Lattice-Based Graded Logic: a Multimodal Approach
  Experts do not always feel very, comfortable when they have to give precise
numerical estimations of certainty degrees. In this paper we present a
qualitative approach which allows for attaching partially ordered symbolic
grades to logical formulas. Uncertain information is expressed by means of
parameterized modal operators. We propose a semantics for this multimodal logic
and give a sound and complete axiomatization. We study the links with related
approaches and suggest how this framework might be used to manage both
uncertain and incomplere knowledge.
