XML and Validation Tools

SchemaSchematron

XML

•eXtensible Markup Language (XML)– A metamarkup language.– The basic unit is called an element

– Fairly similar to HTML

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<tag attribute="attribute value">element value</tag>

Element

AttributeOpening tag Closing tag

Metamarkup?

•What does metamarkup mean?– There is no predefined and fixed set of tags for

XML– XML allows implementers to define their own set

of tags to meet their needs

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Examples• Office Open XML (ISO/IEC 29500)• Geography Markup Language (ISO 19136)

Markup – ESRI ArcGIS 10 XML

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<idCitation> <resTitle>Title</resTitle> <date> <createDate>20110906</createDate> </date></idCitation>

Markup – ISO 19139 XML

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<gmd:citation> <gmd:CI_Citation> <gmd:title><gco:CharacterString>Title</gco:CharacterString> </gmd:title> <gmd:date> <gmd:CI_Date> <gmd:date> <gco:Date>2011-09-06</gco:Date> </gmd:date> <gmd:dateType> <gmd:CI_DateTypeCode codeList="...#CI_DateTypeCode" codeListValue="creation">creation</gmd:CI_DateTypeCode> </gmd:dateType> </gmd:CI_Date> </gmd:date> </gmd:CI_Citation></gmd:citation>

Well-Formed

•XML has strict rules, e.g.:– There must be one, and only one root

element– All elements must have an opening and

closing tag– Element names are case sensitive:

• <citation/> is different from <Citation/>

– XML conforming to the rules is said to be well-formed

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Well-Formed

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<idCitation> <resTitle>Title</resTitle> <date> <createDate>20110906</createDate> </date></idCitation>

<idCitation> <resTitle>Title</ResTitle> <date> <createDate>20110906 </date></idCitation><idPurp>Summary</idPurp>

No closing tag

Opening and closing tagsare different

Two root elements

Structure

•The markup defines data structure:– It signifies which elements are

associated– It can define semantics:

– It says nothing about how to display data (there are exceptions to this rule)

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<date> <createDate>20110906</createDate></date>

XML is machine readable

•And…– Human readable… honestly

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Schema and Validation

Schema

•Schemas document the elements that are permitted in an XML application

– XML that conforms to a schema is said to be schema-valid

– XML that does not conform to a schema is said to be invalid

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XML Schema Definition Language

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<xs:complexType name="CI_Citation_Type"> ... <xs:complexContent> <xs:extension base="gco:AbstractObject_Type"> <xs:sequence> <xs:element name="title" type="gco:CharacterString_PropertyType"/> <xs:element name="alternateTitle" type="gco:CharacterString_PropertyType" minOccurs="0" maxOccurs="unbounded"/> <xs:element name="date" type="gmd:CI_Date_PropertyType" maxOccurs="unbounded"/> ... </xs:sequence> </xs:extension> </xs:complexContent></xs:complexType>

Markup – ISO 19139 XML

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<gmd:citation> <gmd:CI_Citation> <gmd:title><gco:CharacterString>Title</gco:CharacterString> </gmd:title> <gmd:date> <gmd:CI_Date> <gmd:date> <gco:Date>2011-09-06</gco:Date> </gmd:date> <gmd:dateType> <gmd:CI_DateTypeCode codeList="...#CI_DateTypeCode" codeListValue="creation">creation</gmd:CI_DateTypeCode> </gmd:dateType> </gmd:CI_Date> </gmd:date> </gmd:CI_Citation></gmd:citation>

Schematron

•Schematron is:– A schema language for XML

• Document Schema Definition Language (DSDL)

– Written in XML– It’s an ISO Standard – ISO 19757-3

Find out more at: http://www.schematron.com/

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Why use Schematron?

•XSD schema is unable to test some constraints:

– The ability to specify a choice of attributes

– The ability to vary the content model based on the value of an element or attribute (this sort of constraint is common in the ISO 19115 logical model)

•Implementing profiles (e.g. MEDIN):– With Schematron there’s no need to edit

the underlying standardised XSD

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Validation Workflow

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ISO 19139 Schema Validation

Valid?ISO 19139 Table A.1 Constraints

Schematron

MEDIN Profile Schematron

Valid?

Valid?

END FAIL

END PASS

YES

YES

YES

NO

XSD Schema Validation

Schematron Validation

Validation Tools

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Select profile

XSD Schema

Schematronschemas