1. A method of configuring a system in a computer system comprising the steps of: defining a structural model hierarchy comprised of composite and container hierarchies and port relationships substructures; instantiating in said computer system a configuration instance; modifying said configuration instance in response to a request by creating in said configuration instance instances of one or more model elements based on said request; storing said modifications in a list of modifications; examining said instances to determine if a constraint exists; satisfying in said computer said constraint when said constraint exists; satisfying in said computer a component constraint of said component hierarchy when said instances are constrained by said component constraints; satisfying in said computer container constraints of said container hierarchy when said instances are constrained by said container constraints; satisfying in said computer connection constraints of said port relationship when said instances are constrained by said connection constraints; committing said modifications to said configuration instance and removing said modifications from said modifications list when no constraint exists and when all constraints associated with said instances are satisfied; and removing said modifications from said configuration instance and said modifications list when any constraint associated with said instances is not satisfied.