Neighbors and neighborhoods are found in many places in the DDC. The interdisciplinary number for neighborhoods as a social community is 307.3362, where provision is made for adding from 307.72–307.77 to represent specific kinds of communities—rural communities, suburban communities, urban communities, and self-contained communities. Interpersonal relations with neighbors are classed in 158.25, while the psychological influence of neighbors is classed in 155.925 (built with 155.92 Influence of social environment plus 5 from the numbers following 158.2 in 158.25 Interpersonal relations with neighbors, following the instructions at 155.92). But humans apparently are not the only kinds of things who can be neighbors: over forty Table 2 captions refer either to “neighboring islands” (as part of Indonesia) or to “neighboring counties” (in such states as Texas, Nebraska, South Dakota, and Montana).
In addition to social and geographic neighborhoods, metaphorical senses of neighborhood are also found in mathematics. In topology, the neighborhood of a point in a topological space is defined as an open set containing the point; a topological neighborhood is classed in 514.322 Point set topology (General topology). In graph theory, the neighborhood of a vertex in a graph is the set of all vertices adjacent to it and all edges between the adjacent vertices; a graph theoretical neighborhood is classed in 511.5 Graph theory.
There is also a sense of topic neighborhood relevant to classification schemes, based on the graph theoretical concept of neighborhood. This concept was the subject of a presentation on the ontological character of classes in the Dewey Decimal Classification given by DDC editors Rebecca Green and Michael Panzer at the Eleventh International ISKO Conference, held 23-26 February 2010 in Rome, Italy; the theme of the conference was paradigms and conceptual systems in knowledge organization. (Michael also cooperated with Marcia Lei Zeng and Athena Salaba, both of Kent State University, in a presentation on expressing classification schemes with OWL 2.) Topic neighborhoods in the DDC are classed in a number that this blog has memorialized, 025.431 Dewey Decimal Classification itself.
The gist of the concept of topic neighborhoods recognizes that the category description associated with a class in a classification scheme is seldom limited to a single topic. Instead, the typical class is a gathering place for a set of related topics. But that doesn’t mean that all the topics classed in the same number are part of a single undifferentiated neighborhood. Rather the class is composed of a set of focal topics (topics in class-here and including notes; captions are often sources of focal topics as well) and their individual neighborhoods (the union of which can be referred to as the neighborhood of a set of points).
Using 782.292 Chant as our major exemplar, our presentation explored the many features of the DDC that define the membership of a class neighborhood. Some of these features, like class-here and including notes, are additive in nature, while other features, like class-elsewhere and see-reference notes, are subtractive. Additional features involved in the development of neighborhoods include subsumption (specialization, instantiation), the non-addition of standard subdivision notation for topics in standing room, index terms, hierarchical force, principles of assigning Dewey numbers, diachronic development of the DDC, the existence of the DDC in both full and abridged versions, the classification of bibliographic resources, and—a suggestion from our colleague Hope Olsen—the coordinate numbers of the class. The presentation also addressed issues concerning the representation of topic neighborhoods in knowledge representation systems (a concern that also spilled over into the Zeng/Panzer/Salaba presentation).
(While we’re on the subject of neighborhoods, we also want to acknowledge the innovative application of neighborhoods to the Dewey context that has been adopted by the Topeka and Shawnee County [KS] Public Library.)