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Part: VI Appendix > Glossary

Appendix A. Glossary

The primary references for SVG are the specifications available from http://www.w3.org/Graphics/SVG. In the following glossary definitions, SVG Spec. refers to the SVG 1.0 Specification (http://www.w3.org/TR/SVG/) and XML Spec. refers to the Extensible Markup Language (XML) 1.0 (2nd Edition) Recommendation (http://www.w3.org/TR/REC-xml).

Absolute Positioning—

Placing an element by means of x and y attributes relative to the point (0,0) in the current coordinate system, which, due to transformations, may not be the top-left corner.

See also [Relative Positioning]


In the sense of the W3C's Web Accessibility Initiative (WAI), providing a high degree of usability for people with disabilities. See http://www.w3.org/WAI/.

Alignment Point—

A location within a glyph that is used to decide how to position the glyph in a given piece of text.

Alpha Channel—

The portion of a pixel's data reserved for transparency, used in SVG alongside RGB channels.


The free browser developed by the W3C to act as a testbed for Web technologies. Supports SVG.

Animated Value—

The value of an attribute achieved during an animation.

Animation Target—

The attribute that is the target of an SVG animation.


Application Programming Interface, a specification of how programming language elements should behave to allow code to work with different implementations of a system.


A line that follows the curve of a circle or ellipse, created in SVG using the A or a command as part of the value of a d attribute of a path element.

Aspect Ratio—

The proportion of width to height; for example, 800×600 monitors have an aspect ratio of 4:3.


Active Server Pages, a system developed by Microsoft for dynamically generating Web pages.


Adobe SVG Viewer, a plug-in for Netscape/Internet Explorer available for Macintosh and Microsoft Windows systems. On version 3 at the time of writing (ASV3). See http://www.adobe.com/svg/viewer/install/main.html.


A name-value pair associated with an element. See XML Spec. 3.3.

Aural Style Sheet—

A style sheet used to specify the characteristics of an audio rendition of a document, using a screen reader, for example.


The line along which text is drawn; it provides a series of reference points that determine where individual characters will be positioned.

Basic Shapes—

Certain simple shapes (rect, circle, ellipse, line, polyline, and polygon) that are predefined as SVG elements.


A sophisticated open-source SVG toolkit from the Apache Foundation, built on Java technologies. It includes an SVG viewer and is in very active development. Strongly recommended for any SVG developer.

Bezier Curves—

A way of drawing curved lines specified in terms of their start point, end point, and a number of control points. SVG supports quadratic (two control points) and cubic (three control points) Beziers. Bezier curves are used in the path element.

Bidirectionality (Bidi)

The ability of the characters in a piece of text to run from left to right or vice versa on the same line. This functionality is supported by SVG, based on an algorithm from the Unicode standard.


The way SVG DOM interfaces should be represented in a particular language. The specification includes bindings for ECMAScript and Java.


As opposed to vector graphics, the internal representation of an image using rows and columns of pixels. Also commonly known as raster graphics.

Block Progression Direction—

The direction in which blocks of text progress. See SVG Spec. 10.7.1.

Bounding Box—

The smallest rectangular area into which a given graphical element will fit.

Bump Map—

A means of giving the impression of texture or relief to an image or part of an image. Used in SVG within filter effects such as feDiffuseLighting. See SVG Spec. 15.


The infinite two-dimensional space into which SVG is potentially rendered. Rendering takes place only within a finite rectangular region of this space, which is called the viewport.

Cartesian Plane—

A representation of a two-dimensional area, on which any point can be described using x and y (rectangular) coordinates.

CDATA Sections—

The blocks used in XML to contain characters that should not be parsed by an XML parser. See XML Spec. 2.7.

Character Entity Reference—

A way of referring to a character that cannot be expressed in a given encoding; for example, &lt; represents the symbol <.


Restricting the region in which painting can take place. See SVG Spec. 14.


Blending objects according to their color and opacity at each individual pixel.

Container Element—

An element that can have graphics elements and other elements as child elements, such as svg, g, and defs.


A mathematical technique that can be used to add effects to a digital image, supported in the SVG filter primitive feConvolveMatrix. See SVG Spec. 15.13


Cascading Style Sheets, a means of specifying properties such as color or fonts for HTML/XML document elements. SVG uses many of the same property definitions as CSS2, and styling can be applied using external or inline style sheets. See SVG Spec. 6.9 and CSS2 Syntax and Data: http://www.w3.org/TR/REC-CSS2/syndata.html.

Current Transformation Matrix (CTM)

The mapping between the user coordinate system and the viewport coordinate system, specified as a 3×3 matrix.


The pointer found in interactive display environments. SVG provides support for changing the cursor according to the document context. See SVG Spec. 16.8.

DOCTYPE Declaration—

Within an XML document, the declaration that specifies the element type of the document element and may reference any DTD for the document, which allows validation of the document. See XML Spec. 2.8.

Document Fragment—

Any number of SVG elements nested within an svg element.


Document Object Model, a tree-structured model behind interfaces for HTML, XML, and SVG that allows programs to dynamically access and modify the document content. SVG has a DOM based on DOM Level 2, with numerous additional interfaces. See http://www.w3.org/DOM/ and SVG Spec. Appendix 2.


Document Type Definition, a grammar of legal structure for an XML application language. The SVG DTD can be found in the SVG Spec. Appendix A. See also XML Spec. 2.8.

Dublin Core—

A widely used metadata standard suitable for use in SVG. An RDF vocabulary is available. See http://dublincore.org/.


An open, internationally accepted scripting language specification. A popular implementation of ECMAScript is JavaScript.


A component of XML that may contain attributes and other elements. SVG elements represent graphical components and containers for such elements, with attributes defining their properties.


Communication between entities can be achieved using events and listeners. When a user carries out an action—for instance, clicking a button—this will create a message within the system that will be received by any parts of the system that have declared themselves as listeners. The message is described as an event. SVG supports a set of events that includes much of DOM2 events; these events can be used, for example, to make a script respond to clicking on an element. See SVG Spec. 16.

Feature Strings—

A means by which an implementation can be queried using the hasFeature method to determine whether a specific part of the specification has been implemented. See SVG Spec. B.4.


The operation of painting the interior of a shape or character glyph.

Filter Effect—

An operation or series of operations that dynamically change the appearance of an image or elements of an image. SVG includes a number of fundamental effects (the filter primitives) and provides the facility to combine them, allowing complex effects equivalent to those found in sophisticated commercial graphics applications. See SVG Spec. 15.

Filter Primitive—

A filter effect that defines a single operation, such as feGaussianBlur or feBlend. See SVG Spec. 15.

FIPS Code—

(U.S.) Federal Information Processing Standards code used to identify geographic entities such as states and counties.


A collection of glyphs used to represent characters in a particular script or style.


Formatting Objects Processor, a print formatter from Apache that uses XSL.

Fragment Identifier—

The # symbol followed by an identifier that URIs can use to refer to a location within a document. See SVG Spec. 17.2.2.

Gaussian Blur—

A filter that follows the normal (bell-shaped) distribution curve found in nature and statistics.


The representation of a character or part of a character in a font. In SVG, glyphs can be defined as a series of drawing instructions together with (Unicode) identifiers. See SVG Spec. 10.2.


A smooth transition from one color to another. SVG supports linear and radial gradients. See SVG Spec. 13.2.


In SVG, a set of graphics elements contained within a g element. Grouping allows the treatment of such a set of elements as a single unit.


Hypertext Markup Language, the primary language of the Web. See http://www.w3.org.


Hypertext Transfer Protocol, the primary protocol of the Web. See http://www.w3.org.


i[18 letters]n.

See also [Internationalization]


Interface Definition Language, a programming-language-independent means of specifying interfaces of software objects. Used to specify the SVG DOM interfaces. See http://www.omg.org/gettingstarted/omg_idl.htm.


The Internet Engineering Task Force, an open organization concerned with Internet architecture that maintains an RFC (Request for Comments) document repository.


In SVG, the application of an element's painting and style properties to that element's children that will apply, unless explicitly overridden.

Initial User Coordinate System—

The user coordinate system that applies when an SVG document loads. At this point, the user coordinate system is identical to the viewport coordinate system, with the root origin (0,0) in the top-left corner.

Inline Progression Direction—

The direction in which text flows along a line. In English, the inline progression direction is left to right.

Internationalization (i18n)—

The process of making software and standards work across differing writing systems, languages, and cultures. SVG has extensive support for i18n. See SVG Spec. Appendix I.


International Organization for Standardization, maintainers of various standards, several of which are important in SVG. See http://www.iso.ch.


An implementation of the ECMAScript language.


Java API for XML Processing, a series of specifications from Sun Microsystems that incorporate SAX, DOM, and XSLT. Implementations of these specifications can be found in packages such as Xerces and Xalan. See http://java.sun.com/xml/jaxp/index.html.


Joint Photographic Experts Group, the group that created an image format standard known by this acronym. A lossy, compressed bitmap format appropriate for use with images derived from photographs. Conforming SVG viewers must support JPEG images when using the image element.


Java Server Pages, a technology from Sun Microsystems that allows Java code to run server-side from Web pages.


Adjusting the spacing between certain pairs of letters to improve appearance. See SVG Spec. 10.11.


A graphic found on a path or line, such as an arrowhead. See SVG Spec. 11.6.


Painting an object through a screen that can completely or partially mask parts of the object. In effect, painting blends objects into the background. See SVG Spec. 14.


Machine-readable data about data. Supported in SVG through the metadata element. See SVG Spec. 21 and http://www.w3.org/RDF.

MIME Type—

Multipurpose Internet Mail Extensions, used by a Web server to identify the type of content it is delivering. The MIME type for SVG is image/svg+xml.


An open-source browser on which Netscape browsers from version 6.0 onward are built. An SVG-capable version is under development; see http://www.mozilla.org.


Microsoft XML Parser and related software.


A way of removing ambiguity from XML names. In XML, namespaces are specified as URI references and apply to elements and attributes. The namespace of SVG is http://www.w3.org/2000/svg. See http://www.w3.org/TR/REC-xml-names/.


A collection of nodes (without duplicates) taken from a DOM tree. Produced by various operations in DOM and XSLT.


Non-Uniform Rational B-Spline, a mathematical representation of a shape commonly used in computer graphics.

See also [Spline]

Oblate Spheroid—

A squashed-ball shape that is used as a mathematical approximation to the shape of the earth for mapping purposes, that is, a globe where the equatorial radius is greater than the polar radius.


—The opposite of transparency. SVG allows full control over the opacity of graphical elements and groups. See SVG Spec. 14.5.


A way of putting color onto the canvas. SVG has three types of paint built in: color, gradients, and patterns.

Painter's Model—

The approach to rendering used by SVG which mimics an artist applying paint to a canvas, where each successive application partially or fully obscures whatever was on the canvas already. Elements in an SVG document are painted generally in the order in which they appear in the document.


The operation of moving the visible area of the SVG canvas horizontally, vertically, or diagonally. Implemented by most SVG viewers.


A way to describe lines and curves and draw the outlines of shapes, which can subsequently be filled in as required. A path in SVG is analogous to drawing with a pen on paper. See SVG Spec. 8.


In SVG, a set of graphical elements used to fill in areas by tiling.


Portable Document Format, an open standard developed by Adobe, typically used for print-like documents.


See [Processing Instruction]

Portable Network Graphics, a sophisticated bitmapped graphics format approved as a standard by the W3C. Similar to the GIF format but without patent restrictions.


A user interface device such as a mouse or trackball.


A set of connected straight line segments. See SVG Spec. 9.6.


A short sequence of characters used indirectly to identify the namespace of a particular XML element or attribute, for example, svg:rect. Also known as a namespace prefix. See http://www.w3.org/TR/REC-xml-names.

Processing Instruction—

An instruction declared in XML documents to specify the handling of the data by applications. See XML Spec. 2.6.


A parameter that determines how an element or group of elements should be rendered. As well as SVG-specific properties, SVG also supports properties from other styling languages such as CSS. In general, properties are assigned using XML attributes. See SVG Spec. Appendix N.


Qualified name, the name of an XML element or attribute expressed as [namespace prefix]:[local name], for example, svg:rect. See http://www.w3.org/TR/REC-xml-names.

Range Clamping—

Attaching out-of-range values to the nearest permitted value (such as 0 or 1 for opacity) because numeric values such as those determining colors or opacity have a restricted range of legal values. See SVG Spec. F.4.


Resource Description Framework, a metadata framework that allows anything that can be identified (a resource) to be described. A key element in the W3C's Semantic Web initiative. See http://www.w3.org/RDF.

Reference Orientation—

This is the first consideration when determining the direction of flow of text. For standard horizontal or vertical text in the initial coordinate system, the reference orientation is up. See SVG Spec. 10.7.

Relative Positioning—

Defining a coordinate pair relative to a point other than the origin, (0,0), of the current coordinate system. Relative positioning may be used, for example, within the value of the d attribute of a path element.

See also [Absolute Positioning]

Rendering Model—

The ideal behavior of an SVG implementation, based on the “Painter's Model,” with particular behavior defined for elements and groups. See SVG Spec. 3.


A way of describing a color (hue) in terms of the proportions of red, green, and blue.


Simple API for XML, a set of standard interfaces, implementations of which allow the parsing of XML data.


In SVG, using interpreted languages such as ECMAScript and Python to control rendering behavior or interactivity. See SVG Spec. 18.

Semantic Web—

A vision of the next generation of the Web, in which information is presented in such a way that machine interpretation is possible. See http://www.w3.org/2001/sw/.


A Java class designed to respond to HTTP requests. See http://www.java.sun.com.


Standard Generalized Markup Language, the standard from which HTML and XML was derived.


Synchronized Multimedia Integration Language, a “rich media” format from the W3C. SVG animation elements are based on SMIL version 2 elements. See http://www.w3.org/AudioVideo/.

Specular Lighting—

An effect that mimics the reflective properties of a mirror. SVG has the filter primitive feSpecularLighting for this effect. See SVG Spec. 15.22.


A way of defining a curve by means of control points. SVG supports cubic and quadratic Bezier splines. See SVG Spec. 8.3.5.


The operation of painting the outline of a shape or glyph.


A way of defining how documents and their constituent elements should be rendered. The primary stylesheet languages are CSS and XSL(T), from which many of the properties within SVG are derived. The styling of an SVG document can be determined using these languages. See SVG Spec. 6.


Scalable Vector Graphics, an XML grammar for stylable graphics built from simple geometric objects such as lines and curves. See SVG Unleashed.


The usual extension of SVG files compressed using the gzip compression algorithm. See http://www.ietf.org/rfc/rfc1952.txt.


A set of classes in the Java language for building user interfaces.


Tool Command Language, a scripting language mainly used for user-interface interactions. See http://www.neosoft.com/tcl/.


(U.S.) Topologically Integrated Geographic Encoding and Referencing system used by the Census Bureau, which includes a topographical database. See http://www.census.gov/geo/www/tiger/index.html.


A way of modifying the rendering of a graphical element or group of elements. Transformations can either be specified using simple operations (scale, rotate, or translate) or by providing a matrix describing the required transformation. Transformations are applied on top of the Current Transformation Matrix (CTM), yielding a new CTM.

Transformation Matrix—

The mathematical mapping from one coordinate system into another using a 3×3 matrix using the equation [x' y' 1] = [x y 1] * matrix.


(Perlin Turbulence) “Smooth” randomness that can be used to generate natural-looking effects. Supported in SVG through the feTurbulence filter primitive.


A standard, “universal” character-encoding scheme supported by SVG. See http://www.unicode.org/.


Uniform Resource Identifier, used in SVG to form references to files or elements within files.

User Agent—

A generic term for applications that can retrieve, render, or process Web content. In the context of SVG, the term is usually used to refer to SVG-capable Web browsers or dedicated SVG viewers.

User Coordinate System/User Space—

The coordinate system that is currently active, which is either the initial user coordinate system or that system with transformations applied.


A mathematical term for something with magnitude and direction. A vector can be represented geometrically as a movement from one point to another, and this representation forms the basis of vector graphics.


The rectangular region into which content is rendered. See SVG Spec. 7.


Vector Markup Language, a predecessor of SVG developed by Microsoft.


World Wide Web Consortium. See http://www.w3.org.


Web Accessibility Initiative.

XML Linking Language (XLink)

An XML-based linking language used in SVG.

XML Pointer Language (XPointer)

XPointer is a way of identifying a particular part of a document. It goes beyond XPath, in which a node can be addressed allowing any specific characters to be identified. See http://www.w3.org/XML/Linking, and for an example of its use, http://www.w3.org/2001/Annotea/.


Extensible Stylesheet Language, an XML-based language for expressing style sheets. See http://www.w3.org/Style/XSL/.


XSL Transformations, a rule-based language that forms part of XSL that may be used to transform XML data into other representations (including other XML representations).


In either upper- or lowercase—the closepath command.



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