CSC340: Tutorial 5 Requirements Analysis

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CSC340 Tutorial 5Requirements Analysis

• TA Y. An
• Date 900-1000am, Fri. Nov 7, 2003
• Location BA1130

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Classes

• A class describes a group of objects with
• Similar properties (attributes),
• Common behaviors (operations),
• Common relationships to other objects,
• And common meaning (semantics).
• For example, employee has a name, employee and
  department an employee is hired, and fired an
  employee works in one or more projects.

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Finding classes from use cases
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Identifying classes

• You dont model objects which are beyond the
  scope of the system.
• It is not usually necessary for a model to
  contain classes that represent the entire system.
• You should remove class which is really a synonym
  of others.
• Avoid too vague names which you cannot write
  description.
• Avoid too specific names which are really a
  generalization.
• Dont tie up with physical inputs and outputs.

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Classes and attributes

• A member of staff has one grade at a time, but
  members may have several previous grades, and
  several members may have a same grade.
• A grade has only one rate at a time, and each
  rate has a money value. Grade may have a rate
  attribute.

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Classes and attributes

• A grade may have several previous rates, which
  suggests either that Grade has multiple rate
  attributes, or that Rate and Grade are distinct
  classes.
• Rate must have a date attribute.

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UML class diagram
Where to put the attributes gradeStartDate And
gradeFinishDate?
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Association class