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Figure 3. Example of the ontology being used to instantiate the house objects belonging to the instance “Bedroom”, present in the home
environment.

Figure 4. Example of the knowledge representation of an object in the environment of a house that has been instantiated.

relations is used to help with inferring new conclusions (e.g., If B is a subclass of A and C is a subclass of B,
then C is a subclass of A can be inferred as transitivity holds for the subclass property).

The object property hierarchy view displays the asserted and inferred object property hierarchies. From the
knowledge base built, all existing components from the environment are instantiated. That is, the individuals
are based on their type (Figure 3). This allowed testing the functionality of the ontology. Figure 3 depicts
that each room was instantiated to the corresponding Rooms subclass (e.g., the BedRoom instance is related to
the Bedroom class). Several relations can be drawn from the instances that represent the environment, such
as which objects belong to the BedRoom instance. Although the relations of the BathRoom and LivingRoom
instances do not appear in Figure 3, these can be obtained, based on the created instances present in the
ontology, in order to represent both rooms.

As previously stated, having the environment of a house in an ontological knowledge oriented database is of
special interest, for example, to know where each object belongs. In fact, as depicted in Figure 4, the informa-
tion about the BedsideTable is completely available to the user, using a simple logic description. A query to
the ontology will retrieve useful information, for example where the object is attached. This issue is further
discussed in the next subsection.

Performing logical description reasoning actions to obtain valuable data for the robot’s reasoning can be done,
as presented in Figure 5, namely information about objects, rooms, and their relations defined in the ontology.
For example, what type of object is instantiated as Bed? In which rooms is it present? What is on its left? What
is on its right? Using the ontology and description logic queries, it is straightforward to obtain the following