# Arbital "parent" relationship

https://arbital.com/p/Arbital_parent_child

by Alexei Andreev Apr 1 2015 updated Sep 20 2017

Parent-child relationship between pages implies a strong, inseparable connection.

Most pages in Arbital can be connected. We call these connections relationships. Parent-child relationship is one of the multiple relationship types and is the tightest way to connect pages on Arbital. This relationship is used to indicate that the child is a critical component of the parent, or that the parent is the sum of its children. For example, the [SI_units SI units] parent page will have [kilogram], [second], [meter], etc… as children pages.

It's perfectly fine for a page not to have any parents or children. It can still be found by searching, and can be used as a tag, requisite, or link.

### When to create a parent-child relationship

When the child doesn't make sense outside of the context of the parent. For example:

• Chapter 2 of "Harry Potter and The Sorcerer's Stone" doesn't make a lot of sense by itself. So it's a child of "Harry Potter and The Sorcerer's Stone (book)" page, which is itself a child of "Harry Potter (book series)" page.

When there is some well-known, established hierarchy. For example:

• "C. lupus (species)", or commonly known as gray wolf, is a child of the "Canis (genus)" page, which is a child of "Canidae (family)" page, etc… This taxonomy of biological organisms is pretty well established.

When the parent is defined as the sum of some parts. For example:

• Arithmetic is addition, subtraction, multiplication and division by definition. So "Arithmetic" page will have those pages as children.

More generally the parent-child relationship suggest a "is-a" or a "is-a-part-of" connetion. Sometimes it's also simply used for organizing pages in a hierarchy to make it easier to find them.

### When not to create a parent-child relationships

Just because two concepts are often associated. For example:

• Chlorophyll, an important biomolecule used for photosynthesis, is usually associated with plants. But not all plants have chlorophyll, and chlorophyll can occur outside of plants, e.g. in algae.

Just because two concepts are closely related. For example:

• Plants, chlorophyll, and photosynthesis are pretty closely related. But photosynthesis as a process can happen in things other than plants or using a mechanism that doesn't involve chlorophyll. And some plants don't even have chlorophyll.

Sometimes it can be unclear if the pages should have a parent-child relationship. If you run into a case you can't clearly resolve, please post it here, so we can discuss it, learn from it, and refine these definitions.