Need clarification on section 3.3.1 regarding invalid path

[kyoungyun]

Hi.
In section 3.3.1 (Get), looking at the following particular portion:

path - a set of paths (expressed as per Section 2.2.2) for which the client is requesting a data snapshot from the target. The path specified MAY utilize wildcards. In the case that the path specified is not valid, the target MUST return an RPC response indicating an error code of InvalidArgument and SHOULD provide information about the invalid path in the error message or details.

What is considered an invalid path? There are two possibilities:

• The path is not represented or defined by a model
• The path IS defined by a model but is not instantiated

Are both cases considered an invalid path, OR is an empty value (or null) returned for the second the second case?