Semantic Network (Relational Vocabularies)

Semantic Network (Relational Vocabulary)

Definition

A type of relational controlled vocabulary consisting of lists of valuesMetadata values are the content connected to metadata labels in a metadata element. For example, if the metadata label is "date", the metadata value could be "May 13, 2007". Related Guide/concepts and directed relationshipsConnections between metadata terms within a vocabulary. These relationships can connect terms by scope, provenance, or other well-defined criteria..

Discussion

Semantic networks can be thought of as super-thesauri. Each network can be represented in a directed graph of concept nodes connected by relations established in the NISONational Information Standards organization standardA set of documented rules which define the creation of metadata by providing a combination of terminology (vocabularies), syntactical rules, format rules, and other requirements. Metadata standards are approved, published and governed by a formal body or organization with broad community-based representation (international or national). Related Guide, along with additional relations such as whole-part, cause-effect, or parent-child relationships. Semantic networks tend to deal more in abstractions than concrete terminology.

The participants [in a NISO 1999 workshop on standards for electronic thesauri] recommend that a much richer, hierarchically organized, set of relationships be developed... There is reason to expect that provision for semantic relations in controlled vocabulariesA managed list of terms. In the context of vocabularies, management typically includes careful selection of terms, maintenance of terms over time (i.e. addition, deprecation, modification), and presentation of the vocabulary in an accessible format. Related Guide will become much more extensive in a future standard..."
(Milstead, 2001, p 65).

It is somewhat difficult to identify a finite list of relations utilized in a semantic network. The semantic network relations can extend to provenanceThe record of how a particular metadata value or record came to be. Provenance can include things like when the record was created, accessed or modified. (parent-child), genesis (cause-effect) and complexity (whole-part). There are also relations for opposites, anotonyms, complementary concepts, possessive, passive, and the list could continue. This is in stark contrast to the clear articulation of a finite set of relations (largely based on scope), which are articulated in ANSIAmerican National Standards Institute /NISO Z39.19 - 2003 for thesauri.

Information technology experts tend to use semantic networks to establish complex search interfaces, which can help a user locate the most appropriate results based on the search term selected. Since semantic networks describe somewhat complex relationships, the search interface can be programmed to interpret the user entry into various nodes, which are included in a semantic network. This is stronger than a multi-level set of values, because the system can be set up to return results from different levels or categories based upon relations.

"In parallel with advances in thesauri compilation and manipulation, work was being undertaken by workers in artificial intelligence in their construction of expert systems. in this work they compiled what are called 'semantic networks' described by Milstead (1995) as being "conceptually quite similar to a thesaurus, in that they show terms in the context of their semantic relationships. however, they offer different navigation capabilities, through graphic devices that represent multidimensional spaces, rather than through review of the cross references and scope notes of a thesaurus"... another major difference between them [semantic networks] and thesauri was in the fact that the former went much further in defining the types of relationships between terms...Two things arise from this more complex treatment. The first is that there is no intrinsic reason why a conventional thesaurus should not be extended and elaborated to include, for example, term definitions, notes on term usage, and more explicitly defined relationships. The second is that such enrichment allows the semantic network to be more easily manipulated by an inference engine, typically employing the IF . . . THEN operator. This enrichment of thesauri (see, e. g. Hazewinkel, 1997) is a feature of work in the area of ontologiesA type of relational controlled vocabulary, which provides for categories, relationships, rules and axioms among metadata elements. Typically a hierarchy of classes and terms, an ontology is a machine-readable way of relating metadata terminology. Related Guide..."
(Gilchrist, 2003, p. 9-10).

Note: Semantic networks are prevalent in the fields of linguistics, psychology and philosophy. There is extensive research about the development and use of semantic networks in these fields.

References

Gilchrist, A (2003). Thesauri, taxonomies and ontologies - an etymological note. Journal of Documentation 59(1), 7-18.

Hazewinkel, M. (1996/1997). Enriched thesauri and their uses in information retrieval and storage. Discussion paper. IN: Thanos, C .( Ed.). Proceedings of the First DELOS
Workshop, March 1996, ERCIM, pp. 27-32. (Revised 1997). Available at: http://www.ercim.org/publication/ws-proceedings/DELOS1/hazewinkel.pdf

Milstead, J.L. (1995). Invisible thesauri: the year 2000. Online & CDROM Review, 19(2), 93-94.

Milstead, J.L. (2001). Standards for relationships between subject indexing terms. IN: Bean, C.A. & Green, R. (Eds.). Relationships in the organization of knowledge. Dordrecht: Kluwer Academic Publishers, (pp. 53-66).

Example

This very simple diagram of a semantic network illustrates the directed nature of relationships. For example, using this diagram, you can make the statement "A fish is an animal that lives in the water." Or, "A bear is a mammal (a type of animal with a vertebra) that has fur."