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... Marina 249 Liu, Jiping 273 Makowsky, Johann A. 237 Manuel, Paul 334 Marinelli, Fabrizio 23 Miiller, Haiko 273, 309 Murat, Cecile 346 Mutzel, Petra 261 Nikolopoulos, Stavros D. 358 Okamoto, Yoshio 143 Pagourtzis, Aris 218 Palios,... more
... Marina 249 Liu, Jiping 273 Makowsky, Johann A. 237 Manuel, Paul 334 Marinelli, Fabrizio 23 Miiller, Haiko 273, 309 Murat, Cecile 346 Mutzel, Petra 261 Nikolopoulos, Stavros D. 358 Okamoto, Yoshio 143 Pagourtzis, Aris 218 Palios, Leonidas 358 Paschos, Vangelis Th. ...
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... then verify its correctness, which often includes a check that the string guessed and the computation based on the guess coincide. ... While studying equality sets, we focus on languages of the form Mergek(kCOPY), which are hardest... more
... then verify its correctness, which often includes a check that the string guessed and the computation based on the guess coincide. ... While studying equality sets, we focus on languages of the form Mergek(kCOPY), which are hardest equality sets, and are combinatorially difficult ...
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ABSTRACT Graph grammars are systems for the generation of directed, node and edge labeled graphs. They rewrite single nodes only and establish connections between the inserted graph and the neighbors of the replaced node on the basis of... more
ABSTRACT Graph grammars are systems for the generation of directed, node and edge labeled graphs. They rewrite single nodes only and establish connections between the inserted graph and the neighbors of the replaced node on the basis of node labels and edge labels. If there is only a single edge label, then graph grammars are closely related to NLC graph grammars. A partially ordered graph is a graph together with a spanning tree. These components are distinguished by their edge labels. A partially ordered graph grammar is the union of a graph grammar and a tree grammar. These components fit together such that their rewriting processes yield partially ordered graphs with the tree grammar generating spanning trees. Here we concentrate on the computational complexity of some restricted types of graph grammars and their languages with emphasis on intractability. It turns out that node and edge labeled tree grammars generate PSPACE-complete sets of connected graphs of finite degree, and that one-sided linear edge-unlabeled tree grammars generate NP-complete sets of graphs. However, the complexity is polynomial, if the graphs have finite degree and are generated by a one-sided linear partially ordered graph grammar. This situation closely parallels the case of NLC and regular BNLC grammars. NLC graph grammars can be seen as undirected, edge-unlabeled graph grammars, and, on the other hand, edge-unlabeled undirected one-sided linear partially ordered graph grammars and edge-unlabeled undirected one-sided linear partially ordered tree-graph grammars are special BNLC graph grammars.
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Derivation graphs of arbitrary grammars are transformed into trees. The transformations are based on the notion of ancestors, mapping subderivations into single nodes. Using the weight and the diameter of these nodes as parameters two new... more
Derivation graphs of arbitrary grammars are transformed into trees. The transformations are based on the notion of ancestors, mapping subderivations into single nodes. Using the weight and the diameter of these nodes as parameters two new complexity measures on grammars are introduced, which are compared with the time and the space complexity measures of nondeterministic turing machines.
What do a pushdown and a queue have in common? What is their intersection? Is it a counter? If we add the one-reversal restriction, is a one-reversal counter exactly the intersection of a one-reversal pushdown and a queue or,... more
What do a pushdown and a queue have in common? What is their intersection? Is it a counter? If we add the one-reversal restriction, is a one-reversal counter exactly the intersection of a one-reversal pushdown and a queue or, symmetrically, the intersection of a one-reset tape and a pushdown? These and similar assumptions can be heard here and there, and there are some conjectures by Autebert et al. [1], Book et al. [3] and Rodriguez We disprove all these conjectures and show that counters are strictly weaker than the intersection of pushdowns and queues. This goes through for the restriction to one reversal or one reset. In fact, we obtain new families of languages from intersections of some well-known families.
Layout graph grammars are extensions of context-free graph grammars and are introduced as a tool for syntax directed constructions of graph layouts. The constructions are based on a layout specification of the productions, which are... more
Layout graph grammars are extensions of context-free graph grammars and are introduced as a tool for syntax directed constructions of graph layouts. The constructions are based on a layout specification of the productions, which are consistently transferred to the derivations. The layout specification consists of rules for a placement of the vertices and a partial routing of the edges. It specifies minimal distances between the vertices in X- or Y-dimension. These distances can be optimized according to some formal cost measures.
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Page 1. Designing Graph Drawings by Layout Graph Grammars Franz J. Brandenburg ... Thus, labelled graphs provide a uniform graph theoretic framework, both for the graphs and their layouts. Definition 1. Let Z and A be finite sets of... more
Page 1. Designing Graph Drawings by Layout Graph Grammars Franz J. Brandenburg ... Thus, labelled graphs provide a uniform graph theoretic framework, both for the graphs and their layouts. Definition 1. Let Z and A be finite sets of vertex labels and of edge labels. ...
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ABSTRACT The complexity of node rewriting graph grammars is investigated, i.e. the membership problem for sets of graphs L(G) generated by directed, node and edge label controlled graph grammars G. We improve known results on the... more
ABSTRACT The complexity of node rewriting graph grammars is investigated, i.e. the membership problem for sets of graphs L(G) generated by directed, node and edge label controlled graph grammars G. We improve known results on the membership problem and comprise them into the following sharp characterization of the P vs. NP borderline, which is an "if and only if" result. G: (fCR connected bounded degree) then L(G) is in P. G: not (fCR connected bounded degree) and L(G) is NP hard. Here, fCR means that the graph grammar G has the finite Church Rosser property, and connected and bounded degree means that the graphs in the generated language L(G) are connected and of bounded degree.