You can create a logical diagram in an existing LDM in any of the following ways:
Right-click the model in the Browser and select New
> Logical Diagram.
Right-click the background of any diagram and select Diagram
> New Diagram.
To create a new LDM with a logical diagram, select File
> New Model, choose to create a logical data model from the Model type list, choose Logical Diagram, and click OK.