Open World Assumption

Open versus Closed world assumption. The openness of the Web, described by the AAA Slogan, has additional implications on Semantic Web applications beyond the Nonunique Naming Assumption discussed in Sect. 3.4.1. With respect to reasoning, Semantic Web systems are built on the assumption that the system has incomplete information and therefore adopt an Open World Assumption (OWA). Under the OWA, information that is not explicitly stated is considered unknown rather than false. For example, asking whether mo Engl has Ford as a supplier, will not return No, but an empty value set. By contrast, database systems operate under a Closed World Assumption (CWA) and therefore assume complete information. In other words, information that is not known is considered false. The same query as above will return No as a result under CWA. 

Semantic Web technologies have been designed to comply with the open nature of the Web captured by the Anyone is allowed to say Anything about Any topic slogan (Allemang and Hendler 2011). Some implications of this compliance are the Nonunique Naming Assumption (Sect. 3.4.1) and the Open World Assumption (Sect. 3.5). 

Matching between existing (sub-)products and new (sub-)products is based on the left side of the V-model only. However, Semantic Web s open world assumption (OWA) only uncovers not-matching (sub-)products, but it is not possible to determine a set of matching (sub-)products. Therefore, an external matchmaking algorithm has to support the reasoning. 

Requirements R-1 and R-2 are satisfied by capability C2— formal and flexible semantic modeling—as it is discussed in Table 2.2 of Chap. 2 in this book. Requirement R-3 is covered by the Semantic Web through capability C3—linked data. Requirement R-4 is supported by the Semantic Web only to a certain extent. It is possible to import ontology submodels to a knowledge base. However, reasoning capabilities of the Semantic Web are handicapped due to the underlying open world assumption (OWA). 

In the Semantic Web, the tasks of (i) validating RDF data against a set of integrity constraints and (ii) performing RDFS/OWL reasoning, are grounded on different semantics. While the latter operates under the Open World Assumption (OWA) (i.e., a statement cannot be assumed to be false if it cannot be proven to be true) and the Nonunique Name Assumption (nUNA) (i.e., the same object/resource can have... 

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