Basic questions on data modeling

[Former Member]

Hi experts,

I have some basic questions regarding data modeling within MDM. I understand the available table types and the concept of lookup fields. I know that the MDM data modeling concept is different to the relational concept. But having a strong database background my first step was to design a relational data model which I would like to transfer to a MDM repository. Unfortunately I didn't found good information material on this. So here are some questions maybe you can help me:

1) Is it the right approach to model n:m relationships with multivalued lookup fields? E.g. main table Users with lookup field from subtable SapAccounts (a user can have accounts in different SAP systems, that means more than one account).

2) Has a record always be unique in MDM repositories (e.g. should we use Auto ID's in every table or do we have to mark a combination of fields as unique)? Is a composite key of 2 or more fields represented with marking these fields as unique?

3) The concept of relationships in MDM is only based on relationships between single records (not valid for all records in a table)? Is it necessary to define all relationships similar to the relational data model in MDM? Is there something similar to referential integrity in MDM?

4) Is it possible to change the main table to a sub table later on if we realize that it has also to be used as a lookup table for another table (when extending the data model) or do we have to create a new repository from scratch?

Thank you for your answers.

Regards, bd

[Former Member · Accepted solution]

Yes you are correct. It is almost difficult to map relational database to mdm one. But again MDM is not 'just' a database. It holds much more 'master' information as compared to any relational db.

1) Is it the right approach to model n:m relationships with multivalued lookup fields? E.g. main table Users with lookup field from subtable SapAccounts (a user can have accounts in different SAP systems, that means more than one account).

Yes Here you need to use MV look up tables or can also try Qualifier tables if it gets more complex

2) Has a record always be unique in MDM repositories (e.g. should we use Auto ID's in every table or do we have to mark a combination of fields as unique)? Is a composite key of 2 or more fields represented with marking these fields as unique?

Concept of uniqueness differs here that you also have something called Display Fields (DF). A combination of DF can also be treated as Unique one. For instance while importing records if you select these DF as a combination, you will eliminate any possible of duplicates based on this combination. Auto Id is one of the ways to have a unique id once record is within MDM. While you use UF or DF to eliminate any possible duplicates at import level

3) The concept of relationships in MDM is only based on relationships between single records (not valid for all records in a table)? Is it necessary to define all relationships similar to the relational data model in MDM? Is there something similar to referential integrity in MDM?

Hmm... good one. Referencial Integrity. What I assume you are talking is that if you have relationships between tables then removing a record will not be possible as it is a foreign key for some record. Here MDM does not allow that. As Relationships within MDM are physical and not conceptual. For instance material can have components. Now if material does not exist then any relationship to components is not worthwile to maintain. Hence relationshsip is eliminated. While in relational model relationships are more conceptual. Hence with MDM usage of lookups and main table you do not need to maintain these kind of relationships on your own.

4) Is it possible to change the main table to a sub table later on if we realize that it has also to be used as a lookup table for another table (when extending the data model) or do we have to create a new repository from scratch?

No. It is not possible to convert main table. There is only one main table and it cannot be changed.

I went for the same option but it did not work. What I suggest is to look up your legacy system one by one and see what fields in general can be classified as Master, Reference, Transactional - You will start getting answers immediately.