When go and talk to people about MDM, particularly on the governance side, the first question I ask is 'what do you want to master'. Often the answer is something like 'Customer', a nice big Entity, nice and clear. But then the questions start and suddenly it becomes murky....
'Do you want to master their locations, physical, electronic and virtual'
What about their relationship to your products and services
What about the aspects of their relationships to your products and services, like a billing address for a product
'Umm not so sure'
'What about groups, relationships and preferences?'
This is long before we head into the real detail of defining what a customer actually is, their attributes, their types, classifications, etc. The point is that in order to master something you need to know what you are going to master. While its fine to say that a technical solution could be delivered incrementally its very important to understand the structure and have this widely understood. At Capgemini we use a 'RADAR' concept applied to a Business Information Model to describe which pieces need to be mastered and what mastering strategy applies. Its normally a pretty quick exercise and means that everyone is progressing based on a single view. This view can then be managed via governance and implemented via IT but its the same view and it needs to be public and visibile and clear about what is mastered and what isn't.
You can't master in the dark.