* In the near future

- Write documentation
   Write a HOWTO for users (maybe for R News).

- If possible add a few of the missing operations listed below.

- Add R to C and C to R converters for .C and .Fortran calls.

- Add a BerkeleyDB based externalStorage subclass.

- Add an HDF5 based externalStorage subclass.

- Do profiling
   We need to do profiling both at R and C level. The current
   performance is not very good for most operations. It is not clear
   how much of the performance degradation is unavoidable.

* Missing operations
   Listed below are the generics for which we need to add appropriate
   definitions for the externalVector class.

- vector operations
   "Math2"
   "[["
   "rev"
   "lapply"
   "sapply"
   "summary"

- matrix operations
   "rbind"
   "cbind"
   "t"
   "row"
   "column"

- arrray operations
   "["
   "[<-"
   "aperm"

* Buggy or non-standard operations

- Group generics
   The following methods for group "Math" do not work: "gamma", "lgamma".

- "[" and "[<-"
   Uses drop=FALSE by default.

   Does not handle subsetting correctly when length(dim(x)) == 1 and
   length(dimnames(x)[[1]]) > 0.

- "names"
   Does not handle the case where dim(x) == 1 and
   length(dimnames(x)[[1]]) > 0.
