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Posts on the
Design Decomposition Blog
Iridium Satellite Collision in Space
You might have seen the recent news reports about the collision between U.S. and Russian communication satellites. The U.S. satellite was one of the Iridium satellites. What wasn’t reported and you probably don’t know is that an object database management system (ODBMS) is an important part of the Iridium system. Even though ODBMSs are a [...]
February 13, 2009
(The Acronym) SOA is (Perhaps) Dead (at Some Companies); Long Live Services
I am now also posting on the Cutter Blog. My initial posting is (The Acronym) SOA is (Perhaps) Dead (at Some Companies); Long Live Services. It is a response to Anne Thomas Manes’ SOA is Dead; Long Live Services on her blog at the Burton Group.
January 9, 2009
Atomicity
The typical definition of an atomic task or process is one that cannot be decomposed further. This is vague and subject to interpretation. The Decomposition Matrix on this site uses a specific definition: A task (for business process diagrams) or a process (for data flow diagrams) is atomic if every input relates to every output [...]
December 3, 2008
Well-Formed Business Process Diagrams
My last posting referenced the criteria for a well-formed business process diagram mentioned in Business Process Driven SOA using BPMN and BPEL by Matjaz B. Juric and Kapil Pant. I am going to expand on their criteria to create a more comprehensive definition of a well-formed business process diagram. To start, here are three criteria from [...]
November 18, 2008
Recent Business Process Modeling Books
I recently received two new books on business process modeling. Both books looked interesting because they had great titles. As it turns out, one book is great and the other not so good. The not so good book is Business Process Driven SOA using BPMN and BPEL by Matjaz B. Juric and Kapil Pant. There are [...]
October 9, 2008
The Design Decomposition Blog
is written by Doug Barry.
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Dispatching in the object model is executing the correct code based on the type of a class. In this example, the age method is overloaded in the Student and Employee classes. Overloading occurs because the same name, age, is used for the methods in all three classes. There may be a reason for calculating the age of a Student or an Employee. For example, for insurance reasons, you may want the age of an Employee as of the first of the month instead of using today's date as might be defined in the Person class.

Dispatching
The object system dispatches, or executes, the correct code based on the type. If an object is of type Person, then that age method is executed. If an object is of type Student, then the age method defined for the Student class is executed. Likewise, if an object is of type Employee, then the age method defined for the Employee class is executed.

The object system ensures that the right method is executed on the right data. In other words, it is not possible to execute the wrong age method on the right data, or the right age method on the wrong data.

The ability to redefine methods on a class basis is known a polymorphism.

For this example, you should not see this type of case statement with an object system. It is handled by dispatching.

if type is Person then
    ... calculate age based on Person rules ....
else if type is Student then
    ... calculate age based on Student rules ....
else it type is Employee then
    ... calculate age based on Employee rules

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