Re: [regrep] Re: Core Components Specifications

[David RR Webber - XMLGlobal <Gnosis_@compuserve.com>]

Message text written by Sandy Klausner
> 
Sally,
Not so, "Amount Due" is derived data. A particular relationship between
attribute values may be specified to remain invariant as part of the shared
specification between trading enterprises. A processing engine should be
able to dynamically test this invariant as a final integrity test before
message shipment. The originating application that supplied the origin data
cannot be relied upon to perform this test. So here is a case where
agreement as to a specific constraint was declared at design time, but is
dynamically evoked.
Sandy 

<<<<<<<<

Sandy,

An alternate approach is to have two pieces of XML, one that defines
the quantity "Amount Due" as a physical type (decimal, currency, etc),
and then associated with this a verb script that defines how to 
calculate the result.  A classic example of this is a HTML form with
a field and then JavaScript to compute the value.  The verb script may
also simply point to say a URL where a webservice call returns the
result.

What this shows us is that we need to keep an open mind and an
enabling infrastructure so that the implementation layer can 
marry to the logical model layer and critically the TWO should 
remain in synch' at all times via the registry.   Being able to add
multiple 
physical mechanisms pointing to a core component logical
entity provides us with adaptable behaviour into peoples
existing systems.

Conversely - if I select "Amount Due" in the registry I should
see the available physical methods associated to that
for integrating that into my transaction.  This then empowers
the programmers to empower the business users.

DW.