aid: xml-vocabulary name: XML Vocabulary description: >- Normative and domain vocabulary for XML (Extensible Markup Language), covering W3C specification terms, document constructs, namespace concepts, validation mechanisms, and the broader family of XML-based standards. created: '2026-05-03' modified: '2026-05-03' tags: - Data Formats - Document - Markup Language - Standard - W3C - XML terms: # Core specification terms - term: XML definition: >- Extensible Markup Language. A W3C Recommendation defining a general-purpose markup language for encoding documents that are both human-readable and machine-readable. First published in 1998. category: Standard aliases: - Extensible Markup Language - term: Document definition: >- A unit of XML data consisting of a single root element optionally preceded by an XML declaration, processing instructions, comments, and a document type declaration. category: Core Concept - term: Element definition: >- The fundamental structural unit of an XML document, consisting of a start tag, content (text or child nodes), and an end tag. Elements may be empty (self-closing). category: Core Construct - term: Attribute definition: >- A name-value pair appearing inside an element's start tag that supplies metadata about the element. Attribute values are always strings in XML. category: Core Construct - term: Namespace definition: >- A URI-identified naming context that qualifies element and attribute names, allowing vocabularies from different sources to be combined without name collisions. Defined by Namespaces in XML 1.0. category: Core Concept - term: Prefix definition: >- A short alias bound to a namespace URI via an xmlns:prefix attribute. Prefixes are used to qualify element and attribute names within a document. category: Core Construct - term: Default Namespace definition: >- A namespace declared without a prefix using xmlns="uri". Applies to unprefixed element names within its scope. Does not apply to unprefixed attributes. category: Core Construct - term: Well-Formed definition: >- A document conforms to the XML grammar rules defined in the XML specification. Every XML processor MUST reject documents that are not well-formed. category: Conformance - term: Valid definition: >- A well-formed document that additionally conforms to a specified DTD or schema. Validity is optional in XML; well-formedness is not. category: Conformance - term: XML Declaration definition: >- The optional processing instruction at the start of a document declaring the XML version and character encoding. category: Core Construct - term: Processing Instruction definition: >- A construct of the form used to convey instructions to applications processing the document. The xml-stylesheet PI is the most widely deployed example. category: Core Construct - term: Comment definition: >- A non-content note bracketed by . Comments are visible to applications but are not part of the document's character data. category: Core Construct - term: CDATA Section definition: >- A construct of the form that allows characters which would otherwise need to be escaped (such as <, >, &) to appear literally inside element content. category: Core Construct - term: Entity definition: >- A named storage unit of data — characters, markup, or external content — that can be referenced from within the document using &name; syntax. category: Core Construct - term: DTD definition: >- Document Type Definition. A grammar describing the legal structure of an XML document using element and attribute declarations. The original schema language for XML, defined in the XML specification itself. category: Schema Language aliases: - Document Type Definition - term: XML Schema definition: >- A W3C Recommendation (XSD) defining a more powerful schema language for XML using an XML-based syntax. Adds typed simple values, complex types, keys, and assertions. category: Schema Language aliases: - XSD - XML Schema Definition - term: RELAX NG definition: >- An ISO/IEC 19757-2 schema language for XML using a simpler grammar-based design than XSD. Available in XML and compact (non-XML) syntaxes. category: Schema Language - term: Schematron definition: >- An ISO/IEC 19757-3 rule-based validation language for XML using XPath assertions. Often combined with XSD or RELAX NG to enforce co-occurrence and content rules. category: Schema Language - term: XPath definition: >- A W3C Recommendation expression language for navigating and selecting nodes within an XML document. Used by XSLT, XQuery, XPointer, and many XML APIs. category: Related Standard aliases: - XML Path Language - term: XSLT definition: >- Extensible Stylesheet Language Transformations. A W3C Recommendation for transforming XML documents into other formats using template rules and XPath expressions. category: Related Standard aliases: - Extensible Stylesheet Language Transformations - term: XQuery definition: >- A W3C Recommendation query language designed to query collections of XML data. Shares its data model and type system with XPath and XSLT. category: Related Standard - term: XLink definition: >- A W3C Recommendation defining XML attributes that create and describe links between resources, supporting simple and extended (multi-ended) linking. category: Related Standard - term: XPointer definition: >- A W3C Recommendation framework for identifying fragments of XML documents within a URI, extending the URI fragment-identifier syntax. category: Related Standard - term: SOAP definition: >- Simple Object Access Protocol. A W3C Recommendation defining an XML-based messaging framework for exchanging structured information in web services. category: Application - term: WSDL definition: >- Web Services Description Language. A W3C Recommendation for describing the interface of an XML-based web service. category: Application aliases: - Web Services Description Language - term: XHTML definition: >- Extensible HyperText Markup Language. A reformulation of HTML as an XML application, published as a W3C Recommendation. category: Application - term: SVG definition: >- Scalable Vector Graphics. A W3C Recommendation defining an XML-based language for describing two-dimensional vector graphics. category: Application aliases: - Scalable Vector Graphics - term: RSS definition: >- A family of XML-based syndication formats for publishing frequently updated content such as blog entries, news headlines, and podcasts. category: Application aliases: - Really Simple Syndication - term: Atom definition: >- An IETF-standardized XML-based syndication format (RFC 4287) and protocol for publishing and editing web resources (RFC 5023). category: Application - term: DOM definition: >- Document Object Model. A W3C Recommendation defining a tree-based programming interface for accessing and manipulating XML and HTML documents. category: Programming Interface aliases: - Document Object Model - term: SAX definition: >- Simple API for XML. An event-driven, streaming programming interface for parsing XML documents, originally developed for Java and widely ported. category: Programming Interface aliases: - Simple API for XML - term: StAX definition: >- Streaming API for XML. A pull-parsing programming interface for XML, providing iterator and cursor models for traversing documents. category: Programming Interface - term: XInclude definition: >- A W3C Recommendation defining a mechanism for merging the contents of one XML document into another, using xi:include elements. category: Related Standard - term: Canonical XML definition: >- A W3C Recommendation defining a normalized serialization of XML documents, used to enable byte-for-byte comparison and digital signatures. category: Related Standard - term: XML Signature definition: >- A W3C Recommendation defining XML syntax and processing rules for creating and verifying digital signatures over XML and other resources. category: Security - term: XML Encryption definition: >- A W3C Recommendation defining XML syntax and processing rules for encrypting data and representing the result in XML. category: Security - term: W3C definition: >- World Wide Web Consortium. The international standards organization that publishes and maintains XML and many related specifications. category: Governance aliases: - World Wide Web Consortium