Common middleware services are built upon distribution middleware targeting some business logic to simplify the development in some direction. In most cases, it is an extension of the distribution middleware, which is in a higher-level but still domain-independent. A good example is the OMG's CORBAservices.
CORBAservices provides domain-independent interfaces and capabilities that can be used by many DOC applications. The services are usually in certain generality, such like concurrency service, naming service, security service, etc. These services get a great deal of flexibility for a particular implementation. Different vendors may prefer to add different services into their middleware to support different models. From this point, Sun's Enterprise Java Beans (EJB) is a very successful common middleware service that allows developers to create a distributed system by linking a number of pre-built software services (i.e., ``beans''). Microsoft Web services is developed on the same idea to allow a component-based development, instead of programming from scratch.
One thing we notice from some implementations is that despite CORBAservices is specified to be language-independent, EJB and Microsoft Web services are based on their only language platform. Because common middleware services are associated with the previous level distribution middleware, we suspect the language-independent feature may not be applied here unless strictly follow the CORBA specifications to provide interfaces for this level services, and in most cases, it is obviously impossible to implement all supporting features.