XML Schema for WIREDMark Dnszelmann, Applications for Physics and Infrastructure, IT, CERNXML Detector Description WorkshopCERN, 14 April, 2000

ContentsXML Schema FeaturesToolsXML-Data BindingCurrent Status and Implementation

Features (basic)A better DTD, written in XMLThere is both a DTD and an XSD (recursive) for XML SchemaBasic ConceptsTypessimpleType: boolean, float, double, string, enumeration, ...complexType: may contain primitives and other elementsreuse simpleType and complexType to type elements and attributesAnnotations, Versions and CommentsGroups of elements or attributesone of manyall, in order

Features (advanced)Advanced ConceptsOrganizationSchema inclusionImport of types (from other schema)Schema locationTypesCardinality on elements and attributesDerived Types (Inheritance)by extensionby restrictionEquivalence of typesAbstract ElementsOtherUniqueness of elements or attributesKeys and references

ToolsAny XML Editor will be able to edit XML SchemaIBM Visual XML Tools provide a DTD->Schema converter (as a first start)Same toolset currently has DTD visualization tools, which may migrate to XML SchemaSame toolset can convert DTD in set of Java Classes (see next slide)

XML-Data BindingToday using DTD / Schema:Define a DTD / SchemaWrite/generate XMLUse a SAX or DOM parserWrite a set of Classes for your modelSAX: Write code to handle elements and attributes and build objectsDOM: Write code to browse tree and build objectsSun proposes XML-Data Binding Facility (July 1999)Java Beans Persistency proposed recently

XML-Data BindingSchema CompilerCompiles XML Schemas into a set of ClassesMarshalling FrameworkInternally uses SAX/DOM parserUnmarshals a set XML documents into a set of objectsMarshals a set of objects into a set of XML documentsXML SchemaJava ClassesXML DocumentsJavaObjectsCompileInstanceOfDefinedByMarshalUnmarshal

Current Status and ImplementationXML Schema Standard (Datatypes and Structures)Defined at the World Wide Web ConsortiumProposed Recommendation, since Dec 1999Most recent public draft: 25 Feb 2000XML Schema ImplementationXerces-j 1.0.3 (xml4j, java version) implements the latest standardsome exceptions: Unique, key and key ref no supported limitations on Inheritance elements, types, in same namespaceXerces-c 1.1.0 (xml4c, c++ version) does NOT yet implement XML Schema

ConclusionsWIRED is based on:Its own LoaderOne namespace for all the elementsMultiple DTDs, with some tricks to load themOur own key keyref implementationA small pre-SAX ParserXML Schema will provide WIRED with:Separate namespacesMultiple XSDs, which load properlyType checking on all the inputA standard key keyref implementationXML-Data Binding should:Get rid of the parser and loaderReplace those with a generic one