Diagrams offer :
Locality and Labels: Diagrams group related information in the same area, so searches can be constrained to the scope of a goal. Correspondences can also be established from topological relationships.
Expressive Power and Specificity: Diagrams allow multiple layer abstraction. They have fewer interpretations than unconstrained textual notations.
Pragmatics: Diagrams provide a “vocabulary” for discussing the way that notations are interpreted. Every notation highlights some kind of information and obscures other aspects in which we are not interested in at that moment.
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