Re: [sca-assembly] [ASSEMBLY 127] Need definition of compatible forproperty types - Proposal

[David Booz <booz@us.ibm.com>]

I'm in general agreement with the proposal, with the following comments:

1) specifying a type on a component property element is optional, an aspect which I think needs to be folded into the resolution. That is, I don't think we are trying to assert that in the absence of a type specification on a component property, the runtime would try to ascertain the type of the property from the value and check for compatibility with the type of the underlying componentType property.

2) Editorial wording:

(a) "There are a number of places where the declared type of a property element must be matched... "
- Can we find a better word than places? situations?
- lower case 'must' needs to be corrected.

(b) "Compatible here means that the two types have to be the same XSD type ... "
- can we reword as: Two property types are compatible when they are the same XSD type ...
- Is "same XSD type" sufficiently precise? Surely we mean same complex or simple type (or same global element) in the same namespace.

3) ASM50036 uses the term compatible referring to property types. I think that statement needs to be updated to refer to the new def'n of compatible that is in this proposal.


Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093 or 8-295-6093
e-mail:booz@us.ibm.com

Mike Edwards ---04/20/2009 01:48:00 AM---Discussion: We discussed this a bit on the last Assembly call, but I'll try to

From:	Mike Edwards <mike_edwards@uk.ibm.com>
To:	"OASIS Assembly" <sca-assembly@lists.oasis-open.org>
Date:	04/20/2009 01:48 AM
Subject:	[sca-assembly] [ASSEMBLY 127] Need definition of compatible for property types - Proposal

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Discussion: 

We discussed this a bit on the last Assembly call, but I'll try to summarize it here. 

We could choose to define "compatible property types" in a similar way that we define "compatible interfaces" and 
this could lead us to define "compatible superset" and "compatible subset" for property types. 

However, for property types this seems pretty heavy. 

A simpler approach is to say that the property types of two SCDL elements must be "compatible", pure and simple, 
where in XSD terms this means that they have the same XSD type.  Where one type is declared using a language 
other than XSD, say Java, then the appropriate C&I spec must define the mapping rules of that type to XSD.  So, for 
Java this might be the JAXB rules. 

So this would then apply to all cases where pairs of SCDL elements deal with property types: 

<component/> <property/> and <componentType/> <property/> 
<composite/> <property/> and <component/> <property/> (@source attribute) 
<componentType/> <property/> and <composite/> <property/> (when computing the componentType of a composite) 

Proposal: 

Add a new subsection following section "4.4 Property": 

4.4.1 Property Type Compatibility 

There are a number of places where the declared type of a property element must be matched with the declared type of 
another property element.  These places include: 

o Where a component <property/> sets a value for a property of an implementation, as declared in the componentType of the implementation 
o Where a component <property/> gets is value from the value of a composite <property/> by means of its @source attribute 
o Where the componentType of a composite used as an implementation is calculated and componentType <property/> elements are 
created for each composite <property/> 

In these cases, the types declared for the two <property/> elements MUST be compatible. [ASM50038] 

Compatible here means that the two types have to be the same XSD type (where declared as XSD types) or the same XSD global element 
(where declared as XSD global elements).  For cases where the type of a property is declared using a different type system (eg Java), then the 
type of the property is mapped to XSD using the mapping rules defined by the appropriate implementation type specification 




Yours,  Mike.

Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431  
Email:  mike_edwards@uk.ibm.com

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