Hi Gopala Krishna,

Have you looked at the modelling guidelines and best practices for applications and for IT Components? Try to approach modelling things from a use case perspective and what end result you want to achieve. Also, you can check another community post here where other customers have discussed about modelling of apps vs IT Components.
 

For modelling of integration components, APIs, ESBs, you may consider using Interface Fact Sheet subtypes ‘API’ and logical interfaces with attached IT Component. 

In the case of middleware, if visualizing data flows is important then instead of using IT component you can model it as an application. 

For cloud services, if such services are helping run an application then you may look at subtypes of IT Components, namely, PaaS, SaaS, IaaS.
Hope the above helps!

Like this.  Simple and Clear