Hi @Vandita Tripathi ,
I recommend to take a look at the CSDM and use it as a reference for your own data model. This should be really helpful for you on setting this up. Some info here: https://docs.servicenow.com/bundle/sandiego-servicenow-platform/page/product/csdm-implementation/con...
I can share to you our experience. We are currently mapping IaaS, PaaS and SaaS and other services as "Business Services" relating them to the respective Business Capability. This is how we are specifically handling IaaS, PaaS and SaaS, as you asked. But from there you can have different types of relationships (upstream and downstream) which are very important for your model and for that I invite once again to check the CSDM for reference.
I hope this helps you. Please, mark it as helpful in case it was. 🙂
