Defining Foreign keys/identifiers in CDM models

[former_member217396]

Hi,

is it somehow possible to define foreign keys/identifiers in CDM models?

I know, the relation in a CDM model i on entity and not attribute level, but... did someone found a way how to model such relations? I could of course go with an extension... but... maybe there is an other way to do this?

@George, I've read in your book, PD CDM doesn't support foreign identifiers, but did you found a way to "workaround" this "issue"?

Thanks and regards,

Rafal

[c_baker]

I think this was answered (by Matt Creason or George?) several months back?

It would require migrating the primary key to the child entity as a foreign key and perhaps adjust the subobject format, etc, etc.  Probably an extension could be developed here and there may be such an extension from the old pre-LDM days from someone.

The reality is - this is what the LDM already does.  Is there a reason why this cannot be used?

Chris

[former_member217396]

Hi Chris,

the reason, why we are looking at CDM in this case is:

- this model is developed by business and not IT

- they want to stick to the Data Items concept -> define once, reuse everywhere. Of course we could stick to a similar concept in the LDM, but then you have to reuse entity specific attributes... I belive this is not correct...

- IT is already developing a LDM model for this, and this model looks different to that business is developing... we would have 2 LDM models, one which is near to business, the other one is near to the physical implementation

But maybe we have to have 2 LDM models... the second model will be generated out of the "business" LDM model using some mapping tables to convert the business names of the attributes into technical names found in the database...or we will replace the codes in the "business" LDM model with the names from that mapping table...

Regards,

Rafal

[GeorgeMcGeachie]

I'm typing this as I think, so forgive me itf it's rubbish.

It would be simpler to extend the LDM to derive attributes from Data Items, than it would be to generate FKs in the CDM, making sure that the generation capabilities are not compromised. You could still have the business define Data Items in a CDM (or atomic data objects in a BPM), letting the CDM handle the uniqueness, and use an extension in the LDM to ensure attributes are:

1. all linked to Data Items
2. consistent with the Data Item

Hmm, that sounds like a lot of work, which could go wrong in many ways. Why not let the business maintain the CDM as you say, then generate a matching LDM that you never alter except by generating from the CDM? This is your 'business' LDM, which is mapped to the IT LDM. The question is, which type(s) of links would you use between the two LDMs?

[GeorgeMcGeachie]

By the way, thanks for buying the book

[GeorgeMcGeachie]

Hello Rafal, what did you do in the end?