Chapter 1 – Software and Software Engineering

Overview

• Software is designed and built by software engineers.
• Software is used by virtually everyone in society.
• Software is pervasive in our commerce, our culture, and our everyday lives.
• Software engineers have a moral obligation to build reliable software that does no harm to other people.
• Software engineers view computer software, as being made up of the programs, documents, and data required to design and build the system.
• Software users are only concerned with whether or not software products meet their expectations and make their tasks easier to complete.

 

Important Questions for Software Engineers

• Why does it take so long to get software finished?
• Why are development costs so high?
• Why can’t we find all errors before we give the software to our customers?
• Why do we spend so much time and effort maintaining existing programs?
• Why do we continue to have difficulty in measuring progress as software is being developed?

 

Software

• Software is both a product and a vehicle for delivering a product (information).
• Software is engineered not manufactured.
• Software does not wear out, but it does deteriorate.
• Industry is moving toward component-based software construction, but most software is still custom-built.

 

Software Application Domains

• System software
• Application software
• Engineering or Scientific Software
• Embedded software
• Product-line software (includes entertainment software)
• Web-Applications
• Artificial intelligence software

 

New Software Challenges

• Open-world computing
• Creating software to allow machines of all sizes to communicate with each other across vast networks
• Netsourcing
• Architecting simple and sophisticated applications that benefit targeted end-user markets worldwide
• Open Source
• Distributing source code for computing applications so customers can make local modifications easily and reliably

 

Reasons for Legacy System Evolution

• Software must be adapted to meet needs of new computing environments or technology
• Software must be enhanced to implement new business requirements
• Software must be extended to make it interoperable with more modern system components
• Software must be re-architected to make it viable within a network environment

 

Unique Nature of Web Apps

• Network intensive
• Concurrency
• Unpredictable load
• Availability (24/7/365)
• Data driven
• Content sensitive
• Continuous evolution
• Immediacy (short time to market)
• Security
• Aesthetics

 

Software Engineering Realities

• Problem should be understood before software solution is developed
• Design is a pivotal activity
• Software should exhibit high quality
• Software should be maintainable

 

 

Software Engineering

• Software engineering is the establishment of sound engineering principles in order to obtain reliable and efficient software in an economical manner.
• Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software.
• Software engineering encompasses a process, management techniques, technical methods, and the use of tools.

 

Generic Software Process Framework

• Communication (customer collaboration and requirement gathering)
• Planning (establishes engineering work plan, describes technical risks, lists resources required, work products produced, and defines work schedule)
• Modeling (creation of models to help developers and customers understand the requires and software design)
• Construction (code generation and testing)
• Deployment (software delivered for customer evaluation and feedback)

 

Software Engineering Umbrella Activities

• Software project tracking and control (allows team to assess progress and take corrective action to maintain schedule)
• Risk management (assess risks that may affect project outcomes or quality)
• Software quality assurance (activities required to maintain software quality)
• Technical reviews (assess engineering work products to uncover and remove errors before they propagate to next activity)
• Measurement (define and collect process, project, and product measures to assist team in delivering software meeting customer needs)
• Software configuration management (manage effects of change)
• Reusability management (defines criteria for work product reuse and establish mechanisms to achieve component reuse)
• Work product preparation and production (activities to create models, documents, logs, forms, lists, etc.)

 

Attributes for Comparing Process Models

• Overall flow and level of interdependencies among tasks
• Degree to which work tasks are defined within each framework activity
• Degree to which work products are identified and required
• Manner in which quality assurance activities are applied
• Manner in which project tracking and control activities are applied
• Overall degree of detail and rigor of process description
• Degree to which stakeholders are involved in the project
• Level of autonomy given to project team
• Degree to which team organization and roles are prescribed

 

 

Essence of Practice

• Understand the problem (communication and analysis)
• Plan a solution (software design)
• Carry out the plan (code generation)
• Examine the result for accuracy (testing and quality assurance)

 

Understand the Problem

• Who are the stakeholders?
• What functions and features are required to solve the problem?
• Is it possible to create smaller problems that are easier to understand?
• Can a graphic analysis model be created?

 

Plan the Solution

• Have you seen similar problems before?
• Has a similar problem been solved?
• Can readily solvable subproblems be defined?
• Can a design model be created?

 

Carry Out the Plan

• Does solution conform to the plan?
• Is each solution component provably correct?

 

Examine the Result

• Is it possible to test each component part of the solution?
• Does the solution produce results that conform to the data, functions, and features required?

 

 

Software Practice Core Principles

• Software exists to provide value to its users
• Keep it simple stupid (KISS)
• Clear vision is essential to the success of any software project
• Always specify, design, and implement knowing that someone else will have to understand what you have done to carry out his or her tasks
• Be open to future changes, don’t code yourself into a corner
• Planning ahead for reuse reduces the cost and increases the value of both the reusable components and the systems that require them
• Placing clear complete thought before any action almost always produces better results

 

 

Software Creation

• Almost every software project is precipitated by a business need (e.g. correct a system defect, adapt system to changing environment, extend existing system, create new system)
• Many times an engineering effort will only succeed if the software created for the project succeeds
• The market will only accept a product is the software embedded within it meets the customer’s stated or unstated needs