SE-381Software Engineering

BEIT-V

Lecture # 20(Computer Aided Software Engineering (CASE) Tools)

Computer Aided Software Engineering (CASE)

– Encompasses wide range of Software programs that are used to support Sw Process activities such as Requirements Analysis, System Modeling, Debugging, Testing etc

– All methods/methodologies come with associated CASE Technology such as • Editors with specific notations, • Analysis tools to check system models, • Report Generators to create system documentation, • Code generators to generate source/skeleton code from

system model • Change Management tools to manage changes and system

configurations etc

CASE – Computer Aided (or Assisted) Software Engineering– Note – it is NOT ‘Computer Automated’– Computers are to Assist, and especially in

creative activities like Software Development, they cannot replace humans, the can only aid or assist

– CASE tools are around since the inception of SD arena, their form and shape is constantly improving. • Eg, these used to be Line or Text Editors for now

used context-sensitive Intelligent Editors

CASE Supports– Software process activities such as

Requirements Engineering, Design, Program Development, Testing, Documentation, Project Management, Configuration Management etc.

– CASE Tools include tools like • Design (Textual and Graphical) Editors• Data Dictionaries• Compilers, Debuggers, IPDEs, Context Sensitive

and Structure Editors,• System Building and Change management tools• Resource and Project Management tools• Reverse Engineering Tools etc

CASE Status [Som04]

– In 1980s and 1990s, it was hoped that CASE tools will bring in 3-4 fold productivity enhancement, but according to [Som04] this enhancement has been in the range of 40%.

– The main impediments for the progress has been• Software Development is a creative activity and still

computers and Sw will take a long time to do it without human interaction.

• SD is a team activity and most of the time is spent in mutual communication, CASE has still not addressed that domain

– The areas addressed by CASE are mostly the ones where the recurring procedures have been automated.

CASE Status [Sch07]

• Ref: Myers 1992• Reifer investigated 45 companies in 10 industries.

50% in IS, 25% RT Aerospace and 25% related to Scientific Areas

• Average Annual productivity gains 9% (RTA), 12% (IS). And Costs $125K per user of introducing CASE Technology

CASE Tools

• CASE Tools• handle the repetitive rigor / drudgery of the software process

and in there SD activities eg Word Processors and Drawing Systems facilitate software engineers to maintain up-to-date documentation and design by facilitating Change and easy Reproduction, but documentation is done by humans

• CASE tools help Sw Engineers to encounter complexity of the SD Eg maintenance of a Data Dictionary even of a moderate size software is manually not possible

• These are around since inception of software but their functionality, UI, reliability, form, … has lot changed

Why CASE?

• To – Enhance productivity of developers– Introduce Consistency in deliverables coming from

different phases, stages and tools– Counter rigor and drudgery involved in docum –

entation and analysis of complex software– Intelligently check Consistency and balancing of

different artifacts and diagrams – Support team work at analysis and design levels– Integrate inputs and outputs generated by different

tools for different phases of software development

Various Categorizations of CASE

– Different authors have defined various categories for CASE Tools, in general these are • Function Based CASE Categories [Som04]• Process or Activities Based CASE Categories

[Som04]• Coverage Based Categorization or classification

with Integration perspective [Som04, Sch02]• Depth Base Categorization [Sch02, Bit92]• Phase and Non-Phase wise Categorization and 1st

and 2nd Generations of CASE tools [Mal05]

Function Based Classification of CASE Tools [Sch02]

Activity Based Classification of CASE Tools [Som04]

Taxonomy / Classification of CASE (Depth Based)

– CASE tools can be specific to one or more activities of SDLC. A number of activities can constitute a Phase and vice versa

– There could be many tools to support the same activity and in contrast the functionality of a Sw tool can span to more than one activity

– Further an Activity Eg Coding, may comprise of multiple Tasks, Eg Editing, Compiling, Linking and Loading; and the boundaries of an activity and a phase may not be same.

– Nature wise CASE Tools are categorized by (Bitter 1992 and Schach 2004) as • Upper CASE or Front-End Tools which support the

Requirements, Specification, Planning and Design phases, and

• Lower CASE or Back-End Tools which assist in Implementation, Integration, Testing and Maintenance

Ref: CASE in G G Bitter (Editor); Macmillan Encyclopedia of Computers, 1991, Vol 1, Macmillan Pub Co NY (1992), pp:185-193

Data Dictionary (DD)• Keeps record of all data items i.e. system

variables, data structures - their variable names, data types and locations where each one of these is defined and used, Dimensions, Size etc and enables other parts of the tool (or Tools) to

– Use them– Check consistency of implementation of these data items

in different parts of the system– Ensure completeness i.e. all data items needed by

design are defined in DD and are specified in Specification document

– Provide data to different Report Generators (a component that generates the code needed to produce reports) and Screen Generators (which generate code to assist the developers for generating their Data Capture (input) screens and prototypes)

DD isthe back-bone of any CASE Tool as it integrates different parts of the tool and enables them to share data items unnoticeably and seamlessly

Workbenches

are combinations of various Sw tools to support one or more phases of SDLC Eg DD combined with the set of Graphical Representations, Screen & Report Generators, Consistency Checkers can form a workbench to Specification and Design phases

CASE Environmentsare the integration of Workbenches that support the whole or most part of the Software Process. Late 80s and Early 90s Borland’s Turbo series SDEs or Programming Environments to support Implementation, Integration and Testing phases.

Some Examples: ADW, Excelerator, Analyst/Designer, STP – Software Through Pictures, System Architect, TeamWork, ASCENT

Integration Based Classification

Tools, Workbenches and Environments in CASE – Another View

CASE Environment [Mal05]

Architecture of Repository (DD) Based Integrated CASE Tool [Som04]

CASE Architecture

Scope of CASE• CASE Tools have been around since Software

– Programming-in-the-Small – in Single module• Line-Editors to Page-Editors and Structure-Editors

– Programming-in-the-Large – at multi-Module or Code level• Debuggers and Optimizing Compilers have replaced core dumps

and segmentation faults• Dbx, Make – Unix utilities to debug and compile larger jobs

– Programming-in-the-Many – using teams• On-line Interface Checking – to cure arguments and object file miss-

matches• Non-Phase CASE Tools

– Project Management – MS Project, Prima Veirra– Configuration Management - Versioning, SCCS

Graphical Tool

• Additional features– Data dictionary – Screen and report generators– Consistency checker to ensure that various views

are always consistent • Specifications and design workbench

• Online Documentation– Problems with

• Manuals• Updating

• Essential online documentation– Help information – Programming standards– Manuals

CASE Tool for Structured and OOA/D

ASCENTAutomated Strict CASE Environment at

Teesside(Product of a University at UK)

Software Versions

– Software is composed of modules, each having numerous versions

– Different versions of constituting modules lead to different versions of Software

– For implementation, testing, operation one has to be very specific, which version is being referred

– For User support, or bugs eradication, the respective bugs are to be reproduced using respective versions

– During maintenance, at all times there are at least two versions of the product:• The old version, and • The new version

– Two types of versions: revisions and variations

Revisions and Variations

• Revision– Version to fix a fault in the module, replaces

its predecessor– We cannot throw away an incorrect version– Perfective and adaptive maintenance also

results in revisions– Different versions are to be kept in repository

to reproduce the errors being received, and to analyze and correct them

Revisions and Variations (contd)

• Variation– Version for different operating system–hardware– Variations are designed to coexist in parallel

Configuration Control

• Every module exists in three forms– Source code;

object code; executable load image

• Configuration– Version of each

module from which a given version of a product is built

Pareto Analysis

In any series of elements to be controlled, a selected, small fraction, in terms of the number of elements, always account for the large fraction in terms of effect

Vilfredo Pareto (1848 – 1923)

References

1. Ian Sommerville (2004); Software Engineering, 7th Ed, Pearson Education, New Delhi, Ch-4. (4.5) Computer Aided Software Engineering, pp 108-111

2. Rajib Mall (2005); Fundamentals of SE, 2nd Ed, Prentice-Hall of India, New Delhi, Ch-12 Computer Aided Software Engineering pp 302-309

3. Stephen Schach (2007)l Software Engineering, 7th Ed, Tata McGraw-Hill Publishing Company, New Delhi, Ch-5 (5.4-9) CASE tools, pp 330-341

4. CASE in G G Bitter (Editor); Macmillan Encyclopedia of Computers, 1991, Vol 1, Macmillan Pub Co NY (1992), pp:185-193