The basic idea of service-oriented learning is that a learning environment should be conceived as a set of independent units of learning packaged as learning services. The design, development and deployment of a learning system based on integrating different learning services needs both a technological platform to support the system as well as a methodology that manages the development process. Such technological platform is provided by the Service Oriented Learning Architecture (SOLA). SOLA proposes an architecture style, which defines how to deploy several units of packeged-learning services. The purpose of this paper is to review the SOLA concept and to present a specific method based on specifying instructional domains, to complement the SOLA approach. Our method suggests the definition of a feature model, which represents the characteristics of the instructional domain, in order to address the identification and classification of candidate services. The approach here proposed facilitates the definition of candidate-learning services in order to enhance the integration of such services. (Contains 5 figures.)