30-06-2012, 01:57 PM
information system analysis and designing
Information Systems.pdf (Size: 85.99 KB / Downloads: 100)
What Must a Requirements Model Include?
Must contain an overall description of functions.
Must represent people, physical things and concepts important
to the analyst’s understanding of what is going on in the
application domain
Must show connections and interactions among these people,
things and relevant concepts.
Must show the business situation in enough detail to evaluate
possible designs.
Should be organized in such a way that it is useful later on
during design and implementation of the software.
Hence a need for more detailed models than use cases!!
Finding Classes
Finding classes in use case:
Look for nouns and noun phrases in the description of a use
case;
These are only included in the model if they explain the nature
or structure of information in the application.
Don’t create classes for concepts which:
Are beyond the scope of the system;
Refer to the system as a whole;
Duplicate other classes;
Are too vague or too specific (few instances);
Finding classes in other sources:
Reviewing background information;
Users and other stakeholders;
Analysis patterns;
CRC (Class Responsibility Collaboration) cards.
Operations
Often derived from actions verbs in use case descriptions.
Some operations will carry out processes to change or do
calculations with the attributes of an object.
For example, the directors of Agate might want to know the
difference between the estimated cost and the actual cost of a
campaign
Relationships
Classes and objects do not exist in isolation from one another
A relationship represents a connection among things.
In UML, there are different types of relationships:
Generalization
Association
Aggregation
Composition
Dependency
Realization
Note: The last two are not useful during requirements analysis
and will be discussed later.
campaign would need an operation CostDifference()