منابع مشابه
Comparing Complexity Classes of Formal Languages
A property of polynomial complete languages is extended in order to better compare various classes of formal languages. We consider pairs (̂ ,,̂ 2̂ °̂ classes of languages such that there is a language L e 5?, with the property that L e ^if and / if &-\ Certain longstanding open questions in automata-based complexity have resurfaced recently due to the work on efficient reducibilities among combina...
متن کاملComparing complexity classes relative to physical oracles
We develop the idea of using a physical experiment as an oracle to an algorithm. As a case study, we compare the computational power of deterministic and non-deterministic Turing machines connected to a simple physical oracle, namely, the scatter machine experiment. We prove relativisation theorems for the conjectures concerning P , NP , PSPACE relative to this physical oracle. Finally, we refl...
متن کاملComplexity Classes
The purposes of complexity theory are to ascertain the amount of computational resources required to solve important computational problems, and to classify problems according to their difficulty. The resource most often discussed is computational time, although memory (space) and circuitry (or hardware) have also been studied. The main challenge of the theory is to prove lower bounds, i.e., th...
متن کامل3 Relations Between Randomized Complexity Classes and Other Complexity Classes
Proof Fix a satisfying assignment a. Define the distance of r to a, denoted dist(r, a), as the number of coordinates where ri 6= ai (this is called Hamming distance). Let r = r, r, r, · · · be the assignments generated by the algorithm, and let di = dist(r , a). Note that as we only change one bit of the assignment, di+1 = di + ∆i where ∆i ∈ {−1, 1}. We claim that Pr[∆i = −1] ≥ 1/2. Once this i...
متن کاملComparing Classes or Datatypes
This is the fifth in a series of articles on ontology-based approaches to modeling. The main focus is on popular ontology languages proposed for the Semantic Web, such as the Resource Description Framework (RDF), RDF Schema (RDFS), and the Web Ontology Language (OWL). OWL is based on description logic. A later series of articles will explore other logic-based languages such as datalog. The firs...
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ژورنال
عنوان ژورنال: Journal of Computer and System Sciences
سال: 1974
ISSN: 0022-0000
DOI: 10.1016/s0022-0000(74)80008-5