methodologies such as the Rational Unified Process or Agile methods. Languages for KBE Two critical issues for the languages and formalisms used for KBE are: Knowledge-based vs. procedural programming Standardization vs. proprietary Knowledge-based vs. procedural programming A fundamental trade-off identified with knowledge representation in artificial intelligence is between expressive power and computability. As Levesque demonstrated in his classic paper on the topic, the more powerful a knowledge-representation formalism one designs, the closer the formalism will come to the expressive power of first order logic. As Levesque also demonstrated, the closer a language is to First Order Logic, the more probable that it will allow expressions that are undecidable or require exponential processing power to complete. In the implementation of KBE systems, this trade off is reflected in the choice to use powerful knowledge-based environments or more conventional procedural and object-oriented programming environments. Standardization vs. proprietary There is a trade off between using standards such as STEM and vendor- or business-specific proprietary languages. Standardization facilitates knowledge sharing, integration, and re-use. Proprietary formats (such as CATIA) can provide competitive advantage and powerful features beyond current standardization. Genworks GDL, a commercial product whose core is based on the AGPL-licensed Gendl Project, addresses the issue of application longevity by providing a high-level declarative language kernel which is a superset of a standard dialect of the Lisp programming language (ANSI Common Lisp, or CL). Gendl/GDL itself is proposed as a de facto standard for ANSI CL-based KBE languages. In 2006, the Object Management Group released a KBE services RFP document and requested feedback. To date, no OMG specification for KBE exists; however, there is an OMG standard for CAD services. An example of a system-independent language for the development of machine-readable ontologies that is in the KBE domain is Gellish English. KBE in Academia Knowledge-based engineering at the Norwegian University of Science and Technology (NTNU) Aircraft Design & Design Methodologies department at the Faculty of Aerospace Engineering of the Delft University of Technology See Webliography for AI in Design hosted by Worcester Polytechnic Institute and the NSF Report "Research Opportunities in Engineering Design." Knowledge-based engineering lab at Birmingham City University Implementations The following KBE development packages are commercially available: For CAD ParaPy by ParaPy CADECWorks Solidworks Certified Gold Partner by Mark Design Solutions Pvt Ltd India Mark Design Solutions CADECEdge KBE tool for SolidEdge by Mark Design Solutions Pvt Ltd India Mark Design Solutions Adaptive