Hi Luís,
I would suggest reporting this issue on the Virtuoso open source git issue
tracker at:
https://github.com/openlink/virtuoso-opensource/issues
which is where most now report issues or ask questions since we move to using
git ...
Also, do you have a minimal test case for recreating the issue, as if so that
should be provided as well ...
Best Regards
Hugh Williams
Professional Services
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> On 11 May 2022, at 10:56, Luís Moreira de Sousa via Virtuoso-users
> <virtuoso-users@lists.sourceforge.net> wrote:
>
> Dear all,
>
> after a few more tests it is starting to look like the problem is actually
> with the geof:buffer function. A full example is at the of this message.
> Whatever the function is returning, it is certainly not a 10 metre buffer
> around the point.
>
> What could be going wrong here? If it is relevant the version I am using is
> 07.20.3233.
>
> Thank you.
>
>
> SPARQL
> PREFIX geo: <http://www.opengis.net/ont/geosparql#
> <http://www.opengis.net/ont/geosparql#>>
> PREFIX geof: <http://www.opengis.net/def/function/geosparql/
> <http://www.opengis.net/def/function/geosparql/>>
> PREFIX ex: <https://example.com <https://example.com/>#>
>
> SELECT geof:buffer(?lit_b, 10, <http://www.opengis.net/def/uom/OGC/1.0/metre
> <http://www.opengis.net/def/uom/OGC/1.0/metre>>)
> FROM <https://example.com <https://example.com/>#>
> WHERE {
> ex:point_b geo:asWKT ?lit_b .
> };
> Type the rest of statement, end with a semicolon (;)> Type the rest of
> statement, end with a semicolon (;)> Type the rest of statement, end with a
> semicolon (;)> Type the rest of statement, end with a semicolon (;)> Type the
> rest of statement, end with a semicolon (;)> Type the rest of statement, end
> with a semicolon (;)> Type the rest of statement, end with a semicolon (;)>
> Type the rest of statement, end with a semicolon (;)> Type the rest of
> statement, end with a semicolon (;)> callret-0
> LONG VARCHAR
> _______________________________________________________________________________
>
> POLYGON((61 51,60.807852804032 49.049096779839,60.238795325113
> 47.173165676349,59.314696123025 45.444297669804,58.071067811865
> 43.928932188135,56.555702330196 42.685303876975,54.826834323651
> 41.761204674887,52.950903220161 41.192147195968,51 41,49.049096779839
> 41.192147195968,47.173165676349 41.761204674887,45.444297669804
> 42.685303876975,43.928932188135 43.928932188135,42.685303876975
> 45.444297669804,41.761204674887 47.173165676349,41.192147195968
> 49.049096779839,41 51,41.192147195968 52.950903220161,41.761204674887
> 54.826834323651,42.685303876975 56.555702330196,43.928932188134
> 58.071067811865,45.444297669804 59.314696123025,47.173165676349
> 60.238795325113,49.049096779839 60.807852804032,51 61,52.950903220161
> 60.807852804032,54.826834323651 60.238795325113,56.555702330196
> 59.314696123025,58.071067811865 58.071067811865,59.314696123025
> 56.555702330196,60.238795325113 54.826834323651,60.807852804032
> 52.950903220161,61 51))
>
> 1 Rows. -- 29 msec.
>
>
> --
> Luís
> ------- Original Message -------
> On Tuesday, May 10th, 2022 at 9:25 AM, Luís Moreira de Sousa via
> Virtuoso-users <virtuoso-users@lists.sourceforge.net> wrote:
>
>> Dear all,
>>
>> I am currently unable to use the geof:sfIntersects function as it produces
>> unexpected results. As an example consider the following graph:
>>
>> @prefix geo: <http://www.opengis.net/ont/geosparql#
>> <http://www.opengis.net/ont/geosparql#>> .
>> @prefix ex: <https://example.com <https://example.com/>#> .
>>
>> ex:point_a a geo:Point ;
>> geo:asWKT "POINT(50 50)"^^geo:wktLiteral .
>>
>> ex:point_b a geo:Point ;
>> geo:asWKT "POINT(51 51)"^^geo:wktLiteral .
>>
>>
>> The use case is to identify points that lay within a certain distance from
>> each other. This can be obtained with a query like:
>>
>> SPARQL
>> PREFIX geo: <http://www.opengis.net/ont/geosparql#
>> <http://www.opengis.net/ont/geosparql#>>
>> PREFIX geof: <http://www.opengis.net/def/function/geosparql/
>> <http://www.opengis.net/def/function/geosparql/>>
>> PREFIX ex: <https://example.com <https://example.com/>#>
>>
>> SELECT geo:sfIntersects(?lit_a, geof:buffer(?lit_b, 10,
>> <http://www.opengis.net/def/uom/OGC/1.0/metre
>> <http://www.opengis.net/def/uom/OGC/1.0/metre>>))
>> FROM <https://example.com <https://example.com/>#>
>> WHERE {
>> ex:point_a geo:asWKT ?lit_a .
>> ex:point_b geo:asWKT ?lit_b .
>> };
>>
>> Which produces the following result:
>>
>> INTEGER NOT NULL
>> _______________________________________________________________________________
>>
>> 1
>>
>> 1 Rows. -- 6 msec.
>>
>>
>> One obvious problem is the return type, it should be a xsd:boolean literal
>> (OGC 11-052r4
>> Table 5), but is an integer instead (also not xsd:integer). But beyond that,
>> it seems to point to a "true", whereas those two points lay much farther
>> apart than 10 metres.
>>
>> As a sanity check, with a buffer of width zero the result is 0 (again
>> integer type):
>>
>> SQL> SPARQL
>> PREFIX geo: <http://www.opengis.net/ont/geosparql#
>> <http://www.opengis.net/ont/geosparql#>>
>> PREFIX geof: <http://www.opengis.net/def/function/geosparql/
>> <http://www.opengis.net/def/function/geosparql/>>
>> PREFIX ex: <https://example.com <https://example.com/>#>
>>
>> SELECT geo:sfIntersects(?lit_a, geof:buffer(?lit_b, 0,
>> <http://www.opengis.net/def/uom/OGC/1.0/metre
>> <http://www.opengis.net/def/uom/OGC/1.0/metre>>))
>> FROM <https://example.com <https://example.com/>#>
>> WHERE {
>> ex:point_a geo:asWKT ?lit_a .
>> ex:point_b geo:asWKT ?lit_b .
>> };
>> Type the rest of statement, end with a semicolon (;)> Type the rest of
>> statement, end with a semicolon (;)> Type the rest of statement, end with a
>> semicolon (;)> Type the rest of statement, end with a semicolon (;)> Type
>> the rest of statement, end with a semicolon (;)> Type the rest of statement,
>> end with a semicolon (;)> Type the rest of statement, end with a semicolon
>> (;)> Type the rest of statement, end with a semicolon (;)> Type the rest of
>> statement, end with a semicolon (;)> Type the rest of statement, end with a
>> semicolon (;)> callret-0
>> INTEGER NOT NULL
>> _______________________________________________________________________________
>>
>> 0
>>
>> 1 Rows. -- 5 msec.
>>
>> Looks like something is going wrong. How can I obtain a correct result from
>> geof:sfIntersects?
>>
>> Thank you.
>>
>> --
>> Luís
>>
>
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