Nuspec xml schema from current sources from http://nuget.codeplex.com/SourceControl/changeset/view/6d4458231bb4#src%2fCore%2fAuthoring%2fnuspec.xsd

nuget.xsd

<?xml version="1.0" encoding="utf-8"?>
<xs:schema id="nuspec"
    targetNamespace="{0}"
    elementFormDefault="qualified"
    xmlns="{0}"
    xmlns:mstns="{0}"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
>
    <xs:element name="package">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="metadata" maxOccurs="1" minOccurs="1">
                    <xs:complexType>
                        <xs:all>
                            <xs:element name="id" maxOccurs="1" minOccurs="1" type="xs:string" />
                            <xs:element name="version" maxOccurs="1" minOccurs="1" type="xs:string" />
                            <xs:element name="title" maxOccurs="1" minOccurs="0" type="xs:string" />
                            <xs:element name="authors" maxOccurs="1" minOccurs="1" type="xs:string" />
                            <xs:element name="owners" maxOccurs="1" minOccurs="0" type="xs:string" />
                            <xs:element name="licenseUrl" maxOccurs="1" minOccurs="0" type="xs:anyURI" />
                            <xs:element name="projectUrl" maxOccurs="1" minOccurs="0" type="xs:anyURI" />
                            <xs:element name="iconUrl" maxOccurs="1" minOccurs="0" type="xs:anyURI" />
                            <xs:element name="requireLicenseAcceptance" maxOccurs="1" minOccurs="0" type="xs:boolean" />
                            <xs:element name="description" maxOccurs="1" minOccurs="1" type="xs:string" />
                            <xs:element name="summary" maxOccurs="1" minOccurs="0" type="xs:string" />
                            <xs:element name="releaseNotes" maxOccurs="1" minOccurs="0" type="xs:string" />
                            <xs:element name="copyright" maxOccurs="1" minOccurs="0" type="xs:string" />
                            <xs:element name="language" maxOccurs="1" minOccurs="0" type="xs:string" default="en-US" />
                            <xs:element name="tags" maxOccurs="1" minOccurs="0" type="xs:string" />
                            <xs:element name="dependencies" maxOccurs="1" minOccurs="0">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="dependency" minOccurs="0" maxOccurs="unbounded">
                                            <xs:complexType>
                                                <xs:attribute name="id" type="xs:string" use="required" />
                                                <xs:attribute name="version" type="xs:string" use="optional" />
                                            </xs:complexType>
                                        </xs:element>
                                    </xs:sequence>
                                </xs:complexType>
                            </xs:element>
                            <xs:element name="frameworkAssemblies" maxOccurs="1" minOccurs="0">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="frameworkAssembly" minOccurs="0" maxOccurs="unbounded">
                                            <xs:complexType>
                                                <xs:attribute name="assemblyName" type="xs:string" use="required" />
                                                <xs:attribute name="targetFramework" type="xs:string" use="optional" />
                                            </xs:complexType>
                                        </xs:element>
                                    </xs:sequence>
                                </xs:complexType>
                            </xs:element>
                            <xs:element name="references" maxOccurs="1" minOccurs="0">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="reference" minOccurs="0" maxOccurs="unbounded">
                                            <xs:complexType>
                                                <xs:attribute name="file" type="xs:string" use="required" />
                                            </xs:complexType>
                                        </xs:element>
                                    </xs:sequence>
                                </xs:complexType>
                            </xs:element>
                        </xs:all>
                    </xs:complexType>
                </xs:element>
                <xs:element name="files" minOccurs="0" maxOccurs="1" nillable="true">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="file" minOccurs="0" maxOccurs="unbounded">
                                <xs:complexType>
                                    <xs:attribute name="src" use="required" type="xs:string" />
                                    <xs:attribute name="target" use="optional" type="xs:string" />
                                    <xs:attribute name="exclude" use="optional" type="xs:string" />
                                </xs:complexType>
                            </xs:element>
                        </xs:sequence>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>