The RFC 9253 defines a set of relationships and other useful parameters and parameter types.
In order to claim compatibility, we should have an implementation for those.

• 8.2. Link
  • URI
  • UID
  • XML-REFERENCE
  • LABEL
  • LANGUAGE
  • LINKREL
    • This parameter MUST be specified on all LINK properties
    • LINKREL=latest-version
    • always quoted
  • FMTTYPE
    • check compatibility with existing type - other RFC might be referenced
  • with typing and enum
• RELTYPE: FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH, or STARTTOSTART
• RELTYPE: FIRST, NEXT, DEPENDS-ON, REFID, CONCEPT
• 6.2. Gap
• VALUE=UID - should map to our UID
• VALUE=XML-REFERENCE - new type
• 8.1. Concept
• 8.3. Refid
• 9.1. RELATED-TO
• documentation for compatibility

The RELTYPE parameter is extended to take new values defining temporal relationships, a GAP parameter is defined to provide lead and lag values, and RELATED-TO is extended to allow URI values. These changes allow the RELATED-TO property to define a richer set of relationships useful for project management.