The document discusses the object-relationship model for modeling relationships between classes in object-oriented design. It explains that the first step is to understand the responsibilities of each class using CRC cards. The next step is to define collaborator classes that help achieve each responsibility, establishing connections between classes. Common relationship types like binary relationships are described, with the direction defined by which class acts as client or server. The document outlines steps for deriving an object relationship model from a CRC model by drawing collaborator objects, naming relationships, and determining cardinality.

1. The Object-
Relationship Model
By Balasara kshiar
Mca 4th sem
St anthonys College

2. The Object-Relationship Model
• The first step in establishing relationships is to
understand the responsibilities for each class in
the CRC model.
• The CRC model index card contains a list of
responsibilities.
• The next step is to define those collaborator
classes that help in achieving each responsibility.
• This establishes the “connection” between
classes.

3. The Object-Relationship Model contd..
Control panel
Determine sensor status
Set sensor status
……….
……..
Sensor
Sensor
Recognize smoke
Recognize break-in
………….
………….
Sensor event

4. The Object-Relationship Model contd..
• The most common type of relationship is
binary—a connection exists between two
classes.
• a binary relationship has a specific direction
that is defined based on which class plays the
role of the client and which acts as a server.

5. The Object-Relationship Model contd..
Identifying a relationship:
• Rumbaugh and his colleagues [RUM91] suggest that relationships can be derived by
examining the stative verbs or verb phrases in the statement of scope or use-cases
for the system.
• Using a grammatical parse, the analyst isolates verbs that
 indicate physical location or placement (next to, part of, contained in),
 communications (transmits to, acquires from),
 ownership (incorporated by, is composed of), and
 Satisfaction of a condition (manages, coordinates, controls).
• These provide an indication of a relationship.

6. The Object-Relationship Model contd..
• The object relationship model can be derived in three steps:
 1.Using the CRC index cards, a network of collaborator objects can be drawn
 2.Reviewing the CRC model index card, responsibilities and collaborators are evaluated
and each unlabeled connected line is named.
 3.Once the named relationships have been established, each end is evaluated to
determine cardinality
 Four options exist:
 0 to1
 1 to 1
 0 to many
 1 to many.

7. The Object-Relationship Model contd..
Fig: Relationship between objects