The region connection calculus (RCC) is intended to serve for qualitative spatial representation and

reasoning Reason is the capacity of consciously applying logic by drawing conclusions from new or existing information, with the aim of seeking the truth. It is closely associated with such characteristically human activities as philosophy, science, lang ...

. RCC abstractly describes regions (in

Euclidean space Euclidean space is the fundamental space of geometry, intended to represent physical space. Originally, that is, in Euclid's Elements, Euclid's ''Elements'', it was the three-dimensional space of Euclidean geometry, but in modern mathematics ther ...

, or in a

topological space In mathematics, a topological space is, roughly speaking, a geometrical space in which closeness is defined but cannot necessarily be measured by a numeric distance. More specifically, a topological space is a set whose elements are called points ...

) by their possible relations to each other. RCC8 consists of 8 basic relations that are possible between two regions: * disconnected (DC) * externally connected (EC) * equal (EQ) * partially overlapping (PO) * tangential proper part (TPP) * tangential proper part inverse (TPPi) * non-tangential proper part (NTPP) * non-tangential proper part inverse (NTPPi) From these basic relations, combinations can be built. For example, proper part (PP) is the union of TPP and NTPP.

Axioms

RCC is governed by two axioms. * for any region x, x connects with itself * for any region x, y, if x connects with y, y will connects with x

Remark on the axioms

The two axioms describe two features of the connection relation, but not the characteristic feature of the connect relation.Dong 2008 For example, we can say that an object is less than 10 meters away from itself and that if object A is less than 10 meters away from object B, object B will be less than 10 meters away from object A. So, the relation 'less-than-10-meters' also satisfies the above two axioms, but does not talk about the connection relation in the intended sense of RCC.

Composition table

The composition table of RCC8 are as follows: * "*" denotes the universal relation, no relation can be discarded. Usage example: if a TPP b and b EC c, (row 4, column 2) of the table says that a DC c or a EC c.

Examples

The RCC8 calculus is intended for reasoning about spatial configurations. Consider the following example: two houses are connected via a road. Each house is located on an own property. The first house possibly touches the boundary of the property; the second one surely does not. What can we infer about the relation of the second property to the road? The spatial configuration can be formalized in RCC8 as the following

constraint network Constraint may refer to: * Constraint (computer-aided design), a demarcation of geometrical characteristics between two or more entities or solid modeling bodies * Constraint (mathematics), a condition of an optimization problem that the solution m ...

: house1 DC house2 house1 property1 house1 property2 house1 EC road house2 property1 house2 NTPP property2 house2 EC road property1 property2 road property1 road property2 Using the RCC8

composition table Composition or Compositions may refer to: Arts and literature * Composition (dance), practice and teaching of choreography *Composition (language), in literature and rhetoric, producing a work in spoken tradition and written discourse, to include ...

and the path-consistency algorithm, we can refine the network in the following way: road property1 road property2 That is, the ''road'' either overlaps (PO) ''property2'', or is a tangential proper part of it. But, if the ''road'' is a tangential proper part of ''property2'', then the ''road'' can only be externally connected (EC) to ''property1''. That is, ''road PO property1'' is not possible when ''road TPP property2''. This fact is not obvious, but can be deduced once we examine the consistent "singleton-labelings" of the constraint network. The following paragraph briefly describes singleton-labelings. First, we note that the path-consistency algorithm will also reduce the possible properties between ''house2'' and ''property1'' from ' to just ''DC''. So, the path-consistency algorithm leaves multiple possible constraints on 5 of the edges in the constraint network. Since each of the multiple constraints involves 2 constraints, we can reduce the network to 32 (5^2) possible unique constraint networks, each containing only single labels on each edge (''"singleton labelings''"). However, of the 32 possible singleton labelings, only 9 are consistent. (Se
qualreas
for details.) Only one of the consistent singleton labelings has the edge ''road TPP property2'' and the same labeling includes ''road EC property1''. Other versions of the region connection calculus include RCC5 (with only five basic relations - the distinction whether two regions touch each other are ignored) and RCC23 (which allows reasoning about convexity).

RCC8 use in GeoSPARQL

RCC8 has been partially implemented in

GeoSPARQL GeoSPARQL is a standard for representation and querying of geospatial linked data for the Semantic Web from the Open Geospatial Consortium (OGC). The definition of a small ontology based on well-understood OGC standards is intended to provide a st ...

as described below: Region_Connection_Calculus_8_Relations_and_Open_Geospatial_Consortium_relations

Implementations

GQR
is a reasoner for RCC-5, RCC-8, and RCC-23 (as well as other calculi for spatial and temporal reasoning)
qualreas
is a Python framework for qualitative reasoning over networks of relation algebras, such as RCC-8, Allen's interval algebra and more.

References

Bibliography

* * . * * {{cite journal, ref=tdong, first=Tiansi , last= Dong , title=A Comment on RCC: From RCC to RCC⁺⁺, jstor=41217909, journal=Journal of Philosophical Logic, volume=34, issue=2, pages=319–352, date=2008, doi=10.1007/s10992-007-9074-y, s2cid=6243376 . Reasoning Knowledge representation Constraint programming Computational topology Logical calculi