# OBO: 1.3 Whiteboard

From GO Wiki

This page is intended to be a scratch pad for OBO 1.3 features and proposals.

## Changes to Relations

The following new Typedef tags should be supported in OBO 1.3...

- transitive_under
- always_implies_inverse

**transitive_under** means that **p -transitive_under-> q** and **X -q-> Y** and **Y -p-> Z**, then **X -p-> Y**. Note that every relation is automatically transitive_over and transitive_under IS_A

**always_implies_inverse** is a boolean property. If always_implies_inverse is true for a relation **p**, it means that if **p -inverse_of-> q** and **X -p-> Y**, then **Y -q-> X**. This property could be used to define an **integral_part_of** relationship in OBO_REL, for example:

[Typedef] id: OBO_REL:part_of name: part of inverse_of: has_part [Typedef] id: OBO_REL:has_part name: has part [Typedef] id: OBO_REL:integral_part_of is_a: OBO_REL:part_of always_implies_inverse: true