This paper describes the object-oriented scripting language XOTCL (Extended OTCL), which is a value added replacement of OTCL. OTCL implements dynamic and introspective language support for object-orientation on top of TCL. XOTCL includes the functionality of OTCL but focuses on the construction, management, and adaptation of complex systems. In order to combine the benefits of scripting languages with advanced object-oriented techniques, we extended OTCL in various ways: We developed the filter as a powerful adapation technique and an intuitive means for the instantiation of large program structures. In order to enable objects to access several addition-classes we improved the flexibility of mixin methods by enhancing the object model with per-object mixins. We integrated the object system with the TCL namespace concept to provide nested classes and dynamic object aggregations. Moreover, we introduced assertions and meta-data to improve reliability and self-documentation.