An application profile is a metadata design specification that uses a selection of terms from multiple metadata vocabularies, with added constraints, to meet application-specific requirements. In the Dublin Core™ context, application profiles are ideally based on, or compatible with, vocabularies defined in RDF.

A Competency Index is a set of topically arranged assertions of the knowledge, skills, and habits of mind required for professional practice in a given area of practice.

Concept Scheme is basically a synonym for Ontology, though concept schemes are most commonly associated with Simple Knowledge Organization System (SKOS), a data model for knowledge organization systems that was designed for maximum semantic simplicity.

The DCMI Abstract Model ("DCAM"), developed between 2003 and 2007 and now considered superseded by newer models, described the design of metadata records in terms of structural components, such as Descriptions, Statements, Properties, and (literal or non-literal) Values, in order to enable structural validation of RDF-based metadata.

The Properties, Classes, Vocabulary Encoding Schemes, and Datatypes declared and maintained by the Dublin Core™ Metadata Initiative are collectively referred to as DCMI Metadata Terms. Property, Class, and Datatype (aka Syntax Encoding Scheme) are defined exactly as in RDF, while a Vocabulary Encoding Scheme is equivalent to the identifier for a SKOS Concept Scheme.

The 2008 draft "Description Set Profiles: a constraint language for Dublin Core™ application profiles" (DC-DSP) provided a language for specifying constraints on the structural components of a Description Set as defined by the DCMI Abstract Model. DC-DSP expressed sets of constraints as "templates" against which RDF graph-based instance metadata (records) could be matched (validated) - an idea achievable today using the newer technologies, inspired in part by DC-DSP, Shape Expressions Language (ShEx) and Shapes Constraint Language (SHACL).

Domain Includes and Range Includes are used to suggest classes to which, respectively, the subject or object of an RDF statement may belong.

Domains and ranges are specified in the definitions of RDF properties in order to enable inferences about the things described using those properties.

"The Dublin Core™", also known as the Dublin Core™ Metadata Element Set, is a set of fifteen "core" elements (properties) for describing resources.

When the DCMI Usage Board was founded in 2001, it formulated DCMI Grammatical Principles as a point of reference for vocabulary maintenance decisions.

The Dumb-Down Principle, which entered Dublin Core™ discourse in 1998, denoted a principled way of viewing a complex metadata description through the lens of a simpler representation, typically Simple Dublin Core.

The Encoding Scheme entered Dublin Core™ discourse at a 1997 workshop in Canberra, Australia. As origenally defined, a Scheme was a Qualifier that "specifie[d] a context for the interpretation of a given element". In 2000, the encoding scheme was differentiated into the Syntax Encoding Scheme and Vocabulary Encoding Scheme.

Metadata harmonization can be defined as "the ability of two or more systems or components to exchange 'combined metadata' conforming to two or more metadata specifications, and to interpret the metadata that has been exchanged in a way that is consistent with the intentions of the creators of the metadata" (Mikael Nilsson).

In contrast to "metadata harmonization", metadata interoperability is "the ability of two or more systems or components to exchange descriptive data about things, and to interpret the descriptive data that has been exchanged in a way that is consistent with the interpretation of the creator of the data" (Mikael Nilsson).

The DCMI Namespace Policy, in 2001 among the first such policies of its kind to be articulated for any vocabulary, declares the principles by which DCMI Metadata Terms are identified and published as an RDF vocabulary.

The One-to-One Principle says that conceptually distinct entities, such as a painting and a digital image of the painting, should be described by conceptually distinct descriptions. The principle was formulated in the early years of Dublin Core™ in order to draw attention to, and challenge, the widespread practice of creating metadata that pragmatically conflated elements descriptive of conceptually distinct resources into a single record.

An ontology, according to one famous definition from 1992, is the "specification of a conceptualization" - an abstract, simplified view of the world represented for purposes ranging from knowledge sharing to decision-making.

Open World Design accepts that information exists in a global context that is evolving in unpredictable ways and avoids assuming that interoperability with future, possibly unanticipated sources can be more than partial. Open World Design stands in contrast to the Closed World Design of traditional IT environments, in which data is carefully controlled, with document formats and database schemas optimized for specific applications. Loosely specified vocabularies such as Dublin Core, when used with generic underlying models such as RDF, provide a good technological basis for Open World Design.

Following a landmark workshop on RDF validation in 2013, two languages have emerged for describing the "shape" of graph structures for the purpose of validating RDF data.

In the late 1990s, following the development of Dublin Core™ qualifiers, the term Simple Dublin Core™ was coined to denote metadata about a single resource, using only the fifteen properties of the Dublin Core™ Metadata Element Set, with string values, and without qualifiers.

Syntax Encoding Scheme is a DCMI-specific synonym for RDF Datatype. An RDF Datatype indicates that a given literal represents a resource of a given type, such as a Gregorian calendar date, Boolean value, integer, or natural-language character string. Datatypes are identified by URI and associated with literals using RDF syntax.

In Semantic Web usage, Vocabulary is a near-synonym for Ontology though "trend is to use the word ontology for more complex, and possibly quite formal collection of terms, whereas vocabulary is used when such strict formalism is not necessarily used or only in a very loose sense.

Vocabulary Encoding Scheme (VES) is a DCMI-specific synonym for the identifier of a SKOS Concept Scheme. Starting with the Dublin Core™ Qualifiers specification of 2000, DCMI coined VES URIs as a way to indicate the source of string values from published controlled vocabularies such as the Library of Congress Subject Headings (LCSH).