Hi everyone, Laurence advised me to redirect the following questions to the glue list. Many thanks in advance, David 1) Is this the latest version of the XSD: https://forge.ogf.org/svn/repos/glue/XSD/trunk/schema/GLUE2.xsd 2) (Assuming this is the latest version) - In the GLUE2 specification doc it states "For Grid services requiring a richer set of attributes for the Endpoint, specific models MAY be derived by specializing from the Endpoint class and adding new properties or relationships". However, in the above GLUE2.xsd on line 170, the Service_t defines an 'Endpoint' element that can't be extended with a custom Endpoint specialisation because Endpoint must be of type 'glue:Endoint_t' (<element name="Endpoint" type="glue:Endpoint_t" minOccurs="0" maxOccurs="unbounded"/> ). The problem is that 'Endpoint_t' is not abstract and so can't be substituted with an Endpoint specialisation using a substitution group. Therefore, shouldn't the Endpoint element be defined as abstract? (so that Endpoint could serve as an extension point allowing Endpoint specialisations to be defined using an xsd:substitutionGroup) . E.g. something along the lines of the following (of course this can also be supplemented by also extending base complex types such as your EndpointBase_t): <xsd:element name="Endpoint" abstract="true"/> <xsd:element name="MyEndpoint" substitutionGroup="Endpoint"> Apologies if I have go this wrong or if I have referenced the wrong XSD (or if this question should be re-directed to someone else). Thanks for your help. David Ps, if it's useful, for a more concrete example see the JSDL-PS spec which allows custom sweep functions and parameters to be defined in JSDL (http://www.gridforum.org/documents/GFD.149.pdf) ========================== David Meredith Scientific Computing Technology eScience Daresbury Laboratory Tel: +44 (0) 1925 603762 Fax: +44 (0) 1925 603100 (Site) Email: david.meredith@stfc.ac.uk Skype name: davidismeredith -- Scanned by iCritical.