UML example

UML or Unified modelling language is the best tool for modelling object oriented systems. As we know, in objet oriented modelling and design, we identify objects (entities)within the system and analyze how they interact with each other and thus design an interactive model preserving their individual properties, behavior as well as publicizing their public attributes and behaviors. The interaction of objects is of importance rather than just mere data flow as in traditional system development. Object oriented systems supports encapsulation and protection of data and behaviors, better code maintainability and reusability.

Below is an example UML, which is actually a class diagram for a simple customer appointment model -

Below is an Activity Diagram for Making a customer appointment:

(c) Deepesh Joseph, 2006
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ERD examples

ERD or Entity relationship diagram is the most common database design and modelling tool used in System Design phase. The diagram basically represents all data entities of the targeted system, their attributes and relationships. Database modeller represents ERD in various levels of details such as Context Data Model, Key based model and Fully attributed model. Fully attributed model could be used as the blueprint logical model for implementing the physical database design. Below are some sample ERDs for an IT shop that provide service for its client -

Entity Definition (This is developed first prior to any modelling):

Context Data Model:

Key Based Model:

Fully Attributed Model:

DFDs example

Data Flow Diagram is the widely used system design tool which aids in depicting flow of logic and data (commonly called process flow) within the targeted system, in various levels of detail. Level 0 DFD is usually called 'Context Diagram' and it gives the highest level view. Starting from the black box in Context Diagram, we explode out into further detail as level 1 and level 2 DFDs. We combine detailed DFDs (also called primitive diagram) of various system components and create the System Diagram (are actually considered as level 1 data flows since they show flows at a much higher level). An event decomposition diagram (EDD) is usually drawn after context diagram, to identify major system functionalities as a hierarchical diagram. It is generally considered as a level 1 data flow. Below is the depiction of sample Context Diagram, EDD, DFD and system diagram. The designed system is a typical IT call management system, which is titled here as CTTS.

Context Diagram:

Even Decomposition Diagram:

Detailed DFD (Primitive Diagram for Service Request Function):

System Diagram (Collection of detailed DFDs representing a whole system):

(c) Deepesh Joseph, 2006
Related websites -- http://www.getallarticles.com