Simple Image Access version 2.0 Erratum 2: Possible confusion between FORMAT and RESPONSEFORMAT parameter

Author: François Bonnarel

Date last changed: 2023-01-24

Date accepted: 2023-04-05

Rationale

In section 2.1.17, the text "The FORMAT parameter specifies response format(s) (the access_format column from the ObsCore [7] data model). " may introduce some confusion between FORMAT and the DALI RESPONSEFORMAT definition. While the latter specifies the format of the service response the first one selects only datasets which can be retrieved in the specified format.

This confusion originally described on github in SIA issue #7 (https://github.com/ivoa-std/SIA/issues/7). An attempt to fix it was done in SIA PR#17 (https://github.com/ivoa-std/SIA/pull/17)

Erratum Content

This Erratum proposes following changes.

Fix FORMAT parameter definition

In §2.1.17 "*FORMAT*" of SIA-2.0,

replace the text

The FORMAT parameter specifies response format(s) (the access_format column from the ObsCore [7] data model). This column describes the format of the response from the access_url (see 3.1.3) so the values could be data file types (e.g. application/fits) or they could be the DataLink [8] MIME type.

by

The FORMAT parameter specifies the format returned by the access link. The value is compared with the access\_format column from the ObsCore data model in order to select the datasets with the required format. This column describes the format of the response from the access_url (see 3.1.3) so the values could be data file types (e.g. application/fits) or they could be the DataLink [8] MIME type.

Impact Assessment

Fixing the text will only forbid implementers to make some confusion between FORMAT and RESPONSEFORMAT (for example using FORMAT to specify a txt or json response format for the SIA service).