Requirements Modeling: Techniques and Tools - PDF

Chapter Two Requirements Modeling  Introduction This chapter describes requirements modeling techniques and team-based methods that systems analysts use to visualize and document new systems The chapter then discusses system requirements and fact-finding te...

Chapter Two Requirements Modeling  Introduction This chapter describes requirements modeling techniques and team-based methods that systems analysts use to visualize and document new systems The chapter then discusses system requirements and fact-finding techniques, which include interviewing, documentation review, observation, surveys and questionnaires, sampling, and research Systems Analysis Activities  Systems Analysis Activities Requirements modeling Involves fact-finding to describe Outputs (electronic or printed info produced by the system) Inputs (necessary data that enters the system) Processes (logical rules applied to transform data into info) Performance (systems characteristics such as speed, capacity, reliability, availability, etc.) Security (hardware, software and procedural controls that protect the system and its data)  Systems Analysis Phase Systems Analysis Skills – Analytical skills – Interpersonal skills Team-Oriented Methods and Techniques – Joint application development (JAD) – Rapid application development (RAD)  Joint Application Development User Involvement – Users have a vital stake in an information system and they should participate fully – Successful systems must be user-oriented and users need to be involved – One popular strategy for user involvement is a JAD team approach  Joint Application Development JAD Advantages and Disadvantages – Advantages Allows key users to participate effectively When properly used, JAD can result in a more accurate statement of system requirements, a better understanding of common goals, and a stronger commitment to the success of the new system – Disadvantages More expensive and can be cumbersome if the group is too large relative to the size of the project  Rapid Application Development a team-based technique that speeds up information systems development and produces a functioning information system Relies heavily on prototyping and user involvement Process continues until the system is completely developed and users are satisfied Similarities and differences between JAD and RAD? Like JAD, it uses a group approach End product of JAD is a requirements model. End product of RAD is the new IS.  Rapid Application Development RAD Advantages and Disadvantages – Advantages Systems can be developed more quickly with significant cost savings – Disadvantages RAD stresses the mechanics of the system itself and does not emphasize the company’s strategic business needs Might allow less time to develop quality, consistency, and design standards  Modeling Tools and Techniques CASE Tools – Document business functions and processes – Develop graphical models – Provide an overall framework for IS development Functional Decomposition Diagrams (FDD) – Also called structure charts – Top-down representation of a function or process  Modeling Tools and Techniques Data Flow Diagrams (DFD) – Shows how the system stores, processes and transforms data  Modeling Tools and Techniques Unified Modeling Language – Widely used method of visualizing and documenting software systems design – Uses object-oriented design concepts – Provides graphical tools such as: – Use case diagrams Visually represents the interaction between users and the IS. The User becomes an Actor with a specific role. – Sequence diagrams Shows the timing of interactions between objects  System Requirements Checklist System requirement – A characteristic or feature that must be included in an IS to satisfy business requirements and be acceptable to users. Five general categories: – Outputs – Inputs – Processes – Performance – Controls  Fact-Finding Fact-Finding Overview – The first step is to identify the information you need – Develop a fact-finding plan describing:  Fact-Finding you begin by asking a series of questions, such as these: What business functions are supported by the current system? What strategic objectives and business requirements must be supported by the new system? What are the benefits and TCO of the proposed system?  Fact-Finding What transactions will the system process? What information do users and managers need from the system? Must the new system interface with legacy systems? What procedures could be eliminated by business process reengineering?  Fact-Finding What security issues exist? What risks are acceptable? What budget and timetable constraints will affect system development?  Who, What, Where, When, How, and Why? Fact-finding involves answers to five familiar questions: who, what, where, when, and how. For each of those questions, you also must ask another very important question: why. Some examples of these questions are: 1. Who? Who performs each of the procedures within the system? Why? Are the correct people performing the activity? Could other people perform the tasks more effectively? 2. What? What is being done? What procedures are being followed? Why is that process necessary? Often, procedures are followed for many years and no one knows why. You should question why a procedure is being followed at all. 3. Where? Where are operations being performed? Why? Where could they be performed? Could they be performed more efficiently elsewhere? 4. When? When is a procedure performed? Why is it being performed at this time? Is this the best time? 5. How? How is a procedure performed? Why is it performed in that manner? Could it be performed better, more efficiently, or less expensively in some other manner? Interviews Systems analysts spend a great deal of time talking with people Much of that time is spent conducting interviews  Interview Step 1: Determine the People to Interview Step 2: Establish Objectives for the Interview Step 3: Develop Interview Questions Step 4: Prepare for the Interview Step 5: Conduct the Interview Step 6: Document the Interview Step 7: Evaluate the Interview  Other Fact-Finding Techniques Document Review Observation – Seeing the system in action gives you additional perspective and a better understanding of the system procedures  Other Fact-Finding Techniques Questionnaires and Surveys – When designing a questionnaire, the most important rule of all is to make sure that your questions collect the right data in a form that you can use to further your fact-finding – Fill-in form  Other Fact-Finding Techniques Sampling: collecting examples of actual documents Main objective of a sample is to ensure that it represents the overall population accurately – Systematic sample – Stratified sample – Random sample  Other Fact-Finding Techniques Research – Can include the Internet, IT magazines, and books to obtain background information, technical material, and news about industry trends and developments – Site visit  Other Fact-Finding Techniques Interviews versus Questionnaires – Interview is more familiar and personal – Questionnaire gives many people the opportunity to provide input and suggestions – Brainstorming – Structured brainstorming – Unstructured brainstorming  Documentation Software Tools – CASE Tools – Productivity Software Word processing, spreadsheets, database management, presentation graphics programs Histogram Logical design – the translation of business user requirements into a system model that depicts only the business requirements and not any possible technical design or implementation of those requirements. Common synonyms include conceptual design and essential design. System model – a picture of a system that represents reality or a desired reality. System models facilitate improved communication between system users, system analysts, system designers, and system builders.