Presentation on theme: "Introduction to Systems Analysis. Basic Concepts"— Presentation transcript:
1 Introduction to Systems Analysis. Basic Concepts ITEC 3010 “Systems Analysis and Design, I”Lecture 1.aIntroduction to Systems Analysis. Basic Concepts[Prof. Peter Khaiter]
2 Lecture Outline General Systems Theory System’s Characteristics Feedback and ControlSystem’s StudyInformation SystemConcepts of SeparationTypes of Information SystemsSystems Analyst: problem solverIT and Strategic PlanningRMO Case Study: Intro
3 I. General Systems Theory 1. System’s ConceptDef. A System is a set of components that interact with one another and serve for a common purpose or goal.Systems may be: (1) abstract or (2) physical• An abstract system is conceptual, a product of a human mind. That is, it cannot be seen or pointed to as an existing entity. Social, theological, cultural systems are abstract systems. None of them can be photographed, drawn or otherwise physically pictured. However, they do exist and can be discussed, studied and analyzed.• A physical system, in contrast, has a material nature. It is based on material basis rather than on ideas or theoretical notions.
5 System’s Concept (cont’d) FIGURE 1-1 Characteristics of a system
6 2. System’s Characteristics (1 of 3) • A component is either an irreducible part or an aggregate of parts, also called a subsystem. The simple concept of a component is very powerful. For example, in case of an automobile we can repair or upgrade the system by changing individual components without having to make changes the entire system.• The components are interrelated; that is, the function of one is somehow tied to the function of the others. For example, in the Store system the work of one component, such as producing a daily report of customer orders, may not progress successfully until the work of another component is finished, such as sorting customer orders by date of receipt.
7 System’s Characteristics (2 of 3) • A system has a boundary, within which all of its components are contained and which establishes the limits of a system, separating it from other systems.• All of the components work together to achieve some overall purpose: the system’s reason for existing.• A system operates within an environment – everything outside the system’s boundary. The environment surrounds the system, both affecting it and being affected by it.E.g.: the environment of a university includes prospective students, foundations, funding agencies and the new media. Usually the system interacts with its environment. A university interacts with prospective students by having open houses and recruiting from local high schools.
8 System’s Characteristics (3 of 3) • The point at which the system meets its environment are called interface.• A system must face constraints in its functioning because there are limits to what it can do and how it can achieve its purpose within its environment. Some of these constraints are imposed inside the system (e.g., a limited number of staff available).Others are imposed by the environment (e.g., due to regulations).• A system interact with the environment by means of inputs and outputs. Input is anything entering the system from the environment; output is anything leaving the system crossing the boundary to the environment . Information, energy, and material can be both input and output in relation to the environment.E.g.: People take in food, oxygen, and water from the environment as input. An electrical utility takes on input from the environment in the form of raw materials (coal, oil, water power, etc), requests for electricity from customers. It provides for output to the environment in the form of electricity.
9 3. Feedback and Control in a System (1 of 4) Very often output data are being returned to the input of the system, as shown in Fig. 1-2, and used to regulate the system’s activity.FIGURE 1-2 Regulation of activity
10 Feedback and Control in a System (2 of 4) Such a process is called feedback. It helps to adjust the system to changes so that the system operates in a balanced state, or equilibrium.E.g.: Large hotels and motels, for instance, ask guests to fill out cards evaluating the services. This feature of a system is used in control.Def. Control is the process that measures current performance and guides it toward a predetermined goal.Two types of feedback are related to system control: (1) negative and (2) positive
11 Feedback and Control in a System (3 of 4) Negative feedback is corrective feedback that helps maintain the system within a critical operating range and reduces fluctuations around the norm or standard.Negative feedback is transmitted in feedback control loops.As shown in Figure 1-3, a sensor detects the effect of output on the external environment; this information is returned to the system as an input, and necessary adjustments are made according to predetermined goal.In contrast to negative feedback, which is corrective, positive feedback reinforces the operation of a system by causing it to continue its performance and activities without changes.
12 Feedback and Control in a System (4 of 4) FIGURE 1-3 Feedback control loops
13 4. Methods of system’s study (1 of 3) There are several important system’s concepts that help to study a system and understand its functioning:• Decomposition• Modularity• Coupling• CohesionDecomposition is the process of breaking down a system into its smaller components. These components may themselves be systems (subsystems) and can be broken down into their components as well. How does decomposition aid understanding of a system? It results in smaller and less complex pieces that are easier to understand than larger, complicated pieces.
14 Methods of system’s study (2 of 3) FIGURE 1-4 Decomposing a CD system
15 Methods of system’s study (3 of 3) Modularity is a direct result of decomposition. It refers to dividing a system into chunks or modules of a relatively uniform size. Modules can represent a system simply, making it easier to redesign and rebuild.E.g.: a portable CD player, as a system, accepts CDs and settings of volume and tone as inputs and produces music as output. It includes the separate systems as its subsystems: 1) read the digital signals from CDs; 2) amplify the signals; 3) turn the signals into sound waves; and 4) control the volume and tone of the sound (see Figure 1-4).Coupling means that subsystems are dependent on each other. But they should be as independent as possible. If one subsystem fails and other subsystems are highly dependent on it, the others will either fail themselves or have problems functioning.Cohesion is the extend to which a subsystem performs a single function. In the CD player example, signal reading is a single function.
16 5. “Systems” Thinking Being able to identify something as a system Involves being able to identify subsystemsIdentifying system characteristics and functionsIdentifying where the boundaries are (or should be)Identifying inputs and outputs to systemsIdentifying relationships among subsystems
17 II. Information Systems 1. Information System, Subsystem and SupersystemInformational nature of Control and ManagementPossible inputs and outputs: information, energy, and materialuse only informationInformation is the central core of feedback loops while regulating the system activities.Special systems for processing and handling information neededprovide management with information for making decisions
18 Information SystemsDef. An Information System (IS) is a collection of interrelated components that collect, process, store, and provide as output the information needed to complete a business task.E.g.: A payroll system collects information on employees and their work, processes and stores that information, and than produces paychecks and payroll reports for the organization. Then information is provided to manufacturing so the department can schedule production.
19 Hierarchy of Information Systems (1 of 3) Hierarchy: System, Subsystem, SupersystemE.g.: customer support system: order entry subsystem, order fulfillment subsystem, shipping and back order subsystem, product catalog maintenance, etc.Supersystem – a larger system that includes the system. The system is a subsystem of the larger supersystemE.g.: production system includes other systems, such as inventory management and manufacturing and customer support system (Figure 1-5)Different view of an information system: a list of its components: hardware, software, inputs, outputs, data, people, and procedures (Fig.1-6).
20 Hierarchy of Information Systems (2 of 3) FIGURE 1-5 Information systems and subsystems
21 Hierarchy of Information Systems (3 of 3) FIGURE 1-6 Information system and component parts
22 System Boundary vs. Automation Boundary System boundary: separates system from other systems and from its environmentAutomation boundary - separates the automated part of the IS (where work is done by computers) from the manual part (where work is done by the people).FIGURE 1-7 The system boundary vs. the automation boundary
23 2. Concepts of Separation (1 of 8) Separating Data from Processes That Handle DataEvery IS as a three-component system (Fig. 1-8):• data• data flows• processing logicData are raw facts that describe people, objects and events in organization (e.g. name, age, customer’s account number). Data is used in an IS to produce informationInformation is data organized in a form that human can interpretData flows are group of data that move and flow through a system. They include a description of the sources and destinations for each data flowProcessing logic describes the steps that transform the data and events that trigger these steps
24 Concepts of Separation (2 of 8) FIGURE 1-8 Data, Data Flow and Processing Logic.
25 Concepts of Separation (3 of 8) Two approaches to IS design:• Process-oriented• Data-oriented
26 Concepts of Separation (4 of 8) The process-oriented approach is based on what the system is supposed to do.The focus is on output and processing logic.Although the data are important, but are secondary to the application.Each application contains its own files and data storage capacity.E.g.: Figure 1-9(A): “personnel data” appears in two separate systems – payroll system and the project management system.If a single element changes, it has to be changed in each of the data files.This approach involves creating graphical presentations (data flow diagram and charts).
27 Concepts of Separation (5 of 8) The data-oriented approach: an ideal organization of data, independent of where and how data are used within the systemAvoids data duplication and redundancy (see Figure 1-9(B)).This approach uses data model that describes the kinds of data needed in the system and the business relationships among the data (i.e. business rules).Table 1-10 summarizes the differences between the two approaches.
28 Concepts of Separation (6 of 8) FIGURE 1-9 The Relationship Between Data and Applications:Process-Oriented ApproachData-Oriented Approach
29 Concepts of Separation (7 of 8) Table 1-10 Key Differences Between The Process-Oriented and Data-Oriented Approaches.
30 Concepts of Separation (8 of 8) Separating Databases from ApplicationsWhen the data-oriented approach is applied, databases are designed around subjects, such as customers, suppliers and parts.It allows to use and to revise databases for many different independent applications, what creates the principle of application independence (i.e. separation of data and definition of data from applications).
31 3. Types of Information Systems (1 of 5) Different types of activity require different types of information systems to support all the needs (e.g., transaction processing systems, management information systems, executive information systems, decision support systems, expert systems, communication support systems, and office support systems) - Figure 1-11Transaction processing systems (TPS) capture and record information about the transactions that affect the organization.A transaction occurs each time a sale is made, supplies are ordered, an interest payment is made.Usually these transactions create credit or debit entries in accounting ledgers.This kind of ISs were among the first to be automated by computers.Modern TPS use state-of-the-art technology, e.g., on-line TPS.
32 Types of Information Systems (2 of 5) FIGURE 1-11 Types ofInformationsystems
33 Types of Information Systems (3 of 5) Management information systems (MIS) are systems that take information captured by TPS and produce reports that management needs for planning and controlling the business.MIS are possible because the information has been captured by the TPS and placed in organizational databases.Executive information systems (EIS) provide information for executives to use in strategic planning.Some of the information comes from the organizational databases, but much of the information comes from external sources: news about competitors, stock market reports, economic forecasts, and so on.
34 Types of Information Systems (4 of 5) Decision support systems (DSS) allow a user to explore the impact of available options or decisions.Whereas an MIS produce reports, DSS provide an interactive environment in which decision makers can quickly manipulate data and models of business operations.A DSS has three parts: (1) the first part is composed of a database (which may be extracted from TPS or MIS); (2) the second part consists of mathematical or graphical models of business processes; (3) the third part is made up of a user interface (or dialogue module) that provides a way for the decision makers to communicate with the DSS.An EIS is a DSS that allows senior management to explore data starting at a high level of aggregation and selectively drill down into specific areas where more detailed information and analysis are required.
35 Types of Information Systems (5 of 5) Expert systems (ES) replicate the decision-making process rather than manipulating information.If-then-else rules or other knowledge representation forms describe the way a real expert would approach situations in a specific domain of problems.Typically, users communicate with an ES through an interactive dialogue. The ES asks questions (which an expert would ask) and the end user supplies the answers. Those answers are then used to determine which rules apply, and the ES provides a recommendation based on the rules.Communication support systems (CSS) allow employees to communicate with each other and with customers and suppliers. Communication support now includes , fax, Internet access, and video conferencing.Office support systems (OSS) help employees create and share documents, including reports, proposals, and memos. OSS also help to maintain information about work schedule and meetings.