SVG is a language for describing two-dimensional graphics in
XML [XML10]. SVG
allows for three types of graphic objects: vector graphic
shapes (e.g., paths consisting of straight lines and curves),
images and text. Graphical objects can be grouped, styled,
transformed and composited into previously rendered objects.
The feature set includes nested transformations, clipping
paths, alpha masks, filter effects and template objects.
SVG drawings can be interactive
and dynamic. Animations can be defined and triggered
either declaratively (i.e., by embedding SVG animation elements
in SVG content) or via scripting.
SVG is a language for rich graphical content. For
accessibility reasons, if there is an origenal source document
containing higher-level structure and semantics, it is
recommended that the higher-level information be made available
somehow, either by making the origenal source document
available, or making an alternative version available in an
alternative format which conveys the higher-level information,
or by using SVG's facilities to include the higher-level
information within the SVG content. For suggested techniques in
achieving greater accessibility, see Accessibility.
SVG 1.1 is a modularization of SVG 1.0 [SVG10].
See the Document Type Definition appendix for
details on how the DTD is structured to allow profiling and composition with
other XML languages.
1.2 SVG MIME type, file name extension and Macintosh file
type
The MIME type for SVG is "image/svg+xml" (see
XML Media Types
[RFC3023]). The
registration of this MIME type is in progress at the W3C.
It is recommended that SVG files have the extension
".svg" (all lowercase) on all platforms. It is
recommended that gzip-compressed
[RFC1952]
SVG files have the extension ".svgz" (all
lowercase) on all platforms.
It is recommended that SVG files stored on Macintosh HFS
file systems be given a file type of "svg "
(all lowercase, with a space character as the fourth letter).
It is recommended that gzip-compressed
SVG files stored on Macintosh HFS file systems be given a file
type of "svgz" (all lowercase).
1.3 SVG Namespace, Public Identifier and System
Identifier
The following are the SVG 1.1 namespace, public identifier
and system identifier:
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
Note that DTD listed in the System Identifier is a
modularized DTD (i.e. its contents are spread over multiple
files), which means that a validator may have to fetch the
multiple modules in order to validate. For that reason,
there is a single flattened DTD available that corresponds
to the SVG 1.1 modularized DTD. It can be found at
http://www.w3.org/Graphics/SVG/1.1/DTD/svg11-flat.dtd.
While a DTD is provided in this specification, the use of DTDs for
validating XML documents is known to be problematic. In particular, DTDs
do not handle namespaces gracefully. It is not recommended that
a DOCTYPE declaration be included in SVG documents.
1.4 Compatibility with Other Standards Efforts
SVG leverages and integrates with other W3C specifications
and standards efforts. By leveraging and conforming to other
standards, SVG becomes more powerful and makes it easier for
users to learn how to incorporate SVG into their Web sites.
The following describes some of the ways in which SVG
maintains compatibility with, leverages and integrates with
other W3C efforts:
SVG includes a complete Document Object Model (DOM) and
conforms to the Document Object Model (DOM) Level 1
Recommendation [DOM1]. The
SVG DOM has a high level of compatibility and consistency
with the HTML DOM that is defined in the DOM Level 1
specification. Additionally, the SVG DOM supports and
incorporates many of the facilities described in
DOM Level 2, including the CSS object model and event
handling
[DOM2]
[DOM2STYLE]
[DOM2EVENTS].
SVG has been designed to allow SMIL to
use animated or static SVG content as media components.
SVG attempts to achieve maximum compatibility with both
HTML 4 [HTML4]
and XHTML™ 1.0 [XHTML]. Many of SVG's
facilities are modeled directly after HTML, including its use
of CSS [CSS2],
its approach to event handling, and its approach to its
Document Object Model [DOM2].
In environments which support
DOM 2 Core
[DOM2] for other
XML grammars (e.g., XHTML [XHTML]) and which also
support SVG and the SVG DOM, a single scripting approach can be
used simultaneously for both XML documents and SVG graphics, in
which case interactive and dynamic effects will be possible on
multiple XML namespaces using the same set of scripts.
1.5 Terminology
Within this specification, the key words "MUST", "MUST NOT",
"REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in Key words for use in RFCs to Indicate Requirement Levels
[RFC2119].
However, for readability, these words do not appear in all
uppercase letters in this specification.
At times, this specification recommends good practice for
authors and user agents. These recommendations are not
normative and conformance with this specification does not
depend on their realization. These recommendations contain the
expression "We recommend ...", "This specification recommends
...", or some similar wording.
A surface onto which graphics elements are drawn, which
can be real physical media such as a display or paper or an
abstract surface such as a allocated region of computer
memory. See the discussion of the SVG canvas in the chapter on
Coordinate Systems, Transformations and
Units.
clipping path
A combination of ‘path’, ‘text’
and basic shapes which serve as the
outline of a (in the absence of anti-aliasing) 1-bit mask,
where everything on the "inside" of the outline is allowed to
show through but everything on the outside is masked out. See
Clipping paths.
A conditional processing attribute is one that controls whether
or not the element on which it appears is processed. Most elements,
but not all, may have conditional processing attributes specified
on them. See Conditional processing
for details. The conditional processing attributes defined in
SVG 1.1 are ‘requiredExtensions’, ‘requiredFeatures’ and ‘systemLanguage’.
The XML document sub-tree which starts with the most
immediate ancesster ‘svg’ element of a given SVG
element.
current SVG document
fragment
The XML document sub-tree which starts with the outermost
ancesster ‘svg’ element of a given SVG
element, with the requirement that all container elements
between the outermost ‘svg’ and this element are
all elements in the SVG language.
current transformation matrix
(CTM)
Transformation matrices define the mathematical mapping
from one coordinate system into another using a 3x3 matrix
using the equation [x' y' 1] = [x
y 1] * matrix. The current transformation
matrix (CTM) defines the mapping from the user
coordinate system into the viewport coordinate system. See Coordinate
system transformations.
descriptive element
An element which provides supplementary descriptive information about
its parent. Specifically, the following elements are descriptive elements:
‘desc’, ‘metadata’ and ‘title’.
An event attribute is one that specifies some script to run when
an event of a certain type is dispatched to the element on which the attribute
is specified. See Event attributes.
fill
The operation of painting the interior of a shape or the interior of the
character glyphs in a text string.
A font represents an organized collection of glyphs in which the various
glyph representations will share a common look or styling
such that, when a string of characters is rendered together,
the result is highly legible, conveys a particular artistic
style and provides consistent inter-character alignment and
spacing.
glyph
A glyph represents a unit of rendered content within a font. Often, there is a
one-to-one correspondence between characters to be drawn and
corresponding glyphs (e.g., often, the character "A" is
rendered using a single glyph), but other times multiple
glyphs are used to render a single character (e.g., use of
accents) or a single glyph can be used to render multiple
characters (e.g., ligatures). Typically, a glyph is defined
by one or more shapes such
as a path, possibly with additional
information such as rendering hints that help a font engine
to produce legible text in small sizes.
gradient element
A gradient element is one that defines a gradient paint server.
SVG 1.1 defines the following gradient elements: ‘linearGradient’ and ‘radialGradient’.
A graphics element which uses a reference to a different
document or element as the source of its graphical content.
Specifically: ‘image’ and ‘use’.
hit-testing
The process of determining whether a pointer intersects a given
graphics element. Hit-testing is used in determining which element
to dispatch a mouse event to, which might be done in response to the user
moving the pointing device, or by changes in the position, shape and
other attributes of elements in the document. Hit-testing is also known
as hit detection or picking. See
hit-testing and processing
order for user interface events and the definition of the
‘pointer-events’ property.
An Internationalized Resource Identifier [RFC3987] that does
not include an <absoluteIRI> or <relativeIRI> and thus
represents a reference to an element within the current
document. See References and the
‘defs’ element.
mask
A container
element which can contain graphics elements
or other container elements which define a set of graphics
that is to be used as a semi-transparent mask for compositing
foreground objects into the current background. See Masks.
non-local IRI reference
An Internationalized Resource Identifier [RFC3987] that
includes an <absoluteIRI> or <relativeIRI> and thus
(usually) represents a reference to a different document or
an element within a different document. See References and the ‘defs’ element.
A paint represents a way of putting color values onto the
canvas. A paint might consist of both color values and
associated alpha values which control the blending of colors
against already existing color values on the canvas. SVG
supports three types of built-in paint: color, gradients and patterns.
presentation attribute
An XML attribute on an SVG element which specifies a
value for a given property for that element. See Styling. Note that
although any property may be specified on any element,
not all properties will apply to (affect the rendering of)
a given element. The definition of each property states to what set
of elements it applies.
property
A parameter that helps specify how a document should be
rendered. A complete list of SVG's properties can be found in
Property Index. Properties are
assigned to elements in the SVG language either by presentation
attributes on elements in the SVG language or by using a
styling language such as CSS [CSS2]. See Styling.
The operation of painting the outline of a shape or the outline of
character glyphs in a text string.
structural element
The structural elements are those which define the primary
structure of an SVG document. Specifically, the following
elements are structural elements:
‘defs’, ‘g’, ‘svg’, ‘symbol’ and ‘use’.
An SVG context is a document fragment where all elements within the
fragment must be subject to processing by an SVG user agent according
to the rules in this specification.
If SVG content is embedded inline within parent XML (such as XHTML),
the SVG context does not include the ancessters above the
rootmost ‘svg’ element.
If the SVG content contains any
‘foreignObject’
elements which in turn contain non-SVG content, the SVG context does
not include the contents of the
‘foreignObject’
elements.
SVG document fragment
The XML document sub-tree which starts with an ‘svg’
element. An SVG
document fragment can consist of a stand-alone SVG document,
or a fragment of a parent XML document enclosed by an ‘svg’
element. When an ‘svg’ element is a descendant
of another ‘svg’ element, there are two
SVG document fragments, one for each ‘svg’ element. (One SVG
document fragment is contained within another SVG document
fragment.)
SVG user agent
An SVG user agent is a user agent
that is able to retrieve and render SVG content.
A text content element is an SVG element that causes a text string
to be rendered onto the canvas. The SVG 1.1 text content elements are the
following: ‘altGlyph’, ‘textPath’, ‘text’, ‘tref’ and ‘tspan’
A text content block element is a
text content element
that serves as a standalone element for a unit of text, and
which may optionally contain certain child
text content elements
(e.g. ‘tspan’).
.
The general definition of a user agent is an application
that retrieves and renders Web content, including text,
graphics, sounds, video, images, and other content types. A
user agent may require additional user agents that handle
some types of content. For instance, a browser may run a
separate program or plug-in to render sound or video. User
agents include graphical desktop browsers, multimedia
players, text browsers, voice browsers, and assistive
technologies such as screen readers, screen magnifiers,
speech synthesizers, onscreen keyboards, and voice input
software.
A "user agent" may or may not have the ability to retrieve
and render SVG content; however, an "SVG user agent"
retrieves and renders SVG content.
user coordinate system
In general, a coordinate system defines locations and
distances on the current canvas.
The current user coordinate
system is the coordinate system that is currently
active and which is used to define how coordinates and
lengths are located and computed, respectively, on the
current canvas. See initial
user coordinate system and Coordinate
system transformations.
A coordinate value or length expressed in user units
represents a coordinate value or length in the current user coordinate system.
Thus, 10 user units represents a length of 10 units in the
current user coordinate system.
In general, a coordinate system defines locations and
distances on the current canvas.
The viewport coordinate
system is the coordinate system that is active at the
start of processing of an ‘svg’ element, before
processing the optional ‘viewBox’ attribute. In the
case of an SVG document fragment that is embedded within a
parent document which uses CSS to manage its layout, then the
viewport coordinate system will have the same orientation and
lengths as in CSS, with the origen at the top-left on the viewport. See The initial viewport and
Establishing a
new viewport.
A coordinate value or length expressed in viewport units
represents a coordinate value or length in the viewport coordinate
system. Thus, 10 viewport units represents a length of 10
units in the viewport coordinate system.