When a number of conventions deal with a particular question in a way
that may require unification and modernization, model provisions can be developed
and recommended for use in future conventions and in revisions of existing
ones. In 1982, for example, UNCITRAL formulated a model provision establishing
a universal unit of account of constant value that could be used, in particular,
in international transport and liability conventions, for expressing amounts in
monetary terms.41 In conjunction with that model provision, UNCITRAL adopted
two alternative model provisions for the adjustment of an amount set forth in
an international convention: a sample price index clause and a sample amendment
procedure for a limit of liability. Model provisions may also assist in supplementing
a provision of a convention. The United Nations Convention on the
Assignment of Receivables in International Trade (New York, 2001) contains an
annex (of optional substantive law provisions) supplementing the conflicts of
laws rules of the Convention that deal with priority issues. In 2003, UNCITRAL
adopted the Model Legislative Provisions on Privately Financed Infrastructure
Projects, which complement the legislative guide on the same topic