CSEB233 Fundamentals of Software Engineering
اسلاید 1: CSEB233 Fundamentals of Software EngineeringModule 4: Software DesignBadariah Solemon 2011
اسلاید 2: ObjectivesTo explain set of design principles, concepts, and practices. To describe four design models required for a complete design specification: data design, architectural design, user interface design, and component-level design.To introduce design support tools and evaluation.To introduce design specification document.Badariah Solemon 2011
اسلاید 3: What is Desig/900726Design creates a representation or model of the software but unlike the analysis model, the design model provides detail about:software architecture, data structures, interfaces, andcomponents that are necessary to implement the system.Why is it important? Because the model can be assessed for quality and improved before code is generated, tests are conducted, and more users are involved.Badariah Solemon 2011
اسلاید 4: Analysis Models Design ModelThe four design models: Each of the elements of the analysis/requirements model provides information that is necessary to create the design models required for a complete design specification.Badariah Solemon 2011
اسلاید 5: Characteristics of Good DesignAccording to McGlaughlin(1991):Must implement all of the explicit requirements contained in the analysis model, and it must accommodate all of the implicit requirements desired by the customer.Must be a readable, understandable guide for those who generate code and for those who test and subsequently support the software.Should provide a complete picture of the software, addressing the data, functional, and behavioral domains from an implementation perspective.Badariah Solemon 2011
اسلاید 6: Design PrinciplesAccording Davis(1995 ):The design process should not suffer from ‘tunnel vision.’ The design should be traceable to the analysis model. The design should not reinvent the wheel. The design should “minimize the intellectual distance” [DAV95] between the software and the problem as it exists in the real world. The design should exhibit uniformity and integration. Badariah Solemon 2011
اسلاید 7: Design Principle: Badariah Solemon 2011The design process should not suffer from ‘tunnel vision.’The design should not reinvent the wheel.Reinventing the wheel is a phrase that means to duplicate a basic method that has already previously been created or optimized by others.
اسلاید 8: Design Principles (cnt’d)The design should be structured to accommodate change. The design should be structured to degrade gently, even when irregular data, events, or operating conditions are encountered. Design is not coding, coding is not design. The design should be assessed for quality as it is being created, not after the fact. The design should be reviewed to minimize conceptual (semantic) errors.Badariah Solemon 2011
اسلاید 9: Generic Task Set for DesignRefer to the “Task Set” in page 222.Badariah Solemon 2011
اسلاید 10: Design ConceptsFundamental design concepts that span both traditional and OO software development include:Abstraction ArchitecturePatternsSeparation of concernsModularityInformation hidingFunctional IndependenceRefinementAspectsRefactoringOO Design conceptsDesign classesBadariah Solemon 2011
اسلاید 11: AbstractionDesigners should work to derive both procedural and data abstractions that serve the problem.Procedural abstraction – sequence of instructions that have a specific and limited functionData abstractions – a named collection of data that describes a data objectBadariah Solemon 2011
اسلاید 12: Abstraction (cnt’d)Badariah Solemon 2011door manufacturer model number type swing direction weightimplemented as a data structuredoordetails of enter algorithmimplemented with a knowledge of the object that is associated with “enter”
اسلاید 13: Abstraction (cnt’d)Data abstraction refers to, providing only essential features by hiding its background details. class result{int marks;float percentage;char name[20];void input();void output();} main(){bank b1;b1.input();b1.output();}b1 is an object calling input and output member functions, but that code is invisible to the object b1.Badariah Solemon 2011
اسلاید 14: Architecture Is concerned on:describing the fundamental organization of the system, identifying its various components and their relationships to each other, and the environment in order to meet the systems quality goals.Also, describe the overall structure of the software : organization of program modules, the manner in which these modules interact, and the structure of data used by the components.Badariah Solemon 2011
اسلاید 15: PatternsOnline pattern searching:http://inventors.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%Fpatents.uspto.gov%2Fpatft%2Findex.html Under Quick Search, try to search pattern no. 7669112.You will get ‘automated spell analysis’ pattern.Badariah Solemon 2011
اسلاید 16: Separation of ConcernsActually, it is a rule of thumb to define how modules should be separated to each other: different or unrelated concerns should be restricted to different modules.Suggests that any complex problem can be easily handled if it is sub-divided into pieces that can be solved independently. Why? So that a problem takes less time and effort to solve.Is manifested in other design concepts: modularity, aspects, functional independence and refinement.Badariah Solemon 2011
اسلاید 17: ModularityWhen software is divided into components (modules).Modularize a design: To ease the planning for implementation (coding, To define and deliver software increments,To easily accommodate changes,To efficiently test and debug program, andTo conduct long-term maintenance without serious side effects Badariah Solemon 2011
اسلاید 18: Modularity : ExamplexBadariah Solemon 2011#include <stdio.h>main() { …printf(“This program draws a rectangle”);…}#include <stdio.h>void print_menu(void);main() { …print_menu();…} /* end main */void print_menu(void) {printf(“This program draws a rectangle”);} /* end function */Without ModuleWith Modulevs.
اسلاید 19: Information HidingSuggests that modules should be specified and designed so that information (data structures and algorithm) contain within a module is inaccessible to other modules that have no need for such information.Implies that effective modularity can be achieved by defining a set of independent modules that communicate with one another only necessary information.Badariah Solemon 2011
اسلاید 20: Information Hiding (cnt’d)Serves as an effective criterion for dividing any piece of equipment, software or hardware, into modules of functionality. Provides flexibility. This flexibility allows a programmer to modify functionality of a computer program during normal evolution as the computer program is changed to better fit the needs of users. When a computer program is well designed decomposing the source code solution into modules using the principle of information hiding, evolutionary changes are much easier because the changes typically are local rather than global changes.Badariah Solemon 2011
اسلاید 21: Information Hiding: ExampleSuppose we have a Time class that counts the time of day:class Time{public:void Display();private: int ticks;};The Display() member function prints the current time onscreen. This member function is accessible to all. Its therefore declared public.By contrast, the data member ticks is declared private. Therefore, external users cant access it.Badariah Solemon 2011
اسلاید 22: Information Hiding: Example (cnt’d)Regardless of how Display() extracts the current timestamp from ticks, users can be sure that it will do the right thing and display the correct time onscreen.Badariah Solemon 2011
اسلاید 23: Functional Independence Achieved by developing independent modules – each module address a specific subset of requirements.Is assessed using cohesion and coupling.Cohesion - is an indication of the relative functional strength of a module.a cohesive module should (ideally) do just one thing.Coupling - is an indication of the relative interdependence among modules.depends on the interface complexity between modules, the point at which entry or reference is made to a module, and what data pass across the interface.Badariah Solemon 2011
اسلاید 24: Functional Independence (cnt’d) This class lacks cohesion:public class CashRegister { public void enterPayment(int dollars, int quarters, int dimes, int nickels, int pennies) . . . public static final double NICKEL_VALUE = 0.05; public static final double DIME_VALUE = 0.1; public static final double QUARTER_VALUE = 0.25; . . . }Badariah Solemon 2011
اسلاید 25: Functional Independence (cnt’d) The CashRegister, as described above, involves two concepts: cash register and coin Solution: Make two classes:public class Coin { public Coin(double aValue, String aName){ . . . } public double getValue(){ . . . } . . . } public class CashRegister { public void enterPayment(int coinCount, Coin coinType) { . . . } . . . } Badariah Solemon 2011
اسلاید 26: Functional Independence (cnt’d) Coupling:Badariah Solemon 2011
اسلاید 27: Refinement Badariah Solemon 2011openwalk to door;reach for knob;open door;walk through;close door.repeat until door opensturn knob clockwise;if knob doesnt turn, then take key out; find correct key; insert in lock;endifpull/push doormove out of way;end repeat
اسلاید 28: RefactoringAccording to Fowler (1999):Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code [design] yet improves its internal structure.”When software is refactored, the existing design is examined for redundancyunused design elementsinefficient or unnecessary algorithmspoorly constructed or inappropriate data structuresor any other design failure that can be corrected to yield a better design. Badariah Solemon 2011
اسلاید 29: Design Model ElementsData/Class DesignClass diagrams transformed into the design class realization and the data structures required to implement the software.Architectural DesignProvides high-level overview of the system with detailed descriptions to be given by other design elements.Defines the relationship between major structural elements of the software, the architectural styles and design patterns that can be used to achieve the requirements of the system and the constraints that affect the way in which the architecture can be implemented.Badariah Solemon 2011
اسلاید 30: Design Models (cnt’d)Interface DesignDescribes how the software communicates with systems that interoperate with it, and with human who use it.Component-Level DesignDefines the data structures, algorithms, interface characteristics, and communication mechanisms allocated to each software component or module.Badariah Solemon 2011
اسلاید 31: Data/Class Design Elementsexample: High-level DFDSource: http://yourdon.com/strucanalysis/wiki/index.php?title=Chapter_9Badariah Solemon 2011
اسلاید 32: Data/Class Design Elements (cnt’d)example: ERDSource: http://www.svgopen.org/2003/papers/SvgInterfaceElectricalSwitching/index.htmlBadariah Solemon 2011
اسلاید 33: Data/Class Design Elements (cnt’d)example: Class DiagramSource: http://www.agiledata.org/essays/objectOrientation101.htmlBadariah Solemon 2011
اسلاید 34: Architectural Design ElementsThe architectural model [Sha96] is derived from three sources: information about the application domain for the software to be built; specific requirements model elements such as data flow diagrams or analysis classes, their relationships and collaborations for the problem at hand, and the availability of architectural patterns (Chapter 12) and styles (Chapter 9). Badariah Solemon 2011
اسلاید 35: Architectural Design Elements (cnt’d)Example: architecture diagramSource: http://blog.tmcnet.com/blog/tom-keating/2004/10/index.asp?page=7Badariah Solemon 2011
اسلاید 36: Architectural Design Elements (cnt’d)Example: Architectural stylesSource: xBadariah Solemon 2011
اسلاید 37: Interface Design Elements External interfaces to other systems, devices, networks or other producers or consumers of informationBadariah Solemon 2011
اسلاید 38: Interface Design Elements (cnt’d) The user interface (UI)Badariah Solemon 2011
اسلاید 39: Component Design ElementsSource: http://edn.embarcadero.com/article/31863#component-and-deployment-diagransBadariah Solemon 2011UML Component Diagram
اسلاید 40: Design Support ToolsAll aspects of the software engineering can be supported by software tools:from project management software through tools for business and functional analysis, system design, code storage, compilers, translation tools, test software, and so on.However, tools that are concerned with analysis and design, and with using design information to create parts (or all) of the software product, are most frequently thought of as CASE tools. List of CASE tools: http://www.unl.csi.cuny.edu/faqs/software-enginering/tools.html Badariah Solemon 2011
اسلاید 41: CASE Tool: ExampleSource: http://www.ibm.com/developerworks/rational/library/10/whats-new-in-rational-software-architect-8/index.html Badariah Solemon 2011IBM Rational Software Architect
اسلاید 42: CASE Tool: Example (cnt’d)Source: http://www.sparxsystems.com/images/screenshots/platforms/databasemodeling_tn.jpg Badariah Solemon 2011Database Modeling: Enterprise Architect by Sparx Systems Pty Ltd.
اسلاید 43: Design EvaluationA good software design minimizes the time required to create, modify, and maintain the software while achieving run-time performance.“ (Shore and Chromatic, 2007)According to Elssamadisy (2007):Design quality is people-sensitive.For instance, design quality is dependent upon the programmers writing and maintaining the code.Design quality is change-specific.There are two general ways to make designs of higher quality with respect to this aspect: generalizing from the tools like design patterns, and using tests and refactoring as change-enablers.Badariah Solemon 2011
اسلاید 44: Design Evaluation (cnt’d)Modification and maintenance time are more important than creation time. Because:time spent in maintenance is much more than creation time of a software, and in iterative development, modification happens during the initial creation of the software.Design quality is unpredictable.Because quality is really dependant on the team developing the software. As the team changes, or evolves, then the design quality also evolves.You really only know how good a design is by it standing the test of time and modifications.Badariah Solemon 2011
اسلاید 45: Design Evaluation (cnt’d)Points to ponder: to maintain the quality of the design, we must maintain the theory of the design as the programming team evolves,That design quality is tied to the people who are building and maintaining the software(Shore and Chromatic, 2007). Badariah Solemon 2011
اسلاید 46: Design SpecificationIEEE Standard for Information Technology -Systems Design - Software Design Descriptions (IEEE 1016-2009) an improved version of the 1998 version.This standard specifies an organizational structure for a software design description (SDD). An SDD is a document used to specify system architecture and application design in a software related project.Provides a generic template for an SDD.Badariah Solemon 2011
اسلاید 47: SDD: ExamplesRefer to http://www.cs.uofs.edu/~dmartin/exsesrm.htm#_Toc514249734 Refer to SDDSample.docBadariah Solemon 2011
اسلاید 48: SummaryThis module has:Introduced set of design principles, concepts, and practices. Described four design models required for a complete design specification: data design, architectural design, user interface design, and component-level design.Introduced design support tools and evaluation.Introduced design specification document (SDD).Badariah Solemon 2011
اسلاید 49: ReferencesPressman, R. (2003). Software Engineering: A Practitioners Approach. 6th & 5th edition. New York: McGraw-Hill.Somerville I. (2001). Software Engineering. 6th edition. Addison Wesley http://www.allinterview.com/showanswers/66313.htmlhttp://www.augustana.ab.ca/~mohrj/courses/2006.winter/csc120/slides/ch09/ch09.htmlhttp://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=78 Shore, J. and Chromatic, (2007). The Art of Agile Development. OReilly Media.Elssamadisy, A. (2007). Defining Design Quality. http://www.infoq.com/news/2007/04/defining-design-quality Badariah Solemon 2011
نقد و بررسی ها
هیچ نظری برای این پاورپوینت نوشته نشده است.