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ACG 4401

ACG 4401. XML Schemas XML Namespaces XMLink. The XML Foundation. Many participants – an extended family! XML documents – carry data in context Each must be parsed into its component parts XML schemas – define the rules a class of documents must follow

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ACG 4401

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  1. ACG 4401 XML Schemas XML Namespaces XMLink

  2. The XML Foundation • Many participants – an extended family! • XML documents – carry data in context • Each must be parsed into its component parts • XML schemas – define the rules a class of documents must follow • Can be used to validate documents & contents • XSLT – provide processing instructions • Can be used to process XML documents • Namespaces – qualify elements & attributes • Differentiate & associate them with a URI • XPath … XLink … XQuery … • XML Processors are not designed equally!

  3. XML Languages - Schema • Instance Document • Elements (tag sets) meta-data about data • Schema • Well-formatted XML document • Definition: “provide a means for defining the structure, content and semantics of XML documents. in more detail.” (W3C) • Defines structure and contents of Instance Document • Similar to an ER-Diagram for databases • Defines Each Element and Attribute • Its Structure • Includes Business Rules • Cardinalities • Used to Validate Instance Document • Means Instance Document conforms to Schema Rules

  4. XML Schema • .xsd extension • Defines each attribute and extension

  5. Non-Vocabulary Schemas • Root element is a namespace • <xs:schemaxmlns:xs=“http://www.w3.org/2001/XMLSchema”> • xs: = namespace prefix • xmlns:xs defines prefix to use for namespace • “http:www.w3.org/2001/XMLSchema” location of Namespace, where the dictionary is • Prefix is used before each tag xs:tagname • Identify type of Element: • Simple • contain only data • Complex • contain other elements (i.e. Root & Parent) • contain attributes

  6. Simple Element Definition • Declare Name • Declare Type <xs:element name=“ID” type=“xs:string”/> • Type= • Defines the data type: • string • Integer • date • decimal • other types

  7. Complex Element (Parent) • Declares Name • Declares type • Declares Structure

  8. Complex Element (Parent) xml <xs:element name="Party"> <xs:complexType> <xs:sequence> <xs:element ref="PartyName" minOccurs="1"maxOccurs="1"/> <xs:element ref="PostalAddress" minOccurs="1" maxOccurs="1"/> <xs:element ref="Contact"minOccurs="0" maxOccurs="1"/> </xs:sequence> </xs:complexType> </xs:element>

  9. Complex Element (attribute) • Declare Name • Declare Type • Define element and attribute(s)

  10. Complex (Attribute) xml <xs:element name="PriceAmount"> <xs:complexType> <xs:simpleContent> <xs:extension base="xs:decimal"> <xs:attribute name="currencyID" type="xs:string”use="required"/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element>

  11. Create a Schema from a non-vocabulary instance document • Identify types of elements • Simple • Complex – Parent • Complex – Attribute • Create Prolog • Create Root element • Work down from 1st element to last

  12. Vocabularies & Schemas • XBRL & UBL are vocabularies • XBRL for Financial Reporting • UBL for Business Documents • Vocabularies are designed using • Agreed upon element names • Agreed upon element types • Agreed upon element sequence/structure • Defined by Schemas

  13. Vocabularies and Namespaces • Namespace • A Unique Identifier • Unique Prefix refers to URI • Points to where information in an XML Document can be found. (URI) • Attribute of Root Element • Definition: “XML namespace: In XML, a namespace is a collection of names, identified by a URI reference, that are used in XML documents as element types and attribute names. In order for XML documents to be able to use elements and attributes that have the same name but come from different sources, there must be a way to differentiate between the markup elements that come from the different sources.” (Webopeida) (Technical Information from W3.org) • Used to preclude naming collisions • Method for distinguishing between the same element name for different elements • <inv:id>10001</inv:id> ... • <employee:id>18897</employee:id>

  14. UBL Schemas • Schemas for each document type • Common Basic Components • Defines Simple Elements • Defines Complex (attribute) Elements • Prefix: cbc • Common Aggregate Components • Defines Complex (Parent) Elements • Prefix: cac

  15. Declaring a Namespace (in the UBL instance document) <Catalogue xmlns="UBLCatalogueDocument" xmlns:cbc="UBLCommonBasicComponents" xmlns:cac="UBLCommonAggregateComponents"> • Since UBLCatalogueDocument does NOT have a prefix any element in the instance document without a prefix relates to this namespace. • UBL Catalogue Instance with namespaces

  16. Creating UBL Document Schemas • Declare NameSpaces and qualifiers • Import necessary Schemas • Define Root Element • Reference Reusable data components • Declare Cardinalities

  17. 1. UBL Namespace Declaration in Root Element <?xml version="1.0" encoding="UTF-8"?> <xs:schemaxmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="UBLCatalogueDocument" xmlns="UBLCatalogueDocument" xmlns:cbc="UBLCommonBasicComponents" xmlns:cac="UBLCommonAggregateComponents" elementFormDefault="qualified" attributeFormDefault="unqualified">

  18. Namespace Clarification • targetNamespace="UBLCatalogueDocument“ • The schema being created/used is applied to the UBLCatalogueDocument namespace • elementFormDefault="qualified“ • Element names will use a namespace prefix • CAC: • CBC: • attributeFormDefault="unqualified“ • Attribute names will not use a namespace prefix

  19. 2. UBL Import <xs:importnamespace="UBLCommonBasicComponents" schemaLocation="http://www.buec.udel.edu/whitec/UBLCommonBasicComponents/UBLCommonBasicComponentsSchema.xsd"/> <xs:importnamespace="UBLCommonAggregateComponents" schemaLocation="http://www.buec.udel.edu/whitec/UBLCommonAggregateComponents/UBLCommonAggregateComponentsSchema.xsd"/>

  20. 3. UBL Root Element (Catalogue) <xs:element name="Catalogue"> <xs:complexType> <xs:sequence> <xs:elementref="cbc:ID" minOccurs="1" maxOccurs="1"/> <xs:element ref="cbc:Name" minOccurs="1" maxOccurs="1"/> <xs:element ref="cbc:IssueDate" minOccurs="1" maxOccurs="1"/> <xs:element ref="cac:ProviderParty" minOccurs="1" maxOccurs="1"/> <xs:element ref="cac:ReceiverParty" minOccurs="1" maxOccurs="1"/> <xs:element ref="cac:CatalogueLine" minOccurs=”1” maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> </xs:element> Put it all together: The Entire Schema

  21. Validating XML • Ensure that Instance Document • Follows business rules • Data types are correct • Data is properly sequenced

  22. XML Linking Language • XLink • Uses attributes to describe relationships between elements • Simple: HTML type links • Extended: More complex Relationship links

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