Software Development
Through
Software Reuse, CASE tools,
Lecture 8
Software Reuse
• In most engineering disciplines, systems are
designed by composing existing components that
have been used in other systems.
– Software engineering has been more focused on original
development but it is now recognised that to achieve
better software, more quickly and at lower cost, we need
a design process that is based on systematic software
reuse.
– There has been a major switch to reuse-based
development over the past 10 years.
• “Reuse” means to “use” something again,
preferably “as-is”.
– In the SE context, software reuse is [Pressman97]:
• ...any
procedure that produces (or helps produce) a system by
reusing something from a previous development effort.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Software Reuse
• Software reuse claims to improve:
• • Experience
Quality: makes it clear that reuse is not always
entirely
• Errorsafe.
fixes accumulate from reuse to reuse
The explosion of the Ariane Five rocket is a vivid
• • Reliability:
reminder to the developers of safety-critical software
• Well-tested components increase the reliability.
of what can happen if software is reused without
• Productivity:
proper care.
• •Less
code
has to beused
developed.
The
software
on the Ariane Five was
originally intended
• Maintenance
cost: for the Ariane Four and worked
properly
that
platform.
• Fewer
defects,on
less
maintainability.
• However, the launch characteristics of the Ariane
• TimeFour
to market:
and Five rockets were different.
• •Reduction
of the
time of the Ariane Four software caused
Improper
reuse
the Ariane Five to explode.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Reuse Terminologies
• Library
– Set of individual functions or classes that can be reused mostly
independently (functional reuse).
• "a discrete, stand-alone, context independent part of a solution“
• C++ Standard Template Library (STL)
• Framework
– A unit of design reuse; coupling several library classes.
• "an abstract design for a particular kind of application"
• Component
– Independent unit of reuse.
– Technical definition by given set of import and export mechanism.
– Interface is usually restricted to an in/out mechanism.
• Automated parts (J2EE, interface query COM)
• API: Usually a framework plus library parts (for
instance JDK).
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Reused based Software Engineering
• An Approach to maximize the reuse of existing software
– Application system reuse
• The whole of an application system may be reused either by
incorporating it without change into other systems (COTS reuse) or
by developing application families.
– Component reuse
• Components of an application from sub-systems to single objects
may be reused.
– A pattern matching system developed as pert of text processing system,
can be reused in database management system
– Object and function reuse
• Software components that implement a single well-defined object or
function may be reused.
– Mathematical function , Object class using standard libraries
• Software systems and Components are potentially
reusable entities
– Expensive to modify for new situation
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Software Reusability Framework
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Reuse – General issues
• Software Reuse definition
– Software reuse is the process whereby an organization
defines a set of systematic operating procedures to
specify, produce, classify, retrieve, and adapt software
artifacts for the purpose of using them in its development
activities.
• Black box and white box reuse
– Black-box reuse aims to integrate assets into a target
system without modification of the original assets.
– White-box reuse, assets may be modified before
integration into target system.
• White box reuse is easier to realize, but yields a smaller benefit
than black box reuse because more effort is required for
understanding the asset and for redoing validation (e.g. testing)
for the modified asset.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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CBSE Vs Reuse
• From business perspective, CBSE and Reuse have the same
goals: increasing productivity and quality.
– Reuse aim at the dissemination of knowledge within an
organization.
– CBSE approaches focus on improving productivity by reduction
of development time and by improving flexibility of systems
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Reuse – General issues
• Economic issues
– Reuse based approaches emphasize cost reduction as a
means of increasing productivity.
• From an accounting perspective there are different ways of
achieving this.
– Paying back of the development and maintenance cost of assets
over multiple projects.
– Avoidance of cost in later projects through the use of results of
earlier projects.
– Consumer benefits: Reduced cost of
• Design, Document, Implement,
• Design tests, unit test, document tests, implement & execute tests
• Maintenance, tools, equipment
– Potential additional benefits are
• Improved sales due to increased quality or shorter time-to-market,
• Delivering product early.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Reuse- Technical Issues
• Reuse Methodology
– The reuse activity is divided into six major steps
performed at each phase in preparation for the next
phase.
– These steps are:
• Developing a reuse plan or strategy after studying the problem
and available solutions to the problem,
• Identifying a solution structure for the problem following the
reuse plan or strategy,
• Reconfiguring the solution structure to improve the possibility of
using predefined components available at the next phase,
• Acquiring and modifying predefined components,
• Integrating the components into the products for this phase, and
• Evaluating the products.
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Reusable assets
• An asset can be any artifact that is used in the
development and maintenance of a software system
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Reuse Assets
• Requirements
– Typically requirements process involve analysts and domain
experts.
• They codify important domain knowledge.
– Organizations that make multiple systems in the same domain can
benefit from reusing requirements.
– In the transition from requirements to architecture, analysis
models and feature models may be reused.
• Architectures
– Architectures are the result of discussions of experienced
architects.
– Architectures codify valuable knowledge about systems in a
specific domain, and may be the most commonly reused
assets.
• The presence of design rationale is important for knowing whether
some design decisions need to be reconsidered when an
architecture is used in a different context.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Reuse Assets
• Design
– A design is a moderately detailed specification of a
subsystem or part of a subsystem.
• Design assets can be generic or specific to a domain or
application.
– The most widespread generic design-level assets are
probably design patterns.
• A design pattern is a solution to a commonly recurring problem.
• More and more support for the (re)use of patterns is being
integrated in software development tools.
• A typical example of a domain specific design level
asset is a UML model.
– Such a UML model may be reused as the basis for
implementations on different platforms or for subsequent
designs.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Reuse Assets
• Implementation
– Program code is the most common type of
implementation artifact.
• Different types of data may be valuable assets.
– for example:
• Executable, source, macro’s, scripts for building/compiling,
configuration files, template’s, libraries
– Reuse of program code is attractive because it
immediately provides tangible results.
– Data: for example
• In route-navigation system, the key data is the set of roads and
their GPS positions.
• A hospital information system maintains a list of possible medical
diagnoses.
• A computer game may contain graphic designs (fonts, characters,
scenery) that can be used in other games.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Reuse Assets
• Quality Assurance / Validation
– Assets that may be reused across projects for quality
assurance are:
• Review and inspection forms (e.g. checklists)
• Testing: Reuse test scenario’s e.g. after a modification/extension
of the system.
• Test scenario’s capture knowledge about typical faults.
• Documentation templates
• Operating System or Database System? reuse?
Assets??
– OS or DB system is typically not considered reuse.
• As a rule of thumb, if a component is not considered as part of the
design of a system, it is not considered as being reuse.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Benefits of Reuse
Benefit
Explanation
Increased dependability
Reused software, which has been tried and
tested in working systems, should be more
dependable than new software. Its design and
implementation faults should have been found
and fixed.
The cost of existing software is already known,
whereas the costs of development are always a
matter of judgment. This is an important factor for
project management because it reduces the
margin of error in project cost estimation.
Reduced process risk
Effective
specialists
use
of Instead of doing the same work over and over
again, application specialists can develop
reusable software that encapsulates their
knowledge.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Benefits of Reuse
Benefit
Explanation
Standards compliance
Some standards, such as user interface
standards, can be implemented as a set of
reusable components.
For example, if menus in a user interface are
implemented using reusable components, all
applications present the same menu formats
to users.
The use of standard user interfaces improves
dependability because users make fewer
mistakes when presented with a familiar
interface.
Bringing a system to market as early as possible
is often more important than overall development
costs. Reusing software can speed up system
production because both development and
validation time may be reduced.
Accelerated
development
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Approaches that support Software Reuse
Approach
Description
Architectural patterns Standard software architectures that support
common types of application systems are used as
the basis of applications.
Design patterns
Generic abstractions that occur across applications
are represented as design patterns showing
abstract and concrete objects and interactions.
Component-based
Systems are developed by integrating components
development
(collections of objects) that conform to componentmodel standards.
Application
Collections of abstract and concrete classes are
frameworks
adapted and extended to create application
systems.
Legacy system
Legacy systems are ‘wrapped’ by defining a set of
wrapping
interfaces and providing access to these legacy
systems through these interfaces.
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
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Approaches that support Software Reuse
Approach
Service-oriented
systems
Software product
lines
Description
Systems are developed by linking shared
services, which may be externally provided.
An application type is generalized around a
common architecture so that it can be adapted
for different customers.
COTS product reuse Systems are developed by configuring and
integrating existing application systems.
ERP systems
Large-scale systems that encapsulate generic
business functionality and rules are configured
for an organization.
Configurable vertical Generic systems are designed so that they can
applications
be configured to the needs of specific system
customers.
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Approaches that support Software Reuse
Approach
Program libraries
Model-driven
engineering
Program generators
Aspect-oriented
software
development
Description
Class and function libraries that implement
commonly used abstractions are available for
reuse.
Software is represented as domain models and
implementation independent models and code is
generated from these models.
A generator system embeds knowledge of a type
of application and is used to generate systems in
that domain from a user-supplied system model.
Shared components are woven into an
application at different places when the program
is compiled.
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CASE
• Computer-Aided Software Engineering:
– The use of software tools to assist in the development and
maintenance of software.
• Tools used to assist in this way are known as CASE Tools.
– program editors, debuggers, code analyzers, Web
development tools, Database management tools
– CASE tool is a computer-based product aimed at supporting
one or more software engineering activities within a software
development process
• Process modeling and management tools, Project planning tools,
Risk analysis tools, Project management tools, Requirement tracing
tools
• Prerequisites to tool use
– Need a collection of useful tools that help in every step of
building a product
– Need an organized layout that enables tools to be found
quickly and used efficiently
– Need a skilled craftsperson who understands how to use the
tools effectively
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CASE Tools
• CASE tools are those software which are used in any
and all phases of developing an information system,
including:
– Analysis, design and programming.
• For example, data dictionaries and diagramming tools aid in the
analysis and design phases,
• Application generators speed up the programming phase.
– CASE tools provide automated methods for designing and
documenting traditional structured programming techniques.
• The ultimate goal of CASE is to provide a language for describing the
overall system that is sufficient to generate all the necessary
programs needed.
• Properly used, CASE tools help improve productivity
during the development process and the quality of the
resulting system
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Components of CASE Tools
• The components of CASE Tools are categorized
into:
– UpperCASE Tool:
• Supports the software development activities upstream from
implementation.
– Focus on the analysis phase (but sometimes also the design
phase) like (diagramming tools, report and form generators, and
analysis tools)
» Requirements, specification, planning and design
– LowerCASE Tool:
• Directly supports the implementation (programming) and
integration tasks.
– Support database schema generation, program generation,
implementation, testing, and configuration management.
» Implementation and maintenance
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Components of CASE Tools
– I CASE:
• Tools that integrate both upper and lower CASE:
– For example making it possible to design a form and build the
database to support it at the same time.
• An automated system development environment that
provides numerous tools to create diagrams, forms and
reports.
– It also offers analysis, reporting, and code generation facilities
and seamlessly shares and integrates data across and
between tools.
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Functions of a CASE Tool
• Analysis:
– CASE analysis tools automatically check for incomplete,
inconsistent, or in correct specifications in diagrams, forms and
reports.
• Design:
– Technical blueprint of the system is created by:
• Designing the technical architecture
• Designing the systems model
– Graphically creating a model from graphical user interface, screen
design, and databases, to placement of objects on screen
• Code generation:
– Enable the automatic generation of program and data base
definition code directly from the documents, diagrams, forms,
and reports.
• Documentation:
– CASE Tool has documentation generators to produce technical
and user documentation in standard forms
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Classifications of software tools
• Sommerville suggests three dimensions such as:
– Functionality, Process Support, and Breadth of Support with
which software tools can be classified
• Emphases on Functionality and Process Support in the SDLC
– Software tools can support one or more phases in the form of
Workbenches or Environments
• Tools and methods can be classed into general
categories –
–
–
–
–
–
Data Modelling
Model and Program Transformation
Refactoring
Source Code Generation
Unified Modelling Language
Documentation
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CASE Tools Classification
• Process modeling and management tools
– represent key elements of processes and provide links to
other tools that provide support to defined process
activities
• Project planning tools
– used for cost and effort estimation, and project scheduling
• Risk analysis tools
– help project managers build risk tables by providing
detailed guidance in the identification and analysis of risks
• Requirements tracing tools
– provide systematic database-like approach to tracking
requirement status beginning with specification
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CASE Tools Classification
• Metrics and management tools
– management oriented tools capture project specific metrics that
provide an overall indication of productivity or quality, technically
oriented metrics determine metrics that provide greater insight into
the quality of design or code
• Documentation tools
– provide opportunities for improved productivity by reducing the
amount of time needed to produce work products
• System software tools
– network system software, object management services, distributed
component support, and communications software
• Quality assurance tools
– metrics tools that audit source code to determine compliance with
language standards or tools that extract metrics to project the quality
of software being built
• Database management tools
– RDMS and OODMS serve as the foundation for the establishment of
the CASE repository
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CASE Tools Classification
• Prototyping tools
– enable rapid definition of screen layouts, data design,
and report generation
• Programming tools
– compilers, editors, debuggers, OO programming
environments, fourth generation languages, graphical
programming environments, applications generators, and
database query generators
• Web development tools
– assist with the generation of web page text, graphics,
forms, scripts, applets, etc.
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CASE architecture
• CASE is an environment that
supports the software
engineering process:
– consists of distinct tools:
• Editing tools, programming
tools, v&v tools,
configuration management
tools, metrics and
measurement tools e.t.c
– central repository:
• the most critical component
in a CASE environment
• CASE Repository is nothing
more than an off-the-shelf
DBMS into which
specification information is
directly placed
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A standard CASE architecture
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CASE architecture
• Editing tools
– Include traditional tools (such as word-processing and
programming editors)
• Helps in creating documentation and diagramming tools that
provide graphical capabilities such as:
– Drawing a data flow diagram , entity-relationship diagram , or classstructure diagram .
• Programming tools
– Coding and debugging tools are the standard tools used
to compile (or interpret), run, and debug a program.
– Code generators are tools that write code from a highlevel specification of an application. For example:
• In an OO application a code generator might write the code for the
class given the object-class diagrams.
• In a visual programming, a code generator might write the code
for the underlying interface given a user interface.
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CASE architecture
• Verification and validation tools
– Verifiers ensure that the syntax is correct.
• Ensures that the requirements are correct and the product functions
are the functions desired or requested by the customer.
– Within this classification is a variety of tools:
• Static analyzers generate cross-references, check for syntax, and
enforce standards on a program without executing the code.
• Dynamic analyzers (tracers and profilers), monitor program
execution.
• Comparators check for differences or similarities between files;
– They are used for checking test output and expected program results.
• Correctness proof assistants prove mathematically the correctness of
the code and evaluate the consistency between the code and the
specification.
• Test management tools include test case generators that generate a
variety of input test data based on the test criteria and the program’s
input data structures.
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CASE architecture
• The repository: All the tools are integrated via the
repository.
– A holding area for storing and integrating diagrams, descriptions,
specifications, test data, and other items relevant to the development
process.
– Allows users and developers to share information, supports team-based
developmental activities, provides a mechanism for integrating a diverse set
of CASE tools.
• Repository models must be open and extensible (must
accommodate other vendors’ tools).
– Focus on standardization
• For example, Rational’s CASE tool allows the import and export of their
models to Microsoft’s repository product.
• Vendors are also starting to provide access to the data in their
repositories via the World Wide Web.
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Integration CASE
• Integration in a CASE environment takes place
along four dimensions.
– Data integration:
• Ensures that the data are managed in a consistent manner across
the entire environment.
– Control integration:
• Allows for combining the various tools and functions according to
the needs of the project and the environment it supports.
– Presentation integration:
• Allows the users to see a consistent interface across the entire
tool spectrum.
– Process integration:
• Ensures that tools interact effectively in support of a specific
process.
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CASE Workbenches
• Workbenches provide integration for only a portion of
the system development life cycle.
– Upper CASE tools support the earlier phases (problem
definition, analysis, and design), but provide little or no support
for the back end (code generation, implementation, etc.).
– Lower CASE tools support the design, implementation, testing,
and maintenance phases of the system development life cycle
(in general the back end).
• Typical lower CASE tools include application generators for dialogue
design, screen painting, code generation, etc.
• They provide little or no support for the earlier phases of the
development life cycle.
• Both upper and lower CASE tools work in conjunction
with implementation or programming workbenches
(editors, compilers, debuggers, test tools, etc.).
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CASE Workbenches
• A coherent set of tools that is designed to support
related software process activities such as analysis,
design or testing
– Analysis and design workbenches support system modelling
during both requirements engineering and system design
– These workbenches may support a specific design method or
may provide support for a creating several different types of
system models
• Advantages:
– Tools can work together to provide more comprehensive
support
– Common services can be implemented and called by all the
tools
– Integration possible through shared files, shared repository, or
shared data structures
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An analysis and design workbench
• Analysis & design workbench components:
–
–
–
–
–
–
–
–
Diagram editors
Model analysis and checking tools
Repository and associated query language
Data dictionary
Report definition and generation tools
Forms definition tools
Import/export translators
Code generation tools
Data
Structured
diagramming
tools
Report
generation
facilities
Code
generator
Central
information
repository
Query
language
facilities
Forms
creation
tools
Design, analysis
and checking
tools
Import/export
facilities
dictionary
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Workbenches
• Programming
Workbenches
–
–
–
–
–
Language compiler
Structured editor
Linker
Loader
Static & Dynamic
analyser
– Interactive debugger
Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST
• Testing workbenches
– Test manager
– Test data generator
– Oracle - generates
predicted results
– File comparator
– Report generator
– Dynamic analyser
– Simulator
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Testing Workbenches
• Testing is an expensive process phase.
– Testing workbenches provide a range of tools to reduce
the time required and total testing costs
– Most testing workbenches are open systems because
testing needs are organization-specific
– Difficult to integrate testing with closed design and
analysis workbenches
Test data
generator
Specification
Test
manager
Test data
Oracle
Dynamic
analyser
Program
being tested
Test
results
Test
predictions
Execution
report
Simulator
Source
code
File
comparator
Report
generator
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Test results
report
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Further reading
• Increasing Software Quality through Design Reuse
by Fernando Barros
• A Comparison of Software Reuse in Software
Development Communities by Meena Jha the
University of New South Wales,
• A Reuse-Based Software Development
Methodology by K. C. Kang
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