System Analysis and Design PDF

# SYSTEM ANALYSIS AND DESIGN ## Unit One: Organization and Information **Organization(s)** * A consciously coordinated social unit, composed of two or more people that functions on a relatively continuous basis to achieve a common goal or set of goals. * Persons or groups united for some purpose....

# SYSTEM ANALYSIS AND DESIGN ## Unit One: Organization and Information **Organization(s)** * A consciously coordinated social unit, composed of two or more people that functions on a relatively continuous basis to achieve a common goal or set of goals. * Persons or groups united for some purpose. * Can be described using system theory. * Consist of a process of accepting inputs to produce outputs. **Organization Study is Important in Two Dimensions** 1. To understand organization culture. 2. To analyze the impact of organizational change on a system. **Information** * Is a vital resource to every organization in its day-to-day operations. * Information system is a means of communicating within and other organizations. * The behavior of organizations has a significant impact on information systems. **Organization Culture** * Is a complex pattern of shared philosophies, ideologies, values, beliefs, assumptions, exceptions, attitudes & norms. * Has effects in four key ways: 1. Provides employees with an understanding of the organizations history & current approach. 2. Provides employees with shared feelings of working towards goals they believe in. 3. Provides a control mechanism to channel employee behavior towards what is desired and away from what is undesired. 4. Related to effectiveness & productivity in many ways. ## Information Technology * Is one of the largest sources of change in organizations. * Success use of information technology requires understanding the basic concepts of organization change. * Usage of latest information technology must be continuously involved with rapid change. ## Organizational Change * Has a significant relationship with information systems. * Usually resisted by individuals and groups within the organization who might perceive the change as a threat to their power or influence. * Organizational structure is often an impediment to change. Structure implies some degree of stability. * Organizations generally don't perform well when rapid change is occurring; thus, some stability is necessary. ## Systems in General * Organizations can also be described as composite systems. ### System * A set of interacting components that operates within a boundary for some kind of purpose. * Filters the types of flow rates of inputs and outputs between the system and its environment. ### Sub-System * Is a possible form of system within a system. * The ability to adjust the level of abstraction by altering the boundary. ### Components of a System * Are units (sub-systems) acting in combination with other units to modify inputs in order to produce outputs. * Components within a system don't have to be homogeneous. * Each component is separated from one another with a boundary. * In an information system, the boundary isn't physical in nature. * It is a region through which inputs and outputs pass during the transactions with the system’s environment, ## Defining the Boundary Of a System * Is an important function in systems analysis. * It is essential to know whether the given object or activity is within the boundary of the system. * Boundary is always considered as an essential criteria for determining the influence in a system. ## The Environment of A Sub-System * Anything outside the boundary of the system that influences the operation of the system and cannot be controlled by the analyst. * For example, weather is a part of the environment that influences vegetables in one’s garden for the cultivator of vegetables. ## Inputs * Are the energies taken into the system. * Classified into maintenance and signal. * _Maintenance_ energizes the system to make it ready to operate. * _Signal inputs_ are energies processed to produce the outputs. * For example, electricity and computer programs are maintenance inputs in a computerized information system. * Data is the raw material (signal input) processed as inputs in order to produce outputs as information ## Outputs * Are the resultant energies discharged from the system into the supra-system. * Classified as products, goods, or services, or both. * Useful to the supra-system. ## The Primary Medium Of The Systems Analyst Is Documentation * The intent of analysis is to examine and document all language and terminology should be as precise as possible. * This isn't to say that the documentation should be pompous or stilted, but rather that all parties would agree on the meaning of what has been written. ## System (Dictionary Definition) * A group of interacting, interrelated, or interdependent (business functions, processes, activities or elements) forming a complex whole. * A functionally related group of (business functions, processes, activities, or elements), for instance, a network of structures or channels, as for communication, travel or distribution (The American Heritage Dictionary, 4th College Edition). ## The Word “System” Has Many Meanings * It means different things in all contexts: * To the system is that which resides in the computer center and consists of programs or files being processed in an automated fashion. * To others, the system is a complex of procedures, work flows, and tasks that are performed to accomplish the requirements of the business. * To the system analyst, the system’s files are tapes & disks. * To the user, the system files are papers, folders, and drawers. * The user and the analyst agree that the system is the automated version. * To the system analyst, the system consists of jobs, programs, files, & software; those things which reside in the machine. * To the user, the system is what appears on a report or on a computer terminal screen. ## For The Purposes Of System Analysis, A System Is A Business System * Systems that are described and viewed from the user's perspective. * Analysts must understand the user's perspective. ## Interface * A term frequently used in systems analysis. * Is the region between the boundaries of systems. * Is the medium for transporting the output from one system to the input of another system. * Doesn’t alter the output of one system that is input to another system. * For example, air is the interface that transmits sound between two or more people on a conversation. * The interface between two computer systems can be a telephone line or microwave transmission system. ## Open Systems * A term widely used in information systems. * Refers to those systems that can inter-operate directly with hardware or software from multiple vendors. * Accepts inputs from the environment. * For example, a respirator system is an open system. ## Closed Systems * Can only use hardware and software from a single vendor. * Don’t interact with the environment. ## Feedback * Systems survive and adapt to their environment through feedback. * Is a process by which the output of a system is measured against the standard. * Output from the feedback in an information system is used in decision-making. * If the output isn’t relevant to the decisions, then the system is of little use to management. * Feedback loops are incorporated into a system to determine the relevance of output to the decision environment. * For example, a feedback loop in an information system is the inclusion standard costs in purchasing a system. ## IS (Information System) * A formalized computer system required for management decision-making. * Is a manual and computerized information system. * Information can be collected and stored through manual processes. * Manual information systems are becoming relatively less significant. * Information requirements of managers vary depending on their specific roles. * Within the organization, management levels are categorized into three levels. Expected information will vary from the lower level of management to the strategic level of management. ## The Three Levels Of Management’s Processes Information * **Strategic Information** * Can be both historical and futuristic (forecasted). * A mixture of subjective and objective information. * Satisfies the dual attributes of qualitative and quantitative constraint in information. * **Tactical Information** * Consists of forecasted historical data. * Largely objective in nature and voluminous in size. * **Operational Information** * Possesses the characteristics of historical information (as described above), objective in nature, and quantitative in volume, completeness, accuracy, precise, and detailed. ## Different Levels Within An Organization Need Different Types Of Information * The information systems providing that information must therefore vary so that appropriate information is provided to each level of management. * The information system must vary accordingly. ## In General Terms, There Are Three Basic Types Of Information Systems Required To Support The Three Levels Of Management. * **Strategic Level of Management** * Requires a wide range of information, like, operational, historical, informal and futuristic information. * For example, information systems at this level are decision support systems, executive information systems, and expert systems. * **Tactical Level Of Management** * **Operational Level Of Management** ## Issues & Principles in Systems Development **1. Business Strategy** * *Strategy* refers to long-term, overall planning. * *Business strategy* is the art and science of employing the resources of a firm to achieve its business objectives. * **Facilities Planning** - Determining how a firm's resources best support achieving the business objectives. * This is a strategic process and must be an integral part of overall corporate strategy. * A winning facilities plan must consider integrating all elements that will impact the plan. * If the relationship between manufacturing decisions and corporate strategy isn’t known, then a company may be stuck with some very non-competitive production systems that are expensive and time-consuming to change. * Manufacturing strategies must be integrated with the other elements of overall business strategy. **2. Functional Information** * Marketing decisions as one of the functional information can affect: * The location of facilities. * Marketing decisions about unit volume, packaging, and delivery times heavily influence the material handling system design. * Product design decisions affect the processing sequence and material requirements, which, in turn, affect the layout and material handling system. * Manufacturing decisions can affect the location and design of the facilities. * Production planning and inventory control decisions will impact the facilities plan. * Human resources and finance decisions will impact the site design o facilities as well as the number of facilities and location. ## Data Modeling * The analyst must be familiar with the major modeling techniques with their most appropriate application. * Entity-relationship modeling is one of the newest of least-documented modeling techniques; we will give particular emphasis to the entity-relationship model. ### Model * A representation, graphic, narrative, or both, of a physical or conceptual environment. * It must identify the major components of the environment, describe those components in terms of their major attributes, depict the relationship between the components, and describe the conditions under which the components exist and interact with each other. * It should depict, in graphic or narrative form, the entities and their relationship within the application environment. * It can be composed of several independent or interdependent sub-models. ### The Entity-Relationship Model * One of the newest modeling techniques and one of the most powerful is the entity-relationship model, or entity-relationship diagram, which is the modeling technique employed by the Entity-Relationship approach to analysis and design. * Dr. Peter Chen (in his 1976 paper): * Described the analytical basis for the entity-relationship approach. * Included a description of the modeling technique. * The multilevel analysis portion of the entity-relationship approach produces a series of entity definitions, each of which is accompanied by a diagrammatic representation of that level. * These diagrams are simple clear pictures of the environment in terms that any user can understand. ### Entity-Relationship Models (Diagrams) * Aren’t data structure models. * Although at their most detailed level, they contain and identify data elements; they aren’t data processing models. * Are business models. * Model business environments and depict business components. * Consist of representations of the various levels and parts of the organization, from the strategic to the operational level. ### The Three Basic Notation Components Of The Entity-Relationship Model. 1. Symbols representing an entity, a relationship between two entities, the attributes, or descriptors, of either entities or relationships. 2. These symbols are: * Entity Symbol * Relationship Symbol * Attribute Symbol ### Figure Describing Entity, Relationship, and Attribute Symbol: * **Rectangle:** Each unique entity type or subtype is represented by a rectangle. Contains the name of that unique entity type or subtype. * **Diamonds:** Represents each relationship that exists between any two different entities or between two occurrences of the same entity. Contains the name of the relationship. * **Circles:** Contains the name of that attribute represents each unique attribute of either an entity or a relationship. ### Entity-Relationship (ER) Models * Applied to individual business units, or to individual business functions. * The full ER approach model addresses the whole organization and each of its parts in a top-down manner (pyramid fashion). * The ER approach produces a different type of diagrams or set of diagrams for each of the three basic organizational levels (strategic, managerial & operational): * The enterprise level. * The entity-relationship level. * The relationship-attribute level. ### The Enterprise Level * Level One, the _e.i.l._, consists of an identification of the major entities of the firm and an indication as to whether a relationship exists between them. * The entities relationships are represented in binary state, that is, they either exist or they do not. * At this level, only the major entity classes are named. * By definition, there can only be one enterprise-level model. * Every firm, large or small, deals with many different types of entities in the course of conducting its business. * Although the names of the various entities will vary from firm to firm, at most, the general level, they can be grouped into four major categories: * People * Places * Physical things (a product, a machine, etc.) * Logical or legal things (a corporation, a business unit). * Using these four major categories, we can identify some of the most commonly occurring entities regardless of the type of business a company does: * **People Entities** fall into three major classes: * The people who make up the firm's workforce * The people who are its customers or clients. * The people who supply it with raw materials, products, parts, and financial or other services. * **Place or Location Entities** fall into three major classes: * The places where its services are offered, or its products are made, stored, or sold. * The places where its workforce is located, or otherwise located. * The places where its customers reside or are otherwise located. * **Physical Thing Entities** include: * The actual products of the firm, its physical assets, its financial assets, or the documents, memoranda, accounts, contracts, orders, invoices, statements, checks, vouchers, reports, and files which record its business transactions and activities. * **Logical or Legal Thing Entities** include: * The services offered by the firm. * The firms that are its customers or clients. * The firms or people who supply it with raw materials, products, parts, and financial or other services. * The markets within which the firm operates. * The governmental and regulatory units under whose jurisdiction the firm operates. * The original units into which the firm's workforce is grouped for business, functional, and reporting purposes. ## At The Enterprise Level * Entities are identified and named. * Relationships are defined as either existing or not existing between any given pair of entities. * All entities, relationships are viewed from a single perspective. * Business rules stated are at a strategic or policy level and apply firm-wide. * Business activities are stated as functions. * Business entities are portrayed at a Class or universal level. * There is no differentiation between the various subtypes of a given entity, unless those differences have meaning at a firm-wide or functional level. ## The Creation Of An Enterprise-Level Diagram Is A Two-Step Process. 1. Identify, select, name the relevant entities. 2. Connect each pair of related entities with a single line between them. ## The Entity-Relationship Level * Is an expansion of the enterprise level. * The entities which were previously identified only at the class level can now be brought into sharper focus. * Recognizes of names both of the different subtypes of the major entities, and the various distinct relationships that exist between them. * All models below the enterprise-level business model are more detailed. ## At The Managerial Level. * Entities and entity subtypes are named. * Each relationship between the pairs of entities or entity subtypes is identified. ## The Creation Of The Entity-Relationship-Attribute Diagram Is Also A Two-Step Process. 1. Begins with the major entities represented at the class level on the enterprise-level diagram and differentiate them into their meaningful components, subtypes, subclasses, etc. 2. Define each of the relationships between each primary entity and its related secondary entities. ## The Entity-Relationship-Attribute Level * Is similar to the Level Two diagrams with the exception that named attributes are added to both the entity and the relationship symbols. * Describe entities in terms of their attributes or characteristics. * Beyond just knowing that the entity exists, we must also know what the entity looks like, how it is identified, or what it does. ## The Creation Of An Entity-Relationship-Attribute Diagram Is A Multiple-Step Process. ## Documentation of The Model ### Diagrams * **Data Flow Diagrams.** * Yourdon De Marco are developers and primary proponents of data flow diagramming technique. * Depict data flows and data transformation processes. * **Data Transformation Process: ** * Transforms input data into some form of output data. ### Orientation of Data Flow Diagrams. * Toward business processes, the data that feed them. * Toward the data that they generate. * Toward the system level and resulting system-processing specifications. ### Data Flow Diagram * Utilizes three symbols. * **A circle** represents a process. * **A curved line with an arrowhead** represents the flow data to or from the process. * **Two short parallel lines** represent a data store. * **Rectangles** represent terminators. * **A terminator** is synonymous with a file and holds data between processes. * Data flow diagrams (all processes and data stores must have at least one input & one output). ### Data Flow Diagrams (Construction) * As with ER diagrams, data flow diagrams are constructed in stages or levels. * The first, or level Zero, diagram is called _the Context Diagram_ and contains a single bubble that represents the entire system. ### Flow Chart Diagrams * Are useful tools when one wishes to represent either the processing and decision logic flows within a particular process. ## Technological Impact On Analysis * Information technology (IT) is no longer a business resource, it is the business environment (_The Economist_, John Browning [1990]). * Not much attention has been given to the integration of technology or its use as a coordinating mechanism for organizational units. * IT should be studied as an independent variable affecting organizational structure.