Requests are held by the query tag with the attribute type holding the type of the request:

<?xml version="1.0" encoding="UTF-8"?>
<envelope>
    <header>
        <actor>test</actor>
        <user>test</user>
        <password>test</password>
        <version>1.6.1</version>
        <timestamp>20030424170000</timestamp>
    </header>
    <query type="type" product="hotel">
        <!-- QUERY -->
    </query>
</envelope>

The response is held by the response tag with the attribute type holding the type of the response:

<?xml version="1.0" encoding="UTF-8"?>
<envelope>
    <header>
        <version>1.6.1</version>
        <timestamp>20030424170000</timestamp>
    </header>
    <response type="type">
        <!-- RESPONSE -->
    </query>
</envelope>

In case of error the type attribute will contains the word error

<?xml version="1.0" encoding="UTF-8"?>
<envelope>
    <header>
        <version>1.6.1</version>
        <timestamp>20030424170000</timestamp>
    </header>
    <response type="error">
        <!-- ERROR MESSAGE -->
    </response>
</envelope>