Object Diagram Notation Lecture Oo11 Object Visibility

References n Booch, et al, The Unified Modeling Language User Guide, Chapt 18.

Teaching Points n Object visibility n Message Synchronization

Review n Why/when would we use parameterized classes n Parameterized classes vs. Generalization

Analysis/Design Method n Notation –The language for expressing each model n Process –The activities leading to the orderly construction of the system’s models n Tools –The artifacts that eliminate the tedium of modeling building and enforcing rules about the models themselves, so that errors and inconsistencies can be exposed

Object Interaction Diagrams n We will look at some additional concepts that can be expressed on object interaction diagrams

Object Visibility n It is often not apparent to when first studied that the design of object visibility is complex and fundamental n The design of the web of object visibility's is critical to a project solution n It is this web of visibility that provides the vehicle for the object communication which provides the solution to the problem

Object Visibility n Associated with the understanding of object visibility for a system, is object creation n Initially only an object’s creator has visibility, any other object which needs access to this newly created object must get the visibility from the creator either directly or indirectly n visibility can flow through object references or environment scope rules

Object Visibility n The supplier object provides services through its interface n The client object uses services of the supplier –this means the client initiates a message to the supplier –this means the client must have visibility to the supplier –the supplier need not have visibility to the client

Four Kinds of Visibility n Global –The supplier object is in a global scope to the client n Field –The supplier object is a part of the client

Four Kinds of Visibility n Parametric –The supplier object is a parameter to some operation of the client –The client gains visibility of the supplier through some exchange message with another object n Local –The supplier object is a locally declared object in the scope of the object diagram

Visibility Notation

Examples in Java

Message Synchronization Notation n The message synchronization we have seen so far has represented simple sequential message passing n In the presence of multiple threads of control we must specify other forms of synchronization

Message Synchronization Notation

Teaching Points n Object visibility n Message Synchronization