arXiv subjects
Publications and source records attributed to Ewa Orłowska.
A discrete duality is a relationship between classes of algebras and classes of relational systems (frames) resulting in two representation theorems building on the early work of Jónsson and Tarski, Kripke, and van Benthem. In this section we recall discrete dualities for various types of algebras arising from rough sets.
In this note research and publications by Zdzisław Pawlak and his collaborators from 1970s and 1981 are recalled. Focus is placed on the sources of inspiration which one can identify on the basis of those publications. Finally, developments from 1981 related to rough sets and information systems are outlined.
The aim of this note is to characterize those doubly ordered frames $\langle X, \leq_1, \leq_2 \rangle$ which are embeddable into the canonical frame of its Urquhart complex algebra.
We investigate the join semilattice of modal operators on a Boolean algebra $B$. Furthermore, we consider pairs $(f,g)$ of modal operators whose supremum is the unary discriminator on $B$, and study the associated bi--modal algebras.
We present a first result towards the use of entailment in- side relational dual tableau-based decision procedures. To this end, we introduce a fragment of RL(1) which admits a restricted form of composition, (R ; S) or (R ; 1), where the left subterm R of (R ; S) is only allowed to be either the constant 1, or a Boolean term neither containing the complement operator nor the constant 1, while in the case of (R ; 1), R can only be a Boolean term involving relational variables and the operators of intersection and of union. We prove the decidability of the fragment by defining a dual tableau- based decision procedure with a suitable blocking mechanism and where the rules to decompose compositional formulae are modified so to deal with the constant 1 while preserving termination. The fragment properly includes the logics presented in previous work and, therefore, it allows one to express, among others, the multi-modal logic K with union and intersection of accessibility relations, and the description logic ALC with union and intersection of roles.