Lesson 1
Introduction to Systems Analysis & Design
LESSON 1 Introduction
1. Introduction to Systems Analysis and Design (SAD) In this unit, a system is also referred to as a “software” or “information system” or “computer-based information system”. Systems Analysis and Design is a disciplinedprocess to create information systems that perform basic business processes such as keeping track of customer names and addresses, processing orders, and paying employees. In the early years of computing, analysis and design of a system has considered to be an art. Now that the need for systems has become so great, people in the industry and academia have developed work methods or methodologies that make analysis and design a disciplined-process. The goal in this unit is to give students the knowledge and skills needed to understand and follow the system development process that leads to the creation of information systems.
2. The evolution and history of systems development The analysis and design of computer-based information systems began in the 1950s. Since then, the development environment has changed dramatically, driven by organizational needs as well as by rapid changes in the technological capabilities of computers. In the 1950s, the focus of system’s development was placed on computerizing existing business processes such as purchasing or paying, often within single departments. All applications had to be developed in machine language and they had to be developed from scratch, as there was no software industry. In the beginning 1960s, the first procedural or third-generation computer programming languages were available and it was the beginning of software industry. Most organizations still developed their systems from scratch, using their in-house development staffs. System development was more of an art than a science. This view of systems development began to change in 1970s, however, as organizations began to realize how expensive it was to develop customized information systems. Systems development came to be more disciplined as many people worked to make it more like Page 1
Lesson 1
Introduction to Systems Analysis & Design
engineering. Early database management systems helped bring discipline to the storage and retrieval of data. The development of database management systems helped shift the focus of the systems development from processes first to data first. The 1980s, as computers continued to get smaller, faster, and cheaper, the software industry expanded greatly. Developers began to write more and more systems in fourthgenerations languages, which unlike procedural languages, instructed a computer on what to do instead of how to do it. Operating systems for computers moved away from line prompt interfaces to window and icon-based interfaces. Organizations moved to systems with more graphics. Organizations developed less software in-house and bought relatively more from software vendors. The systems developer’s job went through a transition from builder to integrator. The systems development environment in the 1990s focused on systems integration. Developers assemble systems by choosing and implementing specific modules. Starting in the middle years of the 1990s, more and more systems development efforts focused on the Internet, especially the Web. In the early years of the 2000s, there continued to focus on developing systems for the internet and for firms’ Intranets and Extranets. Another important development is the move to wireless components in systems. Wireless devices, such as cell phones and personal digital assistants (PDAs), e.g. Pocket PCs, are increasingly able to access Webbased applications from almost anywhere. Finally, the trend continues toward integrating systems from programs or components purchased off the shelf.
3. Developing Information Systems Developing an information system needs to follow a methodology. Most organizations find it beneficial to use a standard set of steps, called a systems development methodology, to develop and support their information systems. The systems development life cycle (SDLC) is a common methodology for systems development in many organizations, featuring several phases that mark the progress of the systems analysis and design effort. Every textbook author and information systems development organization uses a slightly different life cycle model, with anywhere from three to almost twenty identifiable phases. In this unit, we will look at two approaches of SDLC. The first approach is Structured Systems Analysis and Design (SSAD) developed by Ed Yourdon and his colleagues in the 1970s. The second approach is Object-oriented Systems Analysis and Design (OOSAD) which is based on object-oriented concepts and is different from the still-popular SSAD approach but the overall focus on the development of effective information systems is the same.
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Lesson 1
Introduction to Systems Analysis & Design
3.1 Structured Systems Analysis and Design (SSAD) The SSAD approach is essentially a process modeling-based SDLC methodology. Process modeling involves graphically representing the processes, or actions, that capture, manipulate, store, and distribute data between a system and its environment and among components within a system. A common form of a process model is a data flow diagram (DFD). A data flow diagram is a graphical diagram that illustrates the movement of data between external entities and the processes and data stores within a system. The structured approach also is based on the decomposition concept. A business process is decomposed into smaller processes, which in turn are decomposed into still smaller pieces, and the decomposition continues until a process of size appropriate for the problem at hand is obtained. DFDs were common mechanism for systems analysis during the 1980s. DFDs are excellent representation tools for studying processes, and a systems analyst should not ignore them merely because they are not the latest fad in the market. Despite the success of SSAD and DFD, there are still limitations pointed out by practitioners. 3.2 Object-oriented Systems Analysis and Design (OOSAD) During the 1990s, several researches and practitioners were working on a new approach based on the notion of an object. The methodologies developed before this, separated data and processes. Analysts found this division unnatural because a real-world object has properties (akin to data) and behavior (akin to processes). Using this perspective, there was no reason to separate the two in the information systems world. In an attempt to improve development productivity, the OOSAD approach was proposed. This approach combines data and processes (called methods) into single entities called objects. Objects usually correspond to real things an information system deals with, such as customers, suppliers, etc. Putting data and processes together in one place recognizes the fact that there are a limited number of operations for any given data structure. Putting data and processes together makes sense even though typical systems development keeps data and processes independent of each other. The goal of OOSAD is to make system elements more reusable, thus improving system quality and the productivity of systems analysis and design.
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