Using formal specifications to represent software components facilitates the determination of reusability because they more precisely characterize the functionality of the software, and the well-defined syntax makes processing amenable to automation. We present specification matching as a method for classification, retrieval, and modification of reusable components. A software component is specified in terms of order-sorted predicate logic. For both components and methods, we consider not only exact match, but also relaxed match and logical match for peforming specification matching over a library of reusable software components.