BIND syntax

Robert Syme

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May 15, 2012, 9:18:48 AM5/15/12

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Not the segfaults I promised, but some behaviour that I was not expecting. This might just a SPARQL misunderstanding on my part, but I thought I'd post it here just in case it's not what we would expect.

wget https://gist.github.com/raw/2700250/1f42d12e78e56886951b96dd42fb66aa065c9231/test.rdf

sudo 4s-backend-setup test

sudo 4s-backend test

sudo 4s-import test.rdf

4s-query demo -f tsv "PREFIX eg: <http://example.org/>

SELECT * WHERE {

?gene eg:start ?start .

?gene eg:stop ?stop

BIND(?stop - ?start AS ?length)

}" | column -t

I was hoping that ?length would be evaluated for each solution to the query, but instead ?length is bound to the first solution (120) for all three genes:

?gene ?start ?stop ?length

<http://example.org/gene_01> 300 420 120

<http://example.org/gene_00> 100 200 120

<http://example.org/gene_02> 150 180 120

Is this the expected result?

Steve Harris

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May 15, 2012, 9:59:09 AM5/15/12

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Nope, that's a bug.

There's a test for this case though - does the bind test pass for you? cd tests/httpd ; ./run.pl bind

One thing of note is that you use two different KB in your test below (test and demo) but the result is still wrong.

- Steve

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Steve Harris, CTO

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Rob Syme

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May 16, 2012, 2:56:17 AM5/16/12

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All tests pass:

Just bind:

$ sudo ./run.pl bind

4store[2411]: backend-setup.c:186 erased files for KB http_test_root

4store[2411]: backend-setup.c:318 created RDF metadata for KB http_test_root

../../src/http/4s-httpd -c ../tests_4store.conf -X -D -p 13579 http_test_root

4s-httpd running on PID 2416

[PASS] bind

Tests completed: passed 1/1 (0 fails)

`sudo make test` from the 4store repo root also looks clean.

I've had a look through some of httpd/scripts and I didn't see a test that uses the arithmetic supported by sparql (+ - / * etc). Perhaps the subtraction inside bind is my issue? This is some pretty wild speculation on my part though. I just wish my C was better so I could help.

-r

Robert Syme

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May 16, 2012, 10:45:05 PM5/16/12

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Also, the KB mixup was just a copy/paste error on my part. The tenacious ?length binding persists without the typo.

Also, when 4store doesn't seem to like it when it is forced to cast an http://www.w3.org/2001/XMLSchema#integer into something else. Using the same test dataset from before, division of an integer returns a variable with datatype "¡resource e73e2da015326373 not found!". See below.

I'm submitting unexpected results not because I demand they be fixed, but rather to try and expand the test suite. I hope they help. Would you prefer I submit them to the githup repo as "Issues" to keep the mailing list clean?

$ 4s-query test "SELECT * WHERE {?gene <http://example.org/start> ?start BIND(?start / 2 AS ?bound)}"

<?xml version="1.0"?>

<head>

</head>

<binding name="gene"><uri>http://example.org/gene_00</uri></binding>

</result>

<binding name="gene"><uri>http://example.org/gene_01</uri></binding>

</result>

<binding name="gene"><uri>http://example.org/gene_02</uri></binding>

</result>

</results>

</sparql>

-r

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Registered in England and Wales 653331 VAT # 887 1335 93
Registered office: Landmark House, Experian Way, NG2 Business Park, Nottingham, Nottinghamshire, England NG80 1ZZ

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Steve Harris

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May 17, 2012, 5:42:24 AM5/17/12

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Yeah, I managed to reproduce the sticky value bug yesterday afternoon, but I'm in the hospital today and can't work on it for a few days. Oddly it seemed to only happen with minus, things like STR() and CONCAT() seemed to work. Possibly other mathematical operators have the same problem I don't think there's anything special about minus.

The division case is interesting, that was one of the hard challenges in implementing BIND in 4store, must have slipped through the net somehow.

Sent on the move.

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Rob Syme

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May 17, 2012, 5:44:32 AM5/17/12

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No worries. Get well soon!

-r

Steve Harris

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May 25, 2012, 6:43:42 AM5/25/12

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This is now fixed in Git HEAD

- Steve

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Steve Harris, CTO

Garlik, a part of Experian

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+44 20 8439 8203 http://www.garlik.com/

Registered in England and Wales 653331 VAT # 887 1335 93

Registered office: Landmark House, Experian Way, Nottingham, Notts, NG80 1ZZ

Rob Syme

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May 25, 2012, 9:05:10 AM5/25/12

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Thanks Steve!
-r

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