Spider diagram

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A spider diagram adds existential points to an Euler or a Venn diagram. The points indicate the existence of an attribute described by the intersection of contours in the Euler diagram. These points may be joined together forming a shape like a spider. These represent an OR condition, also known as a logical disjunction.

Euler diagram In the image shown, the following conjunctions are apparent from the Euler diagram.

A \land B
B \land C
F \land E
G \land F

In the universe of discourse defined by this Euler diagram, in addition to the conjunctions specified above, all possible sets from A through B and D through G are available separately. The set C is only available as a subset of B. Often, in complicated diagrams, singleton sets and/or conjunctions may be obscured by other set combinations.

The two spiders in the example correspond to the following logical expressions:

Red spider: (F \land E) \lor (G) \lor (D)

Blue spider: (A) \lor (C \land B) \lor (F)


Further reading

  • Stapleton, G. and Howse, J. and Taylor, J. and Thompson, S. What can spider diagrams say Proc. Diagrams, (2004) v. 168, pgs 169-219 Accessed on May 17, 2007 here

External links