SSA v1.1 Erratum 2: Invalid UCDs required in specification 1.0

Author: Mireille Louys

Date last changed: 2022-01-17

Date accepted: -

Issue: SSA Issue #1

Rationale

Appendix D: SSA Data Model Summary p.64 lists the data model elements supported by this specification with Utypes and UCDs.

Some of the UCDs proposed lead to ambiguous interpretation and do not strictly follow the combination rules proposed in the UCD specification,namely intsr.fov

UCD requires instr.fov to be secondary. Hence, the UCDs for the fields with utypes

Char.SpatialAxis.Coverage.Bounds.Extent, Char.SpatialAxis.Coverage.Support.Area, Char.SpatialAxis.Coverage.Support.Extent

as prescribed by SSAP 1.1 are invalid and need to be repaired.

This erratum provides valid UCDs, which not only have proper semantics but also enable UCD-aware clients to determine the nature of the fields if they do not know the SSAP data model.

Erratum_Content

This erratum makes the following changes in the table P. 64:

Impact Assessment

SSAP clients do not identify fields by UCDs and hence are unaffected by this change.

Clients relying on UCDs to determine how to treat individual columns will now be able to gain some basic
understanding of the affected columns, which they could not before (as the UCDs were invalid and hence meaningless).

Most importantly, valid SSAP services will raise fewer errors in UCD validation.

Topic_action

UCDList EN-1.4 defines /instr.fov/ as

S | instr.fov | Field of view

This definition is fuzzy, and can be clarified and replaced by