an associative class is used to model associations that 
have methods and attributes. Associative classes are 
typically modeled during analysis and then refactored 
during design.

same operation in some classes and that classes must have 
the generalisation among them is called Associative Classes

Attribute is the property or state of a class and
association is the relationship between two classes.

By Attribute be\haviour we cam\n give the relation either 
Association, Dependancy, Generalisation, Realisation

OCL is used to define pre conditions, post conditions and
other conditional statements in UML.

Design by contract :Design by contract, DBC or Programming 
by contract is an approach to designing computer software. 
It prescribes that software designers should define precise 
verifiable interface specifications for software components 
based upon the theory of abstract data types and the 
conceptual metaphor of a business contract.Because "Design 
by Contract" is a trademark of Eiffel Software, the 
maintainers of Eiffel, many developers will refer to it 
only as programming by contract or contract-first 
development. The principal idea of Design by Contract (DBC) 
is that a class and its clients have a contract with each 
other: The client must guarantee certain conditions before 
calling a method specialized on the class (the 
preconditions), the class guarantees certain properties 
after the call (the postconditions). If the pre- and 
postconditions are included in a form that the compiler can 
check, then any violation of the contract between caller 
and class can be detected immediately.

CRC cards are used to idenity classes,responsibilities
(methods/behaviour) and colloboration(interaction) with 
other classes.once identified they are used to draw refined 
class diagram

class response collaboration

ATM users(if expanded), can act as different actors for the
use of an ATM machine.

Credit card user                -------------------
   |--------------------------> | ATM machine     |
Debit card user                 -------------------

1.Form classes as generic classes whenever it is possible.
2.Set coupling to be low when deciding the message passing

Composition is a stronger form of aggregation. If you are
sure that the life of the part is managed entirely by the
whole then you can go for composition. Without whole, the
part can't exist also.

Class diagram will give you a static picture of the system
irrelevant to time. It also represents the relationship
between classes.

Inception
Elaboration
Construction
Transition

Four Process Phases

The Unified Process consists of cycles that may repeat over
the long-term life of a system. A cycle consists of four
phases: Inception, Elaboration, Construction and Transition.
Each cycle is concluded with a release, there are also
releases within a cycle. Let's briefly review the four
phases in a cycle:

    * Inception Phase - During the inception phase the core
idea is developed into a product vision. In this phase, we
review and confirm our understanding of the core business
drivers. We want to understand the business case for why the
project should be attempted. The inception phase establishes
the product feasibility and delimits the project scope.
    * Elaboration Phase - During the elaboration phase the
majority of the Use Cases are specified in detail and the
system architecture is designed. This phase focuses on the
"Do-Ability" of the project. We identify significant risks
and prepare a schedule, staff and cost profile for the
entire project.
    * Construction Phase - During the construction phase the
product is moved from the architectural baseline to a system
complete enough to transition to the user community. The
architectural baseline grows to become the completed system
as the design is refined into code.
    * Transition Phase - In the transition phase the goal is
to ensure that the requirements have been met to the
satisfaction of the stakeholders. This phase is often
initiated with a beta release of the application. Other
activities include site preparation, manual completion, and
defect identification and correction. The transition phase
ends with a postmortem devoted to learning and recording
lessons for future cycles.

1.Visualisation2.
Specifying
3.Construction and
4.Documentation