Model Based Schema: Ivoa Registry Videocon 2004/05/13-14 Gerard Lemson 1

Model based schema

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

1

UML to XSD binding • • • • •

Start with UML model Generate XMI from UML Define UML to XSD binding Implement binding as XSLT script Run script

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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Sample UML aas::A aas

-f

-id : integer -description : string

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aas::F

0..1

-c

aas::B -data : real

cees::C -name : string

*

1

*

cees::D

cees

cees::D1

IVOA Registry videocon 2004/05/13-14

-dees

Gerard Lemson

cees::D2

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Mapping “methodology” • Simple: as “1-1” as possible • Preserve semantics – Attributes owned by class – Children in parent-child composition relation owned by parent/container

• Focus on type definitions, complexType-s mainly • Valid documents (global elements) defined with respect to, but separate from the type definitions • Default document: contains an element definition under the root for each “root-entity-class”. • Possibility of reuse of schema type definitions in different special purpose document definitions. IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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Mapping: packages aas

• •

Package -> (target)namespace, in own file Dependency -> import of dependent namespace and file

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"

targetNamespace="urn://xml.registry.gavo.org/aas" elementFormDefault="qualified" attributeFormDefault="unqualified" version="0.1"

xmlns:aas="urn://xml.domainmodel.gavo.org/aas" xmlns:base="urn://xml.domainmodel.gavo.org/"

xmlns:cees="urn://xml.domainmodel.gavo.org/cees">

cees

IVOA Registry videocon 2004/05/13-14

... <xsd:import namespace="urn://xml.registry.gavo.org/cees" schemaLocation="./cees.xsd" />

Gerard Lemson

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Mapping Classes aas::A -id : integer -description : string

• • •

Every class -> globally defined complexType isAbstract -> abstract=“true” Attribute -> element of simplish-type, either built-in, or also generated

<xsd:complexType name="A" abstract="true"> <xsd:complexContent> <xsd:extension base="base:DataObject">

<xsd:sequence> <xsd:element name="id" type="xsd:integer" /> <xsd:element name="description" type="xsd:string"/>

aas::B

<xsd:element name="f" type="aas:F" minOccurs="0"/>

-data : real



IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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Mapping Classes II aas::A -id : integer -description : string

•

Inheritance -> extension of base class

<xsd:complexType name="B"> <xsd:complexContent>

<xsd:extension base="aas:A"> <xsd:sequence> <xsd:element name="data" type="xsd:double" /> <xsd:element name="c" type="cees:CProxy" />

aas::B -data : real

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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Mapping Associations I cees::C -name : string

*

-dees

cees::D

IVOA Registry videocon 2004/05/13-14

• •

Parent-child relationship Composition -> element of appropriate complexType

<xsd:complexType name="C"> <xsd:complexContent> <xsd:extension base="base:DataObject"> <xsd:sequence> <xsd:element name="name" type="xsd:string"/>

<xsd:element name="dees" type="cees:D" minOccurs="0" maxOccurs="unbounded" />

Gerard Lemson

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Mapping associations II aas::A -id : integer -description : string

-f 1

aas::F

0..1

• “Owned references” -> element of appropriate type <xsd:complexType name="A" abstract="true"> <xsd:complexContent> <xsd:extension base="base:DataObject"> <xsd:sequence> <xsd:element name="id" type="xsd:integer" /> <xsd:element name="description" type="xsd:string" />

<xsd:element name="f" type="aas:F" minOccurs="0"/>

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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Mapping associations III -c

aas::B -data : real

-name : string *

• • • •

cees::C

1

Problem: shared references (also aggregations), many-to-1/many relations Does one want to replicate elements that are shared ? Multiple B-s can reference same C. Solutions: – Don‘t care, map ala composition, with cardinality maxOccurs=“0” – Use ID/IDREF or KEY/KEYREF declarations. Requires the C to exist in same document, possibly completely, i.e. containing all substructure. – Use explicit “proxy ” element, for example using a GUID (IVOA identifier?), which can/must be resolved before the referenced object can be obtained. This is the most tricky thing I think about XML schemas, how to properly embed the semantics of the shared association into a logical schema design.

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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Default Document •

Root entity classes map also to an element in a document, but in a separate schema doc, depending on the type defining schema documents.

<xsd:schema targetNamespace="urn://xml.registry.gavo.org/doc" ...

xmlns:doc="urn://xml.registry.gavo.org/doc" xmlns:cees="urn://xml.registry.gavo.org/cees" xmlns:aas="urn://xml.registry.gavo.org/aas"> <xsd:import namespace="urn://xml.registry.gavo.org/cees" schemaLocation="./cees.xsd" /> <xsd:import namespace="urn://xml.registry.gavo.org/aas" schemaLocation="./aas.xsd" /> <xsd:element name="sample"> <xsd:complexType><xsd:sequence>

<xsd:element name="c" type="cees:C" minOccurs="0" maxOccurs="unbounded" /> <xsd:element name="a" type="aas:A" minOccurs="0" maxOccurs="unbounded"/> <xsd:element name="b" type="aas:B" minOccurs="0" maxOccurs="unbounded"/>

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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Comments • • • •

Single inheritance mapping, only extension, no substitutionGroup Requires xsi:type construct (next slide) to indicate which precise class is used. No element ref construct. No global elements for attributes and contained classes. Analogy to Java binding : – Complex type <=> class – Typed <element> declarations <=> Fields in class definition – Default document <=> a main method using the classes. – Global elements <=> variable declarations local to main method

• Can support a more involved special purpose document to/from the “official” default registry document using XSLT scripts for example (view concept). • See also: http://www.xml.com/pub/a/2002/08/07/wxs_uml.html and others •

Probably more …

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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xsi:type • xsi:type=‘’ construct from the xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance” in document required to indicate precise class: <doc:sample xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:doc="urn://xml.registry.gavo.org/doc" xmlns:cees="urn://xml.registry.gavo.org/cees"> <doc:c> a C a D1 a D2

IVOA Registry videocon 2004/05/13-14

Gerard Lemson

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