A relationship is “an association among several things, with that association having a particular significance.”
(See §5.1, “Introduction”)
Just identifying the resources involved is not enough because several different relationships can exist among the same resources.
Most relationships between resources can be expressed using a subject-predicate-object model.
(See §5.3, “The Semantic Perspective” and §5.7.1, “Choice of Implementation”)
For a computer to understand relational expressions, it needs a computer-processable representation of the relationships among words and meanings that makes every important semantic assumption and property precise and explicit.
Three broad categories of semantic relationships are inclusion, attribution, and possession.
A set of interconnected class inclusion relationships creates a hierarchy called a taxonomy.
(See §5.3.1.1, “Inclusion”)
Classification is a class inclusion relationship between an instance and a class.
(See §5.3.1.1, “Inclusion”)
Ordering and inclusion relationships are inherently transitive, enabling inferences about class membership and properties.
(See §5.3.2.2, “Transitivity”)
Class inclusion relationships form a framework to which other kinds of relationships attach, creating a network of relationships called an ontology.
(See §5.3.3, “Ontologies”)
When words encode the semantic distinctions expressed by class inclusion, the more specific class is called the hyponym; the more general class is the hypernym.
A thesaurus uses lexical relationships to suggest which terms to use.
(See §5.4.2, “Thesauri”)
Morphological analysis of how words in a language are created from smaller units is heavily used in text processing.
Many types of resources have internal structure in additional to their structural relationships with other resources.
(See §5.5.2, “Structural Relationships within a Resource” and §5.5.2, “Structural Relationships within a Resource”)
The XPath language defines the structures and patterns in XML documents used by XML forms, queries, and transformations.
Many hypertext links are purely structural because there is no explicit representation of the reason for the relationship.
(See the sidebar, Perspectives on Hypertext Links)
Using the pattern of links between documents to understand the structure of knowledge and the structure of the intellectual community that creates it is an idea that is nearly a century old.
The essential technologies for making the web more semantic and relationships among web resources more explicit are XML, RDF, and OWL.
Much of our thinking about relationships in organizing systems for information comes from the domain of bibliographic cataloging of library resources and the related areas of classification systems and descriptive thesauri.
The Resource Description and Access (RDA) next-generation cataloging rules are attempting to bring together disconnected resource descriptions.
Integration is the controlled sharing of information between two (or more) business systems, applications, or services within or between firms.
Interoperability goes beyond integration to mean that systems, applications, or services that exchange information can make sense of what they receive.