Shapes and complex shapes define elements that are closed. A shape is a single element. A complex shape is a single element comprised of multiple segments.
Although a single line, arc, and point is rather easily identified, certain other elements are more difficult to assess. MicroStation uses line strings, complex chains, shapes, and complex shapes to define elements that appear to made up of multiple primitives, but are actually a single element or act like a single element. For example, a rectangular shape can be created in several different ways.
One method is to draw four lines bounding the rectangular shape using the PLACE LINE tool. In this case, the rectangle is comprised of four line elements. Another approach is to draw the rectangle as a shape using the PLACE BLOCK tool. With a shape, the four sides of the rectangle are comprised of a single element rather than the four elements that result from using lines.
Another approach is to draw four lines to form a rectangle and then combine those lines into a complex shape. A complex shape, much like a shape, treats the four lines as if they are a single element.
Although they are treated as a single element, MicroStation refers to each component as a “segment.” A rectangular complex shape would be a single element comprised of four line segments.