People are innately drawn to things in threes; to objects in triplicate. There's the classic Christian trinity, where God is divided up neatly into three parts: the father, the son, and the holy spirit. But there are many other trinities:
- mind, body and soul
- thinking, feeling and acting
- work/life/play balance
- the division of pregnancy into three trimesters
- animal, vegetable and mineral
- Christians, Muslims and Jews
- protons, neutrons and electrons
- the First, Second and Third Worlds
- sex, politics and religion
- family, friends and co-workers
It could be that three represents a careful, comforting and symbiotic balance. While it's true that just two things can "balance" each other (picture two equal riders on a see-saw), extending the number to three seems to add that extra element of desired symmetry. Each of three balances out each other in a psychologically pleasing way.
DITA, an XML markup language that is revolutionizing how content is stored, created and managed, also uses a trinity. In DITA, all content is stored as individual, modular topics. There are three basic DITA topic types in which all content can be classified: concepts, tasks, and references.
- A concept topic describes what something is or why you would perform a task. It gives the idea behind something; the background information that the reader needs to know.
- A task topic gives detailed, step-by-step procedures for a specific action. It can include pre-requisites and expected results. It is one of the most common topic types.
- A reference topic contains technical material, specifications, lookups and other detailed information, often in a table form. Examples include command references, allowed values, lists and catalogues.
For example:
- In a task, do not include a detailed explanation of why you would perform this task. Maintain this background information in a concept, then, if necessary, link it to the task topic.
- In a concept, do not include procedural steps. Keep these steps in a task topic.
- If there are many possible values to choose from in a task, do not include them in the task, but in a reference topic instead.
And it's as easy as 1-2-3....