Entities, Instances and Identifiers, and More

Ch 5

This is the draft section¹ for Entities, Instances, Identifiers, and More of Chapter 4 (Data Modeling Building Blocks). It will be included in Chapter 4 and subject to revision.

A significant departure from prior discussions on entities and identifiers is surveying the topic across the various forms of data - structured, semi-structured, and unstructured. Please leave comments if something is unclear or you disagree with it. I am always happy to have a look and improve things where they make sense.

Thanks,

Joe Reis

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In data modeling, you’ll frequently see three words: “entity, relationship, attribute.” These terms describe battle-tested ways to translate things you’re trying to represent in the world into a data model. Let’s look at the first term, entity.

A big part of data modeling is learning to see and ask questions to understand what to pay attention to. And this involves diving beneath the surface of what you’re told. At a high level, asking questions, actively listening, and getting these entities is the start of data modeling. Understanding entities is the first thing you should do in data modeling to answer the question of what you’re trying to model and describe.

Entities are abstractions of things that may or may not tangibly exist, but you can identify them as something that exists in your business. You can see these things in your business vocabulary, workflows, and systems. This might be a bit terse, so let me illustrate with a simple example.