Topics in this document:

• Introduction
• DesignXML Document Structure
• Fundamental Types of Geometry and Graphics
• Linear Geometry Elements
• Nonlinear Geometry Elements
• DesignXML Reference

This document is intended for design professionals who are interested in reading and writing geometric model information specified in XML according to the rules of the DesignXML schema. For example, software application developers can use this information to determine the design and implementation of their applications that read and write models in DesignXML-conformant XML.

Sections in this topic:

• About DesignXML
• Terminology

About DesignXML

• Defines a vocabulary for representing high-precision geometric models
• Leverages existing schemas, such as SVG, and standard raster image formats such as JPEG, GIF, and BMP
• Provides a low barrier to entry without sacrificing the potential for richness of expression
• Holds its own set of design elements, as well as data from other schemas
• Defines constructs in a modular manner to promote reuse of utility definitions between different schema
• Represents complete model state, partial model state, and abstract views of the model
• Facilitates processing by standard XML tools, such as XSL and XSLT

Terminology

Data Channel

A view of a particular geometric model. Each channel is one way of looking at the data; each channel represents a different level of complexity and detail with respect to the actual model information in the design. For example, the Administrative data channel describes only the document summary information, such as title, author, and keywords; the Facetted3D data channel provides a way to describe the model using linear geometry only.

SVG

SVG (Scalable Vector Graphics) is a language for describing two-dimensional graphics in XML. See the W3C (World Wide Web Consotium, http://www.w3c.org) SVG specification for details.

URI, URL, URN

A Uniform Resource Identifier (URI) is either a locator, a name, or both. Uniform Resource Locator (URL) refers to the subset of URI that identifies resources via a representation of their primary access mechanism (for example, their network "location"). Uniform Resource Name (URN) refers to the subset of URI that serves as persistent, location-independent, resource identifiers.

A DesignXML document consists of an object element containing zero or more data channel elements.

Sections in this topic:

• DesignXML Document
• Objects and Channels
• Administrative, Raster2D, and Vector2D Channels
• Facetted3D Channel
• Geometry3D Channel
• Model Channel
• Geometry and Graphics Elements

DesignXML Document

<?xml version="1.0" encoding="UTF-8"?>
		<dxml:Object	
                        xmlns="urn:schemas-microsoft-com:xml-data"
                        xmlns:dt="urn:schemas-microsoft-com:datatypes"
                        xmlns:dxml="x-schema:http://www.DesignXML.org/schema/DesignXML_V_100.xdr">
		</dxml:Object>
    

• Objects, which represent a geometric model, composed of redundant data channels
• Double-precision 3D/2D geometry and graphics elements

Objects and Channels

A DesignXML object is logically equivalent to a geometric model or drawing. The object's channels appear as sections of a DesignXML file, or as a set of files (a DesignXML file or set of files is called a DesignXML "stream"). A DesignXML stream need not have all of the available channels present. More channels mean more information for the stream's client to use.

While each channel is optional, when they appear at all in a DesignXML file, they must appear in the top-to-bottom sequence shown in the illustration of the DesignXML channels. Simpler, lower-resolution, but more universally readable channels come first, and subsequent channels add successively greater fidelity to the original model, ending with an application Model channel, or possibly multiple Model channels that define the model data exactly.

A summary of the DesignXML data channels follows.

DesignXML specifies the file formats to be used for the 2D channels and completely defines the formats used in the 2D/3D channels.

Administrative, Raster2D, and Vector2D Channels

The definitions for the Administrative, Raster2D, and Vector2D channels are simple and self-descriptive. The Administrative channel defines summary information. The Raster2D and Vector2D channels are simply containers for a systemId attribute that holds the URI or file path to a raster format file and SVG file, respectively.

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Facetted3D Channel

The Facetted3D channel supports a model representation using only a reduced set of 2D geometric constructs. For example, a 3D wireframe representation of the model can be delivered in the Facetted3D channel.

The FacettedSubmodel element provides a means for grouping instances of the other geometry elements in the Facetted3D channel and referencing them as needed, while applying an independent linear transform to each element.

Geometry3D Channel

The Geometry3D channel is essentially the Facetted3D channel plus additional, nonlinear geometric elements.

Model Channel

The Model channel is where geometric modeling software applications define the schemas for their particular model representations. For example, a DesignXML Object can contain or point to model channels created by AutoCAD software or Intergraph Microstation software. The <Model> element's app attribute distinguishes one application's model channel from another's. For example,

specifies a Model channel using the Autodesk AcDbXML schema.

Geometry and Graphics Elements

In addition to the channel structures, DesignXML provides definitions for reusable graphical objects and their properties, primarily for use in Model channel schemas. The DesignXML graphical elements and their properties are the following:

• Linear geometry, quadratic curves, and solid elements.
• Text geometry with associated fonts and properties
• Raster image data, bound to geometric faces and surfaces
• Double-precision for all relevant values
• Quantities with built-in units relevant to geometric model elements, namely length and angle
• 3D View and rendering specifications, such as view direction, clip boundaries, Model Z axis display angle, perspective viewing angle, and rendering mode.

These elements can have color—either presentational (LUT indices) or material (32-bit color space).

The DesignXML elements and attributes that model such fundamental properties as angle, distance, transformation, view, rendering, and color are described in the following.

Sections in this topic:

• Basic Measure Elements
• Linear Transforms
• View and Rendering Model
• Color
• The Link Element

Basic Measure Elements

Fundamental to any geometric modeling system is the specification of distance and angle. What differentiates distances and angles from scalar values is that distance and angle have dimension or units. Length is usually defined using points and vectors, which represent locations, directions, and directed distances. Modeling systems have widely differing representations for, and assumptions concerning, units.

DesignXML specifies units as follows:

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These unit types represent the quantities covered in the International Metric System (SI), plus other quantities of interest. All values are represented as single, real numbers. All real numbers in the geometric model are stored and manipulated as double precision floating point values, as specified in the Microsoft XML Schema dt:r8 extended data type.

The DesignXML attributes used to denote the X, Y, and Z Cartesian coordinates are x, y, and z but note that x is also used for scalar length values:

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The t (theta) attribute is used for angle values:

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The basic DesignXML measure elements are the following:

• #ELEMENT_jc

Linear Transforms

Every channel is assumed to be in a single coordinate system. SubmodelReference elements apply a 2D or 3D linear transform to their respective submodel elements. The constructs described in this section are used to produce linear transformations.

Linear transform elements are as follows:

• #ELEMENT_jc

View and Rendering Model

The 2D channels as well as some model channel elements can benefit from specifying a 2D projection onto a 3D model.

View and rendering elements are as follows:

• #ELEMENT_jc

Color

There are two principal ways you can specify color: as an index into a lookup table, or palette, or as a true color, specified as a 3D point in a specified color space. The dxml:Color element allows either color mode to be used, the former in conjunction with a dxml:ColorPalette. Only one ColorPalette per object data channel is allowed.

In general, Color can be specified, or omitted, at any level of composition of a model. For dxml channels, the color specified at the level closest to an element (or, lowest level above its element in a DOM tree) dictates its color

Color elements are as follows:

• #ELEMENT_jc

The Link Element

The following linear geometry elements can be used in both the Facetted3D and Geometry3D channels. These are the only elements that can be used in the Facetted3D channel.

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Linear geometry elements are the following:

• #ELEMENT_jc

The nonlinear geometry elements can be used in the Geometry3D channel only. The advantage of this set of geometric constructs is that they require far less data to specify a nonlinear surface to a specific tolerance than corresponding Facetted3D elements would. The disadvantage is that the software supporting nonlinear geometry is more complex and difficult to write or procure. Multiple DesignXML channels give developers a choice for accomplishing what they want, or need, to do.

Nonlinear geometry elements are a follows:

• #ELEMENT_jc

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The following sections contain descriptions of the elements and attributes defined in the DesignXML schema.

Sections in this topic:

• DesignXML Schema Elements
• DesignXML Schema Attributes
• DesignXML Schema Element-specific Attributes
• Source
• Schema Attributes Reference
• Datatypes Reference

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