JCSS
2000
13 years 4 months ago
2000
It is a well-known result of Fagin that the complexity class NP coincides with the class of problems expressible in existential second-order logic ( 1 1), which allows sentences c...
STACS
2001
Springer
13 years 9 months ago
2001
Springer
In 1974 R. Fagin proved that properties of structures which are in NP are exactly the same as those expressible by existential second order sentences, that is sentences of the form...