book

XML Schema

Name: XML Schema
Author: Eric van der Vlist
ISBN: 9780596002527

by Eric van der Vlist

June 2002

Intermediate to advanced

396 pages

11h 8m

English

O'Reilly Media, Inc.

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A Note Regarding Supplemental Files
Preface
Who Should Read This Book?Who Should Not Read This Book?About the ExamplesOrganization of This BookConventions Used in This BookHow to Contact UsAcknowledgments
1. Schema Uses and Development
What Schemas Do for XMLValidationDocumentationQuerying SupportData BindingGuided EditingW3C XML Schema
2. Our First Schema
The Instance DocumentOur First SchemaFirst FindingsW3C XML Schema Is ModularW3C XML Schema Is Both About Structure and DatatypingFlat Design, Global Components
3. Giving Some Depth to Our First Schema
Working From the Structure of the Instance DocumentNew LessonsDepth Versus Modularity?Russian Doll and Object-Oriented DesignWhere Have the Element Types Gone?
4. Using Predefined Simple Datatypes
Lexical and Value SpacesWhitespace ProcessingString DatatypesNo Whitespace ReplacementNormalized StringsCollapsed StringsTokenssQualified namesURIsNotationsBinary string-encoded datatypesNumeric DatatypesDecimal TypesFloat Datatypes xs:boolean Date and Time DatatypesThe Realm of ISO 8601DatatypesList TypesWhat About anySimpleType?Back to Our Library
5. Creating Simple Datatypes
Derivation By RestrictionFacetsWhitespace collapsed strings xs:enumeration xs:length xs:maxLength xs:minLength xs:pattern Other strings xs:whiteSpace Float datatypes xs:enumeration xs:maxExclusive xs:maxInclusive xs:minExclusive xs:minInclusive xs:pattern Date and time datatypes xs:enumeration xs:maxExclusive xs:maxInclusive xs:minExclusive xs:minInclusive xs:pattern Integer and derived datatypes xs:totalDigits Decimals xs:fractionDigits Booleans xs:pattern List datatypesMultiple Restrictions and Fixed AttributeFacet that can be changed but needs to be more restrictiveFacet that cannot be changedFacet that performs the intersection of the lexical spacesFacet that does its job before the lexical spaceFixed facetsDerivation By ListList DatatypesDerivation By UnionSome Oddities of Simple TypesBeware of the OrderUsing or Abusing Lists to Change the Behavior of Length Constraining FacetsBack to Our Library
6. Using Regular Expressions to Specify Simple Datatypes
The Swiss Army KnifeThe Simplest Possible PatternsQuantifyingMore AtomsSpecial CharactersWildcardCharacter ClassesClassical Perl character classesUnicode character classesUser-defined character classesOring and GroupingCommon PatternsString DatatypesUnicode blocksCounting wordsURIsNumeric and Float TypesLeading zerosFixed formatDatetimesTime zonesBack to Our Library
7. Creating Complex Datatypes
Simple Versus Complex TypesExamining the LandscapeContent ModelsNamed Versus Anonymous TypesCreation Versus DerivationSimple Content ModelsCreation of Simple Content ModelsDerivation from Simple ContentsDerivation by extensionDerivation by restrictionComparison of these two methodsComplex Content ModelsCreation of Complex ContentCompositors and particlesElement and attribute groupsUnique Particle Attribution RuleConsistent Declaration RuleLimitations on unordered content modelsLimitations of xs:all Adapting the structure of your documentUsing xs:choice instead of xs:all Derivation of Complex ContentDerivation by extensionDerivation by restrictionAsymmetry of these two methodsMixed Content ModelsCreating Mixed Content ModelsDerivation of Mixed Content ModelsDerivation by extensionDerivation by restrictionDerivation between complex and mixed content modelsEmpty Content ModelsCreation of Empty Content ModelsAs simple content modelsAs complex content modelsDerivation of Empty Content ModelsDerivation by extensionDerivation by restrictionSimple or Complex Content Models for Empty Content Models?Back to Our LibraryDerivation or Groups
8. Creating Building Blocks
Schema InclusionSchema Inclusion with RedefinitionRedefining of Simple and Complex TypesRedefinition of Element and Attribute GroupsExtensionRestrictionOther AlternativesExternal Parsed EntitiesXIncludeSimplifying the Library

9. Defining Uniqueness, Keys, and Key References
xs:ID and xs:IDREF XPath-Based Identity ChecksUniquenessComposite FieldsKeysKey ReferencesPermitted XPath ExpressionsID/IDREF Versus xs:key/xs:keyref Using xs:key and xs:unique As Co-occurrence Constraints
10. Controlling Namespaces
Namespaces Present Two Challenges to Schema LanguagesNamespace DeclarationsTo Qualify Or Not to Qualify?Disruptive AttributesNamespaces and XPath ExpressionsReferencing Other NamespacesSchemas for XML, XML Base and XLinkXML AttributesXLink AttributesNamespace Behavior of Imported ComponentsImporting Schemas with No NamespacesChameleon DesignAllowing Any Elements or Attributes from a Particular Namespace
11. Referencing Schemas and Schema Datatypes in XML Documents
Associating Schemas with Instance DocumentsDefining Element TypesDefining Simple TypesDefining Complex TypesDefining Nil (Null) ValuesBeware the Intrusive Nature of These Features...
12. Creating More Building Blocks Using Object-Oriented Features
Substitution GroupsUsing a “Traditional” GroupSubstitution GroupsUsing substitution groupsAbstract elementsTrees of substitution groupsTraditional Declarations or Substitution Groups?Fuzzy RecommendationExtension of xs:choice through group redefinitionsRestricting substitution groupsControlling DerivationsAttributesElementsBlock attributeFinal elementsAbstract elementsComplex TypesBlocking complex typesFinal complex typesAbstract complex typesSimple TypesOther Components and Redefinitions
13. Creating Extensible Schemas
Extensible SchemasGlobal ComponentsElementsAttributesfinal and fixed AttributesSplitting Schema ComponentsThe Need for Open Schemasxsi:typeWildcardsAnd Substitution Groups?
14. Documenting Schemas
Style MattersKeep It SimpleThink GloballyWhen It’s Similar, Show ItThe W3C XML Schema Annotation ElementForeign AttributesXML 1.0 CommentsWhich One and What For?
15. Elements Reference Guide
xs:all(outside a group) — Compositor describing an unordered group of elements.
xs:all(within a group) — Compositor describing an unordered group of elements. The number of occurrences cannot be defined when xs:all is used within a group.
xs:annotation — Informative data for human or electronic agents.
xs:any — Wildcard to replace any element.
xs:anyAttribute — Wildcard to replace any attribute.
xs:appinfo — Information for applications.
xs:attribute(global definition) — Global attribute definition that can be referenced within the same schema by other schemas.
xs:attribute(reference or local definition) — Reference to a global attribute definition or local definition (local definitions cannot be referenced).
xs:attributeGroup(global definition) — Global attributes group declaration that can be referenced within the same schema by other schemas.
xs:attributeGroup(reference) — Reference to a global attributes group declaration.
xs:choice(outside a group) — Compositor to define group of mutually exclusive elements or compositors.
xs:choice(within a group) — Compositor to define group of mutually exclusive elements or compositors. The number of occurrences cannot be defined when xs:choice is used within a group.
xs:complexContent — Definition of a complex content by derivation of a complex type.
xs:complexType(global definition) — Global definition of a complex type that can be referenced within the same schema by other schemas.
xs:complexType(local definition) — Complex type local definition (local definitions cannot be referenced).
xs:documentation — Human-targeted documentation.
xs:element(global definition) — Global element definition that can be referenced within the same schema by other schemas.
xs:element(within xs:all) — Reference to a global element declaration or local definition (local definitions cannot be referenced). The number of occurrences can only be zero or one when xs:element is used within xs:all..
xs:element(reference or local definition) — Reference to a global element declaration or local definition (local definitions cannot be referenced).
xs:enumeration — Facet to restrict a datatype to a finite set of values.
xs:extension(simple content) — Extension of a simple content model.
xs:extension(complex content) — Extension of a complex content model.
xs:field — Definition of the field to use for a uniqueness constraint.
xs:fractionDigits — Facet to define the number of fractional digits of a numerical datatype.
xs:group(definition) — Global elements group declaration that can be referenced within the same schema by other schemas.
xs:group(reference) — Reference to a global elements group declaration or local definition (local definitions cannot be referenced).
xs:import — Import of a W3C XML Schema for another namespace.
xs:include — Inclusion of a W3C XML Schema for the same target namespace.
xs:key — Definition of a key.
xs:keyref — Definition of a key reference.
xs:length — Facet to define the length of a value.
xs:list — Derivation by list.
xs:maxExclusive — Facet to define a maximum (exclusive) value.
xs:maxInclusive — Facet to define a maximum (inclusive) value.
xs:maxLength — Facet to define a maximum length.
xs:minExclusive — Facet to define a minimum (exclusive) value.
xs:minInclusive — Facet to define a minimum (inclusive) value.
xs:minLength — Facet to define a minimum length.
xs:notation — Declaration of a notation.
xs:pattern — Facet to define a regular expression pattern constraint.
xs:redefine — Inclusion of a W3C XML Schema for the same namespace with possible override.
xs:restriction(simple type) — Derivation of a simple datatype by restriction.
xs:restriction(simple content) — Derivation of a simple content model by restriction.
xs:restriction(complex content) — Derivation of a complex content model by restriction.
xs:schema — Document element of a W3C XML Schema.
xs:selector — Definition of the the path selecting an element for a uniqueness constraint.
xs:sequence(outside a group) — Compositor to define an ordered group of elements.
xs:sequence(within a group) — Compositor to define an ordered group of elements. The number of occurrences cannot be defined when xs:all is used within a group.
xs:simpleContent — Simple content model declaration.
xs:simpleType(global definition) — Global simple type declaration that can be referenced within the same schema by other schemas.
xs:simpleType(local definition) — Local simple type definition (local definitions cannot be referenced).
xs:totalDigits — Facet to define the total number of digits of a numeric datatype.
xs:union — Derivation of simple datatypes by union.
xs:unique — Definition of a uniqueness constraint.
xs:whiteSpace — Facet to define whitespace behavior.
16. Datatype Reference Guide
xs:anyURI — URI (Uniform Resource Identifier).
xs:base64Binary — Binary content coded as “base64”.
xs:boolean — Boolean (true or false).
xs:byte — Signed value of 8 bits.
xs:date — Gregorian calendar date.
xs:dateTime — Instant of time (Gregorian calendar).
xs:decimal — Decimal numbers.
xs:double — IEEE 64 bit floating point.
xs:duration — Time durations.
xs:ENTITIES — Whitespace separated list of unparsed entity references.
xs:ENTITY — Reference to an unparsed entity.
xs:float — IEEE 32 bit floating point.
xs:gDay — Recurring period of time: monthly day.
xs:gMonth — Recurring period of time: yearly month.
xs:gMonthDay — Recurring period of time: yearly day.
xs:gYear — Period of one year.
xs:gYearMonth — Period of one month.
xs:hexBinary — Binary contents coded in hexadecimal.
xs:ID — Definition of unique identifiers.
xs:IDREF — Definition of references to unique identifiers.
xs:IDREFS — Definition of lists of references to unique identifiers.
xs:int — 32 bit signed integers.
xs:integer — Signed integers of arbitrary length.
xs:language — RFC 1766 language codes.
xs:long — 64 bit signed integers.
xs:Name — XML 1.O names.
xs:NCName — Unqualified names.
xs:negativeInteger — Strictly negative integers of arbitrary length.
xs:NMTOKEN — XML 1.0 name token (NMTOKEN).
xs:NMTOKENS — List of XML 1.0 name token (NMTOKEN).
xs:nonNegativeInteger — Integers of arbitrary length positive or equal to zero.
xs:nonPositiveInteger — Integers of arbitrary length negative or equal to zero.
xs:normalizedString — Whitespace-replaced strings.
xs:NOTATION — Emulation of the XML 1.0 feature.
xs:positiveInteger — Strictly positive integers of arbitrary length.
xs:QName — Namespaces in XML qualified names.
xs:short — 32 bit signed integers.
xs:string — Any string.
xs:time — Point in time recurring each day.
xs:token — Whitespace-replaced and collapsed strings.
xs:unsignedByte — Unsigned value of 8 bits.
xs:unsignedInt — Unsigned integer of 32 bits.
xs:unsignedLong — Unsigned integer of 64 bits.
xs:unsignedShort — Unsigned integer of 16 bits.
A. XML Schema Languages
What Is a XML Schema Language?XML Schema Languages Are Not SchemasFirewalls Against DiversityIntrusive Modeling ToolsEarly Binding ToolsClassification of XML Schema LanguagesRule-Based XML Schema LanguagesGrammar-Based XML Schema LanguagesObject-Oriented XML Schema LanguagesA Short History of XML Schema LanguagesThe DTD FamilyThe W3C XML Schema FamilyThe RELAX NG FamilySchematronExamplotronSample ApplicationXML DTDsExampleW3C XML SchemaExampleRELAX NGExampleSchematronExampleExamplotronExampleDecisions
B. Work in Progress
W3C ProjectsXPath, XSLT, and XQueryDOMRDFISO: DSDLOtherPSVI SerializationAPIsSchema Extensions: Error Messages
Glossary
Index
About the Author
Colophon
Copyright

Content preview from XML Schema

Appendix B. Work in Progress

Although W3C XML Schema was approved as a W3C Recommendation in May 2001, it is still just getting started. This chapter identifies a short list of schema-related projects that seem either promising, useful, or just on the way.

W3C Projects

Edited by the W3C, the W3C XML Schema is considered by the consortium to belong to the very foundation of XML—together with XML 1.0 and namespaces in XML—and it does impact virtually all the other XML specifications. The most heavily affected seem to be the triumvirate XPath/XSLT/XQuery (and by consequence, XPointer- and XPointer-based specifications), DOM, and RDF.

XPath, XSLT, and XQuery

One of the most amazing things about XPath and XSLT 1.0 is that queries and transformations can be executed by applications with no prior knowledge of the structure of the documents on which they work. This is a major difference from previous information systems, such as RDBMS, in which the layout of the tables needs to be defined before any query can be run. Even though this works just fine in many circumstances, there are two main areas in which improvements can be obtained if the structure of the instance documents is known.

The first of these areas is optimization. This is not crucial for small documents, but as soon as the size of the document grows (which is typically the case in a XML database), any optimizer will need food for thought to perform his job. The first piece of basic information that is required is about the structure ...

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XML Schema

by Eric van der Vlist

Appendix B. Work in Progress