Wikidata nodeID values sometimes start with numbers, causing parsing issues.
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	Vahurzpu
	May 14 2020, 1:05 AM

Description

Problem:
A user pointed out on the Project Chat (link, permalink) that the current RDF exports are not valid RDF.

Specifically, running the following code (with rdflib 4.2.2):

G = rdflib.Graph()
G.load('https://www.wikidata.org/wiki/Special:EntityData/Q42.rdf')

produces the error

rdflib.exceptions.ParserError: https://www.wikidata.org/wiki/Special:EntityData/Q42.rdf:5125:2: rdf:nodeID value is not a valid NCName: 3d66a9a972a16b3583effd41e5f2aff4

The RDF specification states that a nodeID should have type rdf-id, rdf-id is equivalent to NCName, and NCNames cannot start with numbers.

Example:

import rdflib
rdflib.Graph().load('https://www.wikidata.org/wiki/Special:EntityData/Q42.rdf?revision=1283437880')

Acceptance criteria:

Wikidata's RDF output is valid

Notes:

coordinate this change with Query Service team
It seems that prepending a letter should fix this issue. See also Lucas' comment.

Related Objects

Mentioned In: R2307:7c9772244523: Work around T252731
Mentioned Here: T244341: Stop using blank nodes for encoding SomeValue and OWL constraints in WDQS
T245541: Add a new munge option to do blank node skolemization
R2307:7c9772244523: Work around T252731

Event Timeline

Vahurzpu created this task.May 14 2020, 1:05 AM

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptMay 14 2020, 1:05 AM

Bovlb subscribed.May 14 2020, 4:01 AM

Lucas_Werkmeister_WMDE mentioned this in R2307:7c9772244523: Work around T252731.Aug 28 2020, 12:33 AM

Mentioned in SAL (#wikimedia-cloud) [2020-08-28T00:34:10Z] <wm-bot> <lucaswerkmeister-wmde> deployed 7c97722445 (work around T252731)

Lucas_Werkmeister_WMDE updated the task description. (Show Details)Sep 29 2020, 11:42 AM

If I understand correctly, these node IDs are specifically used for blank nodes. We used to number these sequentially, but then switched to using hashes in generate stable labels for blank nodes (compare T245541); I assume that’s what caused this issue.

Since we only recently changed these node IDs, and I believe they’re not meant to be meaningful, we can probably change them again – but we should coordinate this with the query service team to ensure the query service updater doesn’t get confused by the new format.

no objections to prefixing a letter or a couple chars here, the query service munging process can easily be adapted to remove such prefixes when skolemizing the blank nodes.

Lydia_Pintscher added a project: Wikidata-Campsite.Sep 29 2020, 4:18 PM

Lydia_Pintscher updated the task description. (Show Details)Oct 1 2020, 2:57 PM

Lydia_Pintscher moved this task from Incoming to Unconnected Stories on the Wikidata-Campsite board.

CBogen moved this task from Incoming to Current work on the Wikidata-Query-Service board.Oct 5 2020, 3:43 PM

CBogen added a project: Discovery-Search (Current work).

CBogen moved this task from Incoming to Blocked/Waiting on the Discovery-Search (Current work) board.

I just realized that T244341: Stop using blank nodes for encoding SomeValue and OWL constraints in WDQS would also solve this issue, since we would no longer emit blank nodes at all.

I'm closing this then in favor of T244341 then and we'll push that forward.

Wikidata nodeID values sometimes start with numbers, causing parsing issues.Closed, DeclinedPublicActions

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Wikidata nodeID values sometimes start with numbers, causing parsing issues.
Closed, DeclinedPublic
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