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Unit-10 Re-engineering

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Program : MCA

Semester :

Subject Code : MC 0084 (B)

Subject Name : Advanced Software Project Management

and Quality Assurance

Unit number : 10

Unit Title : Re-engineering

Lecture Number : 10

Lecture Title : Re-engineering

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The objectives of this lecture are to:

define re-engineering

describe the growing problems of software maintenance

distinguish between redevelopment vs. re-engineering

explain business process re-engineering

explain software re-engineering process model

List the technical problem of re-engineering

define common terminologies of software re-engineering

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Objectives

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Re-engineering

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Lecture Outline

Introduction

Growing problems of software maintenance

Re-development or Re-engineering

Business Process Re-engineering

Software Re-engineering Process Model

Technical Problems of Re-engineering

Terminology of Software Re-engineering

Summary

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Activity

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Re-engineering is a set of activities that are carried out to re-structure a

legacy system to a new system with better functionalities and conform to

the hardware and software quality constraint.

Legacy software (old method / technology) needs to be maintained even

though its quality, performance, reliability and maintainability are

deteriorating.Reasons for Re-engineering

Allow legacy software to quickly adapt to changing requirements.

Comply to new organisational standards

Upgrade to newer technologies / platforms / paradigms (e.g., object-

oriented).

Extend the softwares life expectancy.

Identify candidates for reuse

Improve software maintainability

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Introduction

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Growing Problems of Maintaining Software

Software maintenance is the modification of a software product to

correct errors, improve or adapt to new requirements.

Software errors can be very expensive: The most expensive

software errors involved a single line of source code and cost their

respective organisations $1.6 billion, $900 million and $245 million.

Software maintenance is very costly: Maintenance costs (includingpersonnel and hardware / software usage fees) run as high as 50-80%

of the software life cycle resources or $30 billion a year in the United

States alone.

Maintenance personnel are getting scarce: Software maintenance

faces problems such as frequent failure rates, Complex design,

Unpredictable ripple effects, Unreliable or missing documentation and

Loss of experienced maintenance programmers.

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Re-engineering problem become severe enough then redevelopment is

the traditional solution.

Following are the reasons not to prefer redevelopment:

o Critical corporate knowledge is contained within the legacy

software: If the legacy software has been in use for a long time in

an organisation, then it has most likely survived by providing acritical service.

o Legacy software is a valuable asset: According to some

estimates, software development runs about $8-20 per LOC.

o Reusable, re-engineered software costs much less than

redeveloped code: Estimates of reusing re-engineered software

is about $2-$5 per LOC.

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Redevelopment Vs Re-engineering

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Business Process Re-engineering (BPR) is the fundamental rethinking

and radical redesign of business processes, to achieve dramatic

improvements in critical, contemporary measures of performance, such

as cost, quality, service and speed.

Legacy software was developed to support business functions within the

traditionally vertical organisation structure. Thus, organisations havesoftware to support marketing, manufacturing, etc.

Software re-engineering uses new tools and techniques to capture the

software design information and breaks up into functionally cohesive

chunks. These chunks are then analysed and regrouped around the

newly identified key business process.

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Business Process Re-engineering

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Re-engineering takes time, costs significant amounts of money and

absorbs resources.

Re-engineering of information systems is an activity that will absorb

information technology resources for many years.

The steps of re-engineering are as represented in this following figure.

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Software Re-engineering Process Model

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Every software organisation should have an inventory of all applications.

It is spreadsheet model containing information that provides a detailed

description (e.g., size, age, business criticality) of every active

application.

By sorting this information according to business criticality, longevity,

current maintainability and other locally important criteria, candidatesfor reengineering appear.

Resources can then be allocated to candidate applications for

reengineering work.

The status of applications can change as a function of time and as a

result, priorities for reengineering will shift.

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Inventory Analysis

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Creating documentation is too time consuming. It is not possible to re-

create documentation for hundreds of computer programs.

Documentation must be updated, with the limited resources. A new

approach called document when touched is used. So that it may not

be necessary to fully re-document an application.

The system is business critical and must be fully re-documented. Asoftware organisation must choose the one that is most appropriate for

each case.

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Document Restructuring

(Contd)

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Reverse engineering derives one or more design and manufacturing

specifications for a product by examining actual specimens of the

product.

Reverse engineering for software is the process of analysing a program

in an effort to create a representation of the program at a higher level of

abstraction than source code. Reverse engineering is a process of design recovery. Reverse

engineering tools extract data, architectural and procedural design

information from an existing program.

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Reverse Engineering

(Contd)

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Some legacy systems have relatively solid program architecture, but

individual modules are coded in a way that is difficult to understand, test

and maintain.

In such cases, the code within the suspect modules can be restructured.

To accomplish this activity, the source code is analysed using a

restructuring tool. Violations of structured programming constructs are noted and code is

then restructured.

The resultant restructured code is reviewed and tested to ensure that no

anomalies have been introduced.

Internal code documentation is updated.

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Code Restructuring

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In most cases, data restructuring begins with a reverse engineering

activity.

Data objects and attributes are identified and existing data structures

are reviewed for quality.

When data structure is weak, the data are re-engineered.

Data architecture has a strong influence on program architecture. The algorithms that populate it, changes to the data will invariably result

in either architectural or code-level changes.

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Data Restructuring

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In an ideal world, applications would be rebuilt using an automated re-

engineering engine.

The old program would be fed into the engine, analysed, restructured

and then regenerated in a form that exhibited the best aspects of

software quality.

CASE vendors have introduced tools that provide a limited subset ofthese capability-ties that addresses specific application domains (e.g.,

applications that are implemented using a specific database system).

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Forward Engineering

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Mainframe-based organisations are interested in re-engineering face

downsizing / downloading of their software to run on these platforms.

An interface issue is introduced both for input to the tool and returning

its output to the production platform.

Re-engineering tools have a serious problem in handling software

written in multiple languages or with embedded macros, DBMS calls,etc.

Some re-engineering tools problem include significantly slower tool

response times, insufficient memory, downloading congestion and

difficulty in re-integrating different software modules.

Even the graphics will have problems displaying excessive design

information.

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Technical Problems of Re-engineering

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Terminologies of Re-engineering

SystemEngineering The top level process of engineering a system to meet overallrequirements

Software Re-engineering

The combination of sub-processes such as reverse engineering,

restructuring, re-documentation, forward engineering and

retargeting

Reverseengineering

The engineering process of understanding, analysing and

abstracting the system to a new form at a higher abstraction level

Forwardengineering

The set of engineering activities that consume the products and

artifacts derived from legacy software and new requirements to

produce a new target system

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A set of activities that are carried out to re-structure a legacy

system to a new system with better functionalities andconform to the hardware and software quality constraint is

known as re-engineering.

Business Process Re-engineering (BPR) is the fundamental

rethinking and radical redesigning of business processes to

achieve dramatic improvements in critical, contemporarymeasures of performance, such as cost, quality, service and

speed.

Software maintenance is the modification of a software

product to correct errors and to improve or adapt to new

requirements. The steps of re-engineering are: Inventory analysis,

document restructuring, reverse engineering, code

restructuring, data restructuring and forward engineering.

Summary

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U it 10 R i i

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1. What is re-engineering?

Ans: Re-engineering is a set of activities that are carried out tore-structure a legacy system to a new system with better

functionalities and conform to the hardware and software

quality constraint.

2. List the steps involved in software re-engineering process

model.

Ans: 1. Inventory analysis

2. Document restructuring

3. Reverse engineering

4. Code restructuring

5. Data restructuring

6. Forward engineering

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Check Your Learning

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Activity 1

Visit an organisation to find the growing problems for

maintaining software.

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Activity

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Documents

MC0084(B)-Unit-10-PPT.pptx