1. Software Development Through Software Reuse, CASE tools, Lecture 8

2. 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 2

3. Software Reuse Software reuse claims to improve: Quality: Error fixes accumulate from reuse to reuse Reliability: Well-tested components increase the reliability. Productivity: Less code has to be developed. Maintenance cost: Fewer defects, less maintainability. Time to market: Reduction of the time Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 3 Experience makes it clear that reuse is not always entirely safe. The explosion of the Ariane Five rocket is a vivid reminder to the developers of safety-critical software of what can happen if software is reused without proper care. The software used on the Ariane Five was originally intended for the Ariane Four and worked properly on that platform. However, the launch characteristics of the Ariane Four and Five rockets were different. Improper reuse of the Ariane Four software caused the Ariane Five to explode.

4. 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 4

5. 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 5

6. Software Reusability Framework Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 6

7. 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 7

8. 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 8

9. 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 9

10. 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. Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 10

11. Reusable assets An asset can be any artifact that is used in the development and maintenance of a software system Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 11

12. 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 12

13. 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 13

14. 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 14

15. 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 15

16. Benefits of Reuse Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 16 BenefitExplanation Increased dependabilityReused 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. Reduced process riskThe 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. Effective use of specialists Instead of doing the same work over and over again, application specialists can develop reusable software that encapsulates their knowledge.

17. Benefits of Reuse Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 17 BenefitExplanation Standards complianceSome 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. Accelerated development 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.

18. Approaches that support Software Reuse Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 18 ApproachDescription Architectural patternsStandard software architectures that support common types of application systems are used as the basis of applications. Design patternsGeneric abstractions that occur across applications are represented as design patterns showing abstract and concrete objects and interactions. Component-based development Systems are developed by integrating components (collections of objects) that conform to component- model standards. Application frameworks Collections of abstract and concrete classes are adapted and extended to create application systems. Legacy system wrapping Legacy systems are ‘wrapped’ by defining a set of interfaces and providing access to these legacy systems through these interfaces.

19. Approaches that support Software Reuse Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 19 ApproachDescription Service-oriented systems Systems are developed by linking shared services, which may be externally provided. Software product lines An application type is generalized around a common architecture so that it can be adapted for different customers. COTS product reuseSystems are developed by configuring and integrating existing application systems. ERP systemsLarge-scale systems that encapsulate generic business functionality and rules are configured for an organization. Configurable vertical applications Generic systems are designed so that they can be configured to the needs of specific system customers.

20. Approaches that support Software Reuse Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 20 ApproachDescription Program librariesClass and function libraries that implement commonly used abstractions are available for reuse. Model-driven engineering Software is represented as domain models and implementation independent models and code is generated from these models. Program generatorsA generator system embeds knowledge of a type of application and is used to generate systems in that domain from a user-supplied system model. Aspect-oriented software development Shared components are woven into an application at different places when the program is compiled.

21. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 21

22. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 22

23. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 23

24. 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. Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 24

25. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 25

26. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 26

27. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 27

28. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 28

29. 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. Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 29

30. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 30 A standard CASE architecture

31. 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 class- structure 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 high- level 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. Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 31

32. 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. Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 32

33. 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. Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 33

34. 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. Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 34

35. 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.). Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 35

36. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 36

37. 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 37 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST

38. Workbenches Programming Workbenches –Language compiler –Structured editor –Linker –Loader –Static & Dynamic analyser –Interactive debugger Testing workbenches –Test manager –Test data generator –Oracle - generates predicted results –File comparator –Report generator –Dynamic analyser –Simulator Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 38

39. 39 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST

40. 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 Adv Software Engineering, by Asst Prof Athar Mohsin, MSCS 19, MCS-NUST 40