PowerDesigner: Inheritance for CDM Associations

[jziemer]

I am still new to the Community Q&A. This post is a feature/change request:

The Conceptual Data Model (CDM) is an essential first artifact in the design process. PowerDesigner is the only tool to support a dedicated CDM notation with Data Items and Association as model objects.

The model objects are a close representation of Ontology Web Language (OWL) Data and Object Properties, making PowerDesigner CDM the target model of choice for ontology derived data models.

However, unlike associative entities, the CDM Associations do not support inheritance. The hierarchy of associations is an important design pattern in Entity-Relationship Models and Ontologies. For example:

comprises-> has Contractual Element->has Repayment Terms->has Call Feature

The request: SAP PowerDesigner should extend the CDM metamodel and user interface, enabling the modeler to create an inheritance from “has Repayment Terms” to “has Contractual Element” in the above example. In other words, I want to use Associations rather than the workaround of Associative Entities in the screenshot.

Thanks

[GeorgeMcGeachie]

You can convert associations to entities very easily - either do it one a time (right-click one and select change to entity), or change the model notation to Entity/Relationship (after adding the stereotype "Associative Entity".

At least, that's the theory. When I tried it changing the model options on my copy of the model, PD objected to a lot of things and would not let me change the Notation.

I tried generating a new CDM, and changing the model options for the new model befeore generating it. Associations with >2 links were converted to entities, associations with only 1 or 2 links became relationships.

[GeorgeMcGeachie]

Go to this site - https://support.sap.com/en/index.html - click on "Report an incident"

Good luck!

I don't know whether or not they'll go for it, as what you're asking for isn't part of the Merise method (according to my book from 1991 -

https://www.amazon.co.uk/MERISE-Practice-Computer-Science-Quang/dp/033355020X)

[GeorgeMcGeachie]

Hello Jurgen

Sounds useful to me, though I suspect that only a few PowerDesigner users use the Merise methodology. I was trained in it once, but that was a long time ago.

You could build this yourself but it could be a lot of work - you'd need to use as much of the standard PD features as you can, to minimise the amount of work you need to customise the model generation for your LDM.

In this diagram I've added Association Inheritances as extended objects, and the inheritance links as extended links. Creating the visual diagram is the easy part! I could have used traceability links instead of extended links.

You would need to build event handlers to ensure that you only link associations, and build a Transformation that converts the extended stuff (on the left) into the kind of objects you have on the right before generating your LDM.

[GeorgeMcGeachie]

I forgot to say that I also added Parent and Children properties to the new Association Inheritance object. These could be used to transform the extended objects into standard inheritances.

[jziemer]

Hello George,

Thank you very much for taking a look. Indeed, your diagram is the feature. I want SAP to add. Although, I would use the standard diagram icons, like on the right-hand side, for subtypes and links.

I see your picture is from the same Open Source Finance model (https://fib-dm.com/). You probably noticed the current mix of Associations and Associative Entity objects in the CDM. Too much work: Besides the LDM you must also generate PDM and implement compare/merge. For future releases, I will change all Associations into Associative Entities.

You are a veteran PD user community expert. What is the quick link to raise a feature request with SAP support?

Thanks and regards

Jurgen