Systems analysis and design methods 7th whitten and benley chapter 07

Network Modeling Introduction  The chapter will address the following questions:      Why may network modeling become an important skill for applications developers in the next several years? What is the description network modeling and explain why it is important? What is the definition of a system in terms of locations, location types, and clusters? How can you factor a system’s or application’s locations into component locations using a special location decomposition diagram? How can you document the connections and essential data flows between locations using location connectivity diagrams (LCDs)? Network Modeling Introduction  The chapter will address the following questions:    What is the complementary relationship between network, process, and data models? How can you synchronize data, process, interface, and network models to provide a complete and consistent logical system specification? How is network modeling useful in different types of projects and phases? Network Modeling Network Modeling - Not Just For Computer Networks  Computer Networks   Have become the nervous system of today’s information systems The computer network is a physical component of an information system  Must be created to support the logical distribution of data, processes, and interfaces of an information system  Network modeling is a technique for documenting the geographic structure of a system Synonyms include distribution modeling and geographic modeling Network Modeling INFORMATION SYSTEMS FRAMEWORK FOCUS ON SYSTEM DATA FOCUS ON SYSTEM PROCESSES FOCUS ON SYSTEM GEOGRAPHY FAST Methodology Operating Locations Survey Phase (establish scope & project plan) FOCUS ON SYSTEM INTERFACES SYSTEM OWNERS (scope) Location Decomposition Data Requirements Business Processes Interface Requirements Communication Reqts EDI Cust S Y S T E M A N A L Y S T S SYSTEM USERS or der St Louis HQ ship order West Cust omers cat alog changes Products Catalog East Cust om ers cr edit credit LA Off ice (requirements) Study Phase (etablish system improvemetn objectives) ship order Indy Warehouse ship order NY Office service Maint enance Records Logical Data Model Logical Process Model Logical Interface Model Location Connectivity Diagram SYSTEM DESIGNERS (specification) SYSTEM BUILDERS (components) Database Technology (and standards) Software (and Hardware) Technology Interface Technology Networking Telchnology (and standards) (and standards) (and standards) Definition Phase (establish and prioritize business system requirements) Network Modeling Network Modeling - Not Just For Computer Networks  Computer Networks  The need for network modeling is being driven by a technical trend – distributed computing  Distributed computing is the assignment of specific information system elements to different computers which cooperate and interoperate across computer network A synonym is client/server computing; however, client/server is actually one style of distributed computing  The distributed computers include: • desktop and laptop computers, sometimes called clients • shared network computers, called servers • legacy mainframe computers and minicomputers Network Modeling System Concepts For Network Modeling  Today’s systems analyst must seek answers to new questions:       What locations are applicable to this information system or application? How many users are at each location? Do any users travel while using (or potentially using) the system? Are any of our suppliers, customers, contractors, or other external agents to be considered locations for using the system? What are the user’s data and processing requirements at each location? How much of a location’s data must be available to other locations? What data is unique to a location? Network Modeling System Concepts For Network Modeling  Today’s systems analyst must seek answers to new questions: (continued)    How might data and processes be distributed between locations? How might data and processes be distributed within a location? A network modeling tool is needed to document what we learn about a business system’s geography and requirements  Network modeling is a diagrammatic technique used to document the shape of a business or information system in terms of its business locations Network Modeling System Concepts For Network Modeling  Business Geography    Logical network modeling is the modeling of business network requirements independent of their implementation All information systems have geography The location connectivity diagram (LCD) models system geography independent of any possible implementation  A location connectivity diagram (LCD) is a logical network modeling tool that depicts the shape of a system in terms of its user, process, data, and interface locations and the necessary interconnections between those locations Network Modeling Buyers (20) on-the-road Suppliers (275) Purchasing Clerks (3) Atlanta Accounts Payable Office (Atlanta) Inventory Control Manager's Office (Atlanta) Central Warehouse (Atlanta) Distribution Center (New York) Distribution Center (Chicago) Distribution Center (Los Angeles) Network Modeling System Concepts For Network Modeling  Business Geography  The location connectivity diagram (LCD) illustrates two concepts – locations and connectivity  The concept of geography is based on locations • A location is any place at which users exist to use or interact with the information system or application It is also any place where business can be transacted or work performed Location   Business management and users will tend to identify logical locations where people work or business Information technologists will tend to discuss physical locations where computer and networking technology is located 10 Network Modeling System Concepts For Network Modeling  Synchronizing of System Models  Process and Network Model Synchronization:  Process models illustrate the essential work to be performed by the system as a whole  Network models identify the locations where work is to be performed  Some work may be unique to one location Other work may be performed at multiple locations  Before designing the information system, what processes must be performed at which locations should be identified and documented 27 Network Modeling System Concepts For Network Modeling  Synchronizing of System Models  Process and Network Model Synchronization:  Synchronization of the process and network models can be accomplished through a Process-to-Location-Association Matrix • A Process-to-Location-Association Matrix is a table in which the rows indicate processes (event or elementary processes); the columns indicate locations, and the cells (the intersection rows and columns) document which processes must be performed at which locations 28 Process Customer Application X Process Customer Credit Application X Process Customer Change of Address X X X X X X Warehose San Diego Sales San Francisco Warehouse Sales Bost on Account s Receivable Sales Warehouse Advert sing Market ing Kansas Cit y Process Cust omers Network Modeling X X X Process Internal Customer Credit Chnage Process New Customer Order X X X X Process Customer Order Cancellation X X X X Process Customer Change to Outstanding Order X X X X X X X Process Internal Change to Customer Order Process New Product Addition X Process Product Withdrawal from Market X Process Product Price Chnage X Process Product Chnage to Product Specification X X X Process Product Inventory Adjustment 29 X X Network Modeling The Process of Logical Network Modeling  Network Modeling during Strategic Systems Planning Projects  Many systems planning methodologies and techniques result in a network architecture to guide the design of all future computer networks and applications that use those networks  May be a traditional map, or a top-down decomposition diagram that logically groups locations  Association matrices are also typically used to provide an initial mapping of data entities to locations, and processes to locations 30 Network Modeling The Process of Logical Network Modeling  Network Modeling during Systems Analysis   During the study phase of systems analysis, a project team should review any existing network models, logical or physical In the definition phase of systems analysis, network modeling becomes more important  If a network model already exists, it is expanded or refined to reflect new application requirements  If a network model does not exist, a network model should be built from scratch 31 Network Modeling The Process of Logical Network Modeling  Looking Ahead to Systems Design   The logical application network model from systems analysis describes business networking requirements, not technical solutions In systems design, network models must become more technical – they must become physical network models that will guide the technical distribution and duplication of the other physical system components, namely, DATA, PROCESSES, and INTERFACES 32 Network Modeling The Process of Logical Network Modeling  Fact-Finding and Information Gathering for Network Modeling    Like all system models, network models are dependent on appropriate facts and information as supplied by the user community Facts can be collected by sampling of existing forms and files; research of similar systems; surveys of users and management; and interviews of users and management The fastest method of collecting facts and information, and simultaneously constructing and verifying the process models is Joint Application Development (JAD)  JAD uses a carefully facilitated group meeting to collect the facts, build the models, and verify the models – usually in one or two full-day sessions 33 Network Modeling The Process of Logical Network Modeling  Computer-Aided Systems Engineering (CASE) for Network Modeling   Network models should be stored in the repository Computer-aided systems engineering (CASE) technology provides the repository for storing various models and their detailed descriptions 34 Network Modeling How to Construct Logical Network Models  Location Decomposition Diagram   Decomposition diagrams are used to logically decompose and group locations Building The Location Decomposition Diagram    First, brainstorm your locations Think of all of the places where direct and indirect users of your system will be located To group locations in the decomposition diagram, keep similar locations on the same level or within the same branch of the tree Clustering reduces clutter through simplification; however, there is a danger of oversimplifying the model  Cluster a location or its users if the data and processing requirements for all users are expected to be the same 35 Network Modeling Member Services Sys Geography Prospective Members Marketing Office Members Advertising Office Indianapolis Sales Office Baltimore Warehouse Sales Office Warehouse Seattle Portland Sales Office Warehouse Sales Managers Sales Managers Sales Managers Order Entry Clerks Order Entry Clerks Order Entry Clerks 36 Network Modeling How to Construct Logical Network Models  Location Connectivity Diagram   Location connectivity diagrams can be initially drawn at a highlevel to communicate general information More detailed information can be added to subsequent diagrams In the following slides, the first location connectivity diagram drawn is a systemwide model It will include any external locations and locations that have sublocations The second diagram reveals an exploded view 37 Network Modeling Baltimore Prospective Members 575 miles indeterminate distance Indianapolis Seattle 2250 miles Members indeterminate distance 2250 miles Portland 38 Network Modeling Members (n) Indeterminate Distance Balt Order Entry Clerks (8) < 20 feet 575 miles Prospective Members (n) Indpls Warehouse Stations (3) Indeterminate Distance Indpls Order Entry Clerks (12) 2250 miles Balt Warehouse Stations (3) < 150 feet Balt Sales Managers (2) 200 miles Seattle Sales Managers (2) 2800 miles Port Warehouse Stations (2) < 50 feet 575 miles 580 feet < 40 feet 2250 miles Members (n) Indeterminate Distance Indpls Sales Managers (3) Members (n) Indeterminate Distance Seattle Order Entry Clerks (7) 250 feet Figure 7.10 Indpls Advertising Office (4) 39 50 feet Indpls Marketing Office (3) Network Modeling The Next Generation  The Next Generation   The demand for logical network modeling skills will remain strong so long as the trend towards distributed computing remains strong CASE tool support will evolve after methodologies, since CASE tool engineers are reluctant to invest time and effort prior to some semblance of a widely accepted methodological standard 40 Network Modeling Summary       Introduction Network Modeling - Not Just For Computer Networks System Concepts For Network Modeling The Process of Logical Network Modeling How to Construct Logical Network Models The Next Generation 41 ... SYSTEM DESIGNERS (specification) SYSTEM BUILDERS (components) Database Technology (and standards) Software (and Hardware) Technology Interface Technology Networking Telchnology (and standards) (and. .. subset of that system In systems analysis, decomposition allows you to partition a system into logical subsets of locations for improved communication, analysis, and design  A location decomposition... during Strategic Systems Planning Projects  Many systems planning methodologies and techniques result in a network architecture to guide the design of all future computer networks and applications