The link that you specified above currently marked as an internal document so it is not available to the public. Not sure if this is allowed for anyone outside the company without some sort of permission.
Anyway, to answer the previous question, as I see it, Pega is a build for change product. Working with fixed entity relationship would be too restrictive, not flexible enough to embrace customer requirements.
Hi Marissa, Thank you for your prompt reply. But I'm looking for the Pega knowledgebase article that describes the entity relationships between various Pega internal tables in the database. Please share the article if you can, even if its archived. Thanks!
Find it by clicking this path from the Pega Community menu: Knowledgebase > Capabilities > All Capabilities > Data Integration > Get Started > Data Management article index
As Marc Lasserre stated in his reply of July 31, 2018, Pega's built-in data modeling capabilities -- based on the Pega concept of "properties" -- are intended to preclude the need for a visual data modeling tool like the standard ERDs.
From this main KBA, notice the left-hand navigation pane of expandable-collapsible Data Management articles. This is your Data Management article index or mini table of contents. Expand this list to see the full scope of the content, learn from it, and navigate to articles of interest.
Notice, too, that the bottom of each KBA displays a green navigation button to move forward and backward (Next and Previous) through the KBA series.