Thanks Andy, I now no longer use the ARQParser directly, but do as you
suggested. I wrap the graph pattern in `SELECT * { ... }` and parse it as a
regular Query and retrieve the ElementPathBlock using getQueryPattern(). Thanks!
-----Original Message-----
From: Andy Seaborne <[email protected]>
Sent: vrijdag 8 april 2022 15:42
To: [email protected]
Subject: Re: ARQ variables with dashes
On 08/04/2022 14:00, Nouwt, B. (Barry) wrote:
> Hi Andy and Lorenz, thanks for your quick replies. I am not trying to parse
> full SPARQL, but actually only the Basic Graph Pattern part of a query.
The most robust way is to wrap in enough query text, "SELECT * {"+ + "}"
and pull out the WHERE clause with getQueryPattern().
> Is the org.apache.jena.sparql.lang.arq.ARQParser class not parsing SPARQL 1.1?
Yes, it is. ARQ is a superset of SPARQL 1.1
> Based on Andy's directions it seems like doing the following additional check
> after parsing the string works for detecting graph patterns with dashes in
> their variable name at the object location.
>
> if (parser1.token.next.kind == ARQParser.EOF) {
> // found valid graph pattern
> System.out.println("Graph pattern parse successful!"); } else {
> // stream not empty, so not a valid graph pattern
> System.out.println("Graph pattern parse failed!"); }
That assumes the parser did not peek ahead.
token.next may be null and you need to call getNextToken() -- from looking at
the parser have code. Or maybe check parser.token.endColumn /
parser.token.endLine ;
Best is to use a parser rule - either full query or modify the parser.
>
> Thanks for your help!
>
> Best regards,
>
> Barry
>
> -----Original Message-----
> From: Andy Seaborne <[email protected]>
> Sent: dinsdag 5 april 2022 14:07
> To: [email protected]
> Subject: Re: ARQ variables with dashes
>
> Inline.
>
> Summary : it didn't consume the whole input, only up to the end of the legal
> part.
>
> On 05/04/2022 12:43, Lorenz Buehmann wrote:
>> Hi Barry,
>>
>>
>> Did you try SPARQL1.1 parser instead? Afaik, ARQ was always beyond
>> SPARQL 1.1 or better said, already before SPARQL 1.1 with some extensions.
>>
>> Indeed, Andy will correct me soon :D
>>
>> The grammar files for JavaCC are here:
>>
>> https://github.com/apache/jena/tree/main/jena-arq/Grammar
>>
>> You can check arq.jj and sparql_11.jj
>>
>>
>> Or just wait for Andy's response ...
>>
>>
>> Cheers,
>>
>> Lorenz
>>
>>
>>
>> On 05.04.22 13:21, Nouwt, B. (Barry) wrote:
>>> Hi everyone,
>>>
>>> We are using ARQ's SPARQL parser to parse graph patterns and noticed
>>> that it allows dashes in variable names if these variables occur as
>>> the *object* location of a triple pattern. If the variable names at
>>> the *subject* location of a triple pattern contains dashes, it fails
>>> with a ParseException. As far as we could tell the SPARQL
>>> specification does not allow dashes in variable names at all
>>> (https://www.w3.org/TR/sparql11-query/#rVARNAME). The pattern1 and
>>> pattern2 below should both fail, but the first one does not fail and
>>> the second does fail.
>>>
>>> String pattern1 = "<test> https://www.tno.nl/example/b ?community-ID
>>> ."; ARQParser parser1 = new ARQParser(new StringReader(pattern1));
>>> parser1.GroupGraphPatternSub();
>
> Calling into the middle of the parse doesn't work so easily.
>
> It has parsed up to the end of legal triple pattern.
>
> "<test> https://www.tno.nl/example/b ?community"
>
> when it sees the "-" the variable name has ended and (because the "."
> is not required) it is a legal GroupGraphPatternSub
>
> The "-ID ." is left in the token input stream.
>
> You have to test whether end-of-input has been reached.
>
>
> try
>
> qparse 'SELECT * { <test> <p> ?o-1 }'
>
> Parse error because "-1", the next token (tokenizing is done ahead of where
> the parser grammar is the 1 in LL(1)) is not legal.
>
> This is illegal because there is check for end of input:
>
> qparse 'SELECT * { <test> <p> ?o } XXX'
>
> The top level entry point is
>
> void QueryUnit(): { }
> {
> ByteOrderMark()
> Query()
> <EOF>
> }
>
> so the parser must see <EOF> to be valid and exit without error.
>
> Andy
>
>>>
>>> String pattern2 = "?community-ID https://www.tno.nl/example/b <test>
>>> ."; ARQParser parser2 = new ARQParser(new StringReader(pattern2));
>>> parser2.GroupGraphPatternSub();
>>>
>>> Is this a bug?
>>>
>>> Best regards,
>>>
>>> Barry
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