Chapter 6 System Engineering 1 System Engineering l

Chapter 6 System Engineering 1

System Engineering l What is a computer-based system? l l Elements of a computer-based system l l l l A set or arrangement of elements that are organized to accomplish some predefined goal by processing information Software Hardware People Database Documentation Procedures Systems l A hierarchy of macro-elements 2

The Hierarchy e. g. , School Administrative Information System 3

System Modeling l l l Define the processes that serve the needs of the view under consideration. Represent the behavior of the processes and the assumptions on which the behavior is based. Explicitly define both exogenous and endogenous input to the model. l l l exogenous inputs link one constituent of a given view with other constituents at the same level of other levels; endogenous input links individual components of a constituent at a particular view. Represent all linkages (including output) that will enable the engineer to better understand the view. 4

Business Process Engineering (BPE) Uses an integrated set of procedures, methods, and tools to identify how information systems can best meet the strategic goals of an enterprise Focuses first on the enterprise and then on the business area Creates enterprise models, data models and process models Creates a framework for better information management distribution, and control 5

System Architectures l Three different architectures must be analyzed and designed within the context of business objectives and goals: l l l data architecture applications architecture technology infrastructure 6

System Architectures (cont. ) l Data architecture l l l Application architecture l l l provides a framework for the information needs of a business or business function i. e. , database schema encompasses those elements of a system that transform objects within the data architecture for some business purpose i. e. , programs Technology infrastructure l l provides the foundation for the data and application architectures i. e. , hardware, software, 7

The BPE Hierarchy l Information strategy planning (ISP) l Business area analysis (BAA) l processes/services modeled interrelationships of processes and data Application Engineering l strategic goals defined success factors/business rules identified enterprise model created a. k. a. . . software engineering modeling applications/procedures that address (BAA) and constraints of ISP Construction and delivery using CASE and 4 GTs, testing 8

The BPE Hierarchy (cont. ) The enterprise Information strategy planning (World view) Business area analysis (Domain view) A business area Processing requirement Information system Business system design (Element view) Software Engineering Construction & Integration (Detailed view) 9

Information Strategy Planning l Management issues l define strategic business goals/objectives isolate critical success factors conduct analysis of technology impact perform analysis of strategic systems Technical issues create a top-level data model cluster by business/organizational area refine model and clustering 10

Defining Objectives and Goals l l Objective—general statement of direction Goal—defines measurable objective: “reduce manufactured cost of our product” Subgoals: l decrease reject rate by 20% in first 6 months gain 10% price concessions from suppliers re-engineer 30% of components for ease of manufacture during first year Objectives tend to be strategic while goals tend to be tactical 11

Business Area Analysis l l l Define “naturally cohesive groupings of business functions and data” (Martin) Perform many of the same activities as ISP, but narrow scope to individual business area Identify existing (old) information systems / determine compatibility with new ISP model define systems that are problematic defining systems that are incompatible with new information model begin to establish re-engineering priorities 12

The BAA Process admin. manufacturing sales QC distribution acct eng’ring Process Flow Models Process Decomposition Diagram Data Model Matrices e. g. , entity/process matrix 13

Product Engineering l l Goal: To translate customer’s desire into a working product Consist of four system components l l Software Hardware Data People 14

Product Engineering (cont. ) 15

Product Architecture Template l Proposed by Hatley and Pirbhai, also known as Hatley. Pirbhai modeling 16

Architecture Flow Diagram (AFD) 17

SFD Hierarchy Top level AFD A B AFD for A AFD for B C AFD for C 18

System Modeling with UML l Deployment diagrams (Modeling hardware) l l Activity diagrams (Modeling software) l l Represent procedural aspects of a system element Class diagrams (Modeling data) l l Each 3 -D box depicts a hardware element that is part of the physical architecture of the system Represent system level elements in terms of the data that describe the element and the operations that manipulate the data Use-case diagrams (Modeling people) l Illustrate the manner in which an actor interacts with the system *These and other UML models will be discussed later 19

Deployment Diagram 20

Activity Diagram 21

Class Diagram 22

Use-Case Diagram Request bar code Request shunt control status Request box processing report CLSS operator Update product database Run system diagnostics 23