Are you confused about how and when to use the Chamber, Division and Keyboard elements? This page should help.

First, an example: consider the following specification. While it's obviously phony, it illustrates a number of interesting practices that are not uncommon, such as one division that's split between two chambers, one chamber that contains two divisions, and floating divisions.

A Simple Representation

Below is a simple representation of the specification given above. The representation, while legal, is a little bogus in that it shows keyboards as being enclosed and containing chambers; strictly speaking, keyboards are not themselves enclosed, nor can they contain chambers. Likewise, stops are not really contained in chambers, ranks are (the Doppelflote). However, the implied meanings should be obvious. Notice how the Division element is used here to represent floating divisions.

<Organ>
    <Keyboard name="Great" order=2>
        <Stop name="Principal" pitch="8"> </Stop>
        <Stop name="Doppelflote" pitch="8" chamber="CHOIR"> </Stop>
        <Coupler from="SOLO" label="Solo on Great"> </Coupler>
        <Coupler from="BOM" label="Bombarde on Great"> </Coupler>
    </Keyboard>
    <Keyboard name="Swell" order=3>
        <Chamber name="flues" enclosed="yes">
            <Stop name="Salicional" pitch="8"> </Stop>
        <Chamber name="reeds" enclosed="yes">
            <Stop name="Oboe" pitch="8"> </Stop>
        <Coupler from="BOM" label="Bombarde on Swell"> </Coupler>
    </Keyboard>
    <Keyboard name="Choir" order=1 enclosed="yes" id="CHOIR">
        <Stop name="Harmonic Flute" pitch="8"> </Stop>
        <Coupler from="SOLO" label="Solo on Choir"> </Coupler>
    </Keyboard>
    <Division name="Solo" id="SOLO" enclosed="yes">
        <Stop name="Clarinet" pitch="8"> </Stop>
    </Division>
    <Division name="Bombarde" id="BOM" chamber="SOLO">
        <Stop name="Tuba" pitch="16" extension="TUBA"> </Stop>
        <Stop name="Tuba" pitch="8" id="TUBA"> </Stop>
        <Stop name="Tuba" pitch="4" extension="TUBA"> </Stop>
    </Division>
</Organ>

A Complex Representation

Below is another representation of the same specification, and this time the representation gives a much more accurate picture of the instrument: chambers contain ranks, some chambers are enclosed, and the console contains stops which control the ranks. Notice that the Division element is used in two ways: first, to separate ranks within a chamber, and secondly, as before, for floating divisions on the console.

<Organ>
    <Chamber name="Great" enclosed="no" id="GtCham">
        <Rank name="Principal" pitch="8" id="GtPrin"> </Rank>
    </Chamber>
    <Chamber name="Swell Flues" enclosed="yes" id="SwFlCham">
        <Rank name="Salicional" pitch="8" id="SwSal"> </Rank>
    </Chamber>
    <Chamber name="Swell Reeds" enclosed="yes" id="SwRdCham">
        <Rank name="Oboe" pitch="8" id="SwOboe"> </Stop>
    </Chamber>
    <Chamber name="Choir" enclosed="yes" id="ChCham">
        <Rank name="Harmonic Flute" pitch="8" id="ChHarmFlt"> </Rank>
        <Division name="Great">
            <Rank name="Doppelflote" pitch="8" id="GtDplFlt> </Rank>
        </Division>
    </Chamber>
    <Chamber "Solo/Bombarde" enclosed="yes" id="SBCham">
        <Division name="Solo">
            <Rank name="Clarinet" pitch="8" id="SoloClar"> </Rank>
        </Division>
        <Division name="Bombarde">
            <Rank name="Tuba" pitch="16" id="BomTuba"> </Rank>
        </Division>
    </Chamber>

    <Console>
        <Keyboard name="Great" order=2 id="GREAT" chamber="GtCham">
            <Stop name="Principal" pitch="8" rank="GtPrin"> </Stop>
            <Stop name="Doppelflote" pitch="8" rank="GtDplFlt"> </Stop>
            <Coupler from="SOLO" label="Solo on Great"> </Coupler>
            <Coupler from="BOMB" label="Bombarde on Great"> </Coupler>
        </Keyboard>
        <Keyboard name="Swell" order=3 id="SWELL" chamber="SwCham">
            <Coupler from="BOMB" label="Bombarde on Swell"> </Coupler>
        </Keyboard>
        <Keyboard name="Choir" order=1 id="CHOIR" chamber="ChCham">
            <Stop name="Harmonic Flute" pitch="8" rank="ChHarmFlt"> </Stop>
            <Coupler from="SOLO" label="Solo on Choir"> </Coupler>
        </Keyboard>
        <Division name="Solo" id="SOLO" id="SOLO" chamber="SBCham">
            <Stop name="Clarinet" pitch="8" rank="SoloClar"> </Stop>
        </Division>
        <Division name="Bombarde" id="BOM" id="BOMB" chamber="SBCham">
            <Stop name="Tuba" pitch="16" rank="BomTuba"> </Stop>
            <Stop name="Tuba" pitch="8" rank="BomTuba"> </Stop>
            <Stop name="Tuba" pitch="4" rank="BomTuba"> </Stop>
        </Division>
    </Console>
</Organ>

In this example, the complex representation doesn't really convey any more information than the simple representation, and the simple representation is probably a better choice. However, the specifications of larger instruments may necessitate the use of some of the techniques illustrated in the complex representation, especially if there are multiple consoles controlling different subsets of a single instrument.