The Software Product

What is Software?

Software is a set of items or objects that form a "configuration" that includes

• programs
• documents
• data ...

• Software Engineers

• Affects nearly every aspect of life.

By applying a structured process.

What are the Work Products?

• programs
• documents
• data

• Product
• Process that delivers products

• Why does it take so long to finish software?
• Why are development costs so high?
• Why can’t we find all the bugs before delivery?
• Why do we continue to have difficulties measuring progress in the software development process?

Software Characteristics

• software is engineered
• software doesn’t wear out
• software is complex
• software is like an ‘aging factory’

• Hardware based on standards.
• Software standard components exist.

Software Applications

• system software
• real-time software
• business software
• engineering/scientific software
• embedded software
• PC software
• AI software
• WebApps (Web applications)

• Service Programs – compilers, editors, OS’s, telecommunications

• Characteristics --

• Heavy interaction with hardware.
• Heavy usage by multiple users.
• Concurrent operation.
• Complex data structures.
• Multiple external interfaces.

• Monitors/analyzes/controls real-world events

• Characteristics --

• Data gathering from external environments.
• Transformation components.
• Control/output components.
• Monitoring components.

• Discrete systems (e.g. payroll, inventory, …)

• Management and decision making.
• Interactive computing.

• Number crunching.
• CAD.
• Simulation / Visualization
• Virtual Reality

• Resides in ROM.
• System Controllers.

• Productivity.
• Graphics / multimedia.
• Etc.

• Browser-based (CGI, HTML, Perl, Java, etc.)

• Expert Systems.
• Pattern Recognition.
• Games.

• How do we ensure the quality of the software we produce?
• How do we meet growing demand and meet budget control?
• How do we upgrade an aging software plant?
• How do we avoid disastrous time delays?
• How do we successfully institute new software technologies?

What is the software process?

• A series of predictable steps.

• It provides stability, control, and organization.

• Depends on software to be developed.

• Programs, documents, and data.

• Quality, timeliness, long-term viability of products.

Software Engineering Definition:

1. The establishment and use of sound engineering principles in order to economically obtain software that is reliable and works efficiently on real machines.
2. (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. The study of approaches, as in (1).

• SE is a layered technology.

• SE foundation – Process Layer
• Process defines framework for set of Key Process Areas (KPAs) that are established for delivery of SE technology.

• KPAs:
• foundation for management control of products
• Set context in which:
• Technical methods are applied.
• Work products produced.
• Milestones established.
• Quality assured.
• Change managed.

• Engineering is:

• Analysis
• Design
• Construction
• Verification
• Management

• Questions to be answered:

1. What is the problem to be solved?
2. What characteristics of entity are used to solve problem?
3. How will entity and solution be realized?
4. What approaches will be used to uncover errors during design and construction?
5. How will entity be supported over long term?

1. Definition Phase – What.

• What information is processed.
• What functions and performance are desired.
• What system behavior is expected.
• What interfaces are to be established.
• What design constraints exists.
• What validation criteria are required.

1. Development Phase – How

• How data are to be structured.
• How functions are to be implemented.
• How procedural details are to be implemented.
• How interfaces are characterized.
• How design translates into programming language.
• How testing will be performed.

1. Support Phase – Change

• Error correction.
• Adaptation.
• Enhancements.
• Prevention.

• Software project management
• Formal technical reviews
• Software quality assurance
• Software configuration management
• Document preparation and production
• Reusability management
• Measurement
• Risk management

Common Process Framework

SEI Capability Maturity Model (CMM)

• Key activities required at different levels of process maturity.
• Measure of SE practice effectiveness.
• Five process maturity levels (higher levels subsume lower):

• Level 1: Initial – Ad hoc, few processes defined, success depends on individual effort.
• Level 2: Repeatable – Basic project management processes established to track cost, schedule and functionality.
• Level 3: Defined – Software process for management and engineering activities are documented, standardized, and integrated into an organization-wide software process.
• Level 4: Managed – Detailed measures of software process and product quality are collected.
• Level 5: Optimizing – Continuous process improvement through quantitative feedback from testing.

• KPAs define SE functions (e.g. plans, reviews) that must be present to satisfy good practice at a particular level.
• KPA characteristics:
• Goals
• Commitments
• Abilities
• Activities
• Methods of monitoring
• Methods of verifying

General Problem Solving Process

• General Model Characteristic: Adaptable.

Framework activities will always be applied on every project ... BUT the tasks (and degree of rigor) for each activity will vary based on:
• The type of project (an "entry point" to the model).
• Characteristics of the project.
• Common sense judgment; concurrence of the project team

• Oldest model – widely used.
• Problems:
• Real projects rarely follow sequential flow.
• Often difficult to specify all requirements explicitly.
• Long process.
• Parallel development slowed.

• Problems:
• First System: Not usually written very well.
• Customer thinks it is working version.
• Implementation compromises made to build prototype.

• Usefulness:
• Good communication tool.
• Fleshes out system requirements.

Characteristics:

• Iterative model with short development time.
• High-speed adaptation of linear model.
• Focuses on building systems as collection of components.
• Phases:
• Business Modeling

Information flow modeled: who, what, where info comes and goes.
• Data Modeling

Information transformed to data objects.
• Process Modeling

Data objects transformed
• Application Generation
4GL methods used.
• Testing and turnover
Reuses modules.

• Large projects require sufficient human resources.
• Requires commitment of time by all.
• Does not work with high-tech projects.

Incremental Model

• Evolutionary model
• Modified linear model
• Each sequence delivers an "increment" – 1^st increment core product, 2^nd enhanced, etc.
• Intends to deliver functioning product

• Combines concept of prototyping with linear model
• Process:
• Movement counterclockwise from center.
• First circuit: produces product specifications.
• Second circuit: prototype.
• Third circuit: refined versions.
• Each pass through each regions produces adjusted products.
• Adapted to complete life cycle