Algebra based modeling systems are becoming essential elements in the
application of large and complex mathematical programs. These systems
enable the abstraction, expression and translation of practical
problems into reliable and effective operational systems. They provide
the bridged between algorithms and real world problems by automating
the problem analysis and translation into specific data structures and
provide computational services required by different solvers. The
modeling system GAMS will be used to illustrate the design goals and
main features of such systems. Applications in use and under
development will be used to provide the context for discussing the
changes in user focus and future requirements. This presents new sets
of opportunities and challenges to the supplier and implementer of
mathematical programming solvers and modeling systems.