@InProceedings{Lawrence98a, title = "{E}xtending {CSP}", author= "Lawrence, Adrian E.", editor= "Welch, Peter H. and Bakkers, Andr\`{e} W. P.", pages = "111--132", booktitle= "{P}roceedings of {W}o{TUG}-21: {A}rchitectures, {L}anguages and {P}atterns for {P}arallel and {D}istributed {A}pplications", isbn= "90 5199 391 9", year= "1998", month= "mar", abstract= "CSP, timed or untimed, has not included a general treatment of priority, although the PRI ALT constructor is an essential part of occam. This paper introduces CSPP which includes a generalization of PRI ALT in the form of a prioritized external choice P \<pribox\> Q. PRI PAR is also included. A new denotational semantics is introduced, although only the simplest model is outlined. The work is intended to provide a solid rogorous foundation for hardware-software codesign. And a companion paper describes untimed HCSP which is a further extension of CSP built upon these foundations. It was first presented informally at the Twente WoTUG-20 technical meeting." }