Maniphest T196798

SPARQL federated query SERVICE endpoint syntax (variable instead of uri)
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	Esc3300
	Jun 9 2018, 3:59 AM

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Esc3300

Gehel

• Lucas_Werkmeister_WMDE

Smalyshev

Zache

Description

Current samples for federated queries in SPARQL with blazegraph suggest the following format:

SERVICE <http://data.cervantesvirtual.com/openrdf-sesame/repositories/data>  { .. }

SERVICE SILENT <http://data.cervantesvirtual.com/openrdf-sesame/repositories/data>  { .. }

Following the discussion here, it seems that the following should be valid as well:

BIND(uri("http://data.cervantesvirtual.com/openrdf-sesame/repositories/data") as ?endpoint)
SERVICE ?endpoint  { .. }

?item wdt:P123456 ?endpoint .
SERVICE ?endpoint  { .. }

Obviously, provided that the endpoint is accessible from query.wikidata.org. If not:

?item wdt:P123456 ?endpoint .
SERVICE SILENT ?endpoint  { .. }

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		Status	Subtype	Assigned	Task
		Resolved		None	T197530 [tracking] federation query issues on Wikidata Query Server
		Declined		None	T196798 SPARQL federated query SERVICE endpoint syntax (variable instead of uri)

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Esc3300 created this task.Jun 9 2018, 3:59 AM

Restricted Application added projects: Wikidata, Discovery-ARCHIVED. · View Herald TranscriptJun 9 2018, 3:59 AM

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Esc3300 updated the task description. (Show Details)Jun 9 2018, 4:10 AM

Using a variable as the service endpoint is syntactically valid, but the semantics of it is undefined per SPARQL 1.1 Federated Query, section 4:

In the this section we do not present official evaluation semantics for the SPARQL pattern SERVICE VAR. We only provide indications about how the evaluation of the SPARQL pattern SERVICE VAR can be evaluated.

In T196798#4269194, @Lucas_Werkmeister_WMDE wrote:

Using a variable as the service endpoint is syntactically invalid,

Shouldn't that read valid instead of invalid ?

Indeed, thank you (edited).

Coming to the second part:

In T196798#4269194, @Lucas_Werkmeister_WMDE wrote:

the semantics of it is undefined per SPARQL 1.1 Federated Query, section 4:

Would this have an actual impact?

It seems that even when using URI, the same service can be called just once.

Esc3300 added a parent task: T197530: [tracking] federation query issues on Wikidata Query Server.Jun 17 2018, 7:58 AM

Smalyshev triaged this task as Medium priority.Jun 21 2018, 10:42 PM

• Vvjjkkii renamed this task from SPARQL federated query SERVICE endpoint syntax (variable instead of uri) to pcbaaaaaaa.Jul 1 2018, 1:05 AM

• Vvjjkkii raised the priority of this task from Medium to High.

• Vvjjkkii added projects: CheckUser, Connected-Open-Heritage-Batch-uploads (RAÄ-KMB_1_2017-02), Tamil-Sites, Gamepress, Hashtags, Jade, KartoEditor, Language-2018-Apr-June, New-Editor-Experiences, Mail, TCB-Team (now WMDE-TechWish).

• Vvjjkkii updated the task description. (Show Details)

• Vvjjkkii removed a subscriber: • Aklapper.

CommunityTechBot renamed this task from pcbaaaaaaa to SPARQL federated query SERVICE endpoint syntax (variable instead of uri).Jul 2 2018, 3:02 PM

CommunityTechBot lowered the priority of this task from High to Medium.

CommunityTechBot updated the task description. (Show Details)

CommunityTechBot removed projects: TCB-Team (now WMDE-TechWish), Mail, New-Editor-Experiences, Language-2018-Apr-June, KartoEditor, Jade, Hashtags, Gamepress, Tamil-Sites, Connected-Open-Heritage-Batch-uploads (RAÄ-KMB_1_2017-02), CheckUser.

CommunityTechBot added a subscriber: • Aklapper.

Zache subscribed.Feb 5 2019, 10:44 AM

Gehel moved this task from Incoming to Scratch on the Wikidata-Query-Service board.Feb 13 2020, 2:15 PM

Changing the syntax of SERVICE calls would require changing the Blazegraph implementation, which should be done upstream. I'm closing this, feel free to reopen if you feel strongly about it.

SPARQL federated query SERVICE endpoint syntax (variable instead of uri)Closed, DeclinedPublicActions

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SPARQL federated query SERVICE endpoint syntax (variable instead of uri)
Closed, DeclinedPublic
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