1、 Unit 11. XML Schema What This Unit About This unit will describe the use of the Xml Schema to define the syntax, structure and vocabulary that can be used within an XML document.What You Should Be Able to Do After completing this unit, you should be able to: Define a document element Describe attri

2、bute declarations Describe entity declarationsHow You Will Check Your Progress Accountability: Lab exercise Nov. 2000Unit 11. XML Schema References /TR/xmlschema-1/ XML Schema Part 1:Structures w3.ort/TR/xmlschema-2/ XML Schema Part 2:Datatypes Objectives Define a document element Describe ent

3、ity declarations Describe attribute declarationsNov. 2000Unit 11. XML SchemaWhat is a Schema? Next generation of DTDs Simple text file Can be a separate file Can be embedded within the XML file Nov. 2000 Unit 11. XML SchemaThe Root Element Hello,world! Goodbye,world! Nov. 2000 Unit 11. XML SchemaEle

4、ment Type Declaration Syntax: Allowed Element Contents For Example:An element declaration in the DTD and the corresponding tag in the XML document: Hello,world! Nov. 2000 Unit 11. XML SchemaDeclaring Child Elements Where one element will contain other elements. For Example: John smith Nov. 2000 Unit

5、 11. XML SchemaCompositor Compositor(sequence,choice,all)specifies required occurences. minOdccurr and maxOccur parameters specify the the minimum and maximum number of occurrences. Default is 1. Parameters are on elementTypeRef in compositor OR compositor itself to allow person to contain any numbe

6、r of fname/iname sequences where the Iname i s option,eg: Nov. 2000Unit 11. XML SchemaSchema Content Model ElementselementMeaningExampleDescriptionsequence“and” in specified orderTITLE and AUTHOR in that order choice“or”TITLE or AUTHORall“and” in any orderITLE and AUTHOR in any orderNov. 2000Schema

7、Content Model Elements (Cont) ElementMeaningExampleDescriptionminOccur=“0”“optional”,but no more than one is allowedTITLE element does not have to be present, but if it is, there can be no more than onemaxOccur=“*”minOccur=“0”element can be present in any number,including 0Any number(including 0)of

8、TITLE elements can be presentMaxOccur=“*”At last one of the element must be presentAt last one or more TITLE elements must be presentNov. 2000 Unit 11. XML SchemaContent Types Element content:Where an element contains only child elements. Compositor of elementReference Mixed content:Where an element

9、 may contain a mixture of text and additional child elements. elementType name=REVIEW Nov. 2000 Unit 11. XML SchemaDeclaring an Empty Element Syntax: eg:definition eg:XML Document Nov. 2000 Unit 11. XML SchemaIncluding Comments in a Declaration Syntax: eg: Nov. 2000 Unit 11. XML SchemaReferencing Sc

10、hema Declaration Schema file and XML file are always separate files: Filename:hello.xml Hello,world! Filename:greeting.xsr Nov. 2000 Unit 11. XML SchemaAttributes in an XML Document Example usage within an XML file: Why did the chicken cross the road? To get to the other side. Nov. 2000 Unit 11. XML

11、 SchemaDeclaring Attributes in a Schema Attribute-list declarations Syntax: attributeDefault attributeValue The attribute declaration is defined within the element or within an attribute Group. Nov. 2000Declaring Attributes in a Schema(Cont) The Schema declarations: Hardcover Paperback Hardcover Nov

12、. 2000Unit 11. XML SchemaAttribute TypesAttribute Type Description IDMust have unique values within the element.In the example below, TYPEID is of the ID type, and so requires unique values within the range of ROOK element.See Spot Run Jack and JillIDREF,IDREFSMust contain an ID valuestringCan conta

13、in any kind of character databooleanstring with two values,true or falseintegerMathematical concept of integer, no fixed maximum sizedecimalNumbers,including non-integer,with precision and scale 53.22realNumbers,including non-integer, with exponent 5.33E12datetimeSQL and ISO standards of data 2019-1

14、2-31binaryStrings of binary datauriUniform Resource identifier Reference as defined by IETFNov. 2000 Unit 11. XML SchemaAttributes Example The XML file: The Joys of Computing Nov. 2000 Unit 11. XML SchemaEntities Schema does not currently have any built-in entities. It is likely that the current XML

15、 1.0 built-in entities will be used. The five built-in entities in XML 1.0: - greater than“ -":quote -&apos:apostrophe -&ersand & Nov. 2000 Unit 11. XML Schema Declaring Entities Syntax: character sting represented For example: schema declaration: textEntity name=prodnameACME Calendar XML fil

16、e: -Thank you for choosing &prodname;as your primary scheduling program. When rendered by a user agent,the final text would read: -Thank you for choosing ACME Calendar as your primary scheduling program. Nov. 2000 Unit 11. XML SchemaParameter Entity Next Generation Parameter Entities in XML 1.0 will

17、 be replaced by: Attribute Groups-for grouping attribute definitions together. Model Groups-for grouping content model definitions together Archetypes-for group attribute definitions and model definitions together Nov. 2000 Unit 11. XML SchemaArchetypes Syntax: content type attribute specification w

18、here content type is datatypeRefcontent modelmodelGroupRef attribute specification is attrDeclattrGroupRef to refer to the archetype entity: Nov. 2000 Unit 11. XML SchemaArchetype-Example Nov. 2000 Unit 11. XML SchemaAttribute Groups Syntax: Attribute Declarations Example: . to refer to the attribute group: Nov. 2000 Unit 11. XML SchemaModel Groups Specify groups of element references Syntax: compositormodel group referenceelement reference to define and refer to the model group: . Nov. 2000 Unit 11. XML SchemaWhat We Didnt Cover Archetype refinement Schema Composition-Import/Expor