Leftist Grammars and the Chomsky Hierarchy


     Related Videos

     Related Hubpages

    •  Doc. Url:    Embed Code: 

    • citeseer  status
      (0) (0 Votes)
      Views: (1122)   Date: (22-01-08)   Pages: ()
    • Author:  by Tomasz Jurdzinski  

    • Abstract:  Abstract. Leftist grammars can be characterized in terms of rules of the form a ? ba and cd ? d, without distinction between terminals and nonterminals. They were introduced by Motwani et. al. [9], where the accessibility problem for some general protection system was related to these grammars. This protection system was originally proposed in [3, 10] in the context of Java virtual worlds. Here, the accessibility problem is formulated in the form ?Can object p gain (illegal) access to object q by a series of legal moves (as prescribed by the policy)??. It was shown [9] that the membership problem for leftist grammar is decidable what implied the decidability of the accessibility problem for the appropriate protection system. We study relationships between language classes defined by various types of leftist grammars and classes of the Chomsky hierarchy. We show that general leftist grammars can recognize languages which are not context free, answering in negative the question from [9]. Moreover, we study some restricted variants of leftist grammars and relate them to regular, deterministic context free and context free languages. Topics: formal languages; accessibility problem in protection systems. 1

         Related Documents

           Related Groups

             Related Science News

               More on Sciencestage

                 Answers

                 News
            • Peru: Leftist rebel leader found badly wounded
              Peruvian troops captured on Sunday the wounded leader of a remnant of the once-powerful Shining Path rebel group, effectively dismantling a well-armed outlaw band that lived off the cocaine trade, President Ollanta Humala said.
            • Peru: Leftist rebel leader captured wounded
              Peruvian troops captured on Sunday the wounded leader of a remnant of the once-powerful Shining Path rebel group, effectively dismantling a well-armed outlaw band that lived off the cocaine trade, President Ollanta Humala said.
            • Leftist Rebels Go Total Gangster
              February 4, 2012: The remnants of the leftist FARC rebels are surviving by working closer with all sorts of common criminals and the gangs that specialize in cocaine production and smuggling.
            • AFP blocks demand to free top leftist
              THE Armed Forces of the Philippines has strongly objected on the renewed demand of the Communist Party of the Philipines (CPP) for the release from detention of its top leader, Allan Jasminez, for humanitarian reasons and in compliance with the agreement between the Government of the Republic of the Philippines and the National Democratic Front of the Philippines (NDFP) peace panels.
            • Jordan- New coalition formalises Islamist-leftist 'divorce'
              (MENAFN - Jordan Times) When leftist and nationalist parties reached across the aisle to form a political coalition recently, the move marked rifts between the Islamist movement and other opposition ...
            • Jordan- Pro-reformers, teachers join forces in Friday demos
              (MENAFN - Jordan Times) Dozens of leftist activists and educators rallied in downtown Amman on Friday in a show of support for public schoolteachers' nationwide work stoppage. In a so-called ...
            • Leftist spoof of ‘Last Supper’ creates furore in Kerala
              A controversy has broken out over a flex board erected in an exhibition organized by the CPM, spoofing Leonardo Da Vinci’s painting, ‘The Last Supper’.
            • Video: Leftist protesters attack British banks in Buenos Aires
              Leftist protesters hurled paint bombs and rocks at British banks in Buenos Aires demanding London handover control of the Falkland Islands.
            • Leftist spoof on 'Last Supper' leaves CPI-M red-faced
              Barely days after it faced flak for displaying a painting of Jesus alongside Communist icons at an exhibition, the Communist Party of India-Marxist in Kerala has landed itself in another soup after a billboard carrying a political spoof, allegedly put up by party workers, raised hackles here.
            • CPAC 2012: English-Only Advocate Blasts 'Leftist Thugs' for Attacking 'White Nationalist' Peter Brimelow
              Robert Vandervoort, head of the English-only group ProEnglish, thanked the Conservative Political Action Committee Thursday for not giving in to "liberal thugs" who criticized its annual conference for featuring so-called white nationalist Peter Brimelow.

                 Related on Wikipedia




























             

            Powered free by PHPmotion