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Subject: RE: [sdo] ISSUE 124: Proposal


This is a very interesting proposal. Obviously I like the aspect of
having DataGraph take on the extra duties. Two comments:

1) I think this "sdo:orphan" property is still special: even if one can
only get it, still, this get is different than the normal SDO get which
simply returns the reference. In this case, get() will involve building
the closure of the tree starting at the node the method is called on,
because between any two calls, the set of orphans might change. That's
not necessarily a show-stopper, but it's still "special behavior", even
compared with getChangeSummary().

2) I am wondering if we should also have the restriction that the type
of the property must be "DataObject", so that we can use xsi:type to
transmit the type information for the orphans. I don't think we need the
element names for the orphans, but the types we probably do.

Radu

> -----Original Message-----
> From: ron.barack@sap.com [mailto:ron.barack@sap.com] 
> Sent: Monday, April 28, 2008 4:40 PM
> To: sdo@lists.oasis-open.org
> Subject: [sdo] ISSUE 124: Proposal
> 
> Hi,
> 
> I would like to formulate my idea, expressed in another 
> thread, as a proposed approach to issue 124.
> 
> I think that the approach combines some of the positive 
> features of both Oracle's and XCalia's proposal, reuses a 
> pattern already used in SDO 2.1, therefore fits in well with 
> the rest of SDO, and is backwards compatible.
> 
> Types may have one or more properties annotated as "orphan" 
> properties.  Orphan properties that are defined through an 
> XSD are annotated with sdo:orphan="true".  Orphan properties 
> that are defined through the API have an open content 
> property {commonj.sdo}Orphans with value true.
> 
> This annotation may only be used on a read-only multivalued 
> property.  The annotation may not be used on a property with 
> a data type.
> 
> This annotation may only be used on a property with 
> containment="true".
> 
> Calling a set method on a property, or modifying the list 
> returned by this property must throw an exception.
> 
> Getting the value of this property (either through 
> DataObject.get() or through the static interface) returns a 
> list of objects that are referenced by the graph, but not 
> contained in the tree whose root is the node having the 
> "orphans" property and whose type matches the type of the property.
>  
> {commonj.sdo}DataGraph gets a new property with the orphans 
> annotation, and type DataObject.  However, other types may 
> also have a similarly annotated properties.
> 
> The orphan property may appear in a tree:  at the root or at 
> a leaf node.  Types with orphan properties may even appear 
> with trees whose roots have orphan properties, or as 
> "brothers" of such, etc.  In such cases, an implementation is 
> free to place the referenced object in the list of any 
> suitible property, however, the implementation must also 
> assure that the normal rules of containment apply, namely, 
> that the referenced object appears exactly once in the graph.
> 
> Having such a property, it is easy to create a technical root 
> type.  Users can specify if they what the technical root to 
> give the referenced objects in a "heap" or to sort them by type.
> 
> By putting an orphan property on a Business Object (like 
> Employee, Department, Address), we get XML that looks like 
> the XML produced from Blaise's algorithm.  That is, without 
> unexpected root nodes.
> 
> Best Regards,
> Ron
> 

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