As part of my ongoing mission to help everyone in my family - and beyond - understand ServiceNow, I started writing a series of articles titled ELI5, which stands for Explain Like I’m 5. If you haven’t read the first one about Domain Separation, you can find it here, where I also share a bit more background on how this idea came to life.
One of my favourite topics to cover on any project is Common Service Data Model, or CSDM for short. Despite being around for several years, it remains one of the most misunderstood parts of ServiceNow. Many customers still struggle with it - some implement it incorrectly, while others skip it entirely and end up using four layers of categorisation in Incidents (yes, I actually saw exactly that a few months ago).
So, with all that in mind - and with my non-ServiceNow friends absolutely dying to learn about CSDM, I wrote the next instalment of ELI5, focused entirely on this topic.
Quick disclaimer (same as in my previous article): This is a light-hearted take on a topic that is, in reality, quite complex. It’s not a deep-dive or a step-by-step implementation guide. But it might just help spark a few lightbulb moments for customers - or anyone around you who isn’t yet fluent in ServiceNow.
What is CSDM?
Let’s start with the official ServiceNow definition:
A Common Service Data Model (CSDM) is a standardized framework that defines service-related terms and relationships for all ServiceNow products. It links IT assets to services, users, costs, and more - facilitating accurate reporting and aligning business strategies with technical implementations.
Sounds straightforward, right? But when you Google it, you’re often met with a spaghetti diagram full of bubbles labelled “service” and “business,” and you’re left just as confused as when you started.
And that’s completely understandable. The terminology can feel abstract, and the diagrams - while technically accurate - don’t always help newcomers connect the dots. That’s why analogies like the one we’re about to explore can be so powerful: they turn abstract concepts into something tangible and familiar.
So let’s break it down. And since this is ELI5, let’s do it with toys.
CMDB: The Toy Closet
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Before we dive into CSDM, we need to understand the CMDB - the Configuration Management Database. And to do that let's think of it like a toy closet.
When I was a kid, I had a toy closet filled with boxes of action figures, cars, toy houses, and more. I knew all my toys were in there (not because I was tidy, mind you), and whenever I wanted to play, I’d rummage through the closet to find what I needed. That closet? That was my CMDB. I didn’t know it at the time, but I was managing configuration items like a pro.
Now, imagine if I could search for my favourite toy car the way we can search in ServiceNow. Back then, my “search function” was just dumping everything out because, of course, the toy I wanted was always at the bottom of the box in the back of the closet.
Toys = Configuration Items (CIs)
In this analogy, the toys are CIs - Configuration Items. Each toy had specific characteristics.
For example, my favourite toy car was a blue convertible Dodge Viper with white stripes. It belonged in the “Car” box (or table), which extended from the general Toy (Configuration Item) table. It was manufactured by “Random Toy Company,” and its model was “Dodge Viper.”
I also had action figures. My favourite? Super Saiyan 3 Goku, made by “Another Random Toy Company.” He belonged in the “Action Figure” box (another table).
Both toys had an owner - me, Sergio Carneiro - and were supported by a group called “Parents,” made up of, you guessed it, my parents.
Here’s how that maps to ServiceNow:
| Field | Toy Example | ServiceNow Example |
| Name | Super Saiyan 3 Goku - SSG3-X1 | Apple MacBook Pro 16” - XYZ123 |
| Serial Number | SSG3-X1 | XYZ123 |
| Model ID | Super Saiyan 3 Goku | Apple MacBook Pro 16” |
| Owner | Sergio Carneiro | Your User(s) |
| Support Group | Parents | IT Service Desk |
So now we understand one of the “bubbles” in the CSDM diagram:
But what about all those arrows between the boxes in the full diagram above?
Relationships: Who Drives What?
Let’s five-year-oldify the relationships now.
As much as I loved my Dodge Viper and Goku, he was too big to fit in the car. So I picked my smaller Spider-Man figure to drive it. That means: Spider-Man drives the Dodge.
Meanwhile, Goku could swim in the imaginary lake I had on my tapestry - something neither Spider-Man nor the Dodge could do.
What we’ve just done is define relationships between toys (CIs) from different tables. These relationships help us understand how things interact, their limitations, and their potential. You wouldn’t send Spider-Man to fight the King of Atlantis, right?
In the CMDB, these relationships look like this:
| Toy/CI | Relationship | Toy/CI |
| Spider-Man | Drives | Dodge Viper |
| Goku | Swims in | Lake |
| Software | Runs on | Apple MacBook Pro 16” - XYZ123 |
| Apple MacBook Pro 16” - XYZ123 | Connects to | Netgear Router Pro - ABC123 |
These relationships are critical as they help us understand dependencies. In an organisation, if the router goes down, laptops are impacted. And that impact? That’s where Services and Offerings come in... Which we’ll cover in Part 2.
Wrapping Up
So far, we’ve:
- Introduced the concept of CSDM
- Used toys to explain the CMDB and CIs
- Mapped real-world relationships to ServiceNow relationships
- Set the stage for understanding services and offerings
CSDM isn’t just a diagram or a buzzword - it’s a way to bring structure and clarity to your CMDB. It helps you understand how everything connects, from infrastructure to services, and ultimately to the value delivered to the business. It’s also a foundation for scaling your ServiceNow implementation in a sustainable way. By aligning your data model early on, you reduce rework, improve reporting accuracy, and make your platform easier to govern in the long run.
In Part 2, we’ll dive into Services and Offerings, and how they fit into this toy-filled world.
Until then, keep your toy closet organised - and maybe label a few boxes while you’re at it.
Appendix:
Be sure to read up on the latest CSDM 5.0 White Paper:
https://www.servicenow.com/community/common-service-data-model/csdm-5-finally-get-the-csdm-5-white-p...
