xsi:nil="true" in parameter definition?

[Jaime Stuardo]

Hi everybody,

I have this structure definitions in a webservice:

public struct ReembType
{
public double porcentaje;
public double monto;
}

public struct prestacion
{
public string codigo;
public double copago;
public ReembType reembolso;
};

public struct PersonType
{
public long rut;
public char dv;
};

public struct TransType
{
public DateTime fecha;
public long numero_bono;
public string codigo_isapre;
public string error;
};

public struct QueryType
{
public PersonType titular;
public PersonType beneficiario;
public TransType transaccion;
public prestacion[] prestaciones;
};

One of the input parameters of a web method is of QueryType type.

When I see the SOAP protocol definition, I get this:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<Consulta xmlns="http://security.cl/">
<datos>
<titular>
<rut>long</rut>
<dv>char</dv>
</titular>
<beneficiario>
<rut>long</rut>
<dv>char</dv>
</beneficiario>
<transaccion>
<fecha>dateTime</fecha>
<numero_bono>long</numero_bono>
<codigo_isapre>string</codigo_isapre>
<error>string</error>
</transaccion>
<prestaciones>
<prestacion>
<codigo>string</codigo>
<copago>double</copago>
<reembolso xsi:nil="true" />
</prestacion>
<prestacion>
<codigo>string</codigo>
<copago>double</copago>
<reembolso xsi:nil="true" />
</prestacion>
</prestaciones>
</datos>
</Consulta>
</soap:Body>
</soap:Envelope>

Why does reembolso parameter is shown as xsi:nil="true"? what does it mean?
how can I make it to be shown he same way as, for example, titular type?

Thanks in advance
Jaime