The rapid development of the Internet and of distributed computing has led to a proliferation of online service providers such as digital libraries, web information sources, electronically requestable traditional services, and even software-to-software services such as those provided by persistence and event managers. This has created a need for catalogs of services, based on description languages covering both traditional and electronic services. This paper presents a classification and a domainindependent characterisation of services, which provide a foundation for their description to potential consumers. For each of the service characteristics that we consider, we identify the range of its possible values in different settings, and when applicable, we point to alternative approaches for representing these values. The idea is that by merging This work was funded by an Australian Research Council SPIRT Grant entitled "Selfdescribing transactions operating in a open, heterogeneou...