gistfile1.txt

var MyClass = Model("MyClass",
    require("store/xmldb").PropertyStore()),
    {
        properties: {
            foo: {type: String},
            bar: {type: Integer, optional: true, index: true},
            baz: {type: Date, optional: true},
            xml: String /*perhaps some kind of special class I can test with instanceof*/
        }
    }
);


PUT /MyClass/
{id: "hello", foo: "quux", xml: "<a>aaa</a>"}

GET /MyClass/hello
returns =>
{id: "hello", foo: "quux", xml: {"$ref": "#", mediaType: "text/xml"}

GET /MyClass/hello
Accept: text/xml
returns =>
Content-Type: text/xml
<a>aaa</a>

Also,

GET /MyClass/hello.xml
returns =>
Content-Type: text/xml
<a>aaa</a>