When a client requests my .../resources/user URL with a HTTP GET I get the following response:

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<collection>
    <User id="5">
        <Password>DC647EB65E6711E155375218212B3964</Password>
        <FirstName>Super</FirstName>
        <LastName>Admin</LastName>
        <Role id="4">
            <Description>Default Guest Role</Description>
            <Group id="2">
                <Description>Default Guest Group</Description>
                <Name>GuestGroup</Name>
            </Group>
            <Name>Guest</Name>
        </Role>
        <Role id="3">
            <Description>Default Super Admin Role</Description>
            <Group id="1">
                <Description>Default Admin Group</Description>
                <Name>AdminGroup</Name>
            </Group>
            <Name>SuperAdmin</Name>
        </Role>
        <Username>superadmin</Username>
    </User>
    <User id="6">
        <Password>DC647EB65E6711E155375218212B3964</Password>
        <FirstName/>
        <LastName>Guest</LastName>
        <Role id="4">
            <Description>Default Guest Role</Description>
            <Group id="2">
                <Description>Default Guest Group</Description>
                <Name>GuestGroup</Name>
            </Group>
            <Name>Guest</Name>
        </Role>
        <Username>guest</Username>
    </User>
</collection>

For data transport efficiency purposes I would also like the client to be able to request a short version of this response. Something like:

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<collection>
    <User id="5">
        <Password>DC647EB65E6711E155375218212B3964</Password>
        <FirstName>Super</FirstName>
        <LastName>Admin</LastName>
        <Role id="4" />
        <Role id="3" />
        <Username>superadmin</Username>
    </User>
    <User id="6">
        <Password>DC647EB65E6711E155375218212B3964</Password>
        <FirstName/>
        <LastName>Guest</LastName>
        <Role id="4" />
        <Username>guest</Username>
    </User>
</collection>

What is the best way to identify a full and a short request from the client and why? Client technology should be agnostic. Server technology is Java EE 7

A few options I thought of myself:

• Sub level webservices like .../resources/user/short
• Different webservices like .../resources/user2
• Use a custom HTTP parameter lik Accept-Length : Short
• Use the HTTP request field Expect : Short