HDPS is a practical system for designing modeling paradigms, creating hierarchal model definitions, and evaluating multi-paradigm models - particularly in business and finance. HDPS relies on XML (W3C 2004) to create model types, definitions, and instances. A type defines a modeling paradigm; for example, one type might define discrete event simulation while another may specify linear programming. A definition describes a system such as a firm's pricing decision process. A model instance is the state and history of a definition when operated upon by a type. Further, each type relies on one or more implementations to provide its functionality. xHDPS, a .NET version of HPDS, implements several modeling paradigms including simulation (discrete event, continuous time, and Monte-Carlo), optimization (linear and non-linear), knowledge-based expert systems, and general calculation (spreadsheet) models. A multi-generation service adoption model demonstrates a typical HDPS model structure...