Clarifications on "apex group" in CF Groups section

[benjwadams]

Question

I'm trying to implement the various search strategies for CF Conventions for groups. I need some clarification on the lateral search implementation for coordinate variables.

https://cfconventions.org/Data/cf-conventions/cf-conventions-1.11/cf-conventions.html#_search_by_proximity

A special case exists for coordinate variables. Because coordinate variables must share dimensions with the variables that reference them, the ancestor search is executed only until the local apex group is reached. For coordinate variables that are not found in the referring group or its ancestors, a further strategy is provided, called lateral search. The lateral search proceeds downwards from the local apex group width-wise through each level of groups until the sought coordinate is found. The lateral search algorithm may only be used for NUG coordinate variables; it shall not be used for auxiliary coordinate variables.

What is considered a "local apex group" here?

[benjwadams]

Never mind, looks like this is defined section 1.3:

https://cfconventions.org/Data/cf-conventions/cf-conventions-1.11/cf-conventions.html#terminology

Closing.