UML Weekend Crash Course™ - To Parent Directory

Session 13—Modeling the Static View: The Object Diagram 141
Shipment
-date: Date = today
-destination: Address = null
-shipper: Vendor = null
+authorize(empl: Employee)
+seal(empl: Employee)
+ship(shipper: Vendor)
Product
-desc: String = null
delivers
-serialnbr: String = system assigned
-spec_handling: String = null
0..1 1..* +reserve(order: Order)
+stock(loc: Location)
Figure 13-2 UML Class notation for the Shipment and Product
The Object diagram in Figure 13-3 shows that the object 4321 of type Shipment has two
Products. Each attribute for the three objects is assigned a value. Note that the special handling
attribute on one Product is blank. This can be a valid value. It is the class definition
for the attribute that determines the valid values that may be assigned to the attribute
when it appears within an object.
4321 : Shipment
-date= 01-27-02
-destination= Portland, OR
-shipper= Billy Bob's Trucking
21 : Product
-desc= CD Player XL 850
-serialnbr= 123456
-spec_handling =
96 : Product
-desc= Speaker Set SS420
-serialnbr= 234567
-spec_handling = fragile
Figure 13-3 UML Object notation for a Shipment with two Products
Note what is missing from the object notation that was required in every class. The third
compartment, containing the operations, was omitted. But why leave it out of the object if
the class sets the rules that an object must follow When you included the attributes, it was
because each object potentially possessed different values for the attributes defined by the
class. But the class defines an operation that does not have multiple interpretations or values.
Every object of the same class possesses the same operations. To model the operations
again on the Object diagram would add redundancy without adding new information. So you
leave the operations off of the Object diagram.
Having seen examples of the differences between the Class and Object diagrams, you can
now refer to Table 13-1 for a side-by-side comparison of their features. A working knowledge
of the relationship between these two types of diagrams will help you understand how to use
them both to facilitate analysis and test the results of your analysis and design efforts.