DX has a powerful and flexible data model capable of representing many sorts of data. Whilst you do not need to understand the data model in detail, you will be able to use DX more effectively if you have a rudimentary understanding of it. Section 16 gives a very brief summary of the data model. If you do not like reading manuals it might just about give you enough information to get by. Section 17 presents a slightly longer, but still quite short, introduction to the data model. I recommend that you read it if you are planning to make a significant amount of use of DX.
The DX data model is fully described in Chapter 2 Introduction to Visualization, especially Section 2.1, and Chapter 3 Understanding the Data Model of the IBM User’s Guide.