Essential CAD vocabulary

The following table provides generic descriptions for equivalent AutoCAD and MicroStation terminology used by topics within this book. Note that some terms are in direct conflict with standard ArcGIS terms. For example, ArcGIS defines a layer as a cartographic representation of data, whereas AutoCAD defines it as a collection of entities or elements.

AutoCAD	MicroStation	Description
Attribute	Tag	A user-defined graphic or nongraphic textual data element that may be linked to, or embedded in another CAD object. Attributes and tag elements are often embedded in block or cell definitions to store field values.
Block reference	Cell	A user-defined collection of graphic elements and data treated as a single element or object, often used to symbolize point features.
Entity	Element	A generic term used to describe a fundamental component object, usually with graphic representation, such as a point, a line, or text.
Layer	Level	A collection of entities or elements of varied types and styles managed and visualized as a named stratum. It usually includes properties such as visibility and color and other visual characteristics.
	MSLink	A nongraphic named data field element that serves as a primary key for linking a MicroStation graphic element to an external database. There is no equivalent mechanism in AutoCAD supported by ArcGIS.
Point	Zero-length line	A nodal element used for locating a single coordinate location.
Properties	Element attributes	Data values that control specific visual characteristics of an entity or element such as visibility, color, and line style.
Style	Style	A named collection of properties used to classify and define specific geometric and textual elements such as a line style or text style.
Template file	Seed file	A drawing file used to store standard styles and common settings intended for reuse in other drawing files. This is used by the ArcGIS geoprocessing tool Export To CAD as an optional input parameter.
Xrecord		A nongraphic container object used for storing data in a DWG file. Xrecords are similar to Xdata but not limited by size or order. There is no equivalent mechanism in MicroStation.
XREF	Reference	An external drawing file attached to the current drawing file and often used for assembly or overlay purposes. It may also be a raster image in a supported file format.

Essential CAD vocabulary