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

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?

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.

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.

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.  Business management and users will tend to identify logical locations where people do work or business.  Information technologists will tend to discuss physical locations where computer and networking technology is located.

System Concepts For Network Modeling  Business Geography  Example locations include:

System Concepts For Network Modeling  Business Geography  Logical locations can be:  scattered throughout the business for any given information system.  on the move (e.g., traveling sales representatives).  external to the enterprise for which the system is being built. For instance, customers can become users of an information system via the telephone or the Internet.  Logical locations can represent:  clusters of similar locations  organizations and agents outside of the company but which interact with or use the information system; possibly (and increasingly) as direct users

System Concepts For Network Modeling  Business Geography  Derivatives of the rectangle will be used to illustrate different types of locations.  The standard rectangle will be used to represent a specific location.  The rectangle with the double, vertical lines will be used to represent a cluster of locations.  Some locations are not stationary, a rounded rectangle will represent their mobility.  Some locations represent external organizations and agents (such as customers, suppliers, taxpayers, contractors, and the like). A parallelogram to illustrate these external locations.

System Concepts For Network Modeling  Business Geography  Location names should describe the location and/or its users.  Examples of location names follows:  Paris, FranceIndianapolis, IndianaGrissom Hall  Building 105Grant Street buildingRoom 222  WarehouseRooms Shipping Dock  Order ClerkUser names (as locations)Order Entry Dept.  CustomersOrder clerks (a cluster)Suppliers  Students

System Concepts For Network Modeling  Business Geography  Some locations consist of other locations and clusters.  It can be quite helpful to understand the relative decomposition of locations and types of location.  Decomposition is the act of breaking a system into its component subsystems. Each ‘level’ of abstraction reveals more or less detail (as desired) about the overall system or a 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 diagram shows the top down geographic decomposition of the business locations to be included in a system.

System Concepts For Network Modeling  Business Geography  The purpose of network modeling is to help system designers distribute the technical data, processes, and interfaces across the computer network.  The systems analyst needs to specify the technology-independent communications that must occur between business locations.  The communication between business locations requires connectivity.  Connectivity defines the need for, and provides the means for transporting essential data, voice, and images from one location to another.  Connections between locations represent the possibility of data flows between locations.

System Concepts For Network Modeling  Synchronizing of System Models  Data and Process Model Synchronization:  There should be one data store in the process models for each entity in the data model. Also, there are sufficient processes in the process model to maintain the data in the data model.  The synchronization quality check is stated as follows: Every entity should have at least one C, one R, one U, and one D entry for system completeness. If not, one or more event processes were probably omitted from the process models. More importantly, users and management should validate that all possible creates, reads, updates, and deletes have been included.

System Concepts For Network Modeling  Synchronizing of System Models  Data and Network Model Synchronization:  A data model describes the stored data requirements for a system as a whole.  The network model describes the business operating locations.  The goal is to identify what data is at which locations.  Specifically, the following business questions might be asked: Which subset of the entities and attributes are needed to perform the work to be performed at each location? What level of access is required? Can the location create, read, delete, or update instances of the entity?

System Concepts For Network Modeling  Synchronizing of System Models  Data and Network Model Synchronization: (continued)  System analysts have found it useful to define logical requirements in the form of a Data-to-Location-CRUD matrix. A Data-to-Location-CRUD Matrix is a table in which the rows indicate entities (and possibly attributes); the columns indicate locations; and the cells (the intersection rows and columns) document level of access where C = create, R = read or use, U = update or modify, and D = delete or deactivate.

System Concepts For Network Modeling  Synchronizing of System Models  Process and Interface Model Synchronization:  The  The context diagram was previously introduced as an interface model that documents how the system you are developing interfaces to business, other systems, and other organizations.  Data  Data flow diagrams document the system’s process response to various business and temporal events.  Both  Both models should be synchronized.

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.

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.