automated treatment of both the real and the virtual contributions to NLO computations, it is realistic to assume that phenomenological results at this accuracy will become available in the next few years for all of the reactions of interest to the LHC physics programme. The situation is much less encouraging for fixed-order cross sections at ${\cal O}({\alpha_{{\scriptscriptstyle}S}}^{b+2})$ (or NNLO), where only a handful of results are available, for very small final-state multiplicities.

As far as resummed results are concerned, it is in general understood how to achieve a next-to-leading logarithmic (NLL) accuracy, which is equivalent to including terms proportional to ${\alpha_{{\scriptscriptstyle}S}}^n\log^{kn}{{\cal Q}}$ and to ${\alpha_{{\scriptscriptstyle}S}}^n\log^{kn-1}{{\cal Q}}$, with $k=1,2$ depending on the nature of ${{\cal Q}}$; some results are also known to next-to-next-to-leading logarithmic accuracy (NNLL). Unfortunately, resummed computations are in general technically complicated, observable-dependent, and error-prone; although for some observable classes a semi-automated algorithm (CAESAR [@Banfi:2004yd]) is available, the overall situation is far less satisfactory than for NLO computations. For this reason, a very appealing alternative is that provided by Parton Shower Monte Carlos (PSMCs). Although formally PSMCs are equivalent to a LL-accurate resummation (which may become NLL in some corners of the phase space, for some PSMCs and subject 