Tipps, Tricks And Fun

How to design linked but independent data models?

What is actually the background to this question? In some data solution projects, the BI teams would like to work…

What is actually the background to this question? In some data solution projects, the BI teams would like to work on "the data model" with more than one data modeller. One possibility is to create several, separate data models for this purpose and thus be independent of other data modellers with the particular data model. So is the idea.

But every now and then you need a hub (in the case of Data Vault) or a table from another model. 

Most modellers instinctively use a so-called Shortcut for this.

The consequence of this, however, is that the necessary Integrity Load Mapping (ILM, which the ExMeX Framework Core requires) for the source table to be connected to the hub or table must be done in the respective "home data model" of the hub or table.

To do this, the modeller must keep the other model open in order to connect the source table there as well and create the ILM. In this way, he also blocks this data model for the activities of other data modellers.

The solution? Replica

These work similarly to Shortcuts, but give the data modeller the ability to model the ILM within their current model. The “home data model” of the hub or table is no longer needed.

TIP: With a replica it also works if the original of the replica is actually in a different physical database or schema than the tables of the current data model!

Great, isn't it?

Ok, what do you have to do for that?

Well, here's a step-by-step guide:

First: Drag and Drop - Right-click on the object that you want to reuse in the Browser or a diagram, drag and drop it into the diagram (or onto a model or package in the Browser) where you want to create the replica, release the right mouse button, and select Replicate Here (Quote from the PowerDesigner documentation).  More background information on this can be found in the PowerDesigner documentation (State 2021-03-11).

Create Replication of Table by Drag And DropCreate Replication of Table by Drag And Drop

Second: Now you have to do some steps to not mess up things in the meta data:

  • Open table properties (e.g. double-click on hub) of your Replica.
  • Now you have to decouple the "Generate attribute" from the replication: Go to Tab Version Info -> Replication Properties -> Tab Attributes and a) deselect checkbox Generation and b) select checkbox Owner.

    Table Properties - Version Info TabTable Properties - Version Info Tab

    Replication PropertiesReplication Properties
  • Go to Tab General and deselect checkbox Generation. Why? The table or hub has already been generated as a DDL with the "home data model" and the corresponding metadata has been created.

    Table Properties General TabTable Properties General Tab

Third: Business as usual:

  • Create Link to Hub or add other objects to your Replica.
  • Map ILM from your given source table to Replica (Table / Hub)
  • Generate meta data - at least version 1.7.0 of ExMeX Plugin - Metadata Export is needed!
  • Install meta data

That’s it. No need to open any other referenced data model again. And the Replica will synchronize all changes in the original object.

By the way: with the latest plugins provided by TEDAMOH you will recognize which objects are Replicas!

Data Vault Data Model With ReplicaData Vault Data Model With Replica

Posted 1 year agoby Dirk.Lerner