Terminology

Let’s start with some terminology:

  • DRAWING FUNCTION – Intended use of the drawing e.g. Roof Plan.
  • DATABASE – The source of the information is a DATABASE (file).
  • OBJECTS – Drawings consist of graphical OBJECTS represented on a computer screen or printed on paper.
  • OBJECT TYPE – 1. PRODUCT-TYPE e.g. Brick Wall 2. GRAPHICAL-TYPE e.g. Line, Arc, Circle.
  • RECORD – Each object has a RECORD in the DATABASE.
  • PROPERTY – Each RECORD has a list of the PROPERTIES.
  • PROPERTY LIST – The number and names of the properties vary according to the type of object.
  • PROPERTY TYPE – May be a singular ID (e.g. its layer-name), a switch (e.g. ON/OFF) or a selection LIST (e.g. Color Red, Yellow, Green).
  • PROPERTY NAMES – Are consistent and specific to objects of the same product-type. e.g. Color
  • PROPERTY VALUE – Are consistent and specific to objects of the same product-type. e.g. Color
  • PROPERTY ID & NAME- Each property has a NAME and a VALUE.
  • PROPERTY VALUE – Assigned to an object in one of three ways: 1. by the the system as the object is drawn, 2. by individual change, 3. from a PROPERTY LIST.
  • LAYERNAME – Name of a PROPERTY LIST.
  • LAYER – A group of objects with same LAYERNAME,
  • LAYER-STATE – A group of Layers and their display conditions might be used to display a particular DRAWING FUNCTION e.g. Roof Plan.

Key aspects of a drawing database:

  1. Drawing OBJECTS
  2. Object PROPERTIES
  3. Symbol Tables
  4. LAYERS
  5. BLOCK Definitions and References
  6. Layout and Paper Space Information
  7. Named Object Dictionaries
  8. Dimension and Annotation Systems
  9. Display and Visibility Controls
  10. External References (Xrefs)
  11. System Variables and Drawing Settings
  12. Relationships Between Database Elements

OBJECT types:

  • Lines
  • Polylines
  • Arcs
  • Circles
  • Splines
  • Ellipses
  • Hatches
  • Text and MText
  • Dimensions
  • Leaders
  • Tables
  • Blocks (inserted references)
  • 3D solids
  • Surfaces
  • Meshes
  • Point objects

Entries in an object record:

  • A unique object ID (handle)
  • A type definition
  • Geometric data
  • Object properties
  • Relationships to other database objects

A record of a line consists of:

  • Drawing space (paper or model)
  • Layer name
  • Start point coordinates
  • End point coordinates
  • Colour
  • Linetype
  • Line-type scale
  • Lineweight
  • Transparency
  • Plot style information?

(include an example of a record.)

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