CCS without T'S

The main point of this paper is that one can develop an adequate version of CCS which does not use the special combinator ? for internal actions. Instead, the choice operator +, whose semantics is somewhat unclear, is replaced by two new choice operators ? and [], representing internal and external nondeterminism respectively. The operational semantics of the resulting language is simpler and the definition of testing preorders is significantly cleaner. The essential features of the originai calculus are kept; this is shown by defining a translation from CCS to the new language which preserves testing preorders.