Refactorings are transformations that change the structure of a program, while preserving the behavior. The topic has attracted a lot of attention recently, since it is a promising approach towards the problem of program erosion. Nevertheless a solid theoretical foundation is still lacking. In this paper we focus on improving the expressive power of graph rewriting rules, so that more refactori...

We extend the termination method using dynamic dependency pairs to higher order rewriting systems with beta as a rewrite step, also called Algebraic Functional Systems (AFSs). We introduce a variation of usable rules, and use monotone algebras to solve the constraints generated by dependency pairs. This approach differs in several respects from those dealing with higher order rewriting modulo b...

The work reported here is part of the PROGRES (PROgrammed Graph Rewriting Systems) project. PROGRES is a very high level multi paradigm language for the specification of complex structured data types and their operations. The data structures are modelled as directed, attributed, node and edge labelled graphs (diane graphs). The basic programming constructs of PROGRES are graph rewriting rules (...

Proton pumping P systems are a variant of membrane systems with both rewriting rules and symport/antiport rules, where a set of objects called protons is distinguished, every cooperative symport or antiport rule involves a proton, but no rewriting rule does. Time-freeness property means the result of all computations does not depend on the time it takes to execute the rules. The goal of this ar...

In the equivalent transformation (ET) computation model, a program is a set of procedural rewriting rules for answer-preserving transformation of problems with respect to given background knowledge. In this paper, we discuss an approach to program construction by creating and accumulating individually correct and efficient program components one by one, referred to as componentwise program cons...

We consider the scenario of ontology-based query answering. It is generally accepted that true scalability in this setting can only be achieved via query rewriting, which in turn allows for the exploitation of standard RDBMSs. In this work, we close two open fundamental questions related to query rewriting. We establish that linear existential rules are polynomially combined rewritable, while f...

Level-con uence is an important property of conditional term rewriting systems that allow extra variables in the rewrite rules because it guarantees the completeness of narrowing for such systems. In this paper we present a syntactic condition ensuring level-con uence for orthogonal, not necessarily terminating, conditional term rewriting systems that have extra variables in the right-hand side...

In this paper we present a new termination proof and complexity analysis of unfolding graph rewriting which is a specific kind of infinite graph rewriting expressing the general form of safe recursion. We introduce a termination order over sequences of terms together with an interpretation of term graphs into sequences of terms. Unfolding graph rewrite rules expressing general safe recursion ca...

In order to disprove confluence of term rewriting systems, we develop new criteria for ensuring non-joinability of terms based on interpretation and ordering. We present some instances of the criteria which are amenable for automation, and report on an implementation of a confluence disproving procedure based on these instances. The experiments reveal that our method is successfully applied to ...

CafePie is a visual programming system for CafeOBJ, an algebraic specification language based on term rewriting. Program editing and execution in CafePie are performed in one window. All program editing operations are handled in a uniform manner. An abstract visualization schema is necessary to understand the program at the programming language level. In this paper, we propose visualized term r...