From: Chris Britton (firstname.lastname@example.org)
Date: Thu 13 May 2004 - 09:40:05 BST
There was a time when many people thought that objects should not be passed around, only accessed in situ. CORBA for instance, also like UML from OMG, does not (or at least did not) support the notion of passing objects. To be more precise, in CORBA an object can move around so long as the move is invisible to the client program. The rationale was that objects stood for something in the real world therefore it was best to have one copy of the object. Furthermore if you believe that an object has an "identity" then it's hard to associate an identity with a message being passed from one server to another. If you loose the notion of object identity then you can't reference the object from other objects. However in practice it is often a good idea to move objects around. For instance, an order entry system may create an order object which is later moved to a manufacturing system and later to a distribution system. But note, my second paragraph was talking about objects in a different context to the first. Distinguish between "business objects" - the external notion of the object to the end users and "implementation objects" - the object internal to a computer system. Because internal objects have an identity, they can't be moved. Thus to move a business object you must create a message that contains the serialized data of the object and use the data to create a new object at the other end. There is nothing stopping an activity diagram being used at either the business object level (to analyze business processes) or at the implementation level. When doing analysis at the business object level you should probably ignore the physical flow of objects around the system. When doing activity analysis at the implementation object level, the objects don't move. So in either case, activity diagrams don't need to show object movement. I suggest that what's missing in UML is the concept of levels of design and the ability to show how objects at one level map to objects at another level. Although I called them implementation objects they too still map to multiple objects - an object in the database and probably an object in every tier. Best regards, Chris -----Original Message----- From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Shashank Sent: 08 May 2004 10:38 To: UML Subject: Activity diagram Is it a standard practice to show the object getting passed between activities, or is a rarely used . In other words is it a good practice to do this or not? To remove yourself from this list please mail email@example.com with a message containing the word "unsubscribe".