Evaluating Design 2 for Usability

Design 2 for reference

Design 2 for reference

So lets revisit the entire set of parameters once again.

Lets start with usability first.

What do you say whether the usability has improved or reduced or just remained the same?

In this case for the RRC to reserve a ticket, he will have to just call the reserve() method of the RCE passing in all the necessary input parameters and would just get the response from the RCE.

Compare it with the previous case,

  • do you need to know about the domain entities,
  • do u need to keep a reference to each of these domain entities,
  • do you need to know about the different operations that has to be performed on each of the domain entities?


I am sure the answer is NO.

Don't you think this design is more in sync with our definition that the system should be a black box to the end user which takes in some inputs and gives you certain outputs.

So we can see by introduction of this control entity as a level of indirection the usability of the system has increased by a great factor.


We can say as the control entities as a level of indirection are hiding the internal structural details of the system has increased the usability by a great factor.

Hemant Jha
Founder - VPlanSolutions
Researcher, Trainer