Christian Nentwich is Technical Director of Systemwire Ltd. Systemwireproduce the xlinkit suite of products, which is aimed at semantic, orbusiness-level validation of XML documents. xlinkit's rules, which areexpressed in the CLIX constraint language, deal with issues likechecking against reference data, multi-documents checks and complexinternal constraints, that traditional schema languages cannot support.Christian is also chairman of the Validation Working Group of theFinancial Products Markup Language (FpML). The group defines validationrules for financial derivative trades expressed in FpML.