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doc:knowrob_basics [2021/02/18 08:57] – [Querying the KnowRob ontology] daniel86doc:knowrob_basics [2021/02/18 09:25] (current) – [Visualizing objects] daniel86
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 <code prolog> <code prolog>
  ?- subclass_of(A, dul:'PhysicalObject'). <ENTER>  ?- subclass_of(A, dul:'PhysicalObject'). <ENTER>
- A = dul:'BiologicalObject' ; <SPACE> + A = dul:'BiologicalObject' ;  <SPACE> 
- A = dul:'ChemicalObject' ;   <SPACE> + A = dul:'ChemicalObject' ;    <SPACE> 
- A = dul:'DesignedArtifact' ; <SPACE> + A = dul:'DesignedArtifact' ;  <SPACE> 
- A = dul:'DesignedSubstance'  <ENTER>+ A = dul:'DesignedSubstance' . <ENTER>
 </code> </code>
  
 Some notes on the query syntax: Predicates in a query can be linked with a comma, denoting the logical AND, or a semicolon for the logical OR. Each query is finished with a dot (full stop). You can step through the results with the semicolon or <SPACE>, or just hit <ENTER> or <DOT> again to stop generating more results. For more information on query predicates, have a look at KnowRob's [[http://knowrob.org/api|API documentation]]. Some notes on the query syntax: Predicates in a query can be linked with a comma, denoting the logical AND, or a semicolon for the logical OR. Each query is finished with a dot (full stop). You can step through the results with the semicolon or <SPACE>, or just hit <ENTER> or <DOT> again to stop generating more results. For more information on query predicates, have a look at KnowRob's [[http://knowrob.org/api|API documentation]].
  
-Before continuing with the tutorial, try to get familiar with the [[[[http://www.visualdataweb.de/webvowl/#iri=https://ease-crc.github.io/soma/owl/current/SOMA.owl|ontology]] and its main classes and properties.+Before continuing with the tutorial, try to get familiar with the [[http://www.visualdataweb.de/webvowl/#iri=https://ease-crc.github.io/soma/owl/current/SOMA.owl|ontology]] and its main classes and properties.
 The best way to explore the ontology is by loading [[https://ease-crc.github.io/soma/owl/current/SOMA.owl|SOMA]] into [[https://protege.stanford.edu|Protege]]. The best way to explore the ontology is by loading [[https://ease-crc.github.io/soma/owl/current/SOMA.owl|SOMA]] into [[https://protege.stanford.edu|Protege]].
  
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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> +
- +
- +
-===== Visualizing objects ===== +
- +
-KnowRob includes a browser-based visualization canvas that can display 3D data such as the environment map or the robot itself. The canvas is based on [[http://rosbridge.org/|rosbridge]] and the [[http://robotwebtools.org/|robotwebtools]] libraries that provide tools for displaying information from ROS in a browser. To forward information from the ROS world to the browser, you need to launch the rosbridge websocket server in another terminal using the following command: +
-<code bash> +
-roslaunch rosbridge_server rosbridge_websocket.launch +
-</code> +
- +
-You can just leave the rosbridge node running in the background while you are working on KnowRob. The following queries load a semantic environment map with a set of objects inside and push them to the 3D canvas. The result should look like the image below. +
- +
-{{ :tutorial:map-ccrl2-plain.png?nolink&300|}} +
- +
-<code prolog> +
-% Load the visualization Prolog module +
-?- register_ros_package(knowrob_vis). +
- +
-% Load an environment map to get some example objects +
-?- owl_parse('package://knowrob_map_data/owl/ccrl2_semantic_map.owl'). +
- +
-% Start the KnowRob side of the visualization canvas. This will start +
-% a web server at http://localhost:1111 -- open that page in a browser +
-?- visualisation_server. +
- +
-% Select the map instance of type 'SemanticEnvironmentMap'  +
-% and add it to the 3D canvas +
-?- owl_individual_of(A, knowrob:'SemanticEnvironmentMap'),  +
-   marker_update(object(A)).+
 </code> </code>