Software Engineering 1 Some Definitions Lesson 2.

Software Engineering 1

Software Software EngineeringEngineering

Some DefinitionsLesson 2


Some Definitions

Definition of Software:(from the IEEE Glossary of Software Engineering)

software is a set of items or objects that form a “System” that includes programs, functions, rules, documents and data.

Notice:Software is also documents!!!

4.000/5.000 pages only for Analysis


Some Definitions

Definition of Software Engineering:

Software engineering is an engineering discipline which is concerned with all aspects of software production (development, maintainess, replacement …)

Notice:Software Engineering is also

replacing of software!!!


Some Definitions

Definition of Software Engineering:

Software engineers should adopt a systematic and organised approach to their work and use appropriate tools and techniques depending on the problem to be solved, the development constraints and the resources available coherently with the estimated time and costsNotice:

We have to find a precise cost for each Software Development Process


Software EngineeringSoftware Engineering

Software Engineering’s dimensionsLesson 2


Sw Engineering’s dimensions

1. Technological Dimension:

Languages, networks, architectures, …

This is trivial for you!!! But it isn’t enough…



2. Economic Dimension:

• make or buy?

• software costs more to maintain than it does to develop



Approaches to developing software depend on the application

Example:MS Windows is enough to write a document MS Windows isn’t recommended to control a plane



Costs of software are higher than hardware cost

Relation between Software

and Hardware cost



Measure of costs:linesday

How many lines does a programmer write in a day?

10 lines!!!

In the remaining time he makes Software Engineering!!!



3. Social Dimension:

Trouble issues:

• Introduce new software

• Substitute software

• Digital Divide

•Open Source



Basic ConceptsLesson 2


Basic Concepts

Process Product

Set of activities whose goal is the developmentor evolution of software

(Software Life Cycle)

Software


Basic Concepts

This course is about the Process!!!

Notice:

Cost of production of software is zero.

Costs are considered only for their conception (for process).



Process and Product QualitiesLesson 2


Software isn’t only the code but also documentation, comments, reports of the test analysis, …

every derivable of each phase of

Software Development Process

Process and Product Qualities


Tons of problems during Software Development Process:

- during Requirements Analysis

- during Software Implementation

- during Maintenance



Complexity of some kind of problems

during Software Development Process:

• Technological problems

• Economical problems

• Social problems



For any kind of software we could have many products and many Software Development Processes.

Products are classified through their quality

Processes are different sequences of the same set of phases




External Qualities

(Black Box)

What are the users’ needs(Users can see it)

Example: low diesel oil consumption



Internal Qualities

(White Box)

Structural Properties(Users cannot see it)

Example: high thermal insulation



External Qualities

(Black Box)

Requested from users

Example: high portability



Internal Qualities

(White Box)

Requested from developers

Example: software in Java



About 50% of the Process fails because they don't meetthe needs of users and developers



Software QualitiesLesson 2


Software Qualities

• Correct• Dependable• Robustness• Secure & Safe• Usable• Portable

• Maintainable• Reusable• Modular• Understandable• Interoperable

Software Engineering 1 Some Definitions Lesson 2.

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