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The content of a JEST response can be XML or JSON.

String-based representation of persistent Java object graphs in either XML or more succinct JSON form has to address the critical issue of circular reference. Because a query can result
in to an object graph that contains cycles. JSON, at this point of writing, does not address circular reference. Hence JEST introduces special semantics within JSON format to refer to
instances in a serialized graph.

XML Representation

JEST represents persistent Java object graph in a schema-compliant XML.

Example of a serialized object graph

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

<?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>

The above XML document is compliant to a XML schema.
The jest-instance.xsd schema is as follows:

<!-- ========================================================================= -->
<!-- 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="instance" 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 -->
	<xsd:complexType name="instance-type">
		<xsd:sequence>
			<xsd:element name="basic" type="basic-attr-type"  minOccurs="0" maxOccurs="unbounded" />
			<xsd:element name="lob" type="lob-attr-type"      minOccurs="0" maxOccurs="unbounded"/>
			<xsd:element name="embedded" type="instance-type" minOccurs="0" maxOccurs="unbounded" />
			<xsd:element name="singular" type="singular-attr-type"  	minOccurs="0" maxOccurs="unbounded" />
			<xsd:element name="collection" type="collection-attr-type"	minOccurs="0" maxOccurs="unbounded" />
			<xsd:element name="map" 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:attribute name="id" type="xsd:IDREF" />
	</xsd:complexType>
	
	<!-- A null reference                                            -->
	<xsd:complexType name="ref-null">
	</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 can be a reference or another instance. -->
	<xsd:complexType name="singular-attr-type">
		<xsd:choice>
			<xsd:element name="null" type="ref-null" />
			<xsd:element name="ref" type="ref-type" />
			<xsd:element name="instance" type="instance-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="instance" type="instance-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>
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