Collective code ownership is an important factor of XP

Problems of Individual Code Ownership

Among cases I have known, the teamwork is mostly divided according to features. For example, Developer A is responsible for Feature A, and Developer B is responsible for Feature B. One will not take care of the other one's responsibilities. Consequently, a lot of problems are caused.

Since one is only responsible for the module/feature s/he is developing, no one knows/understand the other one's work. It means cooperation and communication are not much.

No cooperation means no teamwork. Besides, there is always developer who claim challenging tasks/bugs and ones who claim easy ones. This will motivate neither of the two kinds.

This is also caused by the lack of communication. Redundant work is a waste of human resource.

4. Knowledge cannot be shared within the team.

When developing modules/features, certain knowledge-silo is build up. Because each one is only taking care his/her responsibility and no cooperation/ communication, the accumulated knowledge cannot be shared with others.

5. It is very risky as only the one who develope the feature know it. Once the developer leaves, it will cause problems and affect the company.

This is the last thing a company would like to see. If the module owner leaves, no one else can take over his/her module due to the individual code ownership.

Therefore, collective code ownership is practiced in Extreme Programming. It is to bridge the barrier within a team. Each module should be understood by at least two developers who back up with each other, and so knowledge could be passed around and developers can come and go without causing problems.