Analysis and Design with UML Copyright © 1997 by Rational Software Corporation 1

Copyright © 1997 by Rational Software Corporation Agenda Benefits of Visual Modeling History of the UML Visual Modeling with UML The Rational Iterative Development Process Copyright © 1997 by Rational Software Corporation 2

What is Visual Modeling? Business Process Order Item Ship via “Modeling captures essential parts of the system.” Dr. James Rumbaugh Computer System Visual Modeling is modeling using standard graphical notations Core Message: Modeling captures essential parts of the system Key Point 1: Computer system basically automate business processes. However, it’s not easy to build software systems on time and within budget. Key Point 2: Building a complex software system requires blueprint. You don’t construct a building without a blueprint. Visual modeling is the blueprint for software systems. Conclusion: VM is a key to successful software development Copyright © 1997 by Rational Software Corporation 3

Visual Modeling Captures Business Process Use Case Analysis is a technique to capture business process from user’s perspective Core Message: VM captures business process Key Point 1: Understanding business process is hard. If an architect and developers don’t understand the business process, which is the requirement for the system, you can’t build the proper system. Key Point 2: Use case is a technique to capture business process from user’s perspective. Use case is easy to understand because business process is defined in textual format, not in computer lingo. Example: Use the previous slide to describe use case. The system may handle order entry, inventory, and payroll processes. This particular use case only looks at order entry process. Conclusion: VM captures business process Copyright © 1997 by Rational Software Corporation 4

Visual Modeling is a Communication Tool Use visual modeling to capture business objects and logic Core Message: VM is a communication tool. Key Point 1: Business analyst and domain experts define requirements. Software architects and developers build systems based on requirements. Typically, they have communication problems due to different use of terminology and different definition of concepts. Key Point 2: Take a look at the Rose development team. The team is distributed in three cities around the world; Sweden, Milwaukee, and Philadelphia. There is a common language - visual modeling. Key Point 3: With VM, there is a smooth transition between business domain and computer domain. Also, you can establish traceability from business domain to computer domain. Conclusion: VM is a communication tool. Use visual modeling to analyze and design your application Copyright © 1997 by Rational Software Corporation 5

Visual Modeling Manages Complexity Core Message: VM manages complexity Key Point 1: This is a model of typical system. Sale has information about purchase order, sales person, and customer. In a system, you may get hundreds or thousands of these things (or objects). Key Point 2: Human mind can only handle 7 plus or minus things at once. VM allows you to raise your level of abstraction. There are constructs to group things into more manageable number of things. Example: One new developer joins the group. How do you describe your software system? Conclusion: VM manages complexity Copyright © 1997 by Rational Software Corporation 6

Visual Modeling Defines Software Architecture User Interface (Visual Basic, Java) Business Logic (C++, Java) Database Server (C++ & SQL) Core Message: VM defines software architecture Key Point 1:Model of a system is essentially a software architecture. You can then map it to the physical architecture. For example, this is a three tier architecture - mapping logical to physical. Key Point 2: Model your system independent of the implementation language. Technology change too much too fast. A few years ago, C++ was the language of the future but today it’s Java. How do you plan to change your system from PowerBuilder to Visual Basic? Reuse models. Conclusion: VM defines software architecture Model your system independent of implementation language Copyright © 1997 by Rational Software Corporation 7

Visual Modeling Promotes Reuse Multiple Systems Reusable Components Core Message: VM promotes reuse. Key Point 1:On previous slide, we talked about reusing a model. Key Point 2:There is a higher leverage of reuse. Reusing parts of the system or an application. For example, a component is an application in a binary format, whether the component is made of objects or not. VM can be used as a component browser and it can also be used to model component assembly. Conclusion: VM promotes reuse. Copyright © 1997 by Rational Software Corporation 8

Copyright © 1997 by Rational Software Corporation What is the UML? UML stands for Unified Modeling Language The UML combines the best of the best from Data Modeling concepts (Entity Relationship Diagrams) Business Modeling (work flow) Object Modeling Component Modeling The UML is the standard language for visualizing, specifying, constructing, and documenting the artifacts of a software-intensive system It can be used with all processes, throughout the development life cycle, and across different implementation technologies Copyright © 1997 by Rational Software Corporation Core message -- second bullet UML can be used to communicate system and software design throughout the life cycle 9

Copyright © 1997 by Rational Software Corporation History of the UML Nov ‘97 UML approved by the OMG Walk the audience through the timeline. Point out that the UML is the natural successor to the notations. 1. Late ‘80s and early ‘90 - there are many (50+) OO methodologies 2. Among the first generation methodologies, Booch and OMT stood out 3. Around 1993, second generation methodologies came out - Booch ‘93 and OMT-II. Methodologist borrowed good concepts from each others so many concepts were the same across the methodologies, but different notations. 4. Oct. 1994 - Dr. James Rumbaugh joined Rational to unify Booch & OMT. 5. At OOPSLA ‘95, Grady and Jim announced Unified Method 0.8. 6. Use Case technique developed by Dr. Ivar Jacobson was adapted by all methodologies by then. 7. Rational acquires Objectory in fall of ‘95 - Dr. Ivar Jaconson joins Rational. 8. Jun of ‘96 - Rational submits UML 0.9 to OMG. 9. UML gains industry support from HP, Microsoft, Oracle + 16 others 10. UML is the defacto standard for OO and component technologies 11. The final submission goes in Sep. ‘97 - expect the announcement in Dec. Copyright © 1997 by Rational Software Corporation 10

UML Supports Application Development Relationships Objects Business Objects large scale system ORDBMS Oracle Classes application partitioning Components Microsoft Scenarios CORBA OMG Use Cases ActiveX/COM Microsoft Transition: So! Who should use UML? Everybody who is doing software development. Core Message: UML supports object and component-based technology. Key Point 1: UML is an expressive language that can be used to describe pretty much everything about software application. - object technology: objet, class, relationships, scenario, Use Case - component-based development: component, ActiveX/COM, CORBA - large scale system, application partitioning Business Process Copyright © 1997 by Rational Software Corporation 11

Copyright © 1997 by Rational Software Corporation UML Concepts The UML may be used to: Display the boundary of a system & its major functions using use cases and actors Illustrate use case realizations with interaction diagrams Represent a static structure of a system using class diagrams Model the behavior of objects with state transition diagrams Reveal the physical implementation architecture with component & deployment diagrams Extend your functionality with stereotypes Copyright © 1997 by Rational Software Corporation The last set of slides briefly introduces most of the UML notations. NOTE: Not all notations are covered due to time constraints 12

Copyright © 1997 by Rational Software Corporation Putting the UML to Work The ESU University wants to computerize their registration system The Registrar sets up the curriculum for a semester One course may have multiple course offerings Students select 4 primary courses and 2 alternate courses Once a student registers for a semester, the billing system is notified so the student may be billed for the semester Students may use the system to add/drop courses for a period of time after registration Professors use the system to receive their course offering rosters Users of the registration system are assigned passwords which are used at logon validation Copyright © 1997 by Rational Software Corporation 13

Copyright © 1997 by Rational Software Corporation Actors An actor is someone or some thing that must interact with the system under development Registrar Professor Student Billing System Copyright © 1997 by Rational Software Corporation 14

Copyright © 1997 by Rational Software Corporation Use Cases A use case is a pattern of behavior the system exhibits Each use case is a sequence of related transactions performed by an actor and the system in a dialogue Actors are examined to determine their needs Registrar -- maintain the curriculum Professor -- request roster Student -- maintain schedule Billing System -- receive billing information from registration Maintain Schedule Maintain Curriculum Request Course Roster Copyright © 1997 by Rational Software Corporation 15

Copyright © 1997 by Rational Software Corporation Documenting Use Cases A flow of events document is created for each use cases Written from an actor point of view Details what the system must provide to the actor when the use cases is executed Typical contents How the use case starts and ends Normal flow of events Alternate flow of events Exceptional flow of events Copyright © 1997 by Rational Software Corporation 16

Maintain Curriculum Flow of Events This use case begins when the Registrar logs onto the Registration System and enters his/her password. The system verifies that the password is valid (E-1) and prompts the Registrar to select the current semester or a future semester (E-2). The Registrar enters the desired semester. The system prompts the professor to select the desired activity: ADD, DELETE, REVIEW, or QUIT. If the activity selected is ADD, the S-1: Add a Course subflow is performed. If the activity selected is DELETE, the S-2: Delete a Course subflow is performed. If the activity selected is REVIEW, the S-3: Review Curriculum subflow is performed. If the activity selected is QUIT, the use case ends. ... Copyright © 1997 by Rational Software Corporation 17

Copyright © 1997 by Rational Software Corporation Use Case Diagram Use case diagrams are created to visualize the relationships between actors and use cases Request Course Roster Professor Student Maintain Schedule Billing System Maintain Curriculum Registrar Copyright © 1997 by Rational Software Corporation 18

Uses and Extends Use Case Relationships As the use cases are documented, other use case relationships may be discovered A uses relationship shows behavior that is common to one or more use cases An extends relationship shows optional behavior Register for courses <<uses>> Logon validation Maintain curriculum Copyright © 1997 by Rational Software Corporation 19

Copyright © 1997 by Rational Software Corporation Use Case Realizations The use case diagram presents an outside view of the system Interaction diagrams describe how use cases are realized as interactions among societies of objects Two types of interaction diagrams Sequence diagrams Collaboration diagrams Copyright © 1997 by Rational Software Corporation 20

Copyright © 1997 by Rational Software Corporation Sequence Diagram A sequence diagram displays object interactions arranged in a time sequence : Student registration form registration manager math 101 math 101 section 1 1: fill in info 2: submit 3: add course(joe, math 01) 4: are you open? 5: are you open? 6: add (joe) 7: add (joe) Copyright © 1997 by Rational Software Corporation 21

Collaboration Diagram A collaboration diagram displays object interactions organized around objects and their links to one another : Registrar course form : CourseForm theManager : CurriculumManager aCourse : Course 1: set course info 2: process 3: add course 4: new course Copyright © 1997 by Rational Software Corporation 22

Copyright © 1997 by Rational Software Corporation Class Diagrams A class diagram shows the existence of classes and their relationships in the logical view of a system UML modeling elements in class diagrams Classes and their structure and behavior Association, aggregation, dependency, and inheritance relationships Multiplicity and navigation indicators Role names Copyright © 1997 by Rational Software Corporation 23

Copyright © 1997 by Rational Software Corporation Classes A class is a collection of objects with common structure, common behavior, common relationships and common semantics Classes are found by examining the objects in sequence and collaboration diagram A class is drawn as a rectangle with three compartments Classes should be named using the vocabulary of the domain Naming standards should be created e.g., all classes are singular nouns starting with a capital letter Copyright © 1997 by Rational Software Corporation 24

Copyright © 1997 by Rational Software Corporation Classes ScheduleAlgorithm RegistrationForm RegistrationManager Course Student Professor CourseOffering Copyright © 1997 by Rational Software Corporation 25

Copyright © 1997 by Rational Software Corporation Operations The behavior of a class is represented by its operations Operations may be found by examining interaction diagrams registration form manager 3: add course(joe, math 01) RegistrationManager addCourse(Student,Course) Copyright © 1997 by Rational Software Corporation 26

Copyright © 1997 by Rational Software Corporation Attributes The structure of a class is represented by its attributes Attributes may be found by examining class definitions, the problem requirements, and by applying domain knowledge CourseOffering number location time Each course offering has a number, location and time Copyright © 1997 by Rational Software Corporation 27

Copyright © 1997 by Rational Software Corporation Classes ScheduleAlgorithm RegistrationForm RegistrationManager addStudent(Course, StudentInfo) Course name numberCredits open() addStudent(StudentInfo) Student name major Professor name tenureStatus CourseOffering location open() addStudent(StudentInfo) Copyright © 1997 by Rational Software Corporation 28

Copyright © 1997 by Rational Software Corporation Relationships Relationships provide a pathway for communication between objects Sequence and/or collaboration diagrams are examined to determine what links between objects need to exist to accomplish the behavior -- if two objects need to “talk” there must be a link between them Three types of relationships are: Association Aggregation Dependency Copyright © 1997 by Rational Software Corporation 29

Copyright © 1997 by Rational Software Corporation Relationships An association is a bi-directional connection between classes An association is shown as a line connecting the related classes An aggregation is a stronger form of relationship where the relationship is between a whole and its parts An aggregation is shown as a line connecting the related classes with a diamond next to the class representing the whole A dependency relationship is a weaker form of relationship showing a relationship between a client and a supplier where the client does not have semantic knowledge of the supplier A dependency is shown as a dashed line pointing from the client to the supplier Copyright © 1997 by Rational Software Corporation 30

Finding Relationships Relationships are discovered by examining interaction diagrams If two objects must “talk” there must be a pathway for communication RegistrationManager Course Registration Manager Math 101: Course 3: add student(joe) Copyright © 1997 by Rational Software Corporation 31

Copyright © 1997 by Rational Software Corporation Relationships RegistrationForm RegistrationManager Course Student CourseOffering Professor addStudent(Course, StudentInfo) name numberCredits open() addStudent(StudentInfo) major location tenureStatus ScheduleAlgorithm Copyright © 1997 by Rational Software Corporation 32

Multiplicity and Navigation Multiplicity defines how many objects participate in a relationships Multiplicity is the number of instances of one class related to ONE instance of the other class For each association and aggregation, there are two multiplicity decisions to make: one for each end of the relationship Although associations and aggregations are bi-directional by default, it is often desirable to restrict navigation to one direction If navigation is restricted, an arrowhead is added to indicate the direction of the navigation Copyright © 1997 by Rational Software Corporation 33

Multiplicity and Navigation RegistrationForm RegistrationManager Course Student CourseOffering Professor addStudent(Course, StudentInfo) name numberCredits open() addStudent(StudentInfo) major location tenureStatus ScheduleAlgorithm 1 0..* 1..* 4 3..10 0..4 Copyright © 1997 by Rational Software Corporation 34

Copyright © 1997 by Rational Software Corporation Inheritance Inheritance is a relationships between a superclass and its subclasses There are two ways to find inheritance: Generalization Specialization Common attributes, operations, and/or relationships are shown at the highest applicable level in the hierarchy Copyright © 1997 by Rational Software Corporation 35

Copyright © 1997 by Rational Software Corporation Inheritance RegistrationForm RegistrationManager Course Student CourseOffering Professor addStudent(Course, StudentInfo) name numberCredits open() addStudent(StudentInfo) major location tenureStatus ScheduleAlgorithm name RegistrationUser Copyright © 1997 by Rational Software Corporation 36

Copyright © 1997 by Rational Software Corporation The State of an Object A state transition diagram shows The life history of a given class The events that cause a transition from one state to another The actions that result from a state change State transition diagrams are created for objects with significant dynamic behavior Copyright © 1997 by Rational Software Corporation 37

State Transition Diagram Add Student / Set count = 0 Add student[ count < 10 ] [ count = 10 ] Cancel Initialization Open do: Initialize course do: Finalize course do: Notify registered students entry: Register student exit: Increment count Canceled Closed Copyright © 1997 by Rational Software Corporation 38

Copyright © 1997 by Rational Software Corporation The Physical World Component diagrams illustrate the organizations and dependencies among software components A component may be A source code component A run time components or An executable component Copyright © 1997 by Rational Software Corporation 39

Copyright © 1997 by Rational Software Corporation Component Diagram Register.exe Billing.exe Billing System Course.dll People.dll Course User Course Offering Student Professor Copyright © 1997 by Rational Software Corporation 40

Copyright © 1997 by Rational Software Corporation Deploying the System The deployment diagram shows the configuration of run-time processing elements and the software processes living on them The deployment diagram visualizes the distribution of components across the enterprise. Copyright © 1997 by Rational Software Corporation 41

Copyright © 1997 by Rational Software Corporation Deployment Diagram Registration Database Main Building Library Dorm Copyright © 1997 by Rational Software Corporation 42

Copyright © 1997 by Rational Software Corporation Extending the UML Stereotypes can be used to extend the UML notational elements Stereotypes may be used to classify and extend associations, inheritance relationships, classes, and components Examples: Class stereotypes: boundary, control, entity, utility, exception Inheritance stereotypes: uses and extends Component stereotypes: subsystem Copyright © 1997 by Rational Software Corporation 43

What the Iterative Life Cycle Is Not It is not hacking It is not a playpen for developers It is not unpredictable It is not redesigning the same thing over and over until it is perfect It is not an excuse for not planning and managing a project It is not something that affects only the developers on a project Copyright © 1997 by Rational Software Corporation Some managers have the perception that “iterative” really means “hacking” or not knowing what you’re doing or not planning anything. Nothing could be further from the truth. 44

What the Iterative Life Cycle Is It is planned and managed It is predictable It accommodates changes to requirements with less disruption It is based on evolving executable prototypes, not documentation It involves the user/customer throughout the process It is risk driven Copyright © 1997 by Rational Software Corporation If anything, the iterative life cycle requires more planning and more thought all along the way. The difference is that instead of doing all of the detailed planning up front, it is done in a distributed fashion, a little at a time along the way, when enough information is available to make the planning worthwhile. 45

Three Important Features of the Iterative Approach Continuous integration Not done in one lump near the delivery date Frequent, executable releases Some internal; some delivered Attack risks through demonstrable progress Progress measured in products, not documentation or engineering estimates Copyright © 1997 by Rational Software Corporation These three characteristics are what make the iterative life cycle particularly attractive to managers. The iterative approach provides managers with more accurate information with which to plan and manage the project. 46

Copyright © 1997 by Rational Software Corporation Resulting Benefits Releases are a forcing function that drives the development team to closure at regular intervals Cannot have the “90% done with 90% remaining” phenomenon Can incorporate problems/issues/changes into future iterations rather than disrupting ongoing production The project’s supporting elements (testers, writers, toolsmiths, CM, QA, etc.) can better schedule their work Copyright © 1997 by Rational Software Corporation 47

Risk Profile of an Iterative Development Waterfall Transition Inception Elaboration Construction Risk Preliminary Iteration Architect. Iteration Architect. Iteration Devel. Iteration Devel. Iteration Devel. Iteration Transition Iteration Transition Iteration Post- deployment Time With a typical waterfall approach, no significant amounts of risk are removed until integration begins near the end of the life cycle. The highest (technical) risks are typically architectural: performance (speed, capacity, accuracy, etc.), system interface integrity, and system qualities (adaptability, portability, etc.). These cannot be verified until a significant portion of the system has been coded and integrated. With an iterative approach, the highest risk items are addressed early in the life cycle, thereby making significant reductions in the risk profile. From a management perspective, the level of confidence in the project plan should correspondingly increase significantly from iteration to iteration. Copyright © 1997 by Rational Software Corporation 48

Risk Management Phase-by-Phase Inception Bracket the project’s risks by building a proof of concept Elaboration Develop a common understanding of the system’s scope and desired behavior by exploring scenarios with end users and domain experts Establish the system’s architecture Design common mechanisms to address system-wide issues Copyright © 1997 by Rational Software Corporation 49

Risk Management Phase-by-Phase (cont.) Construction Refine the architecture Risk-driven iterations Continuous integration Transition Facilitate user acceptance Measure user satisfaction Post-deployment cycles Continue evolutionary approach Preserve architectural integrity Copyright © 1997 by Rational Software Corporation 50

Risk Reduction Drives Iterations Define scenarios to address highest risks Plan Iteration N Cost Schedule Initial Project Risks Initial Project Scope Develop Iteration N Collect cost and quality metrics Iteration N Assess Iteration N Revise Overall Project Plan Cost Schedule Scope/Content Risks Eliminated Revise Project Risks Reprioritize Copyright © 1997 by Rational Software Corporation 51

Use Cases Drive the Iteration Process Inception Elaboration Construction Transition Iteration 1 Iteration 2 Iteration 3 “Mini-Waterfall” Process Iteration Planning Rqmts Capture Analysis & Design Implementation Test Prepare Release Copyright © 1997 by Rational Software Corporation Each phase is divided into one or more iterations. Each iteration is defined in terms of the scenarios it implements. The classes needed to implement all selected scenarios are developed in a mini-waterfall development process. 52

The Iteration Life Cycle: A Mini-Waterfall Selected scenarios Results of previous iterations Up-to-date risk assessment Controlled libraries of models, code, and tests Iteration Planning Requirements Capture Analysis & Design Implementation Test Prepare Release Release description Updated risk assessment Controlled libraries This is what one single iteration looks like. As with any waterfall representation of a process, in the mini-waterfall, many of these activities are occurring concurrently. For example, analysis is not done all in one continuous lump. And it intermingles with design and code, etc. Copyright © 1997 by Rational Software Corporation 53

Detailed Iteration Life Cycle Activities Iteration planning Before the iteration begins, the general objectives of the iteration should be established based on Results of previous iterations ( if any) Up-to-date risk assessment for the project Determine the evaluation criteria for this iteration Prepare detailed iteration plan for inclusion in the development plan Include intermediate milestones to monitor progress Include walkthroughs and reviews Copyright © 1997 by Rational Software Corporation 54

Detailed Iteration Life Cycle Activities (cont.) Requirements Capture Select/define the use cases to be implemented in this iteration Update the object model to reflect additional domain classes and associations discovered Develop a test plan for the iteration Copyright © 1997 by Rational Software Corporation 55

Detailed Iteration Life Cycle Activities (cont.) Analysis & Design Determine the classes to be developed or updated in this iteration Update the object model to reflect additional design classes and associations discovered Update the architecture document if needed Begin development of test procedures Implementation Automatically generate code from the design model Manually generate code for operations Complete test procedures Conduct unit and integration tests Copyright © 1997 by Rational Software Corporation 56

Detailed Iteration Life Cycle Activities (cont.) Test Integrate and test the developed code with the rest of the system (previous releases) Capture and review test results Evaluate test results relative to the evaluation criteria Conduct an iteration assessment Prepare the release description Synchronize code and design models Place products of the iteration in controlled libraries Copyright © 1997 by Rational Software Corporation 57

Work Allocation Within an Iteration Work to be accomplished within an iteration is determined by The (new) use cases to be implemented The rework to be done Packages make convenient work packages for developers High-level packages can be assigned to teams Lower-level packages can be assigned to individual developers Use Cases make convenient work packages for test and assessment teams Packages are also useful in determining the granularity at which configuration management will be applied For example, check-in and check-out of individual packages Copyright © 1997 by Rational Software Corporation Recall that packages are arbitrary groupings of classes and associations. Packages are defined for two reasons: 1. To address complexity. It is bigger than an individual class, but smaller than a system. Most systems are complex enough to need an intermediate-level “chunking” mechanism. 2. To delineate areas of responsibility, i.e., to assign ownership of portions of the system to developers. 58

Copyright © 1997 by Rational Software Corporation Iteration Assessment Assess iteration results relative to the evaluation criteria established during iteration planning: Functionality Performance Capacity Quality measures Consider external changes that have occurred during this iteration For example, changes to requirements, user needs, competitor’s plans Determine what rework, if any, is required and assign it to the remaining iterations This is a critical step in making the iterative approach successful. If it is not done properly, the benefits of the iterative approach will be lessened. Also, remember that sometimes the right thing to do in this step is to revise the evaluation criteria rather than reworking the system. Sometimes, the benefit of the iteration is in revealing that a particular requirement is not important or is too expensive to implement or creates an unmaintainable architecture. In these cases, a cost/benefit analysis must be done. The decision is a business decision. Copyright © 1997 by Rational Software Corporation 59

Copyright © 1997 by Rational Software Corporation Selecting Iterations How many iterations do I need? On projects taking 18 months or less, 3 to 6 iterations are typical Are all iterations on a project the same length? Usually Iteration length may vary by phase. For example, elaboration iterations may be shorter than construction iterations Copyright © 1997 by Rational Software Corporation There is no “right” answer relative to how many iterations are required. It depends on lots of factors such as the overall project length and the degree of risk involved. For most projects, the answer usually ends up being somewhere between 3 and 6 iterations. 60

Copyright © 1997 by Rational Software Corporation The First Iteration The first iteration is usually the hardest Requires the entire development environment and most of the development team to be in place Many tool integration issues, team-building issues, staffing issues, etc. must be resolved Teams new to an iterative approach are usually overly-optimistic Be modest regarding the amount of functionality that can be achieved in the first iteration Otherwise, completion of the first iteration will be delayed, The total number of iterations reduced, and The benefits of an iterative approach reduced A common pitfall is to be too optimistic about how much can be achieved in the first iteration. Since the entire development environment and the entire development team have to be in place and operating effectively for the first iteration to complete, it is wise to be conservative about how much of the system can be completed. The team will be distracted by issues like how to work with a new compiler, how to implement the CM policy, how to get the CM tool tailored for the project, how to put regression testing in place, and all the million other things that must be addressed on the first iteration. For the second iteration, all these things should be in place and everyone will have experience with how to develop the release, so they can attempt larger amounts of functionality. Copyright © 1997 by Rational Software Corporation 61

There Is No Silver Bullet Remember the main reason for using the iterative life cycle: You do not have all the information you need up front Things will change during the development period You must expect that Some risks will not be eliminated as planned You will discover new risks along the way Some rework will be required; some lines of code developed for an iteration will be thrown away Requirements will change along the way Copyright © 1997 by Rational Software Corporation Adopting the iterative approach will not make all your problems go away. It will give you more effective techniques for dealing with them. 62

Copyright © 1997 by Rational Software Corporation 63