Software Engineering

Topics: Software development process, Spiral model, Software engineering Pages: 10 (2867 words) Published: August 13, 2011
Table of Contents
Glass’ Law3
Boehm’s first law3
Boehm’s second law4
Davis’ law5
Waterfall model5
Spiral Model7
Waterfall model with Glass’ Law8
Waterfall model with Boehm’s First Law9
Waterfall model with Boehm’s Second Law9
Waterfall model with Davis Law10
Spiral model with Glass Law10
Spiral model with Boehm’s First Law11
Spiral model with Boehm’s Second Law11
Spiral model with Davis’ Law11
Waterfall Model12
Examples where this model suits12
Examples where this model does not suit12
Spiral Model13
Examples where this model suits13
Examples where this model does not suit13

1. Describe each law in your own words. Illustrate with a practical example.

Glass’ Law

“Requirement deficiencies are the prime source of project failures.” Any coherent and reasonable project must have some requirements that define what that project is supposed to do. The requirements are the basic steps in implementing a project. A requirement is an objective that must be met. There are several types of requirements such as price, performance and reliability objectives. Requirements are instructions describing what functions the project is supposed to provide, what characteristics the project is supposed to have, and what goals the project is supposed to meet. The shortage of requirements causes many problems in starting and implementing a project. This law states that this shortage of requirements is the main source in the failure of the project.


Lack of defined requirements is one of the major reasons for a project to fail. An example project which failed due to lack of requirements is Passport Agency in UK. In this project, the requirements were not defined properly in the defining stage which led to computer problems in the summer of 1998 forcing thousands to cancel their holidays and costing taxpayers £12 million to fix.

Boehm’s first law

“Errors are most frequent during the requirements and design activities and are the more expensive the later they are removed.” There are several errors in the requirements definition stage as well as the design stage. The developer needs to know on what problem he/she is working on or is trying to solve. If they are not working on the exact problem then it costs more later on to solve it. The requirement errors are severe than the design errors. The cost to solve a problem increases as the project moves ahead. This happens because the changes made are more when the project moves ahead.


In April 2003, Germany, an IT project was developed for a child support agency. This website was created to store the details of the children who get the support and the people who supported. This system failed as the errors were not solved at the beginning of the project. Later on these became very serious and exceeded the budget. Due to these errors the project finished two years late and there was an exceed of £56 million pounds.

Boehm’s second law

“Prototyping (significantly) reduces requirement and design errors, especially for user interfaces.” In order to minimize the requirement and design errors, prototyping is used. Prototyping also decreases the gap between implementation and description. Prototyping has the ability to address the rapidly changing software requirements. This reduces the problems between the developers and the users. Prototyping can convert basic, yet sometimes intangible, specifications into tangible specifications. Prototyping can reduce development time, the developers receive quantifiable feedback from the user, also provides with higher user satisfaction. As prototyping has these advantages, the requirement and design errors can be handled.


There was a Programme set up for a company in France, 2003 to streamline payment of benefits through telephone as well as internet. There were several errors in the requirements....

References: Bibliography
Angelfire: Prototyping, retrieved on 111th August, 2009, from
Bing, used on 10th, 11th, 12th, 13th August, 2009, from
David Brown, 1998, Failed IT Projects, retrieved on 12th August, 2009, from,
Google, retrieved on 10th, 11th, 12th and 13th August, 2009, from
Philosophe: Requirements and Specifications, retrieved on 11th August, 2009, from,
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