What is Software Development Life Cycle?

What is Software Development Life Cycle? (SDLC) (2 mks) System Development Life Cycle (SDLC) is the overall process of developing information systems through a multi-step process from investigation of initial requirements through analysis, design, implementation and maintenance. b) Draw a diagram for pure waterfall life cycle. (5 mks) [pic] c)Explain the different phases involved in waterfall life cycle. (8 mks) Phase I – Modeling Phase In this phase we view the software product as part of a larger system or organization where the product is required.

This is basically a system view where all the system elements are created. Phase II – Software Requirements Analysis Here we have a phase where the requirements are gathered. The information domain for the software is understood. The function, behaviour, performance and interfacing of the software are determined. The requirements of the software and the customer are decided upon. Phase III – Design This determines the data structures, the software architecture, the interface representations and the procedural (algorithmic) detail that goes into the software. Phase IV – Code Generation

Here the actual programming is done to obtain the machine code; it is an implementation of the design. Phase V – Testing The testing is a process that goes hand in hand with the production of the machine code. There are a number of testing strategies. First unit testing is done and then integration testing. Alpha testing is to see if the software is as per the analysis model whereas beta testing is to see if the software is what the customer wanted. Phase VI – Installation The software is released to the customer. Phase VII – Maintenance This is the largest phase of the software life cycle.

Maintenance can be of different types: to modify the software as the requirements of the customer evolve, to remove the residual bugs in the software etc. 2)What is feasibility study? What are the contents we should contain in the feasibility report? (5 mks) A feasibility study is an initial look at an existing information processing system to decide how it might be computerized or improved. The contents that a feasibility report are: • A statement of purpose of the system. • A definition of system scope. • A list of deficiencies of the current system. • A statement of user requirements.

The cost and benefits of development. • A conclusion and recommendations. 3)What are the purposes of Data Flow diagrams, Entity-Relationship diagrams? Give an example diagram of each. (10 mks) Data Flow Diagrams Data Flow diagrams are a means of representing a system at any level of detail with a graphic network of symbols showing data flows, data stores, data processes, and data sources/destinations. The purpose of data flow diagrams is to provide a semantic bridge between users and systems developers. The diagrams are: • Graphical –

Eliminating thousands of words; Logical representations – Modeling WHAT a system does, rather than physical models showing HOW it does it • Hierarchical – showing systems at any level of detail; and • Jargonless – allowing user understanding and reviewing. [pic] Entity Relationship Diagram E-R Diagram is a graphical representation of the data layout of a system at a high level of abstraction. It defines data elements and their inter-relationships in the system [pic] 4)What is data modeling? Give 5 examples for data modeling. (5 mks) Data modeling is the act of exploring data-oriented structures.

Like other modeling artifacts data models can be used for a variety of purposes, from high-level conceptual models to physical data models. From the point of view of an object-oriented developer, data modeling is conceptually similar to class modeling. With data modeling you identify entity types whereas with class modeling you identify classes. Data attributes are assigned to entity types just as you would assign attributes and operations to classes. Examples for data modeling include: • Entity-Relationship diagrams • Entity-Definition reports •

Entity and attributes report • Table definition report Relationships, inheritance, composition and aggregation. 5)What is the difference between SRS document and design document? What are the contents we should contain in the SRS document and design document. SRS Document SRS document is a contract between the development team and the customer. Once the SRS document is approved by the customer, any subsequent controversies are settled by referring the SRS document. SRS document defines the customer’s requirements in terms of Functions, performance, external interfaces and design constraints. SRS Includes: • Functional • Non functional User • Interface •

System Design Document The purpose of a design is to describe how the enhancements will be incorporated into the existing project. It should contain samples of the finished product. This could include navigational mechanism screenshots, example reports, and component diagrams. Design Includes: • E-R Diagrams • Data flow diagrams • Data Dictionary 6)Explain all the phases involved in the implementation phase. (10 mks) Conduct system Test In this test software packages and in – house programs have been installed and tested, we need to conduct a final system test.

All software packages, custom- built programs, and many existing programs that comprise the new system must be tested to ensure that they all work together This task involves analysts, owners, users, and builders. Prepare Conversion Plan On successful completion of system test, we can begin preparations to place the new system into operation. Using the design specifications for the new system, the system analyst will develop a detailed conversion plan. This plan will identify Database to be installed, end – user training and documentation that needed to be developed, and a strategy for converting from the old system to the new system.

The conversion plan may include one of the following commonly used installation strategies 1) Abrupt Cut-over 2) Parallel Conversion 3) Location Conversion 4) Staged Conversion Install Databases In the previous phase we built and tested the database. To place the system into operation we need fully loaded databases. The purpose of this task is to populate the new systems databases with existing database from the old system. System builders play a primary role in this activity. Train Users Converting to a new system necessitates that system users be trained and provided with documentation that guides them through using the new system.

Training can be performed one on one; however group training is preferred. This task will be completed by the system analysts and involves system owners and users. Convert to New System Conversion to the new system from old system is a significant milestone. After conversion, the ownership of the system officially transfers from the analysts and programmers to the end users. The analyst completes this task by carrying out the conversion plan Recall that the conversion plan includes detailed installation strategies to follow for converting from the existing to the new production information system.

This task involves the system owners, users, analysts, designers, and builders. 7)List and explain different types of testing done during the testing phase. (10 mks) Unit Involves the design of test cases that validate that the internal program logic is functioning properly, and that program inputs produce valid outputs. All decision branches and internal code flow should be validated. Unit testing involves the use of debugging technology and testing techniques at an application component level and is typically the responsibility of the developers, not the QA staff. Integration

As the system is integrated, it is tested by the system developer for specification compliance. •Concerned with testing the system as it is integrated from its components •Integration testing is normally the most expensive activity in the systems integration process •Should focus on: •Interface testing where the interactions between sub-systems and components are tested •Property testing where system properties such as reliability, performance and usability are tested System Testing the system as a whole to validate that it meets its specification and the objectives of its users.

The testing of a complete system prior to delivery. The purpose of system testing is to identify defects that will only surface when a complete system is assembled. That is, defects that cannot be attributed to individual components or the interaction between two components. System testing includes testing of performance, security, configuration sensitivity, startup and recovery from failure modes. Involves test cases designed to validate that an application and its supporting hardware/software components are properly processing business data and transactions.

System testing requires the use of regression testing techniques to validate that business functions are meeting defined requirements. Black Box This is testing without knowledge of the internal workings of the item being tested. For example, when black box testing is applied to software engineering, the tester would only know the “legal” inputs and what the expected outputs should be, but not how the program actually arrives at those outputs. It is because of this that black box testing can be considered testing with respect to the specifications, no other knowledge of the program is necessary.

For this reason, the tester and the programmer can be independent of one another, avoiding programmer bias toward his own work. White Box Also known as glass box, structural, clear box and open box testing. White Box is a software testing technique whereby explicit knowledge of the internal workings of the item being tested are used to select the test data. Unlike Black Box testing, white box testing uses specific knowledge of programming code to examine outputs. The test is accurate only if the tester knows what the program is supposed to do.

He or she can then see if the program diverges from its intended goal. White box testing does not account for errors caused by omission, and all visible code must also be readable. 8)List and explain all the phases involved in the construction phase. (10 mks) Build and Test Networks • In many cases new or enhanced applications are built around existing networks. If so there is no problem. • However if the new application calls for new or modified networks they must normally be implemented before building and testing databases and writing or installing computer programs that will use those networks. This phase involves analysts, designers and builders •

A network designer and network administrator assume the primary responsibility for completing this task. Build and Test Databases • This task must immediately precede other programming activities because databases are the resource shared by the computer programs to be written. If new or modified databases are required for the new system, we can now build and test those databases. • This task involves system users, analysts, designers, and builders. • The same system specialist that designed the database will assume the primary responsibility in completing this task

Install and Test New Software Packages • Some systems solutions may have required the purchase or lease of software packages. If so, once networks and databases for the new system have been built, we can install and test the new software. • This activity typically involves systems analysts, Designers, builders, vendors and consultants. Write and Test New Programs • In this phase we are ready to develop any programs for the new system. Prototype programs are frequently constructed in the design phase. However, these prototypes are rarely fully functional or incomplete.

This task involves the system analysts, designers and builders. 9)What is data conversion? Why is it necessary? Data Conversion is the changing of the data structure to accommodate new or different needs for the data. Different operating systems have different application software, and each application normally has its own internal way of saving data. There are some standards such as CSV files for databases and RTF files for word processing text, however, these are few and far between and often only save the basic information rather than the full structure. 10)What is change management?

Computer based systems are dynamic. As the business Environment changes, there is a need of some changes to the information system. The changes occur not only during the study, design, and development phases of the life cycle of the system. In this process there are two elements that are essential to the management of change. • The performance review board, which can make management–level decisions about system modifications. • Baseline documentation, which can be referred to, to determine the extent and impact of proposed modifications. 11)What is user acceptance testing?

Explain different testings in user acceptance testing. Why is it necessary? User Acceptance Testing is a phase of software development in which the software is tested in the “real world” by the intended audience. Different testings are: Alpha Testing Alpha testing is the software prototype stage when the software is first able to run. It will not have all the intended functionality, but it will have core functions and will be able to accept inputs and generate outputs. An alpha test usually takes place in the developer’s offices on a separate system. Beta Testing

The beta phase of software design exposes a new product, which has just emerged from in-house (alpha) testing, to a large number of real people, real hardware, and real usage. Beta testing is not a method of getting free software long-term, because the software expires shortly after the testing period. User acceptance testing is used to know if the system is working or not (both clients ; in-house) 12)What are functional and non-functional requirements? Functional • How the system should react to the particular inputs • How the system should behave to the particular situations • What the system should not do

Non functional • Constraints on the services or functions • Time constraints • Constraints on the development process 13)Explain the steps involved in the prototyping 1. Define the goal and purpose of the prototyping. 2. Make plans for iterations (number, range) and evaluations (dates). 3. Transform the conceptual design to a first outline of the user interface and a first synopsis for the users’ information. 4. Design the paper prototype. 5. Let domain experts review the paper prototype regarding completeness and correctness. 6. Test the prototype’s usability.