DISE - Introduction to Software Engineering
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This document provides an overview of software engineering concepts including different types of software, software classification, software attributes, and common software development process models. It describes system software and application software, and distinguishes between generic/off-the-shelf software and custom software. Popular process models covered include waterfall, prototyping, and rapid application development (RAD). The waterfall model and its stages are explained in detail.
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DISE - Introduction to Software Engineering
- 1. Diploma in Software Engineering Module I: Introduction to Software Engineering Rasan Samarasinghe ESOFT Computer Studies (pvt) Ltd. No 68/1, Main Street, Pallegama, Embilipitiya.
- 2. Contents 1. What is software? 2. Software classification 3. Generic Software vs Custom Software 4. Attributes of Software 5. What is Software Engineering? 6. Software Engineering Process Model 7. Waterfall Model 8. Waterfall Model Stages 9. Extended Waterfall Model 10. Prototype Model 11. Throw away prototype model 12. Evolutionary prototype model 13. Rapid application development model (RAD) 14. Stages in the RAD
- 3. What is software? A software is a collection of instructions that enables a user to interact with the computer or have the computer perform special task for them.
- 4. Software classification • System Software – Directly controlling the hardware resources and supports the operation of application software. • Application Software – Serves the user requirements in a particular application domain.
- 5. Software classification • Generic Software (off the shelf) – Available on open market to any customer who is able to buy it. • Custom Software (bespoke) – Developed specially for a customer requirement.
- 6. Generic Software vs Custom Software Less expensive More reliable Immediate installation More user friendly User requirements are not completely satisfied Cannot accommodate future changes More expensive Less reliable Delay due to high development time Less user friendly Completely satisfied Can easily accommodate future changes Generic Software Custom Software
- 7. Attributes of Software • Maintainability • Dependability • Efficiency • Usability • Security • Reliability • Robustness • Customizability • Scalability • Accessibility • Extensibility
- 8. What is Software Engineering? Software engineering is concerned with application of theories, methods and tools to develop and maintain software systems that behave reliably and efficiently, are affordable to develop and maintain, and satisfy all the requirements that customers have defined for them.
- 9. Software Engineering Process ModelA software process model is a set of predicted procedures or set of stages to be use to develop a fully tested software system timely. Software Process Model
- 10. • Waterfall model • Prototyping model • Rapid application development model • Spiral model • V-model • Join application development model • Incremental development model Software Process Models
- 11. Waterfall Model
- 12. Waterfall Model • A linear sequential development model. • Because of the cascade form one stage to another it is known as waterfall model. • Divided project activities into isolated stages and each stage should complete before next started. • Concurrent activities are not possible. • Need to wait until end of the life cycle to see the outcome. • Suitable for develop systems which has stable requirements.
- 13. Waterfall Model Stages Stage 1: Requirement Definition • The system services, constraints and goals are established by consulting with the system users. • They are define in a manner which is understandable by both users and the development staff.
- 14. Waterfall Model Stages Stage 2: System and Software designing • Partitions the requirements either hardware or software. • Involves representing the software system functions in a form the may be transformed into executable programs. • Identifying and describing fundamental software system abstraction and there relationships.
- 15. Waterfall Model Stages Stage 3: Implementation and unit testing • Implementation consists of converting the physical designing into set of actual programs and a set of database tables. • The software is realized as a set of programs or program units. • Unit testing involves verifying that each unit meets it’s requirements.
- 16. Waterfall Model Stages Stage 4: integration and system testing • Individual program units are integrated and tested as a complete system. • Ensure the software requirements have been met. • After testing the software system is delivered to the customer.
- 17. Waterfall Model Stages Stage 5: Operation and maintenance • The system installed and put into practical use. • Involved correcting errors which were not discovered in earlier stages. • Improving implementation as new requirements are discovered. • Normally this is the longest life cycle phase.
- 18. Extended Waterfall Model • Due to the above discussed disadvantages, the waterfall model was modified with the concept of backtracking. • As a result, the Extended Waterfall Model introduced.
- 20. Prototype Model Prototype is a working model of the actual System There are two types of prototype model. 1. Throw away prototype model 2. Evolutionary prototype model
- 21. Throw away prototype model
- 22. Throw away prototype model • Prototype is used to gather requirements and there after it will be thrown away. • Further designing, construction and implementation will be done using the normal life cycle stages. • Requirements gathering can be exactly done by using the prototype. • Even to develop prototype consumes lot of time and effort , therefore once a prototype is thrown away it’s a waste of time and money.
- 23. Evolutionary prototype model System Complete System Architecture Identify Prototype Quick Design Construct And Use The System Revise Prototype Deliver System Yes No
- 24. Evolutionary prototype model • Prototype is used to gather requirements and it will become the final system. • Both the prototyping process as well as the development process will be combine together. • Prototype will not be thrown away and it is not wasting effort and cost like throw away prototype.
- 25. Rapid Application Development (RAD)
- 26. Rapid application development model (RAD) • This is a software process model which uses to develop applications rather quickly. • The entire system is broken down into several manageable stages and each stage analyzed, designed, developed, tested and implemented simultaneously Rapid Application Development (RAD)
- 27. Stages in the RAD 1. Business modeling • The information flow among business functions is modeled. • Find answers for the following questions: What information drives the business process? What information is generated? Who generate it? Where does information go? Who process it?
- 28. Stages in the RAD 2. Data modeling • The information flows are refined into set of data objects. • The attributes of each objects and relationships between these objects defined.
- 29. Stages in the RAD 3. Process modeling • The data objects are transformed to achieve the information flow necessary to implement the business function. • Processes are created for adding, modifying, deleting and retrieving data objects.
- 30. Stages in the RAD 4. Application generation • Using fourth generation techniques rather than using conventional third generation programming languages. • In possible cases automated tools/reusable components are use to facilitate construction of the software. (Ex: DB query tools, reports, graphics manipulation, interface designs)
- 31. Stages in the RAD 5. Testing and turnover • Since the RAD process use many reusable components that have been tested, it reduces the overall testing time. • How ever the new components should be tested.
Editor's Notes
- #8: Maintenability Ability to evolve with the changing needs of the customer Dependability What it is depends on Efficiency Efficiency is the ability of the software to do the required processing on least amount of hardware. Usability Usability is the ability of a software to offer its interfaces in a user friendly and elegant way. Security Security is the ability of the software to remain protected from unauthorized access. This includes both change access and view access. Reliability High Reliability is the measure of how a product behaves in varying circumstances. Robustness Robustness is defined as the ability of a software product to cope with unusual situation. Customizability Customizability is the ability of a software to offer extensions to existing functionality to better suite the needs of a user. Scalability Scalability is the ability of the software to cater for heavier processing loads as the needs arise. Accessibility Accessibility is the ability of a software to be accessible from a multitude of devices and for a number of different types of users. Extensibility (Data model) Extensibility is the ability of the software to be extended beyond the functionality of the original product.