The need for supporting the classification and semantic annotation of services constitutes an important challenge for service-centric software engineering. Late-binding and, in general, service matching approaches, require services to be semantically annotated. Such a semantic annotation may require, in turn, to be made in agreement to a specific ontology. Also, a service description needs to properly relate with other similar services. This paper proposes an approach to i) automatically classify services to specific domains and ii) identify key concepts inside service textual documentation, and build a lattice of relationships between service annotations. Support Vector Machines and Formal Concept Analysis have been used to perform the two tasks. Results obtained classifying a set of web services show that the approach can provide useful insights in both service publication and service retrieval phases.