Current release (v0.3-b52)

With parameter user=$username

<xmlstats>
    <server>
        <version>$bukkit-version</version>
        <name>$server-name</name>
        <ip>$server-ip</ip>
    </server>

    <users count="$count">
        <user>
            <name>$username</name>
            <categories count="$count">
                <category>
                    <name>$catname</name>
                    <items count="$count">
                        <item [id="$itemid"]>
                            <name>$itemName</name>
                            <value>$itemValue</value>
                        </item>
                        ...
                    </items>
                </category>
                ...
            </categories>
        </user>
    </users>
</xmlstats>

With parameter sum=$username

<xmlstats>
    <server>
        <version>$bukkit-version</version>
        <name>$server-name</name>
        <ip>$server-ip</ip>
    </server>

    <sum>
        <users count="$count">
            <user>
                <name>$username</name>
            </user>
        </users>
        <stats>
            <categories count="$count">
                <category>
                    <name>$catname</name>
                    <items count="$count">
                        <item [id="$itemid"]>
                            <name>$itemName</name>
                            <value>$itemValue</value>
                        </item>
                        ...
                    </items>
                </category>
                ...
            </categories>
        </stats>
    </sum>
</xmlstats>

Previous release (v0.2-b35)

Without parameter

<stats>
    <player name="*">
        <category name="$catname">
            <stat [id="$itemID"] name="$itemName" value="$value" />
            ...
        </category>
        <category name="$catname2">
            ...
        </category>
        ...
    </player>
</stats>

With parameter player=$playername

<stats>
    <player name="$playername">
        <category name="$catName">
            <stat [id="$itemID"] name="$itemName" value="$value" />
            ...
        </category>
        ...
    </player>
</stats>