Reuse is a poor objective

This is an example of something that can be  a good outcome can be a poor objective

Increasing re-use is one of the most common goals of Information and Technology organisations. And likely one of the most misleading, even damaging.

Although re-use itself (as a consequence of other activities) may be relatively benign, when it becomes an objective, it can cause undesirable behaviours.

Defining re-use

Let us start by contrasting the behaviours of two persons: Mr Maximise Reuse and Ms Minimise Diversity.

When faced with a new challenge, Mr Maximise Reuse demonstrates behaviours such as:

• Look at existing code.
• Take copies of existing code to use as the basis for new capability
• Modify the copies and integrate into new capability (only developing new code where required)

Ms Minimise Diversity approaches the challenge in a different way:

• Browse and understand the current services and how they interact – where common capabilities are called etc.
• Modify existing services to handle the additional functionality required
• Break large or complex service into component parts
• Eliminate variations of components by pulling common features into shared components

Using simplified terminology, the contrast between the two approaches is total:

Characteristic	Mr Maximise Re-use	Ms Minimise Diversity
Number of “methods”	UP	DOWN
Overall “consistency”	DOWN	UP
Maintenance Overhead	UP	DOWN
Re-use measure	UP	DOWN

Reuse as an objective should only be contemplated if there is a tight and coherent definition of reuse that promotes the desired behaviours.

(See also you get what you measure but perhaps not what you intended)