What is SSADM

What is SSADMThe SSADM methodology is a well-defined (structured) methodology and is quite difficult to use. When used skillfully it can produce well-documented, accurate information systems. It recognises the following stages in the systems development lifecycle.However, it concentrates on the analysis and design phase of the Waterfall Model of the Systems Development lifecycle, as shown in the following diagram:

SSADM Tools

The analysis is done in two stages.

The first task done by the developer is to create the Requirements Specification - this is really a statement of what we are to do with the current system in order to produce the required system.

Stage 2 then develops a range of options that meet the defined requirements, and selects one option as the basis for the desired system.SSADM revolves around the use of three key techniques, namely Logical Data Modelling,

Data Flow Modelling

Entity/Event Modelling.

Logical Data Modelling:

This is the process of identifying, modelling and documenting the data requirements of a system.

A Logical Data Model consists of a Logical Data Structure (LDS - also known as an Entity-Relationship Model) and the associated documentation.

LDS represents Entities (things about which a business needs to record information, and usually proper nouns) and Relationships (links between entities).Data Flow Modelling:

This is the process of modelling and documenting how data flows around a system.

A Data Flow Model consists of a set of connected Data Flow Diagrams (DFDs) supported by appropriate documentation.

Data Flow Diagrams representprocesses and functions of the system(activities that transform data from one form to another),data stores(files or data storage),external entities(things that send data into a system or receive data from a system) and finallydata flows(show the flow of data around the system).Entity Event Modelling:

This is the process of identifying, modelling and documenting the business events that affect each entity and the sequence in which these events occur.

An Entity/Event Model consists of a set of Entity Life Histories (one for each entity) and appropriate supporting documentation.SSADM Views

The methodology examines the system in detail using standard tools, and produces three descriptions of the system under investigation.

The success of SSADM may lie in the fact that it has these multiple techniques.

Each of the three system models provides a different viewpoint of the same system, each of which are required to form a complete model of the system.

Within SSADM, each of the three techniques is cross-referenced against the others to ensure the completeness and accuracy of the complete model.The Data View: A description of all the data and information the system uses (gained from the DFDs above)

The Process View: A description of all the processes or actions carried out by the system (taken from the process descriptions and the process catalogue)

The Event View: A description of the systems events, that is the 'triggers' that set processes running (from the Entity life histories)Taking these different views allows us to gain much more information about the system than we could have done otherwise.Finally we take the current system and apply the requirements to it, and this gives us our required system.The three views gained are:Object Oriented Methodology (OOM) is a system development approach encouraging and facilitating re-use of software components.

With this methodology, a computer system can be developed on a component basis which enables the effective re-use of existing components and facilitates the sharing of its components by other systems.Object Oriented Methodology (OOM) PRINCE2 - A Structured Project Management Methodology

PRINCE stands forProjects in Controlled Environments.

Dealing with a bit of history, this method was first established by the Central Computer and Telecommunications Agency

It has since become a very commonly used project management method in all parts of the world and has therefore proven to be highly effective in various respects.

The method also helps you to identify and thereafter assign roles to the different members of the team based on expertise. Over the years, there have been a number of positive case studies of projects that have used PRINCE2 project management methodology.

This method deals with the various aspects that need to be managed in any given project.

The seven principles shown in the above diagram must be applied if the project is to be called a PRINCE2 project. These principles will show you whether and how well the project is being carried out using this particular project management method.Joint Application Development

Joint application design (JAD) is design methodology where the project team develop a system design in close conjunction with the sponsor/customer.JAD is a methodology where the development team work co-operatively with the customer to develop the processes which the software will support and by corollary the specification for the software. At the core of JAD are 'JAD sessions' which are meetings between the customer team and the developers where the specification is formalized.

Understanding RAID technology

Redundant array of independent disk (RAID) is the technology of grouping severalphysicaldrives in a computer into an array that you can define as one or more logical drives. Eachlogical driveappears to the operating system as a single drive. This grouping technique greatly enhances logical-drive capacity and performance beyond the physical limitations of a single physical drive.Entity Life History Diagram

An Entity Life History (ELH) diagram represents the life cycle of entities within the database.An Entity Life History diagram is used to show the sequencing, iteration or timing of an entity

Unified Modeling Language (UML)

UMLis an industry standard modeling language with a rich graphical notation, and comprehensive set ofdiagrams and elements.UML 2 defines 14 diagrams

Package diagramsClass or Structural diagramsObject diagramsComposite StructureComponent diagramsDeployment diagramsUse Case DiagramsActivity diagramsState Machine diagramsCommunication diagramsSequence diagramsTiming diagramsInteraction Overview diagramsProfile diagrams

Class DiagramsClass diagrams are the backbone of almost every object oriented method, including UML. They describe the static structure of a system.Use Case DiagramsUse case diagrams model the functionality of system using actors and use cases.

Sequence DiagramsSequence diagrams describe interactions among classes in terms of an exchange of messages over time.