Software Engineering

Saeed Akhtar

The University of Lahore

Lecture 6Originally shared fo

r:

mashhoood.webs.com

Review of Last LectureWorking of Agile Model?

Pros and cons of Agile Model?

When to use Agile?

Difference from other Models?

Software Engineering Practices

The Essence of Practice

George Polya, in a book (about problem solving), describes the essence of software engineering practice …

Understand the problem (communication and analysis).

Plan a solution (modeling and software design).Carry out the plan (code generation).Examine the result for accuracy (testing and

quality assurance).

Core Software Engineering Principles

The reason it all exists: Provide value to the customer and the user

KISS—keep it simple, stupid!Does not mean quick and dirty

Maintain the product and project “vision”What you produce, others will consumeBe open to the futurePlan ahead for reuseThink! (before action)

Communication Practice Principles

1. Listen (instead of talking too much)2. Prepare before you communicate

Understand the business domain Prepare an agenda

3. Facilitate the communication, there should be a leader Ensure moving in a productive direction Mediate any conflict Ensure other principles are followed

4. Face-to-face is best5. Take notes and document decisions

Communication Practice Principles Cont’d

6. Collaborate with the customer7. Stay focused, modularize your discussion

(conclude each issue)8. Draw pictures when things are unclear9. Move on …

Once you agree to something If you can’t agree Something is unclear and cannot be resolved at the

moment

10. Negotiation works best when both parties win (not a contest or game).

Compromise when necessary

Planning PracticePrinciples1. Understand the project scope

Scope clears your destination

2. Involve the customer (and other stakeholders) Customer defines priorities and constraints Negotiate order of delivery, timelines, …

3. Recognize that planning is iterative (revised based on feedback)

4. Estimate based on what you know Provide an indication of effort, cost, and task duration

(maybe unreliable)

5. Consider risk

Planning Principles Cont’d6. Be realistic

Noise, change, mistakes, omissions, ambiguity

7. Adjust granularity as you plan (level of details)

8. Define how quality will be achieved (formal technical reviews, pair programming)

9. Define how you’ll accommodate changes10. Track what you’ve planned and make

adjustment

Planning Practices

Ask Boehm’s questions Why is the system being developed?

Justify the expenditure of people, time, and money

What will be done? Identify functionality

When will it be accomplished? Workflow, timeline, milestones

Who is responsible for a function? Where are they located (organizationally)? How will the job be done technically and managerially? How much of each resource is needed? (estimation)

Analysis Modeling PracticeWe create models to gain a better

understanding of the actual entity to be builtAnalysis models represent the customer

requirements by depicting the software in three different domains: the information domain, the functional domain, and the behavioral domain.

Design models represent characteristics of the software that help practitioners to construct it effectively: the architecture, the user interface, and component-level detail.

Analysis Modeling PracticeAnalysis modeling principles1. Represent the information domain

Input data: from end-users, other systems, or external devices Output data: via the user interface, network interface, reports, graphics, … The data stores

2. Represent software functions Different levels of abstraction

3. Represent software behavior As a consequence of external events

4. Partition these representations Partitioning: divide and conquer Layered or hierarchical

5. Move from essence toward implementation

Design Modeling PrinciplesPrinciples

1.Design must be traceable to the analysis model2.Always consider architecture3.Focus on the design of data4.Interfaces (both user and internal) must be designed5.Components should exhibit functional independence6.Components should be loosely coupled7.Design representation should be easily understood8.The design model should be developed iteratively

Construction PracticesPreparation principles: Before you write

one line of code, be sure you: Understand of the problem you’re trying to solve (see

communication and modeling) Understand basic design principles and concepts. Pick a programming language that meets the needs of

the software to be built and the environment in which it will operate.

Select a programming environment that provides tools that will make your work easier.

Create a set of unit tests that will be applied once the component you code is completed.

Construction PracticesCoding principles: As you begin writing

code, be sure you: Constrain your algorithms by following structured

programming practice. Select data structures that will meet the needs of the

design. Understand the software architecture and create

interfaces that are consistent with it. Keep conditional logic as simple as possible. Create nested loops in a way that makes them easily

testable. Select meaningful variable names and follow other local

coding standards. Write code that is self-documenting.

Construction PracticesValidation Principles: After you’ve completed your first coding pass,

be sure you:Conduct a code walkthrough when

appropriate.Perform unit tests and correct errors you’ve

uncovered.Refactor the code.

Construction PracticesTesting Principles

All tests should be traceable to requirements

Tests should be planned

Testing begins “in the small” and moves toward “in the large”

Deployment PracticesPrinciples

Manage customer expectations for each increment

A complete delivery package should be assembled and tested

Instructional materials must be provided to end-users

Buggy software should be fixed first, delivered later

Thank You