Dear all, below "drools-compiler/src/../META-INF/" lies the XML Schema "drools-5.2.xsd". After a removing the namespace "drools", which makes it an invalid schema, and the trivial update of some XML rule files to rerer to "5.2" instead of "5.0", there is a persistent problem that the logical model presently encoded in "drools-5.2.xsd" still fails to validate test_ParseAccumulate.xml test_ParseLhs.xml test_ParseRule.xml test_SimpleRule1.xml All of which are found in drools-compiler/src/test/resources/org/drools/compiler/xml/rules/ QUESTION: Are all XML rule files stored in that directory supposed to correct, and are as such supposed to be valid by whatever XML Schema is developed? The answer to this question is instrumental for my prospects of reformulating the schema into something usable and valid! If the answer is "Yes", then the schema needs several changes, otherwise any intended invalid ingredient in an XML rule file must be properly documented, not tacitly be maintained in a status quo. I can in passing pin-point one issue of the present schema, which in itself does not resolve all problems, but might convince you that not all matters are well with the present formulation. The available schema prefers to use <xs:choice> whenever the human logic indicates so. However, it also combines this with <xs:extension> to construct composite types. This technique has a pitfall: * Extending a sequence by a second sequence, results in a combined sequence. (Expected by a layman.) * Extending a choice by a second choice, results in a (short) sequence of independent choices, choices which both have to be made! (Beware of unwanted consequences!) The expectation that an extension of choices should produce a (larger) combined choice is not the way the XML Schema implementation has been done. This must be taken into account. Please, do give me feed-back on my question, should you consider yourself authoritative enough. Best regards, Mats Andersson