CS 281 Intro to Software Engineering
Lecture 02Software Engineering (1)
Chapter 2 Software Engineering
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 2
Slide Set to accompanySoftware Engineering: A Practitioner’s Approach, 8/e by Roger S. Pressman and Bruce R. Maxim
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These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 3
Software EngineeringSome realities:
a concerted effort should be made to understand the problem before a software solution is developed
design becomes a pivotal activity software should exhibit high quality software should be maintainable
The seminal definition:[Software engineering is] the establishment and use
of sound engineering principles in order to obtain economically software that is reliable and works efficiently on real machines.
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 4
Software Engineering
The IEEE definition:
Software Engineering:
1) The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software
2) The study of approaches as in (1)
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 5
A Layered Technology
Software EngineeringProcess defines a framework that must be established for effective delivery of software engineering technology
Methods provide the technical how-to's for building software
Tools provide automated or semi-automated support for the processand the methods
An organization’s focus on quality fosters a continuous process improvement culture, and it is this culture that ultimately leads to the development of increasingly more effective approaches to software engineering
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 6
A Process FrameworkProcess frameworkProcess framework
Framework activitiesFramework activitieswork taskswork productsmilestones/deliverablesQA checkpoints
Umbrella ActivitiesUmbrella Activities
Process frameworks establish the foundation for a complete software engineering process by identifying framework and umbrella activitiesFramework activities are applicable to all software projects, are applied (at times iteratively) one after the otherUmbrella activities are applicable across the entire software process
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 7
Framework Activities1. Communication2. Planning3. Modeling
a. Analysis of requirementsb. Design
4. Constructiona. Code generationb. Testing
5. Deployment
Communication is done to understand stakeholders' objectives for the project and to gather requirements that help define software features and functions
Planning defines the work by describing the technical tasks to be conducted, the risks that are likely, the resources that will be required, the work products to be produced, and a work schedule
Modeling is done to better understand requirements and the design that will achieve those requirements
Construction activity combines code generation and testing that is required to uncover errors in the code
Deployment is the delivery of the software to the customer who evaluates it and provides feedback
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 9
Umbrella Activities Project tracking and control Risk management Quality assurance Technical reviews Measurement Configuration management Reusability management Work product preparation and production
Project tracking and control allows the software team to assess progress against the project plan and take any necessary action to maintain the schedule
Risk management assesses and plans for tackling risks that may affect the outcome of the project or the quality of the product
Quality assurance defines and conducts the activities required to ensure software quality
Technical reviews assess software engineering work products in an effort to uncover and remove errors before they are propagated to the next activity
Measurement defines and collects process, project, and product measures that assist the team in delivering software that meets stakeholders' needs; can be used along with all other framework/umbrella activities
Configuration management manages the effects of change throughout the software process
Reusability management defines criteria for work product reuse (including software components) and establishes mechanisms to achieve reusable components
Product preparation and production encompass the activities required to create work products such as models, documents, logs, forms, and lists
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 12
Adapting a Process Modelto Project’s and Team’s Needs
the overall flow of activities, actions, and tasks and the interdependencies among them
the degree to which actions and tasks are defined within each framework activity
the degree to which work products are identified and required the manner which quality assurance activities are applied the manner in which project tracking and control activities are
applied the overall degree of detail and rigor with which the process is
described the degree to which the customer and other stakeholders are
involved with the project the level of autonomy given to the software team the degree to which team organization and roles are
prescribed
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 13
The Essence of PracticeGeorge Polya suggested in “How to Solve It” (1957):
1. Understand the problem (communication and analysis)
2. Plan a solution (modeling and software design)
3. Carry out the plan (code generation)
4. Examine the result for accuracy (testing and quality assurance)
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 14
Understand the ProblemWho has a stake in the solution to the problem?
That is, who are the stakeholders?
What are the unknowns?What data, functions, and features are required to properly solve the problem?
Can the problem be compartmentalized?Is it possible to represent smaller problems that may be easier to understand?
Can the problem be represented graphically?Can an analysis model be created?
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 15
Plan the SolutionHave you seen similar problems before?
Are there patterns that are recognizable in a potential solution?Is there existing software that implements the data, functions, and features that are required?
Has a similar problem been solved?If so, are elements of the solution reusable?
Can subproblems be defined?If so, are solutions readily apparent for the subproblems?
Can you represent a solution in a manner that leads toeffective implementation?
Can a design model be created?
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 16
Carry Out the Plan
Does the solution conform to the plan?Is source code traceable to the design model?
Is each component part of the solution provablycorrect?
Has the design and code been reviewed, or better, have correctness proofs been applied to algorithm?
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 17
Examine the ResultIs it possible to test each component part of thesolution?
Has a reasonable testing strategy been implemented?
Does the solution produce results that conform to
the data, functions, and features that arerequired?
Has the software been validated against all stakeholder requirements?
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 18
Hooker’s General SE Principles
1: The Reason It All Exists
2: Keep It Simple, Stupid!
3: Maintain the Vision
4: What You Produce, Others Will Consume
5: Be Open to the Future
6: Plan Ahead for Reuse
7: Think!
The Reason It All Exists. A software system exists for one reason: to provide value to its users. All decisions should be made with this in mind
Keep It Simple, Stupid! All design should be as simple as possible, but no simpler. This facilitates having a more easily understood, less error-prone and easily maintained system
Maintain the Vision. A clear vision is essential to the success of a project. Without conceptual integrity, a system may become a patchwork of incompatible designs, held together by the wrong kind of screws
What You Produce, Others Will Consume. Always specify, design, and implement knowing someone else will have to understand what you are doing.
Be Open to the Future. To ensure long term success, systems must be ready to adapt to future hardware/ software changes. To achieve that, design systems that solve the general problem, not just the specific one.
Plan Ahead for Reuse. Planning ahead for reuse reduces the cost and increases the value of both the reusable components and the systems into which they are incorporated
Think! Placing clear, complete thought before action almost always produces better results.. Applying the first six principles requires intense thought, for which the potential rewards are enormous.
SE382 Software Engineering
Lecture 03aSoftware Engineering (2)
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 22
Software Myths Affect managers, customers (and other non-
technical stakeholders) and practitioners Are believable because they often have
elements of truth,
but … Invariably lead to bad decisions,
therefore … Insist on reality as you navigate your way
through software engineering
Software Myths:Example Management Myth
If we get behind schedule, we can add more programmers and catch up (sometimes called the Mongolian horde concept)
Software Myths:Example Customer Myth
A general statement of objectives is sufficient to begin writing programs – we can fill in details later
Software Myths:Example Practitioner’s Myth
Software engineering will make us create voluminous and unnecessary documentation and will invariably slow us down
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 8/e (McGraw-Hill 2014). Slides copyright 2014 by Roger Pressman. 26
How It all StartsSafeHome:
Every software project is precipitated by some business need:
the need to correct a defect in an existing application
the need to the need to adapt a ‘legacy system’ to a changing business environment
the need to extend the functions and features of an existing application, or
the need to create a new product, service, or system
Project Example:SafeHome
The SafeHome company has developed an innovative hardware box that implements wireless Internet connectivity in a very small form factor
The idea is to use this technology to develop and market a comprehensive home automation product line. This would ultimately provide not only security functions, but also would enable control over telephone answering machines, lights, heating, air conditioning, and home entertainment devices
The first generation of the system will only focus on home security since that is a market the public readily understands.