Retrieving software components that minimize adaptation effort

Given a software library whose entries are represented by formal specifications, we distinguish between two retrieval procedures: exact retrieval, whereby, given a query K, we identify all the library components that are correct with respect to K; approximate retrieval, which is invoked when exact retrieval fails, and identifies the library components that minimize adaptation effort. To this effect, we define four measures of functional distance between specifications, and discuss algorithms that minimize these measures over a set of components; then we discuss whether these measures can be used to predict adaptation effort