1. A method for supporting homeland security decisions made by human system users in a maritime context, said method executed by a client-server based computing architecture comprised of one or more server computers and one or more user computers, said method comprising the computer-based steps of: said server computers accessing data from two or more sources, said two or more sources including one or more structured data sources and one or more unstructured data sources; where said data from any of said sources is not in structured form, structuring the unstructured data by application of information extraction logic to form structured data, whereby said data from said two or more sources is in structured form; where any portion of said data in structured form is not in XML, processing the non-XML structured data by conversion of said non-XML structured data to XML to thereby form structured XML data; said server computers hierarchically organizing conditional decision and simulation logic to: (a) at a 3rd order logic level of XML-based decision logic, establishing and evaluating relationships within the structured XML data environment for at least potential threat entities; (b) at a 2nd order logic level of said XML-based decision logic, comparing to one another entities produced by said 3rd order logic within the operational context, applying user-defined rules establishing user alerts, to thereby generate a representation of the current situation in XML; and (c) at a 1st order logic level of said XML-based decision logic, interpreting the current situation as represented by the 2nd order logic in light of said user-defined rules, and providing recommendations to the system users; and allowing the system users to change the conditional decision and simulation logic, thereby resulting in dynamic modification of system processing at different levels of the conditional logic hierarchy, utilizing COTS XML based software services and communications.