class RooResolutionModel: public RooAbsPdf

  RooResolutionModel is the base class of for PDFs that represent a
  resolution model that can be convoluted with physics a physics model of the form

    Phys(x,a,b) = Sum_k coef_k(a) * basis_k(x,b)

  where basis_k are a limited number of functions in terms of the variable
  to be convoluted and coef_k are coefficients independent of the convolution
  variable.

  Classes derived from RooResolutionModel implement
         _ _                        _                  _
   R_k(x,b,c) = Int(dx') basis_k(x',b) * resModel(x-x',c)

  which RooAbsAnaConvPdf uses to construct the pdf for [ Phys (x) R ] :
          _ _ _                 _          _ _
    PDF(x,a,b,c) = Sum_k coef_k(a) * R_k(x,b,c)

  A minimal implementation of a RooResolutionModel consists of a

    Int_t basisCode(const char* name)

  function indication which basis functions this resolution model supports, and

    Double_t evaluate()

  Implementing the resolution model, optionally convoluted with one of the
  supported basis functions. RooResolutionModel objects can be used as regular
  PDFs (They inherit from RooAbsPdf), or as resolution model convoluted with
  a basis function. The implementation of evaluate() can identify the requested
  from of use from the basisCode() function. If zero, the regular PDF value
  should be calculated. If non-zero, the models value convoluted with the
  basis function identified by the code should be calculated.

  Optionally, analytical integrals can be advertised and implemented, in the
  same way as done for regular PDFS (see RooAbsPdf for further details).
  Also in getAnalyticalIntegral()/analyticalIntegral() the implementation
  should use basisCode() to determine for which scenario the integral is
  requested.

  The choice of basis returned by basisCode() is guaranteed not to change
  of the lifetime of a RooResolutionModel object.