Info Systems Wk 1

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DT249/4

Information Systems Engineering

Lecture 1

Information Systems Engineering:

Introduction

Information Systems • An information system is collection of

– hardware, software, data, people and procedures that are designed to generate information that supports the day-to-day, short-range, and long-range activities of users in an organization.

• Modern information systems solve a variety of data, information, and knowledge-based problems.

• Have always been built in order to satisfy some purpose.

• In the broad sense involve – computerized as well as manual routines, and

– include people involved as agents manipulating and conveying information that concern the things that are dealt within the organization.

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Types of Information Systems

• Pure communication systems – e-mail, voice-mail, synchronous and asynchronous

teleconferencing systems etc.

• Systems that simplify and rationalize normal office work – word processors, spreadsheet systems, and software that allows

you to prepare presentations etc.

• Individual expert support applications. – These may be knowledge-based such as in expert systems or

they may be simpler systems meant to support individuals such as e.g. salesmen, in their daily work.

• Systems that automate normal business transactions, – i.e. modern OLTP (on-line transaction processing) systems .

• Systems that provide strategic and tactic decision support, – i.e. executive information systems, often based on data

warehousing

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Types of Information Systems

• Office information systems

• Transaction processing systems (TPS)

• Management information systems (MIS)

• Decision support systems (DSS)

• Expert systems

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Office Information Systems

• An information system that uses hardware, software and networks to enhance work flow and facilitate communications among employees.

• Supports a range of business office activities such as creating and distributing graphics and/or documents, sending messages, scheduling, and accounting.

• Software: – word processing, spreadsheets, databases, presentation graphics, e-mail, Web

browsers, Web page authoring, personal information management, and groupware.

• Communications technology – voice mail, facsimile (fax), videoconferencing, and electronic data interchange (EDI)

for the electronic exchange of text, graphics, audio, and video.

• Also uses a variety of hardware, including computers equipped with modems, video cameras, speakers, and microphones; scanners; and fax machines.

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Transaction Processing Systems

• An information system that captures and processes data generated during an organization’s day-to-day transactions. – A transaction is a business activity such as a

deposit, payment, order or reservation.

• Batch processing. – With batch processing, transaction data is

collected over a period of time and all transactions are processed later, as a group.

• Online transaction processing systems (OLTP). – The computer processes transactions as they are

entered. 6

Management information systems (MIS)

• An Information system that generates accurate, timely and organized information so managers and other users can make decisions, solve problems, supervise activities, and track progress.

• Sometimes called a management reporting system (MRS). – as it generates reports on a regular basis

• Often integrated with transaction processing systems – E.g. To process a sales order, the TPS records the sale, updates the

customer’s account balance, and makes a deduction from inventory. Using this information, the related management information system can produce reports that recap daily sales activities; list customers with past due account balances; graph slow or fast selling products; and highlight inventory items that need reordering.

• Focuses on generating information that management and other users need to perform their jobs.

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Decision Support Systems

• An information system designed to help users reach a decision when a decision making situation arises.

• Some decision support systems include query language, statistical analysis capabilities, spreadsheets, and graphics that help you extract data and evaluate the results.

• Some also include capabilities that allow you to create a model of the factors affecting a decision. – E.g. A simple model for determining the best product price would

include factors for the expected sales volume at each price level. With the model, you can ask what-if questions by changing one or more of the factors and viewing the projected results.

• Many people use application software packages to perform DSS functions. – E.g. Using spreadsheet software you can complete simple modeling

tasks or what-if scenarios.

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Executive Information System (EIS)

• A special type of DSS – designed to support the information needs of executive

management

• Information in an EIS is presented in charts and tables that show trends, ratios, and other managerial statistics.

• Data warehouses – To store all the necessary decision-making data, DSSs or EISs

often use extremely large databases, called data warehouses.

– A data warehouse stores and manages the data required to analyze historical and current business circumstances.

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Expert Systems

• An expert system is an information system that captures and stores the knowledge of human experts and then imitates human reasoning and decision-making processes for those who have less expertise.

• Composed of two main components: – a knowledge base

• the combined subject knowledge and experiences of the human experts.

– the inference rules • are a set of logical judgments applied to the knowledge base each time a user

describes a situation to the expert system.

• Non-management employees are the main users – help with job-related decisions.

• Part of artificial intelligence (AI) branch

• Used in resolving diverse problems such as diagnosing illnesses, searching for oil and making soup.

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Integrated Information Systems

• With today’s sophisticated hardware, software and communications technologies, it is difficult to classify a system as belonging uniquely to one of the five information system types.

• Most of today’s application software supports transaction processing and generates management information.

• Other applications provide transaction processing, management information, and decision support.

• Organizations are consolidating their information needs into a single, integrated information system.

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• Engineering of information systems – our primary concern

• The process by which information systems are designed, developed, tested, and maintained.

• The application of engineering principles, founded on appropriate scientific and technological disciplines, to the creation, use and support of information systems for the solution of practical problems.

• Involves structured requirement analyses, functional modeling, prototyping, software engineering, and system testing, documentation, and maintenance.

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• Practical – concerned with the actual doing or use of something, rather than with

the theory and ideas

• Involves the activities of – Specification

• identifying, understanding users needs

– Design • solutions / alternatives to meet those needs

– Construction • building agreed solution to meet users needs

– Testing • ensuring solution ‘works’ as required

– Bringing into service • introducing into existing user environment

– Maintenance and enhancement • ensuring solution can be enhanced to meet additional requirements & if

necessary, corrected

– Quality assurance applied to all above.

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Information Systems Engineering - Scope

• The scope

– hardware components

• processors, networks and interface devices;

– software components

• including operating systems software, information

structure software, communications protocol and

application software; and

– the design, development and use of

standards and tools essential for the

engineering of information systems.

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• Attributes of properly engineered system – Fitness for purpose

• meeting users needs

– Range of functionality • Providing appropriate solution

– Economy and efficiency • Optimising performance requirements

– Reliability • Consistent, trustworthy in operation

– Cost-effectiveness • achieving financial versus technical ‘balance’

– Security and safety • health and safety, data, processing,

– Life cycle support • capable of upgrade, change, correction

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System Engineering

• In many cases, the software element of a system does not integrate properly or fails altogether because software engineers treat their system element (software) as if it existed in a vacuum. – It does not.

• What is a system? – A purposeful collection of inter-related components

working together to achieve some common objective. – A system may include software, mechanical, electrical and

electronic hardware and be operated by people.

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System Engineering

• Broader than software engineering

• Concerned with

– the services provided by the system,

– constraints on its construction, and

– operation and the ways in which it is used.

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Software Engineering

• The economies of ALL developed nations are

dependent on software.

• More and more systems are software controlled.

• Software engineering is concerned with theories,

methods and tools for professional software

development.

• Software engineering expenditure represents a

significant fraction of GNP in all developed

countries.

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What is software?

• Computer programs and associated documentation.

• Software products may be developed for a particular customer or may be developed for a general market.

• Software products may be – Generic - developed to be sold to a range of different

customers

– Bespoke (custom) - developed for a single customer according to their specification.

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Important Questions for Software

Engineers

• Why does it take so long to get software

finished?

• Why are development costs so high?

• Why can't we find all errors before we give

the software to our customers?

• Why do we continue to have difficulty in

measuring progress as software is being

developed?

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What is software engineering?

• An engineering discipline which is concerned with all

aspects of software production.

• Adopts a systematic and organised approach, uses

appropriate tools and techniques depending on the

problem to be solved, the development constraints and

the resources available.

• Uses notations (sometimes called method) and

processes.

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Software Costs

• Software costs often dominate system costs.

The costs of software on a PC are often greater

than the hardware cost.

• Software costs more to maintain than it does to

develop. For systems with a long life,

maintenance costs may be several times

development costs.

• Software engineering is concerned with cost-

effective software development.

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Hardware Characteristics

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Software Characteristics

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• Software is engineered, not manufactured

• Software does not ware out • does deteriorate

• no spare parts

• Most software is custom built rather than being

assembled from components

• Software is complex

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What is the difference between software

engineering and system engineering?

• System engineering is concerned with all aspects of

computer-based systems development including

hardware, software and process engineering.

– Software engineering is part of this process.

• System engineers are involved in system specification,

architectural design, integration and deployment.

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What is a software process?

• A set of activities whose goal is the development

or evolution of software

• Generic activities in all software processes are:

– Specification - what the system should do and its

development constraints

– Development - production of the software system

– Validation - checking that the software is what the

customer wants

– Evolution - changing the software in response to

changing demands

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What are the costs of software engineering?

• Roughly 60% of costs are development costs,

40% are testing costs. For custom software,

evolution costs often exceed development costs.

• Costs vary depending on the type of system

being developed and the requirements of

system attributes such as performance and

system reliability.

• Distribution of costs depends on the

development model that is used.

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Legacy Information Systems

• Older programs

• Why must it change? • software must be adapted to meet the needs of

new computing environments or technology. • software must be enhanced to implement new

business requirements.

• software must be extended to make it interoperable with other more modern systems or databases.

• software must be re-architected to make it viable within a network environment.

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Software Evolution

• Regardless of its application domain, size or

complexity, computer software will evolve over

time.

• Change (software maintenance) drives this

process and occurs when errors are corrected,

when the software is adapted to a new

environment, when the customer requests new

features or functions and when application is

reengineered to provide benefit in modern

context.

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Process Framework Activities

• Communication - customer collaboration and requirement gathering;

• Planning - establishes engineering work plan, describes technical risks, lists resource requirements, work products produced, and defines work schedule;

• Modeling

- Analysis of requirements

– Design

• Construction – Code generation

– Testing

• Deployment - software delivered for customer evaluation and feedback

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The Primary Goal of Any Software

Process: High Quality

Remember:

• High quality = project timeliness

Why?

• Less rework!

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References

• Chapters 1 and 2: Software and Software

Engineering, A Practitioner’s Approach, 8/e, R.S.

Pressman

• and

• Discovering Computers 2000, Concepts for a Connected

World, Web and CNN Enhanced; CourseTechnology,

1999

• Information Systems Engineering: What Is It?, B.

Wangler, A. Backlund

Documents

Info Systems Wk 1