1.2 Modeling Requirements

A model is a representation of one or more aspects of the real world.

It captures the important aspects of the thing being modeled and simplifies or omits the rest.

Good models

A model M is the representation of an aspect R of reality, as we said before.

Therefore we can define a mapping between a model M and an aspect R, called interpretation and indicated with the letter I.

Relationships, which are valid in reality R, are also valid in model M

$f_R$: relationship between real things in R $f_M$: relationship between abstractions in M

What are software models for

• Capture and precisely state requirements and domain knowledge

• Think about the design of a software system

• Generate usable work products

• Give a simplified view of complex systems

• Evaluate and simulate a complex system

• Generate potential configurations of systems
  • all consistent configurations should be possible
  • not always possible to represent all constraints in the model (model is an abstraction !)

Modeling issues

• Coherence
  • different views of the system must be coherent

• Variations in interpretation and ambiguity
  • define where different interpretations of the model are acceptable