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Objective of today’s lesson

Software engineering occurs as a consequence of a process called system engineering. Instead of concentrating solely on software, system engineering focuses on a variety of elements, analyzing, designing, and organizing those elements into a system that can be a product, a service, or a technology for the transformation of information or control. The system engineering process is called business process engineering when the context of the engineering work focuses on a business enterprise. When a product (in this context, a product includes everything from a wireless tele phone to an air traffic control system) is to be built, the process is called product engineering.

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Today’s Topics

System Engineering Concepts

Business Process Engineering

Product Engineering

Requirements Elicitation, Analysis & Specification

System Modeling

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System Engineering

Precedes software engineering“Put software into context”

Work flow & other human activitiesBusiness model

Business Process EngineeringFocus on a business enterprise

Product EngineeringFocus on a product to be built

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What is a “System”?

Types of systems:political, educational, avionics, banking,

manufacturing, …

Computer-based system:“A set of elements that are organized to accomplish some predefined goal by processing information”

Goals: Support a business function, develop a product, etc.

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System Elements

• Software• Hardware• People

• Database• Documentation• Procedures

These elements combine in a varietyof ways to transform information

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Software. Computer programs, data structures, and related documentation that serve to effect the logical method, procedure, or control that is required.

Hardware. Electronic devices that provide computing capability, the inter connectivity devices (e.g., network switches, telecommunications devices) that enable the flow of data, and electromechanical devices (e.g., sensors, motors, pumps) that provide external world function.

People. Users and operators of hardware and software.

Database. A large, organized collection of information that is accessed via software.

Documentation. Descriptive information (e.g., hardcopy manuals, on-line help files, Web sites) that portrays the use and/or operation of the system. Procedures. The steps that define the specific use of each system element or the procedural context in which the system resides.

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System Hierarchy

Each computer-based system can be part of a larger system

System Engineering HierarchyOrganize the systems into a set of layered

views (Figure 5.1)

Define the elements for a specific computer-based system in the context of the overall hierarchy of systems

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System Engineering Hierarchy

SoftwareEngineering

InformationStrategy Planning

Business AreaAnalysis

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Stated in a slightly more formal manner, the world view (WV) is composed of a set of domains (D;), which can each be a system or system of systems in its own right.

WV = {D1, D2, D3, . . . ~ Dn}Each domain is composed of specific elements (E~) each of which serves some

role in accomplishing the objective and goals of the domain or component:

Di _ {E1, E2, E3, . . . ' Em}Finally, each element is implemented by specifying the technical components (Ck)

that achieve the necessary function for an element:

Ej _ {C1, CZ, C3, . . . , Ck}In the software context, a component could be a computer program, a reusable pro

gram component, a module, a class or object, or even a programming language state ment.

It is important to note that the system engineer narrows the focus of work as he or she moves downward in the hierarchy just described. However, the world view portrays a clear definition of overall functionality that will enable the engineer to understand the domain, and ultimately the system or product, in the proper context.

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System Modeling

• System engineering is a modeling process

• For each view:– Define processes– Represent process behavior – List process assumptions – Define external and internal inputs– Model linkages (control, data, I/O)

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System engineering is a modeling process. Whether the focus is on the world view or the detailed view, the engineer creates models that

• 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.• Represent all linkages (including output) that will enable the engineer to bet ter understand the view.To construct a system model, the engineer should consider a number of restraining factor

System Modeling[1]

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System Modeling [2]

• Assumptions– range of allowable

data

• Simplifications– partition data into

categories

• Limitations– bounds on

functionality

• Constraints– guide the

implementation

• Preferences– indicate preferred

architecture (data, functions, technology)

Much of this information is derivedfrom customer requirements

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Business Process Engineering

• Data Architecture– Framework for the data objects used by

the business (+ relationships)

• Applications Architecture– Elements which transform data objects for

a business purpose

• Technology Infrastructure– Foundation for data & applications

architectures

Three different architectures must be analyzed and designed within the context of business objectives and goals

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BPEHierarchy

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Information Strategy Planning

• Focus: World View (entire business)

• Goals: – Isolate domains of the business

(engineering, marketing, sales, …)– Define data objects visible at the enterprise

level (+ relationships & data flow)