@article {184851, title = {Simulating without negation.}, journal = {Journal of logic and computation}, volume = {7}, number = {4}, year = {1997}, pages = {501{\textendash}522}, abstract = {

Although negation-free languages are widely used in logic and computer science, relatively little is known about their expressive power. To address this issue we consider kinds of non-symmetric bisimulations called directed simulations, and use these to analyse the expressive power and model theory of negation-free modal and temporal languages. We first use them to obtain preservation, safety and definability results for a simple negation-free modal language. We then obtain analogous results for stronger negation-free languages. Finally, we extend our methods to deal with languages with non-Boolean negation. Keywords: Expressive power, modal logic, negation-free languages.

}, issn = {0955-792X}, author = {Kurtonina, Natasha and De Rijke, Maarten} }