Hi Aditya,
You have to take entity either persistable or non persistable to take input from users.
If you don’t want to store the data just take non persistable entity ->create object and take the input from users and display them.
You will need entities and attributes to be able to enter and display the data. However, if you don't want to store the data, you can take a look at using non persitable entities.
There is an intermediate level learning path called 'Expand your domain modeling skills' that talks about this topic specifically in one of the chapters.