  The International Lattice Datagrid (ILDG) is a federation of several regional
grids. Since most of these grids have reached production level, an increasing
number of lattice scientists start to benefit from this new research
infrastructure. The ILDG Middleware Working Group has the task of specifying
the ILDG middleware such that interoperability among the different grids is
achieved. In this paper we will present the architecture of the ILDG middleware
and describe what has actually been achieved in recent years. Particular focus
is given to interoperability and security issues. We will conclude with a short
overview on issues which we plan to address in the near future.
