What Is Ss. t1c5i

What is SS • The SS methodology is a welldefined (structured) methodology and is quite difficult to use. When used skillfully it can produce welldocumented, 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

SS 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.

SS 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) ed by appropriate documentation. • Data Flow Diagrams represent processes 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

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 ing documentation.

SS Views • The methodology examines the system in detail using standard tools, and produces three descriptions of the system under investigation. • The success of SS 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 SS, each of the three techniques is crossreferenced against the others to ensure the completeness and accuracy of the complete model.

The three views gained are: 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.

Object Oriented Methodology (OOM) • 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.

PRINCE2 - A Structured Project Management Methodology • PRINCE stands for Projects 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 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.

t Application Development

• t 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 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 several physical drives in a computer into an array that you can define as one or more logical drives. • Each logical drive appears 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) • UML is an industry standard modeling language with a rich graphical notation, and comprehensive set of diagrams and elements.

UML 2 defines 14 diagrams • • • • • • • • • • • • • •

Package diagrams Class or Structural diagrams Object diagrams Composite Structure Component diagrams Deployment diagrams Use Case Diagrams Activity diagrams State Machine diagrams Communication diagrams Sequence diagrams Timing diagrams Interaction Overview diagrams Profile diagrams

Class Diagrams Class diagrams are the backbone of almost every object oriented method, including UML. They describe the static structure of a system.

Use Case Diagrams Use case diagrams model the functionality of system using actors and use cases.

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