Language Architecture UML 1.4

Consists of 3 top-level packages and additional specifications for Action Semantics and the Object Constraint Language.

Behavioral Elements
Model Management Packages
Foundation package

Behavioral Elements and Model management packages depends on Foundation package.


Foundation package.

It providing model elements that are required throughout the metamodel.
3 sub-packages

Core elements.
Extension mechanisms.
Data types.

All of the diagram elements in UML derive their basic features from the elements defined in these 3 packages.


Core Package

It contain some classes that cannot be instantiated is called abstract. eg. ModelElement, GeneralizableElement, Classifier.

A class that can be instantiated is called concrete. eg. Core concrete classes include Class, Property, Association.
Other concrete classes include Instance, Operation, Link etc.

1. ModelElement
   It is the definition from which all other modeling metaclasses derive.
   It may have constraints, may be derived, may be stereotyped.
2. GeneralizableElement
   GeneralizableElement contains the features that all the specialized elements have in common. This concept makes it possible to construct a hierachy of elements.
3. Classifier
   Describes a named element with features.
   A classifier is itself a namespace. It can contain other, nested classifiers.
   A classifier declares a collection of features, both structureal and behavioral, like attributes and operations.

Extension Machanisms packages

Provides a means to tailor the use and appearence of existing elements for specific application domains or technologies.

Data Types package

The Data Type package defines a common set of valid data types and enumerations for use in defining the metamodel.

Behavioral Elements packages

Represent how the system works in terms of controlling actions and interactions between elements.
It using different diagrams

collabration diagram.
Use Case diagram.
State Machine.
Activity Graph.

1. collabrations
   Models standard patterns of interactions that appear through the system design.
   Explain how classifiers work together to perform an operation or an interaction between elements.
   Includes 2 key concepts
   
   • The Structure of the participating elements
   • Pattern of messages exchanged between the elements.
   
   
2. Use case diagram - models user interactions with the system.
   
   
3. State machines - models the object lifecycles.
   A State Machine reveals that two key elements are needed to understand and manage the life of the object
   
   • the events that trigger the changes
   • the beheviors that accompany the events and actually make the changes.
   
   
4. Activity graphs - models logic sequence.it is basically old flowchart.
   

Model Management Package

Views of physical system are called models.

Object Constraint Language

Provides the semantics for declaring static requirements for attributes and operations.
eg. a phone number must never be violatedduring the life of the system.

pre-condition - Constraints on an operation define wht must be true in order to invoke the operation.
post-condition - wht must be true when operaton is completed.

Action Semantics

Define the rules that govern the dynamic aspects of a system.
An action is a class that defines a behaviour.
eg. the instance of CreateObjectACtion defines how to create an object.
Actions can be used to define method implementations.