base IRI – An IRI that may represent the location against which Relative IRIs are resolved. In most concrete serialization formats this defaults to the location of the file containing RDF source.
Blank node identifier – Blank node identifiers are local identifiers that are used in some concrete RDF syntaxes or RDF store implementations. They are always locally scoped to the file or RDF store, and are not persistent or portable identifiers for blank nodes.
Blank node – Blank nodes are disjoint from IRIs and literals. Blank nodes are like simple variables in algebra; they represent some thing without saying what their value is.
Dataset-isomorphic – Two RDF datasets (the RDF dataset D1 with default graph DG1 and any named graph NG1 and the RDF dataset D2 with default graph DG2 and any named graph NG2) are dataset-isomorphic if and only if there is a bijection M between the nodes, triples and graphs in D1 and those in D2 (with conditions).
Denote – Any IRI or literal denotes something in the world (the "universe of discourse").
Entailment – An RDF graph A entails another RDF graph B if every possible arrangement of the world that makes A true also makes B true.
Equivalence – Two RDF graphs A and B are equivalent if they make the same claim about the world.
Fragment identifier – RDF uses IRIs, which may include fragment identifiers, as resource identifiers.
Generalized RDF dataset – A generalized RDF dataset comprises a distinguished generalized RDF graph, and zero or more pairs each associating an IRI, a blank node or a literal to a generalized RDF graph.
Generalized RDF graph – A generalized RDF graph is a set of generalized RDF triples.
Graph name – Each named graph is a pair consisting of an IRI or a blank node (the graph name), and an RDF graph. Graph names are unique within an RDF dataset.
Inconsistency – An RDF graph is inconsistent if it contains an internal contradiction. There is no possible arrangement of the world that would make the expression true.
IRI – An Internationalized Resource Identifier as defined in RFC3987.
IRI equality – Two IRIs are equal if and only if they are equivalent under Simple String Comparison according to section 5.1 of [RFC3987].
Isomorphic – Two RDF graphs G and G' are isomorphic (that is, they have an identical form) if there is a bijection M between the sets of nodes of the two graphs ...
Lexical space – The lexical space of a datatype is a set of Unicode [UNICODE] strings.
Lexical-to-value mapping – The lexical-to-value mapping of a datatype is a set of pairs whose first element belongs to the lexical space, and the second element belongs to the value space of the datatype.
Namespace – The term “namespace” on its own does not have a well-defined meaning in the context of RDF, but is sometimes informally used to mean “namespace IRI” or “RDF vocabulary”.
RDF source – We informally use the term RDF source to refer to a persistent yet mutable source or container of RDF graphs. An RDF source is a resource that may be said to have a state that can change over time. A snapshot of the state can be expressed as an RDF graph.
RDF statement – This statement corresponding to an RDF triple is known as an RDF statement.
Recognized datatype IRIs – Datatypes are identified by IRIs. If D is a set of IRIs which are used to refer to datatypes, then the elements of D are called recognized datatype IRIs.
Resource – Any IRI or literal denotes Should this be replaced with a reference to denote in [RDF12-SEMANTICS]? something in the world (the "universe of discourse"). These things are called resources.
Skolem IRI – In situations where stronger identification is needed, systems MAY systematically replace some or all of the blank nodes in an RDF graph with IRIs. Systems wishing to do this SHOULD mint a new, globally unique IRI (a Skolem IRI) for each blank node so replaced.
Subject – An RDF triple consists of three components:the predicate, which is an IRI, and the object, which is an IRI, a literal or a blank node.
URI – A Universal Resource Identifier as defined in RFC3986.
Value space – The lexical-to-value mapping of a datatype is a set of pairs whose first element belongs to the lexical space, and the second element belongs to the value space of the datatype.
class – It is convenient to state the RDFS semantics in terms of a new semantic construct, a class, i.e. a resource which represents a set of things in the universe which all have that class as a value of their rdf:type property.
D-entails – A graph is (simply) D-satisfiable or satisfiable recognizing D when it has the value true in some D-interpretation, and a graph S (simply) D-entails or entails recognizing D a graph G when every D-interpretation which satisfies S also D-satisfies G.
D-satisfiable – A graph is (simply) D-satisfiable or satisfiable recognizing D when it has the value true in some D-interpretation, and a graph S (simply) D-entails or entails recognizing D a graph G when every D-interpretation which satisfies S also D-satisfies G.
D-unsatisfiable – Unlike the case with simple interpretations, it is possible for a graph to have no satisfying D-interpretations i.e. to be D-unsatisfiable. RDF processors MAY treat an unsatisfiable graph as signaling an error condition, but this is not required.
Datatype map – The datatype map corresponding to the set D is the restriction of a D-interpretation to the set D.
Denotation – The words denotes and refers to are used interchangeably as synonyms for the relationship between an IRI or literal and what it refers to in a given interpretation, itself called the denotation or referent.
Denotes – The words denotes and refers to are used interchangeably as synonyms for the relationship between an IRI or literal and what it refers to in a given interpretation, itself called the denotation or referent.
Empty graph – The empty graph is the empty set of triples.
Entail – Following standard terminology, we say that I (simply) satisfies E when I(E)=true, that E is (simply) satisfiable when a simple interpretation exists which satisfies it, otherwise (simply) unsatisfiable, and that a graph G simply entails a graph E when every interpretation which satisfies G also satisfies E.
Entails recognizing D – A graph is (simply) D-satisfiable or satisfiable recognizing D when it has the value true in some D-interpretation, and a graph S (simply) D-entails or entails recognizing D a graph G when every D-interpretation which satisfies S also D-satisfies G.
Equivalent – Following standard terminology, we say that I (simply) satisfies E when I(E)=true, that E is (simply) satisfiable when a simple interpretation exists which satisfies it, otherwise (simply) unsatisfiable, and that a graph G simply entails a graph E when every interpretation which satisfies G also satisfies E.
Extension – IEXT(x), called the extension of x, is a set of pairs which identify the arguments for which the property is true, that is, a binary relational extension.
Generalized RDF (RDFS) closure – Let S and E be RDF graphs. Define the generalized RDF (RDFS) closure of S towards E to be the set obtained by the following procedure.
Ground – A ground RDF graph is one that contains no blank nodes.
Identify – IRI meanings may also be determined by other constraints external to the RDF semantics; when we wish to refer to such an externally defined naming relationship, we will use the word identify and its cognates.
Ill-typed – An ill-typed literal is one whose datatype IRI is recognized, but whose character string is assigned no value by the lexical-to-value mapping for that datatype.
Instance – Any graph obtained from a graph G by replacing some or all of the blank nodes N in G by M(N) is an instance of G.
Instance with respect to – An instance with respect to a vocabulary V is an instance in which all the names in the instance that were substituted for blank nodes in the original are names from V.
Interpretation – An interpretation is a mapping from IRIs and literals into a set, together with some constraints upon the set and the mapping.
Invalid – Any process which constructs a graph E from some other graph S is (simply) valid if S simply entails E in every case, otherwise invalid.
L2V – The function L2V maps datatypes to their lexical-to-value mapping.
Lean – An RDF graph is lean if it has no instance which is a proper subgraph of itself.
Merge – A related operation, called merging, takes the union after forcing any shared blank nodes, which occur in more than one graph, to be distinct in each graph. The resulting graph is called the merge. The merge of subgraphs of a graph may be larger than the original graph.
Merging – A related operation, called merging, takes the union after forcing any shared blank nodes, which occur in more than one graph, to be distinct in each graph. The resulting graph is called the merge. The merge of subgraphs of a graph may be larger than the original graph.
Monotonic – All entailment regimes MUST be monotonic extensions of the simple entailment regime described in the document, in the sense that if A simply entails B then A also entails B under any extended notion of entailment, provided that any syntactic conditions of the extension are also satisfied.
Proper instance – A proper instance of a graph is an instance in which a blank node has been replaced by a name, or two blank nodes in the graph have been mapped into the same node in the instance.
Proper subgraph – A proper subgraph is a proper subset of the triples in the graph.
RDFS interpretation – An RDFS interpretation (recognizing D) is an RDF interpretation (recognizing D) I which satisfies the semantic conditions in the following table, and all the triples in the subsequent table of RDFS axiomatic triples.
Recognize – Datatypes are identified by IRIs. Interpretations will vary according to which IRIs are recognized as denoting datatypes. We describe this using a parameter D on simple interpretations, where D is the set of recognized datatype IRIs.
Referent – The words denotes and refers to are used interchangeably as synonyms for the relationship between an IRI or literal and what it refers to in a given interpretation, itself called the denotation or referent.
Refers to – The words denotes and refers to are used interchangeably as synonyms for the relationship between an IRI or literal and what it refers to in a given interpretation, itself called the denotation or referent.
Reification – Assuming that the IRI can be used to refer to the triple, then the reification vocabulary allows us to describe the first graph in another graph. The second graph is called a reification of the triple in the first graph.
Satisfiable – Following standard terminology, we say that I (simply) satisfies E when I(E)=true, that E is (simply) satisfiable when a simple interpretation exists which satisfies it, otherwise (simply) unsatisfiable, and that a graph G simply entails a graph E when every interpretation which satisfies G also satisfies E.
Satisfiable recognizing D – A graph is (simply) D-satisfiable or satisfiable recognizing D when it has the value true in some D-interpretation, and a graph S (simply) D-entails or entails recognizing D a graph G when every D-interpretation which satisfies S also D-satisfies G.
Satisfies – Following standard terminology, we say that I (simply) satisfies E when I(E)=true, that E is (simply) satisfiable when a simple interpretation exists which satisfies it, otherwise (simply) unsatisfiable, and that a graph G simply entails a graph E when every interpretation which satisfies G also satisfies E.
Semantic extension – A particular such set of semantic assumptions is called a semantic extension.
Simple interpretation – A simple interpretation I is a structure consisting of: 1) A non-empty set IR of resources, called the domain or universe of I. 2) A set IP, called the set of properties of I. 3) A mapping IEXT from IP into the powerset of IR x IR i.e. the set of sets of pairs < x, y > with x and y in IR . 4) A mapping IS from IRIs into (IR union IP), and 5) A partial mapping IL from literals into IR.
Skolemization – Skolemization is a transformation on RDF graphs which eliminates blank nodes by replacing them with "new" IRIs, which means IRIs which are coined for this purpose and are therefore guaranteed to not occur in any other RDF graph (at the time of creation).
Standardize – When graphs are formed by combining RDF from multiple sources, it may be necessary to standardize apart the blank node identifiers by replacing them by others which do not occur in the other document(s).
Subgraph – A subgraph of an RDF graph is a subset of the triples in the graph.
Unsatisfiable – Following standard terminology, we say that I (simply) satisfies E when I(E)=true, that E is (simply) satisfiable when a simple interpretation exists which satisfies it, otherwise (simply) unsatisfiable, and that a graph G simply entails a graph E when every interpretation which satisfies G also satisfies E.
Valid – Any process which constructs a graph E from some other graph S is (simply) valid if S simply entails E in every case, otherwise invalid.