XML is becoming the standard for document description in a B2B setting, and XML Schema is gaining wide acceptance as the schema language to define the structure of these documents. Transactional documents as those currently found in B2B applications, frequently comprise derived elements, ie elements whose content can be calculated through deriving function that examines the content of other elements. Based on this observation, this work advocates incorporating the notion of derived element in XML Schema. Despite its wide presence, the notion of derived element is not yet supported in XML Schema. To this end two issues are addressed:(1) the implicitness of current approaches to deriving function support for XML documents, and (2) the externality of some deriving data which participate in the deriving function. These aspects are respectively tackled both by (1) moving the derivation semantics to the document schema, and (2) by proposing an attachment where the deriving elements are recorded. These ideas have been realized by extending the Oracles XML Parser. Now, this parser can be configured to become “derivation aware”. That is, the deriving functions can now be found in the XML Schema. At parsing time, these functions are interpreted, and the returned values become the content of the associated derived elements.