Reuse-Based Software Engineering :

Reuse-based software engineering:

•      Application system reuse

–      The whole of an application system may be reused either by incorporating it without change into other systems or by developing application families

•      Component reuse

–      Components of an application from sub-systems to single objects may be reused

•      Function reuse

–      Software components that implement a single well-defined function may be reused

Generator-based reuse:

·         Program generators involve the reuse of
standard patterns and algorithms

·         These are embedded in the generator and
parameterised by user commands – a program is then automatically generated

      Advantage:

•      Generator-based reuse is very cost-effective

•      It is easier for end-users to develop programs using generators compared to other component-based approaches to reuse

Disadvantage:

    Its applicability is limited to a relatively small number of application domains

MOTIVATIONS FOR REUSE :

Today's organizations face competitive pressures in shortening the time required to bring a product to the market, reducing software development and maintenance costs, and increasing the quality of their software. While not a panacea, organizations have increasingly turned to a reuse strategy in order to meet their business goals. Implemented appropriately, reuse can aid in achieving some or all of the following goals:

* Increase productivity

After an initial investment, reuse of existing assets will enable projects to decrease the cost of developing and maintaining software. Hewlett-Packard (HP) reuse projects have reported productivity increases from 6 to 40%.

* Shorten time-to-market

By reusing software to shorten the critical path in delivering a product, organizations within HP have reported a reduction in time-to-market from 12 to 42%.

* Improve software quality

Software that has been used multiple times will possess fewer defects than freshly coded components. One HP organization had mature reused code that had a defect density which was ten times better than new code. Quality improvements in HP products from reuse have ranged from 24 to 76%.

* Reduce risk

Risk in creating new software is reduced when available reusable components already encompass the desired functionality and have standard interfaces to facilitate integration.

* Improve functionality and/or performance

Reuse allows for the investment of time to improve functionality and/or performance. Because this time can be amortized over multiple uses of the assets, this investment for such improvements is more economically justified than the case where they would only be for single product.

Requirements for design with reuse:

•      It must be possible to find appropriate reusable components

•      The re user of the component must be confident that the components will be reliable and will behave as specified

The components must be documented so that they can be understood and, where appropriate, modified