<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kurtonina, Natasha</style></author><author><style face="normal" font="default" size="100%">De Rijke, Maarten</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Simulating without negation.</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of logic and computation</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><number><style face="normal" font="default" size="100%">4</style></number><volume><style face="normal" font="default" size="100%">7</style></volume><pages><style face="normal" font="default" size="100%">501–522</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;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.&lt;/p&gt;</style></abstract></record></records></xml>