Metadata – SVG 1.1 (Second Edition)
SVG 1.1 (Second Edition) – 16 August 2011
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21 Metadata
Contents
21.1 Introduction
21.2 The
‘metadata’
element
21.3 An example
21.4 DOM interfaces
21.4.1 Interface SVGMetadataElement
21.1 Introduction
Metadata is structured data about data.
In the computing industry, there are ongoing standardization
efforts towards metadata with the goal of promoting industry
interoperability and efficiency. Content creators should track
these developments and include appropriate metadata in their
SVG content which conforms to these various metadata standards
as they emerge.
The W3C has a
Semantic Web
Activity
which has been established to serve a leadership
role, in both the design of enabling specifications and the
open, collaborative development of technologies that support
the automation, integration and reuse of data across various
applications. The Semantic Web Activity builds upon the earlier
W3C Metadata Activity, including the definition of Resource
Description Framework (RDF). The
RDF Primer
is the first in a set of six documents that define the Resource Description Framework
RDF-PRIMER
].
Another activity relevant to most applications of metadata
is the
Dublin Core
DCORE
], which is
a set of generally applicable core metadata properties (e.g.,
Title, Creator/Author, Subject, Description, etc.).
Individual industries or individual content creators are
free to define their own metadata schema but are encouraged to
follow existing metadata standards and use standard metadata
schema wherever possible to promote interchange and
interoperability. If a particular standard metadata schema does
not meet your needs, then it is usually better to define an
additional metadata schema in an existing framework such as RDF
and to use custom metadata schema in combination with standard
metadata schema, rather than totally ignore the standard
schema.
21.2 The
‘metadata’
element
Metadata which is included with SVG content should be
specified within
‘metadata’
elements. The contents of the
‘metadata’
should be elements from
other XML namespaces, with these elements from these namespaces
expressed in a manner conforming with the
Namespaces in XML
Recommendation
XML-NS
].
Authors should provide a
‘metadata’
child element to the
outermost svg element
within a
stand-alone SVG document. The
‘metadata’
child element to an
‘svg’
element serves the
purposes of identifying document-level metadata.
The DTD definitions of many of SVG's elements (particularly,
container and text elements) place no restriction on the
placement or number of the
‘metadata’
sub-elements. This
flexibility is only present so that there will be a consistent
content model for container elements, because some container
elements in SVG allow for mixed content, and because
the mixed
content rules for XML
([
XML10
], section 3.2.2)
do not permit the desired restrictions. Representations of
future versions of the SVG language might use more expressive
representations than DTDs which allow for more restrictive
mixed content rules. It is strongly recommended that at most
one
‘metadata’
element appear
as a child of any particular element, and that this element
appear before any other child elements (except possibly
‘desc’
or
‘title’
elements) or character
data content. If metadata-processing user agents need to choose
among multiple
‘metadata’
elements for processing it should choose the first one.
‘metadata’
Categories:
Descriptive element
Content model:
Any elements or character data.
Attributes:
core attributes
‘id’
‘xml:base’
‘xml:lang’
‘xml:space’
DOM Interfaces:
SVGMetadataElement
21.3 An example
Here is an example of how metadata can be included in an SVG
document. The example uses the Dublin Core version 1.1 schema.
(Other XML-compatible metadata languages, including ones not
based on RDF, can be used also.)
21.4 DOM interfaces
21.4.1 Interface SVGMetadataElement
The
SVGMetadataElement
interface corresponds to the
‘metadata’
element.
interface
SVGMetadataElement
SVGElement
};
SVG 1.1 (Second Edition) – 16 August 2011
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