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JEST represents persistent Java object graph in a schema-compliant XML. The schema is metamodel-driven and hence invariant to particular domain model.
The schema jest-instance.xsd is as follows:

Code Block
xml
xml
titleMetamodel-driven schema for JEST XMLxml
<!-- ========================================================================= -->
<!-- Schema for serialized persistence instance graph                          -->
<!-- ========================================================================= -->
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
	attributeFormDefault="unqualified" elementFormDefault="qualified"
	version="1.0">

	<xsd:annotation>
		<xsd:documentation><![CDATA[
         Describes closure of managed persistence instance.
         Each instance is described by all its loaded persistent attribute.
         The related instances are resolved within the document root.
         Document root represents zero or more instances. 
          
         The file must be named "jest-instance.xsd".
         ]]>
		</xsd:documentation>
	</xsd:annotation>

    <!-- The root element of the document contains zero or more instances -->
	<xsd:element name="instances">
		<xsd:complexType>
			<xsd:sequence>
			    <xsd:element name="uri"         minOccurs="1" maxOccurs="1" type="xsd:anyURI"/>
			    <xsd:element name="description" minOccurs="0" maxOccurs="1" type="xsd:string"/>
				<xsd:element name="instance"    minOccurs="0" maxOccurs="unbounded" type="instance-type" />
			</xsd:sequence>
			<xsd:attribute name="version" type="xsd:string" />
		</xsd:complexType>
	</xsd:element>

	<!-- The root element for a single instance. Children of this element are persistent attribute -->
	<!-- Persistent Attributes occur in order. The order is determined by the attribute category.  -->
	<!-- Attribute category is determined by the enumerated PersistentAttributeType defined in     -->
	<!-- javax.persistence.metamodel and then further refined by id, version, lob and enum.        -->
	<!-- See org.apache.openjpa.persistence.jest.MetamodelHelper for further details.              -->
	<xsd:complexType name="instance-type">
		<xsd:sequence>
			<xsd:element name="id"           type="basic-attr-type"      minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="version"      type="basic-attr-type"      minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="basic"        type="basic-attr-type"      minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="enum"         type="basic-attr-type"      minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="embedded"     type="instance-type"        minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="lob"          type="lob-attr-type"        minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="one-to-one"   type="singular-attr-type"   minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="many-to-one"  type="singular-attr-type"	 minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="element-collection" type="collection-attr-type" minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="one-to-many"  type="collection-attr-type" minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="many-to-many" type="map-attr-type"        minOccurs="0" maxOccurs="unbounded"/>
		</xsd:sequence>
		<xsd:attribute name="id" type="xsd:ID" use="required" />
	</xsd:complexType>

	<!-- A reference to another instance within the same(?) document -->
	<xsd:complexType name="ref-type">
		<xsd:simpleContent>
			<xsd:extension base="xsd:string">
				<xsd:attribute name="id" type="xsd:IDREF" />
			</xsd:extension>
		</xsd:simpleContent>
	</xsd:complexType>
	
	<!-- A null reference                                            -->
	<xsd:complexType name="ref-null">
		<xsd:simpleContent>
			<xsd:extension base="xsd:string">
			</xsd:extension>
		</xsd:simpleContent>
	</xsd:complexType>

	<!-- Basic Attribute has a name and its runtime type   -->
	<!-- non-null value appears as text content.           -->
	<!-- null value appears as attribute with empty text . -->
	<xsd:complexType name="basic-attr-type">
		<xsd:simpleContent>
			<xsd:extension base="xsd:string">
				<xsd:attribute name="name" type="xsd:string" use="required" />
				<xsd:attribute name="type" type="xsd:string" use="required" />
				<xsd:attribute name="null" type="xsd:boolean" />
			</xsd:extension>
		</xsd:simpleContent>
	</xsd:complexType>
	
	<!-- Large Binary Objects (LOB) represented as hex array -->
	<xsd:complexType name="lob-attr-type">
		<xsd:simpleContent>
			<xsd:extension base="xsd:hexBinary">
				<xsd:attribute name="name" type="xsd:string" use="required" />
				<xsd:attribute name="type" type="xsd:string" use="required" />
				<xsd:attribute name="null" type="xsd:boolean" />
			</xsd:extension>
		</xsd:simpleContent>
	</xsd:complexType>

	<!-- Singular attribute is a reference to another instance or a null reference. -->
	<xsd:complexType name="singular-attr-type">
		<xsd:choice>
			<xsd:element name="null" type="ref-null" />
			<xsd:element name="ref" type="ref-type" />
		</xsd:choice>
		<xsd:attribute name="name" type="xsd:string" use="required" />
		<xsd:attribute name="type" type="xsd:string" use="required" />
	</xsd:complexType>

	<!-- Collection attributes list their members with their runtime type -->
	<!-- Members can be basic or other managed instance                   -->
	<xsd:complexType name="collection-attr-type">
		<xsd:sequence>
			<xsd:element name="member" type="member-type" minOccurs="0"
				maxOccurs="unbounded" />
		</xsd:sequence>
		<xsd:attribute name="name" type="xsd:string" use="required" />
		<xsd:attribute name="type" type="xsd:string" use="required" />
		<xsd:attribute name="member-type" type="xsd:string" use="required" />
	</xsd:complexType>

	<!-- Map attributes list their entries with runtime type of key and value    -->
	<!-- Both key and value can be independently basic or other managed instance -->
	<xsd:complexType name="map-attr-type">
		<xsd:sequence>
			<xsd:element name="entry" type="entry-type" />
		</xsd:sequence>
		<xsd:attribute name="name" type="xsd:string" use="required" />
		<xsd:attribute name="type" type="xsd:string" use="required" />
		<xsd:attribute name="key-type" type="xsd:string" use="required" />
		<xsd:attribute name="value-type" type="xsd:string" use="required" />
	</xsd:complexType>

	<!-- Value of a member of basic type. -->
	<xsd:complexType name="basic-value-type">
		<xsd:simpleContent>
			<xsd:extension base="xsd:string">
				<xsd:attribute name="null" type="xsd:boolean" />
			</xsd:extension>
		</xsd:simpleContent>
	</xsd:complexType>

	<!-- Value of a member of a collection/map -->
	<xsd:complexType name="member-type">
		<xsd:choice>
			<xsd:element name="basic" type="basic-value-type" />
			<xsd:element name="null" type="ref-null" />
			<xsd:element name="ref" type="ref-type" />
		</xsd:choice>
	</xsd:complexType>

	<!-- Denotes entry of a map element -->
	<xsd:complexType name="entry-type">
		<xsd:sequence>
			<xsd:element name="key"   type="member-type" minOccurs="1" maxOccurs="1" />
			<xsd:element name="value" type="member-type" minOccurs="1" maxOccurs="1"  />
		</xsd:sequence>
	</xsd:complexType>
	
</xsd:schema>

...

The example shows a Person (primary key p1) who is her own partner.

Code Block
xml
xml
titleExample of Object Graph with Circular Referencexml
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<instances>
  <instance id="Person-p1">
    <basic name="id" type="String">p1</basic>
    <basic name="dob" type="Date">Fri Sep 08 00:00:00 CDT 1989</basic>
    <basic name="firstName" type="String">Mary</basic>
    <basic name="gender" type="Gender">Female</basic>

    <basic name="lastName" type="String">Smith</basic>
    <singular name="address" type="Address">
      <instance id="Address-101">
        <basic name="id" type="long">101</basic>
        <basic name="country" type="String">C1</basic>
        <basic name="state" type="String">State1</basic>
        <basic name="street" type="String">Street1</basic>

        <basic name="zip" type="int">10001</basic>
      </instance>
    </singular>
    <singular name="partner" type="Person">
      <ref id="Person-p1"/>
    </singular>
  </instance>
</instances>

...