ABS Pourhaghani(Latin)

ABSTRACT:

In this thesis, we present an extension on deontic logic, named input/output logic. Deontic Logic is a branch of modal logic, that considers the statements about ``obligation", ``permission" and ``prohibition", and introduced by von Wright in 1951. But many paradoxis are generated for deontic logic. for this reason, several extentions introduced for solving the paradoxis. One of the newer extension is input/output logics that introduced by David Makinson and Leendert van der Torre in 2000. The contraints for input/output logic published in 2001. When we use this constraints in out deduction about obligations, will be sure that paradoxis won't appear. The notion of permissions based on input/output logic introduced in 2003, and therefore all notions in deontic logic enterd in input/output logic.

By this logic we present conditional obligation by order pair (a,x). a is the conditions is happend and x is the obligation in this conditions. For example, let a is ``It is raining " and x is ``Window is closed". Therefore (a,x) means ``When it is raining window must be closed". This conditional obligation is present by a®OB x in deontic logic. In input/output logic somes rule introduced for deduction about conditional obligations, for example ((a,x),(b,x))/(a,xUy)}AND. This means if x is an obligation in a and y is an obligation in a, both x and y are obligations when a is happend. By input/output logic we can define three permissions that relative to definitions of deriviation systems in input/output logic. These definitions are compatible with obligations. these permissions are ``negative permission", ``static positive permission" and ``dynamic positive permission". Negative permission means if (a,¬x) be not an obligation then (a,x) is permissive. Static positive permission means if (a,x) is included in permission set then we are permitted for x when a is happend. Dynamic positive permission means if (a,Ux) be not consistent with static positive permission then (a,x) is a permission. Negative and static positive permissions are used for people to know their rights, and dynamic positive permission are used for lead of legislators.

Input/output logic is suitable for considering normative systems. The notion of normative system in deontic logic was introdused by anderson in 1956. Input/output logic is a suitable base for considering normative systems in computer science. By input/output logic we can construct models for normative systems. One of these best models