Biyani's Think Tank
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System Analysis and Design
(BCA Part-II)
Elveera Miranda
Revised By: Ms Jyoti Sharma
MCA
Lecturer
Deptt. of Information Technology
Biyani Girls College, Jaipur
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System Analysis and Design: Concepts, Models, and Techniques, Thesis of Systems Design
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Biyani's Think Tank
Concept based notes
System Analysis and Design
(BCA Part-II)
Elveera Miranda
Revised By: Ms Jyoti Sharma MCA
Lecturer
Deptt. of Information Technology
Biyani Girls College, Jaipur
Published by :
Think Tanks
Biyani Group of Colleges
Concept & Copyright :
Biyani Shikshan Samiti
Sector-3, Vidhyadhar Nagar, Jaipur-302 023 (Rajasthan) Ph : 0141-2338371, 2338591-95 Fax : 0141- E-mail : [email protected] Website :www.gurukpo.com; www.biyanicolleges.org
ISBN: 978-93-82801-73-
Edition: 2011 Price:
Leaser Type Setted by : Biyani College Printing Department
While every effort is taken to avoid errors or omissions in this Publication, any mistake or omission that may have crept in is not intentional. It may be taken note of that neither the publisher nor the author will be responsible for any damage or loss of any kind arising to anyone in any manner on account of such errors and omissions.
Syllabus B.C.A. Part-II
System Analysis and Design
Introduction to System Design Environment : Systems Development Approaches- Function Oriented, Object Oriented Development Process, Methodologies, Tools , Modeling Methods, Processing Types and Systems, Batch Processing, Real Time Processing, Management Process, Management, System Analysis, Programmers, Computer Operators, End Users, System Structure, People Processes and Data, Databases, Personal Systems, Centralized Systems, Data Warehousing, Data Mining, Distributed Systems, Evolution of Distributed Processing, Client Server Systems, Agent Oriented Systems.
System Development Life Cycle, Linear or Waterfall Cycle, Linear Cycle Phase Problem Definition, System Specification, System Design, System Development, Testing, Maintenance Problem with Linear Life Cycle, Iterative Cycles, Spiral Model Requirements Analysis, Importance of Communication, Identifying Requirements, Data and Fact Gathering Techniques, Feasibility Studies, Introduction to Prototyping, Rapid Prototyping Tools, Benefits of Prototyping.
Interface Design Tools, User Interface Evaluations, Introduction to Process Modeling, Introduction to Data Modeling.
System Design Techniques, Document Flow Diagrams, Documents, Physical Movement of Documents, Usefulness of Document Flow Diagram, Data Flow Diagrams, DFD Notation, Context Diagram DFD Leveling, Process Descriptions Structured English, Decision Trees and Decision Tables, Entity Relationship Diagrams, Entities, Attributes, Relationship, Degree, Optionality, Resolving Many to Many Relationship, Exclusive Relationship, Structure Charts, Modules, Parameter Passing, Execution Sequence, Structured Design, Conversion from Data Flow Diagrams to Structure Charts.
System Implementation, Maintenance and Documentation, Testing, Evaluation, Maintenance Activities, Documentation, Document Configuration Maintaining a Configuration.
System Analysis and Design 5
Content
S. No. Name of Topic
1. Introduction to System 1.1 Basic Concepts 1.2 Types of System 2. System Development 2.1 SDLC Method 2.2 System Analysts 2.3 Various Models of System Development 2.4 Requirements Analysis 3. Data Modeling 3.1 Basics of Data Modeling 3.2 Entity Relationship Diagram 3.3 Data Dictionary 4. Process Modeling 4.1 Data Flow Diagram 4.2 Decision Tree 4.3 Decision Table 5. Object Modeling 5.1 Structure Chart 5.2 Structured English 6. Important Terms for System Analysis and Design 6.1 Input Design
System Analysis and Design 7
Chapter-
Introduction to System
Q.1 Define System and explain its characteristics.
Ans.: A System means an organised relationship among functioning units or components. It is an orderly grouping of interdependent components linked together according to a plan to achieve a specific objective. The elements of the system are as under : (1) Outputs and Inputs : A major objective of a system is to produce an output that has value to its user. Whatever the nature of the output, it must be in line with the expectations of the intended user. Inputs are the elements that enter the system for processing and output is the outcome of the processing. (2) Processors : The processor is the element of the system that involves the actual transformation of input into output. It is the operational component of a system. Processors modify the input totally or partially. (3) Control : The control element guides the system. It is the decision- making subsystem that controls the pattern of activities governing input, processing and output. (4) Feedback : Control in a dynamic system is achieved by feedback. Feedback measures output against a standard in some form that includes communication and control. Feedback may be positive or negative, routine or informational. (5) Environment : It is the source of external elements that impinge on the system. It determines how a system must function. (6) Boundaries and Interfaces : A system should be defined by its boundaries- the limits that identify its components, processes and interrelationships when it interfaces with another system. The characteristics of a system are as under :
(1) Organisation : It implies structure and order. It is the arrangement of components that helps to achieve objectives. (2) Interaction : It refers to the manner in which each component functions with other component of the system. In an organisation, for example, purchasing must interact with production, advertising with sales, etc. (3) Interdependence : It means that parts of the organisation or computer system depend on one another. They are coordinated and linked together according to a plan. One subsystem depends on the input of another subsystem for proper functioning. (4) Integration : It refers to the completeness of systems. It is concerned with how a system is tied together. It is more than sharing a physical part or location. It means that parts of a system work together within the system even though each part performs a unique function. (5) Central Objective : Objectives may be real or stated. Although a stated objective may be the real objective, it is not uncommon for an organisation to state one objective and operate to achieve another.
Q.2 Explain the different types of Processing Systems.
Ans.: Batch processing is execution of a series of programs ("jobs") on a computer without human interaction. Batch jobs are set up so they can be run to completion without human interaction, so all input data is preselected through scripts or command-line parameters. This is in contrast to "online" or interactive programs which prompt the user for such input. Batch processing has these benefits : It allows sharing of computer resources among many users, It shifts the time of job processing to when the computing resources are less busy, It avoids idling the computing resources with minute-by-minute human interaction and supervision, By keeping high overall rate of utilization, it better amortizes the cost of a computer, especially an expensive one. Distributed computing deals with hardware and software systems containing more than one processing element or storage element, concurrent processes, or multiple programs, running under a loosely or tightly controlled regime.
microseconds. But the timeliness constraints or deadlines are generally a reflection of the underlying physical process being controlled. For example, in image processing involving screen update for viewing continuous motion, the deadlines are on the order of 30 microseconds. An important concept in real-time systems is the notion of an event, that is, any occurrence that results in a change in the sequential flow of program execution. Events can be divided into two categories: synchronous and asynchronous. Synchronous events are those that occur at predictable times such as execution of a conditional branch instruction or hardware trap. Asynchronous events occur at unpredictable points in the flow-of-control and are usually caused by external sources such as a clock signal. Both types of events can be signaled to the CPU by hardware signals
System Analysis and Design 11
Chapter-
System Development
Q.1 Describe System Development Life Cycle and explain its various phases.
Ans.: The Systems Development Life Cycle (SDLC) is a conceptual model used in project management that describes the stages involved in an information system development project from an initial feasibility study through maintenance of the completed application. Various SDLC methodologies have been developed to guide the processes involved including the wate rfall model (the original SDLC method), rapid application development (RAD), joint application development (JAD), the fountain model and the spiral model. Mostly, several models are combined into some sort of hybrid methodology. Documentation is crucial regardless of the type of model chosen or devised for any application, and is usually done in parallel with the development process. Some methods work better for specific types of projects, but in the final analysis, the most important factor for the success of a project may be how closely particular plan was followed. Feasibility : The feasibility study is used to determine if the project should get the go-ahead. If the project is to proceed, the feasibility study will produce a project plan and budget estimates for the future stages of development. Requirement Analysis and Design : Analysis gathers the requirements for the system. This stage includes a detailed study of the business needs of the organization. Options for changing the business process may be considered. Design focuses on high level design like, what programs are needed and how are they going to interact, low-level design (how the individual programs are going to work), interface design (what are the interfaces going to look like) and data design (what data will be required). During these phases, the software's overall structure is defined. Analysis and Design are very crucial in the whole development cycle. Any glitch in the design phase could be very expensive to solve in the later stage of the software development. Much care is taken during this phase. The logical system of the product is developed in this phase. Implementation : In this phase the designs are translated into code. Computer programs are written using a conventional programming language
System Analysis and Design 13
Communication Understanding Foresightedness and Vision Adaptability and Flexibility Skills Teaching Selling Patience and Rationality Management Skills Leadership Quality Training and Documentation Capability Technical skills include : Creativity- Problem solving- Project management- Dynamic interface- Questioning attitude and inquiring mind- Knowledge-
Q.3 Explain the Waterfall Model.
OR Describe the Classic Life Cycle Model. OR Explain the Linear Sequential Model.
Ans.: Sometimes called the classic life cycle or the linear sequential model, the waterfall
model is a systematic, sequential approach to software development in which development is seen as flowing downwards ( like a waterfall ) that begins at the system level and progresses through analysis, design, coding, testing and support. To follow the waterfall model, one proceeds from one phase to the next in a sequential manner. For example, one first completes "requirements specification". When the requirements are fully completed, one proceeds to design. The software is designed (on paper) and this design should be a plan
for implementing the requirements given. When the design is fully completed, an implementation of that design, i.e. coding of the design is made by programmers. After the implementation phases are complete, the software product is tested and debugged; any faults introduced in earlier phases are removed here. Then the software product is installed, and later maintained to add any new functions that the user needs and remove bugs. Thus in a waterfall model, we can move to the next step only when the previous step is completed and removed of all errors. There is no jumping back and forth or overlap between the steps in a waterfall model.
The model consists of six distinct stages, namely : (1) In the Information Modelling phase (a) Work begins by gathering information related to the existing system. This will consists of all items consisting of hardware, people, databases etc. (2) In the requirements analysis phase (a) The problem is specified along with the desired objectives (goals). (b) The constraints are identified.
Information Modeling
Requirements Analysis
Design
Code Generation
Testing
Delivery & Support
converted to the actual system with all considerations for quality and security. The prototype is considered as the „first system‟. It is advantageous because both the customers and the developers get a feel of the actual system. But there are certain problems with the prototyping model too. (1) The prototype is usually created without taking into consideration overall software quality. (2) When the customer sees a working model in the form of a prototype, and then is told that the actual software is not created, the customer can get irritated. (3) Since the prototype is to be created quickly, the developer will use whatever choices he has at that particular time (eg, he may not know a good programming language, but later may learn. He then cannot change the whole system for the new programming language). Thus the prototype may be created with less-than-ideal choices.
Q.5 Describe the Rapid Application Development Model. State its disadvantages.
Ans.: Rapid Application Development (RAD) is an incremental software development process model that focuses on a very short development cycle. The RAD model is a „high-speed‟ version of the linear sequential model. It enables a development team to create a fully functional system within a very short time period (e.g. 60 to 90 days). Business Modeling : The information flow among business functions is modeled in a way that answers the following questions : What information drives the business process? What information is generated? Who generates it? Where does the information go? Who processes it?
System Analysis and Design 17
Data Modeling : It gives all the details about what data is to be used in the project. All the information found in the business modeling phase is refined into a set of data objects and the characteristics and the relationships between these objects are defined. Process Modeling : Here all the processes are defined that are needed to use the data objects to create the system. Processing descriptions are created for adding, modifying, deleting, or retrieving a data object. Application Generation : RAD makes use of the fourth generation techniques and tools like VB, VC++, Delphi etc rather than creating software using conventional third generation programming languages. The RAD reuses existing program components (when possible) or creates reusable components (when necessary). In all cases, automated tools (CASE tools) are used to facilitate construction of the software. Testing and Turnover : Since the RAD process emphasizes reuse, many of the program components have already been tested. This minimizes the testing and development time. If a business application can be divided into modules, so that each major function can be completed within the development cycle, then it is a candidate for the RAD model. In this case, each team can be assigned a model, which is then integrated to form a whole. Disadvantages : · For Large projects, RAD requires sufficient resources to create the right number of RAD teams. · If a system cannot be properly divided into modules, building components for RAD will be problematic · RAD is not appropriate when technical risks are high, e.g. this occurs when a new application makes heavy use of new technology.
Q.6 Explain the Spiral Model. What are the advantages of this model?
Ans.: The spiral model, combines the iterative nature of prototyping with the controlled and systematic aspects of the waterfall model, therein providing the potential for rapid development of incremental versions of the software. In this model the software is developed in a series of incremental releases with the early stages being either paper models or prototypes. Later iterations become increasingly more complete versions of the product.
System Analysis and Design 19
specification or design phases in the model and it encompasses other process models. For example, prototyping may be used in one spiral to resolve requirement uncertainties and hence reduce risks. This may then be followed by a conventional waterfall development. Advantages of the Spiral Model : The spiral model is a realistic approach to the development of large - scale software products because the software evolves as the process progresses. In addition, the developer and the client better understand and react to risks at each evolutionary level. The model uses prototyping as a risk reduction mechanism and allows for the development of prototypes at any stage of the evolutionary development. It maintains a systematic stepwise approach, like the classic life cycle model, but incorporates it into an iterative framework that more reflect the real world. If employed correctly, this model should reduce risks before they become problematic, as consideration of technical risks are considered at all stages.
Q.7 Explain Information Gathering Process for System Development.
OR Explain Fact Finding Method of System Analysis.
Ans.: Fact finding means learning as much as possible about the present system. The tools used in information gathering or fact finding are (1) Review of Written Documents : In all organizations documents such as forms, records, reports, manuals, etc are available. These help in determining how the present system runs. The process of fact finding includes collection of all possible documents and evaluating them. Unfortunately, most manuals are not up to date and may not be readable. The analyst needs to find out how the forms are filled out, what changes need to be made and how easy they are to read. (2) On-Site Observation : The purpose of on-site observation is to get as close as possible to the real system being studied. It is the process of recognizing and noting people, objects and occurrences to obtain information. As an observer the analyst must follow a set of rules. He/she must listen than talk and not give advice or pass a moral
judgment, must not argue or show friendliness towards others. The following questions can serve as a guide for on-site observations: What kind of system is it? What does it do? Who runs the system? Who are the important people in it? What is the history of the system? (3) Interviews : An interview is a face to face interpersonal situation in which a person called the interviewer asks a person being interviewed, questions designed to gather information about a problem. The analyst or interviewer can schedule interviews with key personnel of the organization. The analyst also needs to conduct detailed interviews with all the people who will actually use the system. This will provide all the details the analyst needs and also remove any fear from the users that the computers will replace the. Interviews help gather vital facts about the existing problems, such as lack of quality control or security, etc. Interviewing needs a friendly atmosphere so that the interviewer can ask questions properly, obtain reliable and correct answers and record the answers accurately and completely. (4) Questionnaires : A questionnaire is a tool that has questions to which individuals respond. A questionnaire has the following advantages: It is economical and requires less skill than an interview. It can be used to gather data from large number of people simultaneously It is a uniform method in which all question asked are the same to all people The users are happy as they know that the answers they give are confidential User get time to think about the questions and so can give more accurate results than in an interview
Q.8 What is Feasibility? Describe the different types of Feasibility.
Ans.: Feasibility is the determination of whether or not a project is worth doing. The process followed in making this determination is called feasibility study. A feasibility study is carried out to select the best system that meets performance requirements. When conducting feasibility study, an analyst can consider 7 types of feasibility: