[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: AW: [sdo-comment] support for dynamic containment
Hi Ron, We applied user-defined containment for the exchange of data. To this end, we introduced the concept of a Snapshot (*). A snapshot is an opaque container of data that can be converted to and from DataObjects or normal (of even more exotic) java objects. While creating such a container you have to supply a SnapshotDefinition. The prime example of such a definition is a selectclause that enumerates all properties that you want to include in the snapshot. A select clause is typically created from a comma-separated list of property paths. The SnapshotDefinition defines what part of the object graph can be reached. So we don't attach this information to the dataobjects or types but pass it as a parameter each time we need it. For CopyHelper.copy, this would be something like CopyHelper.copy(DataObject source, Scope scope) // where Scope is something like SnapshotDefinition For XMLHelper.save() I can imagine something similar. However because the structure of your xml depends on the scope, there are issues when you want to be compliant to an xsd. I don't have a good solution there, but I also would not qualify myself as an XML expert so others might have good ideas here. Because this user-defined containment is not a part of the data objects itself, it's not such a problem exchanging them. best regards, Bert PS: Agfa is unfortunately not an OASIS member. Traditionally, we're much more active in the Healthcare standardization sector (IHE etc). PPS: (*) At first I tried to avoid adding this concept, but it turned out that the notion of containment was so deep inside a DataGraph that I either had to distort DataGraph a lot or invent something new. Bert Robben | Agfa HealthCare Platform Architect | HE/Technology Platform Team T +32 3444 8407 | F +32 3444 8401 Quadrat NV, Deinsesteenweg 114, 9031 Drongen, Belgium http://www.agfa.com/healthcare/ R.O.: Septestraat 27, B-2640 Mortsel, Belgium | RLE Ghent | VAT BE 0426.312.921 | IBAN BE95570125275558 | Citibank International PLC, B-1050 Brussels Click on link to read important disclaimer: http://www.agfa.com/healthcare/maildisclaimer "Barack, Ron" <ron.barack@sap.com> 06/12/2007 13:48 To Bert Robben/AMOCZ/AGFA@AGFA, <sdo-comment@lists.oasis-open.org> cc Subject AW: [sdo-comment] support for dynamic containment Hi Bert, Thanks for bringing this up. I think it's very appropriate that the very first message on this list should deal already with the issues surrounding containment. I'm curious exactly how you are imagining the API here. How would containment (and other XML related) information be imposed on a datagraph, eg, when the user wants to do an XMLHelper.save, CopyHelper.copy, or simply turn on change-logging? One way we've considered doing this was to pass in a reference to an XSD as an additional parameter. The disadvantage of such an approach is the extra complexity it introduces into the API. At SAP, we've considered (and prototyped) several approaches towards adding containment information on-the-fly. The approach that we are currently pushing is probably something along the lines of what you mean by option 1, each app defining "its own type". Each application (I mean here Java EE applications, eg, things deployed in an EAR) has its own HelperContext, therefore, its own implicit registry of types. The problem of adding (or changing) containment information on the fly becomes the problem of moving DataObjects between HelperContexts, for which we will be proposing a few specific methods in SDO 3.0. We don't see the disadvantage of a proliferation of types. After, applications typically want to have their own type registry, and not have to worry about conflicts with other applications. By the way, is Agfa an OASIS member? You might want to consider joining our TC. Best Regards, Ron -----Ursprüngliche Nachricht----- Von: bert.robben@agfa.com [mailto:bert.robben@agfa.com] Gesendet: Dienstag, 4. Dezember 2007 16:29 An: sdo-comment@lists.oasis-open.org Betreff: [sdo-comment] support for dynamic containment Support for dynamic containment ------------------------------- In SDO, the boundaries of a datagraph are defined by the containment relation. Only objects which can be reached from the root object by following properties that are contained are part of the datagraph. Containment is defined at the type level. In cases where applications need to dynamically select what information they want, this fixed containment relationship is an issue. For instance, suppose in a medical context you have defined a number of types defines to represent patients together with their clinical (e.g. procedures they have taken) and administrative data (for instance their address). The type definition needs to decide on the containment of the clinical and administrative data. However it is hard to decide whether or not the administrative and clinical data should be contained because some applications might only need clinical or administrative data and others might need both. In cases where the type system is large or where there are large volumes of data involved (for instance in the example, procedures could have an associated pdf-report property) this becomes a real issue. Current solutions within the SDO framework could be (for the interested, there has been a mail thread about this a while ago in the user mailing list) - Each app shoud define its own type with an appropriate containment relation. The downside of this is a proliferation of types. - The main types should not have any containment relations. Containment is specified using a synthetic type. Think of this as a special list type that contains its elements. The root of the datagraph then would be an instance of such a list type. All instances that are needed should be put in this flat list. I would like to propose an alternative solution. In this solution, containment would not be specified at the type level. Whenever the boundary of a datagraph is needed (for instance when an xml document it be generated or a datagraph is to be exchanged between for instance a client and a server), the application should provide appropriate information that specifies exactly what is part of the graph and what not. This can be seen as a select clause for sql, or even better as a set of fetch joins in Hibernate. This would give the application control over exactly what it wants. In the example for instance, the application can easily decide at each point whether or not it would want the address information together with the patient data. This proposal would have a number of interesting implications. - What is the implication of this for cases where datagraphs are represented as xml documents that should be according to an xml schema? - How to deal with links to objects that don't belong to the datagraph? One strategy could be just to drop them. Another one to provide some kind of proxy. Frank Budinsky let me know that this is closely related to charter item (10. Relaxing Containment Requirements). I posted this also as a feature request on the Tuscany JIRA ( https://issues.apache.org/jira/browse/TUSCANY-1918). Interested parties can have a look at our SDO implementation (which we donated to Tuscany) (see also Tuscany JIRA 1527 and 1493) where we try to support this. Bert Robben | Agfa HealthCare Platform Architect | HE/Technology Platform Team T +32 3444 8407 | F +32 3444 8401 Quadrat NV, Deinsesteenweg 114, 9031 Drongen, Belgium http://www.agfa.com/healthcare/ R.O.: Septestraat 27, B-2640 Mortsel, Belgium | RLE Ghent | VAT BE 0426.312.921 | IBAN BE95570125275558 | Citibank International PLC, B-1050 Brussels Click on link to read important disclaimer: http://www.agfa.com/healthcare/maildisclaimer --------------------------------------------------------------------- To unsubscribe, e-mail: sdo-comment-unsubscribe@lists.oasis-open.org For additional commands, e-mail: sdo-comment-help@lists.oasis-open.org
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]