rules
    is enforced by compliant tools

2. the XSD derivation provides a trail 
   - a trace back to the types
    from which derivations were made 
    (helps with audit requirements, etc)
2a. compliant tools provide a better, 
    richer experience to developers

3. this is becoming a more ubiquitous 
    way to extend/restrict - audit
    rules tend to expect financial software 
    to follow such ubiquitous
    software designs and methodologies 
    (in my limited experience)

4. people are wanting XML to deliver 
    on the eXtensible bit (see ubl-dev)

5. software vendors are increasingly 
    investing in substitution group
    support (hence 2a above and more)

6. this delivers on UBL's original 
    promise of polymorphic inheritance
    (albeit at a price of a single rule 
    about sg's being dropped or qualified)

7. this buys into the benefits of using
    global rather than local

8. this best fits the OO development
    practises (see JAXB)

[ ref  - 'ver' our minor versioning working group recommendation ]


I could go on...

All the best

Steve