A higraph is a diagramming object that formalizes relations into a visual structure. It was developed by

David Harel David Harel ( he, דוד הראל; born 12 April 1950) is a computer scientist, currently serving as President of the Israel Academy of Sciences and Humanities. He has been on the faculty of the Weizmann Institute of Science in Israel since 1980, ...

in 1988. Higraphs extend mathematical graphs by including notions of depth and

orthogonality In mathematics, orthogonality is the generalization of the geometric notion of ''perpendicularity''. By extension, orthogonality is also used to refer to the separation of specific features of a system. The term also has specialized meanings in ...

. In particular,

nodes In general, a node is a localized swelling (a "knot") or a point of intersection (a Vertex (graph theory), vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two ...

in a higraph can contain other nodes inside them, creating a hierarchy. The idea was initially developed for applications to

databases In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spa ...

knowledge representation Knowledge representation and reasoning (KRR, KR&R, KR²) is the field of artificial intelligence (AI) dedicated to representing information about the world in a form that a computer system can use to solve complex tasks such as diagnosing a medic ...

, and the behavioral specification of complex

concurrent systems In computer science, concurrency is the ability of different parts or units of a program, algorithm, or problem to be executed out-of-order or in partial order, without affecting the outcome. This allows for parallel execution of the concurr ...

using the higraph-based language of statecharts. Higraphs are widely used in industrial applications like

UML The Unified Modeling Language (UML) is a general-purpose, developmental modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system. The creation of UML was originally m ...

. Recently they have been used by

philosophers A philosopher is a person who practices or investigates philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit=philosophos, meaning 'lover of wisdom'. The coining of the term has been attributed to the Greek th ...

to formally study the use of

diagrams A diagram is a symbolic representation of information using visualization techniques. Diagrams have been used since prehistoric times on walls of caves, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three- ...

mathematical proof A mathematical proof is an inferential argument for a mathematical statement, showing that the stated assumptions logically guarantee the conclusion. The argument may use other previously established statements, such as theorems; but every proo ...

s and reasoning.

References

*{{citation, first=D., last=Harel , title=On Visual Formalisms , publisher=Communications of the ACM, Volume 31, Number 5 , year=1988 * Grossman, O., Harel, D. (1997), ''On the Algorithmics of Higraphs'', Technical Report, Rehovot, Israel * http://plato.stanford.edu/entries/diagrams/ Mathematical structures