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doc:knowrob_basics [2021/02/18 09:00] – [Querying the KnowRob ontology] daniel86doc:knowrob_basics [2021/02/18 09:25] – [Loading and querying environment information] daniel86
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 So far, we only performed reasoning on the class level. For robotic applications, it is also important to reason about instances of these classes, for example observed objects or actions. An example set of instances are the semantic maps, contained as OWL file in the //knowrob_map_data// package. We can parse the OWL file containing the map by using a package:%%//%% URL and the path inside the package: So far, we only performed reasoning on the class level. For robotic applications, it is also important to reason about instances of these classes, for example observed objects or actions. An example set of instances are the semantic maps, contained as OWL file in the //knowrob_map_data// package. We can parse the OWL file containing the map by using a package:%%//%% URL and the path inside the package:
 <code prolog> <code prolog>
- ?- owl_parse('package://knowrob_map_data/owl/ccrl2_semantic_map.owl').+ ?- tripledb_load('package://iai_semantic_maps/owl/kitchen.owl').
 </code> </code>
  
-You can query for properties of instances using the rdf_has(S,P,O) or owl_has(S,P,O) predicates, which retrieve all triples with matching Subject, Predicate, or Object from the knowledge base. The following query, for example, asks for all objects of type knowrob:'Drawer'.+You can query for properties of instances using the holds(S,P,O) predicate, which retrieve all triples with matching Subject, Predicate, or Object from the knowledge base. The following query, for example, asks for all objects of type knowrob:'IAIDrawer'.
 <code prolog> <code prolog>
- ?- owl_has(A, rdf:type, knowrob:'Drawer'). + ?- holds(A, rdf:type, knowrob:'IAIDrawer'). 
- A = knowrob:'Drawer1' ; + A = iai_kitchen:'iai_kitchen_fridge_area_lower_drawer_main' ; 
- A = knowrob:'Drawer103' ; + A = iai_kitchen:'iai_kitchen_kitchen_island_left_lower_drawer_main' ; 
- A = knowrob:'Drawer109' ;+ A = iai_kitchen:'iai_kitchen_kitchen_island_left_upper_drawer_main' ;
  [...]  [...]
 </code> </code>
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 For getting an overview of the information that is available about one object instance, we can query for all triples where the respective instance fills the Subject slot. In this example we pass two unbound variables //P// and //O// as arguments and receive all possible combinations of values as result. For getting an overview of the information that is available about one object instance, we can query for all triples where the respective instance fills the Subject slot. In this example we pass two unbound variables //P// and //O// as arguments and receive all possible combinations of values as result.
 <code prolog> <code prolog>
- ?- owl_has(knowrob:'Drawer1', P, O). + ?- owl_has(iai_kitchen:'iai_kitchen_kitchen_island_left_lower_drawer_main', P, O). 
- P = knowrob:prismaticallyConnectedTo, + P = urdf:hasBaseLinkName, 
- O = knowrob:'Door4' ; + O = kitchen_island_left_lower_drawer_main ; 
- P = knowrob:depthOfObject, + P = urdf:hasEndLinkName, 
- O = literal(type(xsd:double,'0.574538')) ; + O = kitchen_island_left_lower_drawer_handle ; 
- P = knowrob:heightOfObject, + [...]
- O = literal(type(xsd:double,'0.338121')) ; +
- P = knowrob:widthOfObject, +
- O = literal(type(xsd:double,'0.58045006')) ; +
- P = knowrob:properPhysicalParts, +
- O = knowrob:'Door4' ; +
- P = knowrob:properPhysicalParts, +
- O = knowrob:'Handle127' ; +
- P = knowrob:properPhysicalParts, +
- O = knowrob:'Slider4' ; +
- P = knowrob:describedInMap, +
- O = 'http://ias.cs.tum.edu/kb/ias_semantic_map.owl#SemanticEnvironmentMap0' ; +
- P = 'http://ias.cs.tum.edu/kb/srdl2-comp.owl#urdfName', +
- O = literal(drawer_fridge_bottom_fixed_link) ; +
- P = rdf:type, +
- O = owl:'NamedIndividual' ; +
- P = rdf:type, +
- O = knowrob:'Drawer'+
 </code> </code>
- 
  
 ===== Visualizing objects ===== ===== Visualizing objects =====