I agree with Bryan that the "display
the properties and values" is the most "obvious" use case
to suggest some sort of runtime support for additional meta-data on "dynamic"
resource properties. There may be other use cases, but I again
agree with Bryan's observation of the need for the application to have
a-priori understanding of the semantics of those resource properties.
So, in the case of "display the
properties and values" the application would need to know not only
the xsd details of the GED (eg type), but also the cardinality of the resource
property use of the GED (minOccurs and maxOccurs). The xsd details
of the GED can be found (via WS-MetaDataExchange, for example). It
is the cardinality (and maybe other details) of the resource property that
need to be discovered.
sgg
++++++++
Steve Graham
(919)254-0615 (T/L 444)
STSM, On Demand Architecture
Member, IBM Academy of Technology
<Soli Deo Gloria/>
++++++++
"Murray, Bryan P." <>
06/21/2004 01:07 PM
To:
<>
cc:
Subject:
[wsrf] Issue WSRF9
I understand the need to know which properties
are currently
present
in the property document given that the property document
supports
dynamic properties. However, I would like to see a use-case
describing
the need to retrieve at runtime the schema for any properties.
The only reason I can think of for retrieving properties which
an
application does not already understand is if the application
simply
displays properties to a human or copies the property somewhere.
If
the application understands the namespace of the property it can
locate the type from the WSDL/schema for the namespace.
Otherwise,
simple properties (no child XML elements) can be displayed
without
understanding their type by just treating the text node as a
string.
The application can choose to either not display complex
properties or
to list attributes and child elements with their values.
Grandchild
elements or attributes will ultimately make this too complicated
to do
at some point.
Other, more complex, applications will need to understand not
only the
syntax of the properties they are retrieving, but also the
semantics
of those properties in order to interact with them
appropriately. The
syntax can be found in WSDL/schema files, but the semantics
needs to
be understood by the programmer writing the property retrieval
code. I
am confused as to how an application could interact with a
property it
does not understand beyond simply displaying or copying its
value. If
an application does understand a property that falls into the
xsd:any
portion of the resource property document schema, it does not
need the
schema - it already knows the type of this property.
If there is no need beyond displaying or copying the value of an
unknown property I suggest that we not provide the ability to
retrieve
the schema at runtime.
Can someone offer a use-case that shows where my thinking is
deficient?
Bryan
