WARC-Refers-To-Target-URI / WARC-Refers-To-Target-Date header fields not allowed in conversion records

[ikreymer]

The WARC-Refers-To-Target-URI / WARC-Refers-To-Target-Date headers should be allowed wherever the WARC-Refers-To header is used, as these were introduced as an alternative to the WARC-Refers-To header.

But, the spec contains for WARC-Refers-To:

The WARC-Refers-To field may also be used to associate a record of type 'revisit' or 'conversion' with
the preceding record which helped determine the present record content. The WARC-Refers-To field
shall not be used in 'warcinfo', 'response', ‘resource’, 'request', and 'continuation' records. 

While:

The WARC-Refers-To-Target-URI field may be used in ‘revisit’ records and shall not be used in
'warcinfo', 'response', 'metadata', 'conversion', ‘resource’, 'request', and 'continuation' records. 

The WARC-Refers-To-Date field may be used in ‘revisit’ records and shall not be used in 'warcinfo',
'response', 'metadata', 'conversion', ‘resource’, 'request', and 'continuation' records. 

For the same reasons as with revisit records, these headers should also be allowed in conversion records to allow referring to an original record by url / date.

[ato]

I support this. It would go some way to resolving the first problem in #40. I also think its important the standard gives clear guidance that WARC-Date on a conversion record is the date of conversion not of the capture of the original resource.

[anjackson]

For context, here's an example record given to me by @ikreymer

WARC/1.0
WARC-Date: 2019-03-04T22:36:36Z
WARC-Source-URI: file:///Users/ilya/work/videowork/sample/conversions/www.snp.org/blog/post/2012/feb/scottish-independence-good-england/CTOAAND9Y6W.flv/CTOAAND9Y6W.flv.webm
WARC-Refers-To-Target-Date: 2019-02-06T00:29:48Z
WARC-Creation-Date: 2019-03-04T22:44:03Z
WARC-Refers-To: <urn:uuid:d13b3617-141b-4df3-a8cb-d78f43d89815>
WARC-Refers-To-Target-URI: http://www.snp.org/blog/post/2012/feb/scottish-independence-good-england/CTOAAND9Y6W.flv/CTOAAND9Y6W.flv
WARC-JSON-Metadata: {"command": "ffmpeg -y -i {input} -c:v vp9 -c:a libopus -speed 4 {output}", "mime": "video/webm", "ext": "webm", "name": "webm"}
WARC-Type: conversion
WARC-Record-ID: <urn:uuid:b95604c2-dead-497d-8bcd-3895250d47bd>
WARC-Target-URI: http://www.snp.org/blog/post/2012/feb/scottish-independence-good-england/CTOAAND9Y6W.flv/CTOAAND9Y6W.flv.webm
WARC-Payload-Digest: sha1:WH77LXAVIATCUPGDI4E26OXHUBSTXGXT
WARC-Block-Digest: sha1:WH77LXAVIATCUPGDI4E26OXHUBSTXGXT
Content-Type: video/webm
Content-Length: 2209509