Logical Description of Context-free Graph Languages

Logical Description of Contex-Free Graph Languages

A graph language L is in the class C-edNCE of context-free edNCE graph languages if and only if L = f(T) where f is a function on graphs that can be deened in monadic second-order logic and T is the set of all trees over some ranked alphabet. This logical characterization implies a large number of closure and decidability properties of the context-free edNCE graph languages. Rather than context...

Regular Description of Context-Free Graph Languages

A set of (labeled) graphs can be de ned by a regular tree language and one regular string language for each possible edge label, as follows. For each tree t from the regular tree language the graph gr(t) has the same nodes as t (with the same labels), and there is an edge with label from node x to node y if the string of labels of the nodes on the shortest path from x to y in t belongs to the r...

The Bounded Tree-Width Problem of Context-Free Graph Languages

We show that the following (equivalent) problems are P-complete: 1. Does a given connuent NCE graph grammar only generate graphs of bounded tree-width? and 2. is the graph language generated by a given connuent NCE graph grammar an HR language? This settles the complexity of these important problems on graph grammars .

Tree Languages Generated be Context-Free Graph Grammars

A characterization is given of the class of tree languages which can be generated by context-free hyperedge replacement (HR) graph grammars, in terms of macro tree transducers (MTTs). A similar characterization is given of the MSO deenable tree transductions.

Context - Free Languages and