In mathematics, a unitary 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. Joined points represent an "or" condition, also known as a logical disjunction. A spider diagram is a boolean expression involving unitary spider diagrams and the logical symbols ∧ , ∨ , ¬ displaystyle land ,lor ,lnot . For example, it may consist of the conjunction of two spider diagrams, the disjunction of two spider diagrams, or the negation of a spider diagram. Example[edit]
In the image shown, the following conjunctions A ∧ B displaystyle Aland B B ∧ C displaystyle Bland C F ∧ E displaystyle Fland E G ∧ F displaystyle Gland 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 ∧ E ) ∨ ( G ) ∨ ( D ) displaystyle (Fland E)lor (G)lor (D) Blue spider: ( A ) ∨ ( C ∧ B ) ∨ ( F ) displaystyle (A)lor (Cland B)lor (F) References[edit] Howse, J. and Stapleton, G. and Taylor, H.
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