| Digital Signature | Encrypted data blocks proving information came from a trusted source | The Semantic Web |
| Equivalence Statement | Explicit links between different names for the same concept across databases (e.g. "zipcode" = "postal code") | Semantic Web |
| Inference Rules | Logical deductions encoded in ontologies (e.g. "if X is in city Y, and Y is in state Z, then X is in state Z") | Semantic Web |
| Knowledge Representation | Representing a knowledge base in a machine-readable fashion | The Semantic Web |
| Ontology | A document formally defining relations among terms: Taxonomies, inference rules, and equivalence relations | Semantic Web, The Graph Space |
| Proof Verification | Verifying that claims are logically inferred from trusted sources via exchangeable mathematical proofs | The Semantic Web |
| RDF | Resource Description Framework: Triple-based model (subject-predicate-object) encoding meaning via URIs | Semantic Web, The Graph Space |
| Semantic Preservation | Extracting universal logic from systems while discarding system-specific instructions, losing as little meaning as possible | The Semantic Web |
| Semantic Web | Extension of the WWW adding machine-readable meaning to data, enabling computer-human cooperation | Semantic Web |
| Software Agent | Software that harvests data from diverse sources, processes it, and exchanges results with other agents | The Semantic Web |
| SPARQL | Query language for RDF data | The Graph Space |
| Taxonomy | Class hierarchies (classes and subclasses) and their relations within an ontology | Semantic Web |
| URI | Uniform Resource Identifier: A compact character sequence identifying a resource. Strictly means the absolute form (with scheme) | RFC 3986 |
| URI-reference | Either an absolute URI-reference (a full URI) or a relative URI-reference (no scheme, resolved against a base URI) | RFC 3986 |
| URL | Uniform Resource Locator: A URI that also describes the access mechanism (e.g. network location) | RFC 3986 |
| URN | Uniform Resource Name: A URI required to remain globally unique and persistent even when the resource ceases to exist | RFC 3986 |
| Percent-encoding | Representing a data octet as % + two hex digits in a URI (e.g. %20 = space) | RFC 3986 |
| Base URI | The absolute URI that relative URI-references are resolved against | RFC 3986 |
| XML | Adds arbitrary structure to documents via custom tags, structure without meaning | Semantic Web |
| XML Namespace | URI-based prefix system to avoid tag name collisions when combining XML vocabularies | XML Core |
| Well-formed XML | An XML document that follows all syntax rules (proper nesting, quoted attributes, single root, etc.) | XML Core |
| Valid XML | A well-formed XML document that additionally conforms to a DTD or XML Schema | XML Core |
| DTD | Document Type Definition: Defines the legal structure, elements, and attributes of an XML document, uses its own non-XML syntax | XML Core |
| XML Schema (XSD) | XML-based alternative to DTD for defining document structure, supports data types, namespaces, and extensibility | XML Core |
| XPath | Expression language for navigating and selecting nodes in an XML document tree | XPath |
| XSLT | Template-driven language for transforming XML documents into other formats (HTML, XML, text) | XSLT |
| XQuery | Expression-driven query language for XML, built on XPath, similar to SQL for databases | XQuery |
| FLWOR | XQuery's for-let-where-order by-return expression, equivalent to SQL's SELECT-FROM-WHERE-ORDER BY | XQuery |
| XLink | W3C spec for creating hyperlinks in XML via namespace attributes on any element | XLink |
| XPointer | Fragment identifier scheme for XML, uses XPath expressions to point to specific parts of a document | XPointer |
| XSL | eXtensible Stylesheet Language: Family of specs for styling and transforming XML (XSLT, XPath, XSL-FO) | XML Core |
| DOM | Document Object Model: Tree-based API for reading and manipulating XML/HTML documents | DOM |
| IRI | Internationalized Resource Identifier: Generalization of URI that supports Unicode (RFC 3987) | RDF Data Model |
| RDF Triple | A subject-predicate-object statement expressing a directional relationship between two resources | RDF Data Model |
| RDF Graph | A collection of RDF triples, where subjects and objects are nodes and predicates are directed edges | RDF Data Model |
| RDF Literal | A data value (not an IRI) with a datatype, optional language tag, and optional base direction, can only appear in object position | RDF Data Model |
| Blank Node | An unnamed resource without a global IRI, functions like a variable standing for something unspecified | RDF Data Model |
| Triple Term | An RDF 1.2 feature: A triple used as a value (not asserted), enabling annotation of statements via reifiers | RDF Data Model |
| Reifier | A resource that concretizes a statement so properties (date, source, etc.) can be attached to it | RDF Data Model |
| Named Graph | A set of RDF triples associated with an IRI, used for provenance and grouping within an RDF dataset | RDF Data Model |
| RDF Dataset | A collection of named graphs plus at most one unnamed default graph | RDF Data Model |
| RDF Vocabulary | A set of IRIs with documented meanings that give interpretation to otherwise opaque triples | RDF Vocabulary |
| RDFS | RDF Schema: Semi-formal vocabulary level where meanings are defined as RDF triples and processed by RDFS-aware processors | RDFS |
| rdfs:Class | A class (metaclass) whose instances are themselves classes | RDFS |
| rdf:Property | A class whose instances are properties (relationships used as predicates) | RDFS |
| Entailment | Deriving new triples from existing ones through logical inference based on vocabulary definitions | RDFS |