<?xml version="1.0" encoding="utf-8" ?>
<xsd:schema
        xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <xsd:element name="auctions">
        <xsd:complexType>
            <xsd:sequence>
                <xsd:element name="products">
                    <xsd:complexType>
                        <xsd:sequence>
                            <xsd:element name="product" minOccurs="0" maxOccurs="unbounded">
                                <xsd:complexType>
                                    <xsd:sequence>
                                        <xsd:element name="name" type="xsd:string"/>

                                        <xsd:element name="description" minOccurs="0">
                                            <xsd:complexType mixed="true">
                                                <xsd:choice maxOccurs="unbounded" minOccurs="0">
                                                    <xsd:element name="it" type="xsd:string" minOccurs="0"
                                                                 maxOccurs="unbounded"/>
                                                    <xsd:element name="a" minOccurs="0" maxOccurs="unbounded">
                                                        <xsd:complexType>
                                                            <xsd:simpleContent>
                                                                <xsd:extension base="xsd:string">
                                                                    <xsd:attribute name="href" use="required"/>
                                                                </xsd:extension>
                                                            </xsd:simpleContent>

                                                        </xsd:complexType>
                                                    </xsd:element>
                                                </xsd:choice>

                                            </xsd:complexType>
                                        </xsd:element>

                                        <xsd:element name="expired" minOccurs="0">
                                            <xsd:complexType>
                                           <!-- leer Lassen um Tag ohne Content zu haben!-->
                                            </xsd:complexType>
                                        </xsd:element>


                                        <xsd:element name="category" minOccurs="0"
                                                     maxOccurs="unbounded">
                                            <xsd:simpleType>
                                                <xsd:restriction base="xsd:string">
                                                    <xsd:enumeration value="book"/>
                                                    <xsd:enumeration value="movie"/>
                                                    <xsd:enumeration value="music"/>
                                                </xsd:restriction>
                                            </xsd:simpleType>
                                        </xsd:element>
                                    </xsd:sequence>

                                    <xsd:attribute name="id" use="required">
                                        <xsd:simpleType>
                                            <xsd:restriction base="xsd:integer">
                                                <xsd:minInclusive value="0"/>

                                            </xsd:restriction>
                                        </xsd:simpleType>
                                    </xsd:attribute>
                                    <xsd:attribute name="auctionEnd" type="xsd:date"
                                                   use="required"/>


                                </xsd:complexType>
                                <xsd:unique name="productId">
                                    <xsd:selector xpath="products/product"></xsd:selector>
                                    <xsd:field xpath="@id"></xsd:field>
                                </xsd:unique>
                            </xsd:element>
                        </xsd:sequence>
                    </xsd:complexType>

                </xsd:element>


                <xsd:element name="users">
                    <xsd:complexType>
                        <xsd:sequence>
                            <xsd:element name="user" maxOccurs="unbounded" minOccurs="0">
                                <xsd:complexType>
                                    <xsd:sequence>
                                        <xsd:choice>
                                            <xsd:element name="fullname" type="xsd:string"/>

                                            <xsd:element name="name">
                                                <xsd:complexType>
                                                    <xsd:all>
                                                        <xsd:element name="firstname" type="xsd:string"/>
                                                        <xsd:element name="lastname" type="xsd:string"/>
                                                    </xsd:all>
                                                </xsd:complexType>
                                            </xsd:element>
                                        </xsd:choice>

                                        <xsd:element name="email" minOccurs="0" maxOccurs="unbounded" type="xsd:string"/>

                                        <xsd:element name="balance" type="xsd:nonNegativeInteger"/>

                                    </xsd:sequence>
                                    <xsd:attribute name="username" type="xsd:string" use="required"/>

                                    <xsd:attribute name="password" type="xsd:string" use="required"/>
                                </xsd:complexType>
                            </xsd:element>
                        </xsd:sequence>
                    </xsd:complexType>
                </xsd:element>


                <xsd:element name="bids">
                    <xsd:complexType>
                        <xsd:sequence>
                            <xsd:element name="product" minOccurs="0" maxOccurs="unbounded">
                                <xsd:complexType>
                                    <xsd:sequence>
                                        <xsd:element name="bid" maxOccurs="unbounded">
                                            <xsd:complexType>
                                                <xsd:simpleContent>
                                                    <xsd:extension base="bidInt">
                                                        <xsd:attribute name="user" type="xsd:string"/>
                                                    </xsd:extension>
                                                </xsd:simpleContent>
                                            </xsd:complexType>
                                        </xsd:element>
                                    </xsd:sequence>
                                    <xsd:attribute name="id" type="xsd:nonNegativeInteger"/>
                                </xsd:complexType>
                            </xsd:element>
                        </xsd:sequence>
                    </xsd:complexType>
                </xsd:element>

            </xsd:sequence>
        </xsd:complexType>

        <xsd:key name="userKeys">
            <xsd:selector xpath=".//users/user"></xsd:selector>
            <xsd:field xpath="@username"></xsd:field>
        </xsd:key>
        <xsd:keyref name="userRef" refer="userKeys">
            <xsd:selector xpath=".//bids/bid"></xsd:selector>
            <xsd:field xpath="@user"></xsd:field>
        </xsd:keyref>

        <xsd:key name="productKeys">
            <xsd:selector xpath=".//products/product"></xsd:selector>
            <xsd:field xpath="@id"></xsd:field>
        </xsd:key>
        <xsd:keyref name="productRef" refer="productKeys">
            <xsd:selector xpath=".//bids/product"></xsd:selector>
            <xsd:field xpath="@id"></xsd:field>
        </xsd:keyref>

    </xsd:element>

    <xsd:simpleType name="bidInt">
        <xsd:restriction base="xsd:integer">
            <xsd:minInclusive value="0"/>
        </xsd:restriction>
    </xsd:simpleType>


</xsd:schema>