From Randy:
Permanent links have the form:
https://reference.opcfoundation.org/Machinery/Jobs/v100/docs/7.2

Where v100 is the document version (1.0.X) and 7.2 is the section number.

Search links shall not be used at all. They are not guaranteed to return the same results in the future.

While the links are a huge convenience for the reader, they should not be in normative text. The published document is the bible (the standard).
We could allow for non-normative text/examples.

From Jim:
Even the "permanent" links are not really permanent. For example:

1. We make no claim to keep all versions of a spec online, so links to older versions may go dead.
2. With the core specs, only the latest version is online and the section numbering can change between versions, so the permalink may resolve, but it could bring you to the wrong section.
   I suggest we discourage any deep hyperlinks between OPC UA Specs including companion specs.