2. Terms and
Definitions
This section is informative.
While some terms are defined in place, the following definitions
are used throughout this document. Familiarity with the W3C XML 1.0
Recommendation [XML] is
highly recommended.
- abstract module
- a unit of document type specification corresponding to a
distinct type of content, corresponding to a markup construct
reflecting this distinct type.
- content model
- the declared markup structure allowed within instances of an
element type. XML 1.0 differentiates two types: elements containing
only element content (no character data) and mixed content
(elements that may contain character data optionally interspersed
with child elements). The latter are characterized by a content
specification beginning with the "#PCDATA" string (denoting
character data).
- document model
- the effective structure and constraints of a given document
type. The document model constitutes the abstract representation of
the physical or semantic structures of a class of documents.
- document type
- a class of documents sharing a common abstract structure. The
ISO 8879 [SGML] definition
is as follows: "a class of documents having similar
characteristics; for example, journal, article, technical manual,
or memo. (4.102)"
- document type definition (DTD)
- a formal, machine-readable expression of the XML structure and
syntax rules to which a document instance of a specific document
type must conform; the schema type used in XML 1.0 to validate
conformance of a document instance to its declared document type.
The same markup model may be expressed by a variety of DTDs.
- driver
- a generally short file used to declare and instantiate the
modules of a DTD. A good rule of thumb is that a DTD driver
contains no markup declarations that comprise any part of the
document model itself.
- element
- an instance of an element type.
- element type
- the definition of an element, that is, a container for a
distinct semantic class of document content.
- entity
- an entity is a logical or physical storage unit containing
document content. Entities may be composed of parse-able XML markup
or character data, or unparsed (i.e., non-XML, possibly
non-textual) content. Entity content may be either defined entirely
within the document entity ("internal entities") or external to the
document entity ("external entities"). In parsed entities, the
replacement text may include references to other entities.
- entity reference
- a mnemonic or numeric string used as a reference to the content
of a declared entity (eg., "&" for "&", "<" for
"<", "©" for "©".)
- generic identifier
- the name identifying the element type of an element. Also,
element type name.
- hybrid document
- A hybrid document is a document that uses more than one XML
Namespace. Hybrid documents may be defined as documents that
contain elements or attributes from hybrid document types.
- instantiate
- to replace an entity reference with an instance of its declared
content.
- markup declaration
- a syntactical construct within a DTD declaring an entity or
defining a markup structure. Within XML DTDs, there are four
specific types: entity declaration defines the binding between a
mnemonic symbol and its replacement content; element declaration
constrains which element types may occur as descendants within an
element (See also content model); attribute definition list
declaration defines the set of attributes for a given element type,
and may also establish type constraints and default values;
notation declaration defines the binding between a notation name
and an external identifier referencing the format of an unparsed
entity.
- markup model
- the markup vocabulary (i.e., the gamut of element and attribute
names, notations, etc.) and grammar (i.e., the prescribed use of
that vocabulary) as defined by a document type definition (i.e., a
schema) The markup model is the concrete representation in markup
syntax of the document model, and may be defined with varying
levels of strict conformity. The same document model may be
expressed by a variety of markup models.
- module
- an abstract unit within a document model expressed as a DTD
fragment, used to consolidate markup declarations to increase the
flexibility, modifiability, reuse and understanding of specific
logical or semantic structures.
- modularization
- an implementation of a modularization model; the process of
composing or de-composing a DTD by dividing its markup declarations
into units or groups to support specific goals. Modules may or may
not exist as separate file entities (i.e., the physical and logical
structures of a DTD may mirror each other, but there is no such
requirement).
- modularization model
- the abstract design of the document type definition (DTD) in
support of the modularization goals, such as reuse, extensibility,
expressiveness, ease of documentation, code size, consistency and
intuitiveness of use. It is important to note that a modularization
model is only orthogonally related to the document model it
describes, so that two very different modularization models may
describe the same document type.
- parameter entity
- an entity whose scope of use is within the document prolog
(i.e., the external subset/DTD or internal subset). Parameter
entities are disallowed within the document instance.
- parent document type
- A parent document type of a hybrid document is the document
type of the root element.
- tag
- descriptive markup delimiting the start and end (including its
generic identifier and any attributes) of an element.