Similarity-based reasoning and retrieval with order-sorted feature logic

Logic programming languages based on first-order terms (FOTs) have been extended with a similarity relation on functor symbols in order to perform approximate reasoning, which may allow flexible querying and retrieval from a knowledge base. More flexibility is also provided by the terms of Order-Sorted Feature (OSF) logic, which relax a few syntactic restrictions of FOTs. Moreover, OSF term unification takes into account a subsumption ordering on sort symbols, which makes computations more efficient. This document presents the current efforts by the authors in defining similarity-based reasoning with OSF logic: the goal is to achieve a more flexible, but still efficient, processing of queries.