Attributes appear as name-value pairs in the element’s start tag. For example, to assign the value
systemitem, you would use the markup:
- character reference
A character reference is a mechanism for inserting an arbitrary Unicode character into a document. They’re most often used for characters that aren’t available on the author’s keyboard or font. Syntactically, they have the form
;where “number” is the Unicode codepoint of the character expressed as a decimal number. Hexadecimal numbers can also be used with character references of the form
For example, you can type
©) to insert a © symbol.
“Cooked” data, as distinct from “raw,” is a collection of elements and character data that’s ready for presentation. The processor is not expected to rearrange, select, or suppress any of the elements, but simply present them as specified.
See Also raw.
- Document Type Declaration (DTD)
A term used to identify attributes used for profiling or conditional processing. DocBook contains a set of effectivity attributes that allow you to flag elements as being “effective” under particular conditions. For example, you might set the value of the
oseffectivity attribute to “linux” to indicate that this element is applicable to the Linux operating system. With the DocBook stylesheets, if you set the
profile.osparameter to “linux” this element will be included. If you set the parameter to some other value, the element will be excluded. Further information about using the DocBook stylesheets for profiling can be found in Bob Stayton’s DocBook XSL: The Complete Guide.
Elements define the hierarchical structure of a document. Most elements have start and end tags and contain some part of the document content. Empty elements have only a start tag and have no content.
A name assigned (by means of a declaration) to some chunk of data so that it can be referred to by that name; the data can be of various kinds (e.g., a special character or a chapter or a set of declarations in a DTD), and the way in which it is referred to depends on the type of data and where it is being referenced.
- external entity
An external entity is a general entity that refers to another document. External entities are often used to incorporate parsable text documents, like legal notices or chapters, into larger units, like chapters or books.
- external subset
Element, attribute, and other declarations that compose (part of) a document type definition that are stored in an external entity, and referenced from a document’s Document Type Declaration using a system identifier and optionally a public identifier.
Text objects such as sidebars, figures, tables, and graphics are said to float when their actual place in the document is not fixed. For presentation on a printed page, for instance, a graphic may float to the top of the next page if it is too tall to fit on the page in which it actually falls, in the sequence of words and the sequence of other like objects in a document.
- formal public identifier
- general entity
An entity referenced by a name that starts with an ampersand (&) and ends with a semicolon. Most of the time general entities are used in document instances, not in the schema. There are two types, external and internal entities, and they refer either to special characters or to text objects such as commonly repeated phrases or names or chapters.
- internal entity
- internal subset
NVDL is the Namespace-based Validation Dispatching Language; see
- processing instruction
An essentially arbitrary string preceded by a question mark and delimited by angle brackets that is intended to convey information to an application that processes an XML instance. For example, the processing instruction
<?linebreak>might cause the formatter to introduce a line break at the position where the processing instruction occurs.
pitargetshould be a name that the processing application will recognize. Additional information in the processing instruction should be added using “attribute syntax.”
- public identifier
“Raw” data is just a collection of elements, with no additional punctuation or information about presentation. To continue the cooking metaphor, raw data is just a set of ingredients. It’s up to the processor to select appropriate elements, arrange them for display, and add required presentational information.
See Also cooked.
- RELAX NG
RELAX NG is a grammar-based schema language for XML; see
Schematron is a language for making assertions about patterns found in XML documents; see
- system identifier
Uniform Resource Identifier, the W3C’s codification of the name and address syntax of present and future objects on the Internet. In its most basic form, a URI consists of a scheme name (such as file, http, ftp, news, mailto, gopher) followed by a colon, followed by a path whose nature is determined by the scheme that precedes it (see RFC 1630).
Uniform Resource Locator, a name and address for an existing object accessible over the Internet.
http://www.docbook.orgis an example of a URL (see RFC 1738).
Some elements, such as
chapter, have important semantic significance. Other elements serve no obvious purpose except to contain a number of other elements. For example,
infohas no important semantics; it merely serves as a container for the meta-information about a book. Elements that are just containers are sometimes called “wrappers.”
The Extensible Markup Language, a subset of SGML designed specifically for use over the Web.