| attribute | Extra information pertaining to an element that is stored in the start tag of an element (as name="value" pairs) or assigned default values in attribute declarations. Attributes and child elements may sometimes be interchanged; typically, attributes contain information about a particular element, not information that might stand on its own as an extra element. |
| COM | see Component Object Model |
| Component Object Model (COM) | A model used by software developers to create components that can be reused easily with other objects. The model specifies the interfaces between component objects so that software applications can be built out of interchangeable components. |
| DCD | see Document Content Description for XML |
| DDML | see Document Definition Markup Language |
| Document Content Description for XML (DCD) | A schema proposal made to the W3C by Microsoft and IBM. DCD builds on a subset of XML-Data, but uses RDF syntax to describe document structures and data types. |
| Document Definition Markup Language (DDML) | A schema proposal created by the XML-Dev mailing list (where it was known as 'XSchema') and submitted to the W3C. DDML's primary goal was the creation of a highly readable and easily processed language for describing document structures. |
| document type definition (DTD) | A formal description of the structure of a document that may also provide some content information. DTDs effectively describe XML file formats, providing the vocabulary and allowable structure of the elements in an XML document. The DTD for a document is the combination of the internal and external subsets described by the document type declaration. |
| document | In XML, any sequence of text that can be interpreted as well-formed XML. Documents may correspond to 'files', or they may be generated from databases, or by any other process that results in a stream of text that matches the XML specification. (XML documents contain an option prolog and miscellaneous comments and processing instructions, followed by a required root element containing the content of the document, which may be followed by white space and more comments and processing instructions.) |
| DTD | see Document Type Definition |
| EBNF | see Extended Backus-Naur Form |
| element | The unit forming the basic structure of XML documents. Elements may contain attributes (in their start tags), other elements, and textual content. |
| entity | A reference to data that is used for content reuse and document size minimization. Developers can use entities to simplify the management of information that appears repeatedly. XML Authority refers to entities as reusables. |
| Extended Backus-Naur Form (EBNF) | A formal notation used to write standards like XML 1.0 and Resource Description Framework (RDF). |
| Extensible Markup Language (XML) | A markup language defined by the W3C that provides a strict set of standards for document syntax while allowing developers, organizations, and communities to define their own vocabularies. |
| Extensible Style Language (XSL) | A style sheet standard in development at the W3C. XSL uses template rules (written using XML) to transform documents into 'formatting objects' which are then presented on screen, in print, or in other media. |
| fatal error | Any violation of the well-formedness constraints described in XML 1.0. Parsers must stop processing the document and report an error to the application rather than sending it document content. |
| fragment | A portion of an XML document. Fragments are not always well-formed. The W3C XML Activity has formed a working group to describe how to represent fragments and their context, even those which aren't well-formed, without having to transmit XML that isn't well-formed. |
| instance | The use of an element or document type in a document, as opposed to its declaration. The term is also used to refer to documents; a document that conforms to a particular DTD is an 'instance' of that DTD. |
| internal DTD subset | The declarations which appear inside the document type declaration of a document, not those referenced in an external file. The internal DTD subset allows document authors to customize DTDs to meet their needs (typically with extra entities), but can also be difficult to manage as different versions of the DTD spread across a large number of documents. |
| ISO | The international organization (acronym works with French name, but comes from Greek) responsible for the creation and maintenance of SGML and many of its related standards. |
| markup | Information describing the content of a document. Declarations, tags, processing instructions, and comments are all markup. |
| name characters | Characters that are letters, digits, hyphens, underscores, colons, or full stops (like periods). Because XML is based on Unicode, the number of characters that meet this criteria is enormous. Although colons are permitted, their use is strongly discouraged except for applications using the W3C's Namespaces in XML recommendation. |
| ODBC | see Open Database Connectivity |
| Open Database Connectivity (ODBC) | A standard for connecting to database systems, created by Microsoft. |
| parameter entity | An entity which describes content that may be used within a DTD. Parameter entities used within the internal subset must contain complete declarations, while those used in the external subset may contain fragments (like element content models or sets of attributes used for multiple elements.) |
| parent element | An element directly containing another element. In <A><B><C/></B></A>, the A element is the parent element of the B element, and the B element is the parent of the C element, but the A element is not the parent of the C element. |
| parser | A tool used to convert a stream of XML information into a set of structures that an application can use. Typically, applications use parser components built by other developers. Parsers generally come in the two flavors of non-validating and validating, though additional features vary within those two groups and some parsers can be used with validation turned on or off. |
| processing application | An application that receives information from a parser and does something with it, like edit, display, transform, or retransmit it. |
| processing instruction | Directives inside XML documents that float in the structure and which are typically used to pass information about a document that isn't quite structure but isn't quite content either, like references to style sheets. Processing instructions begin with <? and end with ?>. |
| processor | The term used in the XML 1.0 specification for the tool more commonly referred to as a parser. |
| project | |
| RDF | see Resource Description Framework |
| recurse | |
| Resource Description Framework (RDF) | A standard for storing information about information, commonly referred to as metadata. RDF can (but doesn't have to) use XML syntax, and has its own set of rules for creating schemas. |
| root element | The first element in a document, which must contain all the other elements in the document. |
| schema | A set of rules describing a document structure. XML 1.0 Document Type Definitions are one type of schema. The XML-Data, DCD, SOX, and DDML Notes at the W3C represent different proposals for XML schema frameworks. RDF has its own set of schemas separate from those used for XML. |
| Schema for Object-Oriented XML (SOX) | A schema proposal submitted to the W3C by Veo Systems, Inc., that describes XML document structures in terms familiar to object-oriented software developers. SOX allows developers to use tools commonly found in object-oriented development environments, notably inheritance, to describe document types. |
| SGML | see Standard Generalized Markup Language |
| SOX | see Schema for Object-Oriented XML. |
| Standard Generalized Markup Language (SGML) | The 'parent' language to HTML and XML, itself descended from Generalized Markup Language. SGML is an ISO standard and is referenced formally as ISO 8879:1986, though there have been more recent updates. |
| style sheet | A list of specifications describing how to present a document in a particular medium. Cascading Style Sheets (CSS) and Extensible Style Language (XSL) are the dominant style sheet mechanisms in the XML space. |
| UCS-2 | The canonical encoding for Unicode characters, representing characters using the complete 2-byte version of every character. |
| Unicode | A standard for international character encoding, maintained by the Unicode Consortium (http://www.unicode.org). XML supports Unicode 2.0 through its reference to ISO 10646, an ISO standard that supports (and extends) the Unicode standard. |
| UTF-8 | An encoding for Unicode that creates smaller files for documents that use the ASCII character set for most of their characters. Most characters used in English will be represented as a single byte, while characters in other languages will be represented as two or three bytes. |
| valid | Documents are valid according to the XML 1.0 Recommendation if they conform to the content model provided for them in a DTD and are well-formed. Valid documents can be processed successfully with both validating and non-validating parsers. |
| validate | 1. To determine whether a candidate XML document
conforms to its schema, expressed formally in a DTD or
other XML schema. Validation of XML documents helps
ensure that the information is structured in a way that
is sensible for applications that use it. 2. To determine whether a candidate schema conforms to the XML 1.0 specification (if a DTD) or to one of several proposed standards (if schema is written in XML). |
| validity constraint | Rules for processing XML documents that only validating parsers are required to enforce. Parsers should report an error to an application when a validity constraint is violated, but are not required to stop processing. |
| XHTML | A project underway at the W3C in which HTML is expressed as a set of XML modules. (XHTML was previously known as 'Voyager'.) |
| XSchema | see Document Definition Markup Language |
| W3C | The World Wide Web Consortium, which sets the standards for XML, HTML, HTTP, XSL, CSS, RDF, and a number of other Web-oriented standards. |
| well-formed | A document that meets the basic document syntax rules of XML. All elements must be cleanly nested, tags must be properly constructed, and the overall structure of XML documents (in which the XML declaration appears only at the beginning and there is only one root element, for example) is observed. To be an 'XML document', a document must be well-formed. |
| XLink | A proposal in development at the W3C that describes a set of structures for creating sets of linked XML documents and resources. |
| XML Activity | The group of committees at the W3C working on the further development of XML core standards. |
| XML declaration | The declaration at the beginning of an XML document that identifies the version and encoding used in the document, as well as whether the document is a 'standalone' document. |
| XML | see Extensible Markup Language |
| XML-Data | XML-Data is a proposal from Microsoft, Inso, and DataChannel that provides a schema for describing data and data types within XML. A subset of XML-Data is implemented in Microsoft Internet Explorer 5.0. |
| XPointer | A set of tools for selecting document fragments. XPointer is under development at the W3C in conjunction with the XLink project. |
| XSL | see Extensible Style Language |
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