Are the GeoSPARQL RIF rules incorrect

[nicholascar]

While sending our RIF rules out to external review, I got confused with them and need clarity.

The 4 RIF rules are:

1. feature - feature rule
2. feature - geometry rule
3. geometry - feature rule
4. geometry - geometry rule

I understand the feature - feature rule, e.g. for sfEquals:

?f1[geo:sfEquals->?f2

if

(?f1[geo:hasDefaultGeometry->?g1]
 ?f2[geo:hasDefaultGeometry->?g2] 
 ?g1[ogc:asGeomLiteral->?g1Serial] 
 ?g2[ogc:asGeomLiteral->?g2Serial]
 External(ogc:function (?g1Serial,?g2Serial)))

which means:

• if ?g1 is the Geometry of ?f1 and g1Serial is its serialization
• ?g2 is the Geometry of ?f2 and ?g2Serial is its serialization
• and if the external function `geof:sfEquals(?g1Serial, ?g2Serial)
• then it is true

But I do not understand the other rules. For example, the "feature - geometry rule" for sfEquals reads:

(?f1[geo:hasDefaultGeometry->?g1]
 ?g1[ogc:asGeomLiteral->?g1Serial]
 ?f2[ogc:asGeomLiteral->?g2Serial] 
 External(ogc:function (?g1Serial,?g2Serial)))

which I take to mean:

• if ?g1 is the Geometry of ?f1 and g1Serial is its serialization
• ?g2Serial is the serialization of ?f2
• and if the external function `geof:sfEquals(?g1Serial, ?g2Serial)
• then it is true

but ?g2Serial is the serialization of ?f2 be true as GeoSPARQL has no function/rule to extract a geometry serialization from a Feature, only a Geometry which may or may not be related to a Feature. And similarly for the other non feature - feature rules. Also note that GeoSPARQL can't express topological relations between Geometry instances

Q: how are the following rules possible in GeoSPARQL:

2. feature - geometry rule
3. geometry - feature rule
4. geometry - geometry rule

If rules 2 - 4 are not correct, we can still express RIF rules for feature - feature rule x each SF, DEM9 & RCC8 topological relation.

[nicholascar]

@mperry455 can you please shed any light on this, based on the GeoSPARQL 1.0 RIF template unchanged in 1.1?

[situx]

I think the RIF rules are correct, because the range of the topological relations is SpatialObject and not Geometry

[nicholascar]

Thanks @situx, yes, this solves my problem: should have looked at the ontology's range values for the topological properties...