In the first section we make some remarks(witout going into any details) about the main application fields of graph grammars to motivate their investigation. In section 2 and 3 we give a short and informal overview on most of the approaches for sequential and parallel graph grammars known in literature. In the last part we introduce some of the modifications and extensions enforced by several applications and give some comments on implementation of graph grammars realized so far.
i, APPLICATIONS OF GRAPH GRAMMARSPicture and graph grammars have been introduced first for picture processing problems e.g. for the recognition of chromosomes, handprinted letters, bubble and fog chamber pictures of elementary particle physics (see part PA of the bibliography for references corresponding to "grammatical" or "linguistic" pattern recognition).In these fields there is no alternative to automatic picture processing. For bubble and fog chamber pictures we have no finite number of picture classes such that any picture can be related to one of these classes. Any point of a picture can be the origin of a subpicture if a disintegration takes place there. On the other hand it is possible to state recursive rules saying how subpictures are generated and how they are connected. Thus, for any class of such pictures one can give a finite set of rules, i.e. a picture grammar. A part of the picture processing problem is reduced to the problem of syntax analysis of the description of the picture bymeans of a picture grammar. The advantage of this method is that in the case of success of the syntax analysis one has not only a yes-no-decision but a description of the structure of the considered picture. A picture can be described by listing its subpictures and the geometric relations between them as "is right of", "is below of", "lies within", "is connected with" etc.If we introduce for any occurrence of a subpicture a node which is labelled with the subpicture itself and if two nodes are connected by an edge, the label of which expresses a geometric relation iff the corresponding subpictures satisfy this relation,