Keep your documentation simple. Assume that authors have relevant information for the project in their mind, but not necessarily the skills and resources to communicate it. Therefore make it very simply and joyful for them to share their expertise.

Domain: Software Design
Values: Easy to find, Easy to understand, Easy to use, Easy to write, Easy to maintain

KISS - Keep It Simple, Stupid: Complex things need to be explained at an appropriate, simple level. Complex things need not to be complicated.

Everything should be made as simple as possible, but not simpler.
Albert Einstein

To explain complex things in a simple way, may be a lot of work, though.

It seems that perfection is reached not when there is nothing left to add, but when there is nothing left to take away.
Antoine de Saint-Exupéry

Related Practices

The following practices are related to this principle.

Agile Documentation: A document is considered to follow the agile principle if it is valuable, essential, and created or updated just-in-time. A documentation is created and maintained in an agile way, if all its documents follow this practice.
Employ a Style Guide: All publishing organizations define a style guide for their published information. Such a guide supports teams to write in a similar tone, making it easier for readers to digest the information.
Keep a Journal: In order to take personal notes on one's own work and to reflect upon what has to be done or has been done, keep a journal. The information in the journal should be shareable at least with all team members.
Know your Mission: Use charters to define the purpose and benefit of each document. State the expectation of the stakeholders involved.
No Noise: Do not render text to the reader that has no information value.
Use Templates: Define a basic structure for all artifacts of a given type. Readers will have an easier job on finding and learning about the information in your documentation.

Related Principles

The following principles are related to this principle.

DRY Principle: Redundant information is hard to maintain, keeping it in-sync. Therefore strive for reducing redundancy by defining one authoritative location for each piece of information.
Law of Demeter: Documents should not reference details in other documents that may change without notice.
Open Closed Principle: Be open for extension, closed for modification.
Principle of least Astonishment: Documentation should appear to the reader as being written by one single person. Uniformity reduces the chance of astonishment. The principles applies to all areas of documentation, including style and organization.
Self Documentation Principle: There should either be no need for additional documentation for an artifact or that documentation should be as close as possible to the artifact. This make it more probable that the documentation changes with the artifact and therefore keeps up-to-date.
Separation of Concerns: Reduce the amount of documents with overlapping information. Also divide the concerns regarding the formatting and - as far as possible - the structure from the content. Whenever there are different aspects, consider if handling them independently would make things easier.
Single Responsibility Principle: A document should focus to answer one question. This way documents can be more easily reused and combined.
Stable Dependencies Principle: A document should only reference documents that are not less stable than itself.
YAGNI Principle: Assume that an information is not needed to be written down unless proven otherwise.

References

More information on this principle.

Keep It Simple: The principle described as a pattern on wiki.c2.com.
KISS principle: The principle described on Wikipedia.

KISS Principle

Related Practices

Related Principles

References