Methodologies

An engineering approach to building systems requires certain methods and tools to be used to ensure that systems are built in a most effective way. These kind of approach we call as methodologies. A methodology is a set of predefined rules and steps to build a system. Use of methodologies help us to build models of a system and verify requirements, etc. We should use a methodology when we are engaged in a team development environment. There are large number of tools available for different kind of methodologies.

Generally we can identify following methodologies in software system designing and development.

• Hard System Methodology (HSM)

• Structured Methodology 

• SSADM (Structured System Analysis and Development Methodology) 

• JSD (Jackson’s System Development) 

• YSM (Yourdon’s Structured Methodology) 

• Object Oriented Methodology 

• OMT (Object Modeling Techniques) 

• OOSE (Object Oriented Software Engineering) 

• Soft System Methodology (SSM) 

• Hybrid (HSM + SSM) 

• Formal System Methodology

Hard System Methodology (HSM)

We use this method to develop systems that the problem definition is clear and the solution for the problem is therefore direct. So, we assume that there is a solution for the problem and we know what goals exactly to be achieved. You can identified the success and result prior to develop the system. “WHAT” kind of problem and “HOW” to solve it can be identified early in this methodology.

Structured System Analysis and Development Methodology (SSADM)
 

• SSADM Process
• Feasibility Study
• Requirement Analysis
• Requirement Specification
• Logical System Specification
• Physical Design
• Modeling Languages
• Techniques and Tools
• Functional Sub-Modeling (DFD - Data Flow Diagrams)
• Data Sub-Modeling (ERD - Entity Relationship Diagrams)
• Dynamic Sub-Modeling (ELH - Entity Life History)

SSADM Process

1. Feasibility Study - This will analyze and identify technical, operational and economical feasibility of the system.
   
2. Requirement Analysis - Here we gather operational and dynamic user requirements from the new system. This process also include the analysis of the current system using DFD diagrams, etc.
   
3. Requirement Specification - This is a document that explains the requirements of the new system using DFD, ERD and other diagrams.
   
4. Logical System Specification - This will create a model / logical design of the intended new system by identifying various technical options. This is an implementation independent model.
   
5. Physical Design - This step will convert the logical design of the system into an implementation dependent model.

SSADM Modeling Languages / Tools

There are three modeling tools available for modeling of functional, data and dynamic sub models.

• DFD for Functional Sub Modeling
• ERD for Data Sub Modeling
• ELH for Dynamic Sub Modeling

Each of these sub models has its own view of the perspective of the system. Each concentrates on certain aspects and ignorance of others. By combining of these three models gives a whole picture of the new system.