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Subject: AW: [sdo] ISSUE 124: Proposal

sorry, very jet-lagged... hit the wrong button...
During 2.1 there seemed to be pretty good consensus that {commonj.sdo}DataGraph should be deprecated.  Anything you can do with DataGraph, you can do yourself:  DataGraph is simply a type with a ChangeSummary.  If we want to continue in that direction, and follow Radu's advise of combining TechnicalRoot and DataGraph, then we have to have a general property type that exhibits this behavior. 
And again, the trouble with the "fallback" technical root approach is that non-SDO clients may want to know what they are getting.  As far as such clients are concerned, the fact that the technical root is sometimes there and sometimes not (depending on if it is needed) could be problematic.  Packing things in a DataGraph (or any container with an orphans property) is simply a means of getting defined behavior.

Von: Barack, Ron
Gesendet: Dienstag, 6. Mai 2008 03:01
An: 'Christophe Boutard'; sdo@lists.oasis-open.org
Betreff: AW: [sdo] ISSUE 124: Proposal

Hi Christophe,
Whether the implementation stores the referenced objects in memory or calculates them as part of the serialization is an implementation detail.  All we are doing with declaring orphan properties is simply to allow the user control of where there orphans are marshalled, given the user a bit of control over how the XML looks.   If you want to think of the orphans as being only in XML, and not in memory, that's OK.  As far as SDO is concerned, the orphan properties (like the tech root) vanishes when SDO parses the XML,  However, when the XML is processed by some other framework, the fact that SDO produces awkward XML could create a barrier to integrating SDO with other XML frameworks.  As Radu pointed out, it's a little bogus to have a {commonj.sdo}DataGraph object, whose root element is a technical root.   It would be less awkward to combine {commonj.sdo}DataGraph and {commonj.sdo}TechnicalRoot.
Like I said, the only reason to define orphan properties is to control where orphan objects are serialized into the XML.  If it is desireable to seperate the orphans by type (the way XCalia originally suggested), then this can be specified.  If you want the orphans collected at a particular type (eg, Employee or Department), then this is doable too.

Von: Christophe Boutard [mailto:christophe.boutard@xcalia.com]
Gesendet: Montag, 5. Mai 2008 11:50
An: Barack, Ron; sdo@lists.oasis-open.org
Betreff: RE: [sdo] ISSUE 124: Proposal

Hi Ron, everyone,


Here are my comments inline…


Best Regards,




De : Barack, Ron [mailto:ron.barack@sap.com]
Envoyé : mercredi 30 avril 2008 10:40
À : Christophe Boutard; sdo@lists.oasis-open.org
Objet : RE: [sdo] ISSUE 124: Proposal


Hi Christophe, everyone,


I really want to try to resolve SDO-124 at next weeks meeting.  Let's try to find a solution that combines aspects of the various approaches, and see if we can get everyone to sign up to it.


The criticism that the orphan properties are visible through the API is valid, and I agree that users will typically not want to see such properties amoung their business objects.  On the other hand, {commonj.sdo}DataGraph is not a business object, it's already a technical object, but I guess that not everything will be packed in a DataGraph.



I want to be sure to get your point. Are you talking about the DataGraph object in memory or only its XML serialized format. The end of the mail let me think that you are talking about the in memory object.

If it only deals with XML that’s fine for me but in the other case I would not like to have to maintain the graph closure in memory



One solution would be to make orphan properties even more special: to make them invisible.  That is, orphan properties appear neither in the list of propertys defined by a type, nor in the instance properties of the data object.  They appear only when generating XSD from the type metadata, and of course, in the XML generated by an XMLHelper.save().  This is essentially the behaviour that Oracle has proposed for orphans, the only difference is that they are not generated, but created as part of the type definition.




It is almost the same question. You said that the “hidden” properties only appear in the XML, so the question is why do we need to have these properties definitions? I think that they can be generated by the implementation at XML serialization time.

More generally I’m really interested in the concept of having invisible properties in SDO even independently of the Containment discussion



The burden is still on the user to define the appropriate orphan properties, or to pack his objects in a DataGraph.  Therefore, it is still possible to generate GraphNotClosed exceptions.  If we want to make these exceptions a thing of the past, we need to have technical root as a fallback mechanism.  We'd need to extend the proposal as follows:



I’m really not convinced by the first statement  As I said in previous emails I think that these technical things should be managed by the implementation otherwise it will introduce a lot of complexity for the users.

I’ve also a particular question about the way objects are packed in a DataGraph. I’m worrying about seeing some mechanisms that ensure the DataGraph closure in memory.

Let me try to develop this point…

If a user adds an object in the graph, I suppose that the implementation will  automatically ensure that the object will be added to the orphans if it has no container. If it is not done in that way I don’t see why the orphan properties are not only added at serialization time.


If I understand correctly we have three approaches :

1-     The user defines the orphans properties in its Types if there is no real DataGraph envelope.

2-     The user has nothing to do if there is a DataGraph containing the Orphans. I’m not sure about that, I think your answers to the previous questions will help me…

3-     If 1 or 2 are not enough, then the implementation will add the Technical Root.


Having these three approaches could be a good point but it will lead to produce slightly different XMLs depending on the data graph structure to serialize.



1.  Define the type {commonj.sdo}TechnicalRoot as Frank has described it, with 2 properties, a "businessRoot" and an "orphans" property.


2.  The TechnicalRoot is specially treated during parsing (ie, XMLHelper.load):  it does not appear in the resulting XMLDocument.  It is simply an artifact of XML (de-)serialization.


3.  Before serializing to XML, the various XMLHelper.save methods must first assure that the data graph is closed.  If it is not closed, the serialization mechanism must insert a technical root object as the root node of the graph before serializing it.



Agree with the three statements as a definition of technical root.



Like I said, I think it would be good (and I think, it's doable) to resolve SDO-124 next week.  Can I ask everyone to spend a few cycles evaluating the proposals, bringing forward issues.  It's also OK to send an email saying if a solution is satisfactory... this gives me an idea of how far we are from reaching consensus.









Von: Christophe Boutard [mailto:christophe.boutard@xcalia.com]
Gesendet: Dienstag, 29. April 2008 22:24
An: Barack, Ron; sdo@lists.oasis-open.org
Betreff: RE: [sdo] RE: Spam detected by the Fortinet Antispam RE: [sdo] ISSUE 124: Proposal

Hi Ron,


Here are my comments inline...


-----Message d'origine-----
De : Barack, Ron [mailto:ron.barack@sap.com]
Envoyé : mardi 29 avril 2008 19:28
À : Christophe Boutard; sdo@lists.oasis-open.org
Objet : AW: [sdo] RE: Spam detected by the Fortinet Antispam RE: [sdo] ISSUE 124: Proposal


Hi Christophe,


Drawing a distinction between "the role of Containment in the DataGraph Closure and the concept of Composition" sounds very interesting, but I'm not at all sure what exactly you are suggesting.  What API changes are you thinking about?  Would containment no longer be used in generating XML?



I’m not thinking about API modifications but mainly in clarifying things.


Let me try to elaborate…

1.    From my point of view a DataGraph is a set of interconnected DataObjects by Containment or Non Containment. At this point the containment is nothing more than a specific kind of relationship. It does not participate to the DataGraph definition

2.    Then Containment itself should be defined as composition.

3.    Finally from the XML serialization point of view, the concept of DataGraph closure should be introduced. But only at this point in order to maintain the Data Model and its XML serialized format totally decoupled. This closure can rely on Containment and the orphans management has to be integrated in order to ensure a tree based structure because we are dealing with XML.



Whether or not surfacing the orphans through the API is a bug or a feature is a matter of taste.  As with ChangeSummary, I imagine the most common case to be that the user packs his data objects inside of a {commonj.sdo}DataGraph, and since DataGraph has an orphans property, the user will never have to  worry about whether the graph is closed.  In this case, I don't think it's intrusive to say that DataGraph has an orphans property that is accessible through the API... In fact, there could be use-cases for it (though none come to mind right now, other than some sort of error checking).



I think I got your point  but I’m not comfortable with a concept which introduces something (I mean some properties) without any meaning in the business model represented by the SDO Types. As said in my previous email we have to be careful because having this kind of orphan Properties always present in each DataGraph could lead us to problems when trying to create relationships between two DataGraphs.

But I’m interested in concrete use cases for that but basically if we consider that a user has to choose between “containment” and “non containment” for a relationship, I think that he should only be focused on the semantic aspect of that choice which is “composition or not”.

I may be wrong but currently I think these use cases will be more technical than business oriented and in consequence the orphans management should be hidden.



I'm not sure that any of the proposals has any solution for managing references that are unresolved within a graph, but resolvable in some larger context.  For that, we need a concept of identity.  We also need to be able to choose between whether we serialize object or their Ids.  Please see the 4th and 5th paragaphs of http://www.oasis-open.org/apps/org/workgroup/sdo/email/archives/200804/msg00069.html for an idea of how SDO-66 (together with SDO-125 and SDO-128) could maybe help here.



I really like the idea of having KeyTypes compatible with Types in order to represent a kind of “Hollow” DataObjects. Now from a DAS point of view I’ve planned to start ASAP a discussion in order to distinguish the difference between “null” and “not loaded” which means when you call myDO.get(“aDataObjectProperty”) and you get null, does it mean that the property is "loaded and null" or just "not loaded". It seems to be again a new reason for being synchronized between DAS and SDO TCs.



Best Regards,




-----Ursprüngliche Nachricht-----

Von: Christophe Boutard [mailto:christophe.boutard@xcalia.com]

Gesendet: Dienstag, 29. April 2008 16:31

An: sdo@lists.oasis-open.org

Betreff: [sdo] RE: Spam detected by the Fortinet Antispam RE: [sdo] ISSUE 124: Proposal


Hi all,


Due to OASIS membership issues, Xcalia members were temporarily unable to post on and receive messages from the SDO3 mailing list since mid past week.


Now everything has been fixed, and I'll try to provide some points we wanted to make about the containment issue.


First from a pure TechnicalRoot point of view, I really like Frank's proposal which make the TechnicalRoot more generic and so more easy to standardize.

Just as a quick reminder because his email has been sent one week ago, I paste here his XSD proposal :

<xsd:complexType name="TechincalRoot">


      <xsd:element name="buisinessRoot" type="xsd:anyType" minOccurs="1" maxOccurs="1" />

      <xsd:element name="orphans" type="xsd:anyType" minOccurs="0" maxOccurs="unbounded" />




  <xsd:element name="xmlDataGraph" type="TechnicalRoot"/>


From our point of view, this proposal is a very good one and we do not have particular reasons for having a "per type" list of orphans except the following example:

Suppose that a Company has 10000 Employees by non containment. These two employees share the same Address by non containment.

Then the produced XML will be:


    <businessRoot xsi:type="tns:Company"







    <orphans xsi:type="tns:Employee">




    <orphans xsi:type="tns:Employee">





    <orphans xsi:type="tns:Employee">





    <orphans xsi:type="tns:Address">





Now assume that a modification is made on the Address1 instance. The ChangeSummary will reference it but having all the orphans stored at the same level will lead to check the 10000 employees in order to locate the Address. I'm not sure this a SDO specific problem (it may be more a XML parser / XPath / SDO implementation issue) but it may raise a performance issue.



Second point concerns a remark from Blaise saying that the TechnicalRoot does not address the following use case where TypeA has a containment property to TypeB and where we want to have B as the document Root.

Indeed the TechnicalRoot is not (currently) able to deal with that use case for the following reason: We assume that containment relationships are there for defining a "Composition" which means (IMO) that the instance of Type B is only reachable from its parent.

I think that the Oracle's proposal also consider contained object with the same semantic and for that reason I'm a little bit lost by a use case which consider a non identifiable object as a root.



Now I'm back to the last proposal made by Ron (on SDO-124)...


First, the good point is that it seems to allow everyone to produce any kind of XML but based on Xcalia's TechnicalRoot implementation experience, I'm a bit worrying to see that the concept of "orphan properties" accessible from the API.


As I said in our last document and during the F2F meeting, our first TechRoot implementation was still visible for the users. We encountered lots of problems when trying to merge data graphs (e.g. create references from a datagraph to another) and mainly issues to maintain the different "orphans" lists (not only data but also information relative to change summaries).


I would like to spend more time thinking about use cases based on Ron's proposal and summarize up the Xcalia point of view.


The first thing for us is to clarify the "containment" definition which may imply a clean distinction  between the role of Containment in the DataGraph Closure and the concept of Composition.

We believe that the Containment should only be used for the second role.

IMO, this point is very well explained in Blaise's proposal.


Then the second point consists in being able to serialize a non closed graph. For this particular point, I think whatever the solution is (Blaise's proposal, Ron's, TechRoot, a combination of all) the main point is to consider the solution as an artifact for serialization and not an evolution of the SDO model.


In consequence users should not be aware of this technical things and again (IMO) do not have to define themselves the orphan properties.


Best Regards,



-----Message d'origine-----

De : Radu Preotiuc-Pietro [mailto:radup@bea.com]

Envoyé : mardi 29 avril 2008 03:11

À : ron.barack@sap.com; sdo@lists.oasis-open.org

Objet : Spam detected by the Fortinet Antispam 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.




> -----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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