Re: what functions should we include in SPARQL 1.1?

Hi,

For Geo functions, the OGC is working on standardizing a set of 
functions for spatial operations. The functions are basically a direct 
copy of the functions defined for Simple Features (ISO 19125-1). There 
will probably be things like:

ogcf:relate (geom1: rdfs:Literal, geom2: rdfs:Literal, relation: 
xsd:anyURI, srid: xsd:anyURI): xsd:boolean

Where geom1 and geom2 are literals containing standard, text-based 
serializations of geometries (e.g. well-known text, GML, KML). There 
will probably be new datatypes defined e.g. ogc:WKTLiteral.

So you could have,

SELECT
WHERE {?s rdf:type my:LandParcel .
       ?s my:hasPointGeometry ?pg .
       ?pg ogc:asWKT ?wkt
        FILTER (ogcf:relate(?wkt,
                  "POLYGON((-83.3 34.0, -83.3 34.2, -83.1 34.2, -83.1 
34.0, -83.3 34.0))"^^ogc:WKTLiteral,
                  ogc:within, <http://www.opengis.net/def/crs/EPSG/0/4326>))
}

The full set of Simple Features functions is probably too much for most 
implementors, but this can serve as a standard set for those 
implementors that want to do it.

- Matt


Paul Gearon wrote:
> I'm happy to include pretty much any scalar function, so I have no
> problems with anything that's in the list.
>
> Perusing through Leigh Dodds's list of existing functions, I think
> there are a several that may be useful. The overview is at:
>   http://spreadsheets.google.com/pub?key=0AkNZYESXv3IndGwyRkRXZ2hES0RjM0c3MHhLa05vTmc&gid=6
> (the functions are listed in the various tabs)
>
>
> Date Functions
> ARQ, TopQuadrant and Virtuoso have functions for creating a date,
> date-time and/or time that represents "now".  I'm also interested in
> constructing dates, both from strings and also from integers
> (something like fn:date(2010, 11, 3)). Virtuoso also has some
> interesting functions for date arithmetic. These could be calculated
> through decomposition of the dates, but without a day-of-year function
> it would be hard.
>
> Strings
> Most of the useful operations are already covered, but sha1sum and/or
> md5sum would be useful, as they are very common in SQL systems. Also
> given the prevalence of linked data, it would be great to have a
> function to escape text for URIs:
>   http://www.w3.org/2005/xpath-functions/#encode-for-uri
>
> Math/Logic
> Many of these are already covered, but I'd like to see:
>   if(cond, true-expr, false-expr)
> I believe this is already possible, but an if() function makes certain
> tasks much easier. Normally I'd like to see an arithmetic system
> capable of handling more math operations, and include constants like
> pi, but I'm not sure it's useful here. Has anyone found functions like
> exp, sin, cos, etc, to be useful in SPARQL?
>
> Geo Functions
> These are less common, but I know that a lot of people find them
> important. Mulgara does them through inferred graphs, but AllegroGraph
> does them with scalar functions. The functions that accept lat/long
> (distance and pointInBoundingBox) look useful, though perhaps the
> distance calculations are too much of a burden on implementors. I
> thought I'd mention them anyway, given how much demand I see for this
> functionality.
>
>
> Regards,
> Paul Gearon
>
> On Tue, Nov 2, 2010 at 5:16 PM, Lee Feigenbaum <lee@thefigtrees.net> wrote:
>   
>> (This email discharges my ACTION-305,
>> http://www.w3.org/2009/sparql/track/actions/305)
>>
>> Two months ago we all agreed that we want to move forward with the function
>> library work, and we agreed that we need two things:
>>
>> 1) A set of functions to include
>> 2) URIs for these functions
>>
>> This email is to begin a discussion #1 above. AndyS already did much of this
>> work on the wiki page, so I'm pretty much transplanting that here for
>> discussion. Please reply with either concurrence, suggestions & reasons for
>> things to remove or suggestions & reasons for additional things to include.
>>
>> This references functions from http://www.w3.org/TR/xpath-functions/ .
>>
>>
>> Numeric functions:
>>
>>       6.4.1 fn:abs
>>       6.4.2 fn:ceiling
>>       6.4.3 fn:floor
>>       6.4.4 fn:round
>>       6.4.5 fn:round-half-to-even
>>
>> String functions:
>>
>>       7.3.2 fn:compare
>>       7.4.1 fn:concat
>>       7.4.3 fn:substring
>>       7.4.4 fn:string-length
>>       7.4.7 fn:upper-case
>>       7.4.8 fn:lower-case
>>       7.4.10 fn:encode-for-uri
>>       7.5.1 fn:contains     (collation form optional)
>>       7.5.2 fn:starts-with
>>       7.5.3 fn:ends-with
>>
>> DateTime functions:
>>
>>       10.4.6 op:dateTime-equal
>>       10.4.7 op:dateTime-less-than
>>       10.4.8 op:dateTime-greater-than
>>       10.5.7 fn:year-from-dateTime
>>       10.5.8 fn:month-from-dateTime
>>       10.5.9 fn:day-from-dateTime
>>       10.5.10 fn:hours-from-dateTime
>>       10.5.11 fn:minutes-from-dateTime
>>       10.5.12 fn:seconds-from-dateTime
>>       10.5.13 fn:timezone-from-dateTime
>>
>> Misc functions:
>>
>>        3. fn:error
>>
>>
>> Lee
>>
>>
>>
>>
>>     
>
>