SIG Maintainability Model

The degree of effectiveness and efficiency with which it is possible to assess the impact on a product or system of an intended change to one or more of its parts, or to diagnose a product for deficiencies or causes of failures, or to identify parts to be modified.

The degree to which a product or system can be effectively and efficiently modified without introducing defects or degrading existing product quality.

The degree of effectiveness and efficiency with which test criteria can be established for a system, product or component and tests can be performed to determine whether those criteria have been met.

The degree to which a system o r computer program is composed of discrete components such that a change to one component has minimal impact on other components.

The degree to which an asset can be used in more than one system, or in building other assets.

The overall size of the source code of the software product matters.

Avoid occurrence of identical fragments of source code in more than one place in the product.

Keep units smaller than 30 lines.

Keep number of decision points per unit below 5.

Large interfaces are deemed to be harder to maintain.

Software products where more source code resides in modules that are strongly coupled with other modules are deemed to be harder to maintain.

When a system has too much or too few components, it is considered to be more difficult to understand and harder to maintain.

Hide as much as possible of modules. A module is hidden if there are no incoming dependencies from modules in other components.