In finite element analysis, there are several 3D element types commonly used:

ElementType.GIF (5007 bytes)

In order to use the compact data structure

CompactStorage.GIF (5888 bytes)

the topology information for each element is extracted out to be represented in the Element Description Table which can be extanded easily to new element types.
Sample EDT for 8-node block element

Element Name

8-nodes block element

Num of Nodes

8

Element Edge Table Number of Element Edge: 12 Edge1 £ºNode1 -- Node2 Edge2 £ºNode2 -- Node3
Edge3 £ºNode3 -- Node4 Edge4 £ºNode4 -- Node1
Edge5 £ºNode5 -- Node6 Edge6 £ºNode6 -- Node7
Edge7 £ºNode7 -- Node8 Edge8 £ºNode8 -- Node5
Edge9 £ºNode1 -- Node5 Edge10£ºNode2 -- Node6
Edge11£ºNode3 -- Node7 Edge12£ºNode4 -- Node8
Element Face Table Number of Faces: 6

Number of Nodes of Each Face: 4

Face1 £ºEdge1 -- Edge2 -- Edge3 -- Edge4
Face2 £ºEdge8 -- Edge7 -- Edge6 -- Edge5
Face3 £ºEdge9-- Edge5 -- Edge10-- Edge1
Face4 £ºEdge10-- Edge6 -- Edge11 -- Edge2
Face5 £ºEdge11 -- Edge7 -- Edge12 -- Edge3
Face6 £ºEdge4 -- Edge12 -- Edge8 -- Edge9