Aquifer: A geologic unit that is a hydrologically connected body of material and contains water.
Artifact: A thing created by humans, usually for some practical purpose. (Source: http://www.merriam-webster.com/dictionary/artifact)
Attribute: A binding between a property, a data type, and a data item; an implementation of a property.
Cardinality: A constraint on the number of instances of assigned property values associated with an individual data item. A cardinality of 1 indicates exactly one value is required; 0..1 indicates an optional single value; 1..n indicates that one or more values is required; 0..n indicates that a value is optional, and multiple values may be specified.
Content model: A model that identifies and defines the data items and the properties (with cardinality) associated with each data item.
Data item: An identifiable unit of information. Generally represents some entity in the world.
Data type: A specification of the representation of a single value in an information system, using integer, floating point, string, Boolean.
Feature: An information resource representing some identifiable thing of interest in the world.
Feature type: Type for representing a feature.
Geologic structure: A configuration of matter in the Earth based on describable inhomogeneity, pattern, or fracture in an Earth material. The identity of a geologic structure is independent of the material that is the substrate for the structure. Geologic structures are more likely to be found in, and are more persistent in, consolidated materials than in unconsolidated materials. Properties like "clast-supported," "matrix-supported," and "graded bed" that do not involve orientation are considered kinds of geologic structure because they depend on the configuration of parts of a rock body. (Source: http://www.geosciml.org/).
Geologic unit: A body of material in the Earth whose complete and precise extent is inferred to exist (NADM GeologicUnit, Stratigraphic unit in sense of NACSN or International Stratigraphic Code), or a classifier used to characterize parts of the Earth (e.g. lithologic map unit like "granitic rock" or "alluvial deposit," surficial units like "till" or "old alluvium"). (Source: http://www.geosciml.org/).
Geothermal system: A body of material in the Earth from which energy may be extracted as heat in a fluid circulated through the body and transported to an external point of use. A geothermal system does not have to be exploited or exploitable. (provisional definition).
Information resource: A resource that can be transmitted electronically.
Property: A phenomenon that is inherent in the nature of some other phenomenon, and may be used to characterize it by specifying a value.
Protocol: A set of rules which is used by computers to communicate with each other across a network (http://en.wikipedia.org/wiki/Network_protocol).
Representation: A binding between a symbol (in language, text, graphics, computer bits, etc.) and a human concept or resource.
Resource: An identifiable thing that fulfills a requirement. Usage here is close to definition used in RDF (http://www.w3.org/TR/REC-rdf-syntax), generalized from ISO19115, which defines resource as an ‘asset or means that fulfills a requirement’ without defining asset or means. "An object or artifact that is described by a record in the information model of a catalogue." (OGC 07-006r1)
Schema: A formally structured representation of a conceptualization. A model presented using some specific notation.
Specification: A document that describes the technical characteristics of an artifact, possibly including a description of what it should do, or an explicit set of requirements that it must satisfy. (Based on http://en.wikipedia.org/wiki/Specification).
Type: Specification of a collection of attributes and cardinalities for those attributes used to represent a data item.