[SalesForce] Must specify a {http://www.w3.org/2001/XMLSchema-instance}type during creating Approval process using metadata API

I am trying to create Approval process using Metadata API but unable to figure out what i am missing.

One doubt is XML don't have any symbol why which me or Salesforce could identify on which object i am creating the approval process.

I have tried by using wsdl and REST API but no success.

Receiving error:

soapenv:ClientMust
specify a {http://www.w3.org/2001/XMLSchema-instance}type attribute
value for the {http://soap.sforce.com/2006/04/metadata}metadata
element

Using WSDL:

        MetadataService_Chris.Metadata_Chris service = new MetadataService_Chris.Metadata_Chris();
        service.SessionHeader = new MetadataService_Chris.SessionHeader_element();
        service.SessionHeader.sessionId = UserInfo.getSessionId();

        MetadataService_Chris.ApprovalProcess process = new MetadataService_Chris.ApprovalProcess();
        process.fullName = 'TestApproval';
        process.active = true;
        process.allowRecall = true;

        MetadataService_Chris.ApprovalSubmitter submitter = new MetadataService_Chris.ApprovalSubmitter();
        submitter.type_x = 'user';
        submitter.submitter = UserInfo.getUserId();

        List<MetadataService_Chris.ApprovalSubmitter> submitters = new List<MetadataService_Chris.ApprovalSubmitter>();
        submitters.add(submitter);

        process.allowedSubmitters = submitters;
        process.label = 'Test Approval';
        process.showApprovalHistory = true;

        //MetadataService_Chris.Metadata mdata = new MetadataService_Chris.Metadata();
        //mdata.fullName = 'Test Metadata';

        MetadataService_Chris.AsyncResult[] results = service.create(new List<MetadataService_Chris.Metadata> { process });
        System.debug('----------------------------------  '+results);

Using REST:

        HTTP h = new HTTP();
        HTTPRequest req = new HTTPRequest();
        req.setMethod('POST');
        req.setHeader('Content-Type', 'text/xml');
        req.setHeader('SOAPAction', 'create');

        String xml = /*'<?xml version="1.0" encoding="UTF-8"?>'+
        '<env:Envelope xmlns:env="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">'+
           '<env:Header>'+
              '<SessionHeader xmlns="http://soap.sforce.com/2006/04/metadata">'+
                 '<sessionId>'+userinfo.getSessionId()+'</sessionId>'+
              '</SessionHeader>'+
           '</env:Header>'+
           '<env:Body>'+
              '<create xmlns="http://soap.sforce.com/2006/04/metadata">'+
                 '<metadata xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">'+ // xsi:type="Account"
                        '<active>false</active>'+
                        '<allowRecall>true</allowRecall>'+
                        '<allowedSubmitters>'+
                           '<submitter>005i00000033nPoAAI</submitter>'+
                           '<type />'+
                        '</allowedSubmitters>'+
                        '<label>Test Approval</label>'+
                        '<recordEditability />'+
                        '<showApprovalHistory>true</showApprovalHistory>'+
                 '</metadata>'+
              '</create>'+
           '</env:Body>'+
        '</env:Envelope>';

        req.setBody(xml);
        req.setCompressed(false);
        req.setEndpoint('https://na15.salesforce.com/services/Soap/m/29.0');
        HTTPResponse resp = h.send(req);
        System.debug(resp.getBody());

I have tried with several combinations but no success. In back-end XML formed as:

<?xml version="1.0" encoding="UTF-8"?>
    <env:Envelope xmlns:env="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
       <env:Header>
          <SessionHeader xmlns="http://soap.sforce.com/2006/04/metadata">
             <sessionId>00Di0000000k2kv!AR4AQBKoHVPE4sLzQbOuu.CAU0o1qsMldVzPRDGFStoboKik1lt_WUNe.5YiHR2MQOlrKExKf05TnYB_7SO7kPdwQGfjwNis</sessionId>
          </SessionHeader>
       </env:Header>
       <env:Body>
          <create xmlns="http://soap.sforce.com/2006/04/metadata">
             <metadata>
                <active>true</active>
                <allowRecall>true</allowRecall>
                <allowedSubmitters>
                   <submitter>005i00000033nPoAAI</submitter>
                   <type />
                </allowedSubmitters>
                <label>Test Approval</label>
                <recordEditability />
                <showApprovalHistory>true</showApprovalHistory>
             </metadata>
          </create>
       </env:Body>
    </env:Envelope>

The problem is "xsi:type="ApprovalProcess" which throws exception.