Design

Project Title : A point of Sale System for a Fast Food Chain

Description of point of sale system to be implemented 
 - Parts of system : cashier, point of sale system.
 - Input of system : food selected payment mode.
 - Output of system : receipt, total cost, change (for payment by cash)
 - Constraints :customer must pay first before collecting food
 - Performance : fast service, accurate calculation of change
 - Tasks : listed in initial requirement
 - Software maintenance : maintain software, technical support

Class Diagrams

A class diagram is a picture for describing generic descriptions of possible systems. Class
diagrams contain icons representing classes, interfaces, and their relationships. Class
diagrams and collabration diagrams are alternate representations of object models. They
contain classes and object diagrams contain objects, but it is possible to mix classes and
objects when dealing with various kind of metadata, so the separation is not right. 

Collaboration Diagrams

A collaboration diagram is an interaction diagram which shows the sequence of messages that implement an operation or a transaction. These diagrams shows objects, their links and their messages. They can also contain simple class instances and class utility instances. Each collaboration diagram provides a view of the interactions or structural relationships that occur between objects and object-like entities in the current model.

Sequence Diagrams

A sequence Diagram is a graphical view of a scenario that shows object interaction in a time-based sequence - what happens first, what happens next. Sequence diagrams establishthe roles of objects and help provide essential information to determine class responsibilties and interfaces. Sequence diagrams are normally associated with use cases.
This type of diagram is best used during early analysis phases in design because they are
simple and easy to comprehend. A sequence diagram has 2 dimensions: typically, vertical
placement represents different objects.

Sequence diagrams are closely related to collaboration diagrams and each alternate
representation of an interaction.