Analysis and Design for Software Systems: Core Principles and Methodologies, Lecture notes of Systems Design

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Analysis & DesignAnalysis & Design

for software for software

systems systems

History of Software

Engineering

 (^) In1964, for the first time, the features of scientific and business applications have been combined.  (^) This computer system encouraged people to try to develop software for large and complex physical and management systems, which invariably resulted in large software systems.  (^) In 1968 a Conference has been held & SW Engineering has been discussed.  (^) In 2003, Bauer coined the term “Software Engineering”, narrates his experience of the origin of software engineering.  (^) The first International Conference on Software Engineering was held in 1973.

Software Crisis  (^) In Webster’s dictionary the word “crisis” is defined as “a turning point in the course of anything ; decisive or crucial time, stage or event.”  (^) Yet for SW there has been no “Turning point” , no “Decisive time” , only slow evolutionary change.  (^) Whether we call it a Software Crisis or a Software Affliction,,,  (^) “The term alludes to a set of problems that are encountered in the development of computer software.”

Software Crisis  (^) Whether we call it a Software Crisis or a Software Affliction,,,  (^) “The term alludes to a set of problems that are encountered in the development of computer software.”  (^) The problems are not limited to the software that “ doesn’t function properly”

Symptoms of softwareSymptoms of software crisis crisis

• (^) Software maintenance cost has been rising and has surpassed the development cost.
• (^) Software is almost always delivered late and exceeds the budgeted cost, indicating time and cost overruns.
• (^) It lacks transparency and is difficult to maintain.
• (^) Software quality is often less than adequate.
• (^) It often does not satisfy the customers.
• (^) Productivity of software people has not kept pace with the demand of their services.
• (^) Progress on software development is difficult to measure.
• (^) Very little real-world data is available on the software development process. Therefore, it has not been possible to set realistic standards.
• (^) How the persons work during the software development has not been properly understood.

Main Crisis  (^) Software didn’t deliver on time.  (^) Lack of quality.  (^) Cost  (^) Time

Software CharacteristicsSoftware Characteristics

• (^) Software is developed or engineered, it is not manufactured.
• Software development presents a job-shop environment.
• (^) Time and effort for software development are hard to estimate
• (^) User requirements are often not conceived well enough
• (^) No parameter to evaluate software process
• (^) Software does not wear out. Software normally does not lose its functionality with use.

Software crisisSoftware crisis

• Software design evaluation, on the other hand, rests on judgment and intuition
• (^) Software can be highly complex while still conforming to almost any set of needs.
• (^) There are major differences between the management of hardware and software projects.
• (^) Traditional controls for hardware projects may be counterproductive in software projects.

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Heterogeneous System

 (^) Different O.S can be used.  (^) There are four distributed applications.  (^) Fault Tolerance System.  (^) Replication.  (^) How Security Implemented.  (^) How Encryption Implemented.

Delivery on Time Problem  (^) Software didn’t deliver on time which may cause problems.

Problems for Software

Engineers

Essence VS Accidental Difficulties

Essence Difficulties:  (^) Essence the difficulties inherent in the nature of software.

Accidental Difficulties:  (^) Those difficulties that happens by mistake , but not are inherent.

Essence Problems… Complexity  (^) Every software is complex in nature.  (^) Software entities are more complex for their size than perhaps any other human construct because no two parts are alike.  (^) If they are ,we make the two similar parts into a subroutine.  (^) In this respect ,software system differ profoundly from computers ,buildings ,or automobiles ,where repeated elements abound.

 (^) You are not always sure that you are making the perfect software or have done correct.  (^) Software people are not alone in facing complexity.  (^) In many cases ,the software must conform because it is the most recent arrival on the scene

Essence Problems…

Conformity

 (^) Software is invisible and unvisualizeable.  (^) Geometric abstractions are powerful tools. Essence Problems… Invisibility