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Using UML, Patterns, and Java Object-Oriented Software Engineering 15. Software Life Cycle.

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Presentation on theme: "Using UML, Patterns, and Java Object-Oriented Software Engineering 15. Software Life Cycle."— Presentation transcript:

1 Using UML, Patterns, and Java Object-Oriented Software Engineering 15. Software Life Cycle

2 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 2 Outline  Software Life Cycle  Waterfall model and its problems  Pure Waterfall Model  V-Model  Iterative process models  Boehm’s Spiral Model

3 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 3 Inherent Problems with Software Development  Requirements are complex  The client does not know the functional requirements in advance  Requirements may be changing  Technology enablers introduce new possibilities to deal with nonfunctional requirements  Frequent changes are difficult to manage  Identifying milestones and cost estimation is difficult  There is more than one software system  New system must be backward compatible with existing system (“legacy system”)  Phased development: Need to distinguish between the system under development and already released systems  Let’s view these problems as the nonfunctional requirements for a system that supports software development!  This leads us to software life cycle modeling

4 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 4 Definitions  Software lifecycle modeling: Attempt to deal with complexity and change  Software lifecycle:  Set of activities and their relationships to each other to support the development of a software system  Software development methodology:  A collection of techniques for building models - applied across the software lifecycle

5 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 5 Software Life Cycle  Software construction goes through a progression of states Development Post- Development Pre- Development Conception Childhood Adulthood Retirement

6 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 6 Typical Software Lifecycle Questions  Which activities should I select for the software project?  What are the dependencies between activities?  Does system design depend on analysis? Does analysis depend on design?  How should I schedule the activities?  Should analysis precede design?  Can analysis and design be done in parallel?  Should they be done iteratively?

7 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Identifying Software Development Activities  For finding activities and dependencies we can use the same modeling techniques when modeling a system such as creating scenarios, use case models, object identification, drawing class diagrams, activity diagrams  Questions to ask:  What is the problem?  What is the solution?  What are the mechanisms that best implement the solution?  How is the solution constructed?  Is the problem solved?  Can the customer use the solution?  How do we deal with changes that occur during the development? Are enhancements needed?

8 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 8 Possible Identification of Software Development Activities Requirements Analysis What is the problem? System Design What is the solution? Program Design What are the mechanisms that best implement the solution? Program Implementation How is the solution constructed? Testing Is the problem solved? Delivery Can the customer use the solution? Maintenance Are enhancements needed? Problem Domain Problem Domain Implementation Domain Implementation Domain

9 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 9 Software Development as Application Domain: A Use Case Model

10 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 10 IEEE Std 1074: Standard for Software Lifecycle IEEE Std 1074 Project Management Project Management Pre- Development Pre- Development Post- Development Post- Development Cross- Development (Integral Processes) Cross- Development (Integral Processes) > Project Initiation >Project Monitoring &Control > Software Quality Management > Concept Exploration > System Allocation > Requirements Analysis > Design > Implementation > Installation > Operation & Support > Maintenance > Retirement > V & V > Configuration Management > Documentation > Training Process Group Processes

11 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 11 Processes, Activities, and Tasks  Process Group: Consists of Set of Processes  Process: Consists of Activities  Activity: Consists of sub activities and tasks Process Group Process Group Process Activity Development Design Task Design Database Design Database Make a Purchase Recommendation Make a Purchase Recommendation

12 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 12 Example  The Design Process is part of Development  The Design Process consists of the following Activities  Perform Architectural Design  Design Database (If Applicable)  Design Interfaces  Select or Develop Algorithms (If Applicable)  Perform Detailed Design (= Object Design)  The Design Database Activity has the following Tasks  Review Relational Databases  Review Object-Oriented Databases  Make a Purchase recommendation ....

13 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS  Many models have been proposed to deal with the problems of defining activities and associating them with each other  The first model proposed was the waterfall model [Royce 1970] Life Cycle Modeling

14 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 14  Many models have been proposed to deal with the problems of defining activities and associating them with each other  The waterfall model  First described by Royce in 1970  There seem to be at least as many versions as there are authorities - perhaps more Life-Cycle Model: Variations on a Theme

15 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Requirements Process System Allocation Process Concept Exploration Process Design Process Implementation Process Installation Process Operation & Support Process Verification & Validation Process The Waterfall Model of the Software Life Cycle adapted from [Royce 1970]

16 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 16 Problems with Waterfall Model  Managers love waterfall models:  Nice milestones  No need to look back (linear system), one activity at a time  Easy to check progress : 90% coded, 20% tested  V-Model  Software development is iterative  During design problems with requirements are identified  During coding, design and requirement problems are found  During testing, coding, design& requirement errors are found  => Spiral Model

17 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS From the Waterfall Model to the V Model System Design Requirements Analysis Requirements Engineering Object Design Integration Testing System Testing Unit Testing Implementation System Testing Unit Testing Integration Testing Acceptance

18 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Activity Diagram of a V Model precedes Is validated by

19 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Properties of Waterfall -based Models  Managers love waterfall models:  Nice milestones  No need to look back (linear system)  Always one activity at a time  Easy to check progress during development: 90% coded, 20% tested  However, software development is nonlinear  While a design is being developed, problems with requirements are identified  While a program is being coded, design and requirement problems are found  While a program is tested, coding errors, design errors and requirement errors are found

20 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 20  The spiral model proposed by Boehm is an iterative model with the following activities  Determine objectives and constraints  Evaluate Alternatives  Identify risks  Resolve risks by assigning priorities to risks  Develop a series of prototypes for the identified risks starting with the highest risk.  Use a waterfall model for each prototype development (“cycle”)  If a risk has successfully been resolved, evaluate the results of the “cycle” and plan the next round  If a certain risk cannot be resolved, terminate the project immediately Spiral Model (Boehm) Deals with Iteration

21 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Spiral Model Project P1 Project P2

22 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Types of Prototypes  Illustrative Prototype (Revolutionary Prototyping)  Develop the user interface with a set of storyboards  Implement them on a napkin or with a user interface builder (Visual C++,....)  Good for first dialog with client  Functional Prototype (Evolutionary Prototyping)  Implement and deliver an operational system with minimum functionality  Then add more functionality  Order identified by risk  Exploratory Prototype ("Hacking")  Implement part of the system to learn more about the requirements.

23 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 23 Process Maturity  A software development process is mature  if the development activities are well defined and  if management has some control over the quality, budget and schedule of the project  Process maturity is described with  a set of maturity levels and  the associated measurements (metrics) to manage the process  Assumption:  With increasing maturity the risk of project failure decreases

24 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 24 Capability maturity levels 1. Initial Level  also called ad hoc or chaotic 2. Repeatable Level  Process depends on individuals ("champions") 3. Defined Level  Process is institutionalized (sanctioned by management) 4. Managed Level  Activities are measured and provide feedback for resource allocation (process itself does not change) 5. Optimizing Level  Process allows feedback of information to change process itself

25 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Maturity Level 1: Chaotic Process  Ad hoc approach to software development activities  No problem statement or requirements specification  Output is expected  but nobody knows how to get there in a deterministic fashion  Similar projects may vary widely in productivity  "when we did it last year we got it done"  Level 1 Metrics: Rate of Productivity (Baseline comparisons, Collection of data is difficult)  Product size (LOC, number of functions, etc)  Staff effort (“Man-years”, person-months)  Recommendation: Level 1 managers & developers should not concentrate on metrics and their meanings,  They should first attempt to adopt a process model (waterfall, spiral model, saw- tooth, macro/micro process lifecycle, unified process)

26 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Maturity Level 2: Repeatable Process  Inputs and outputs are defined  Input: Problem statement or requirements specification  Output: Source code  Process itself is a black box ( activities within process are not known)  No intermediate products are visible  No intermediate deliverables  Process is repeatable due to some individuals who know how to do it  "Champion"  Level 2 Metrics:  Software size: Lines of code, Function points, classes or method counts  Personnel efforts: person- months  Technical expertise  Experience with application domain  Design experience  Tools & Method experience  Employee turnover within project

27 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Maturity Level 3: Defined Process  Activities of software development process are well defined with clear entry and exit conditions.  Intermediate products of development are well defined and visible  Level 3 Metrics (in addition to metrics from lower maturity levels):  Requirements complexity: Number of classes, methods, interfaces  Design complexity: Number of subsystems, concurrency, platforms  Implementation complexity: Number of code modules, code complexity  Testing complexity: Number of paths to test, number of class interfaces to test  Thoroughness of Testing:  Requirements defects discovered  Design defects discovered  Code defects discovered  Failure density per unit (subsystem, code module, class

28 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Maturity Level 4: Managed Process  Uses information from early project activities to set priorities for later project activities (intra-project feedback)  The feedback determines how and in what order resources are deployed  Effects of changes in one activity can be tracked in the others  Level 4 Metrics:  Number of iterations per activity  Code reuse: Amount of producer reuse (time designated for reuse for future projects?)  Amount of component reuse (reuse of components from other projects and components)  Defect identification:  How and when (which review) are defects discovered?  Defect density:  When is testing complete?  Configuration management:  Is it used during the development process? (Has impact on tractability of changes).  Module completion time:  Rate at which modules are completed (Slow rate indicates that the process needs to be improved).

29 Copyright 2002 Bernd Brügge Software Engineering II, Lecture 3: Scheduling SS Maturity Level 5: Optimizing Process  Measures from software development activities are used to change and improve the current process  This change can affect both the organization and the project:  The organization might change its management scheme  A project may change its process model before completion

30 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 30 Summary  Software life cycle  The development process is broken into individual pieces called software development activities  No good model for modeling the process (black art)  Existing models are an inexact representation of reality  Nothing really convincing is available today  Software development standards  IEEE 1074  Standards help, but must be taken with a grain of salt  The standard allows the lifecycle to be tailored  Capability Maturity Model.


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