When to Capitalize Words and when not to capitalize words

Proposed Convention:
In UBL documentation, adopt the following capitalization rule:

• Use Capitalized Words when referring to specific UBL entities (e.g., Contracting Party when referencing the cac:ContractingParty element in the UBL library).
• Use lowercase words when referring to real-world concepts (e.g., contracting party when discussing an actual person or organization in context).

Question: Where should this convention be documented? The UBL Naming and Design Rules (NDRs)? The main UBL documentation, as a note or instruction to the reader (e.g., "Capitalized terms refer to UBL model elements unless otherwise stated")?