def parseitemclassdata(data):
    """Turns a JSON dictionary of class/subclass item data into:

    data[class][subclass] = (classname, subclassname)

    Args:
        data (dict): JSON dictionary containing class/subclass data

    Returns:
        dict: Multidimensional dictionary containing class/subclass data
    """
    classes = {}
    data = data["classes"]

    for c in data:
        sc = c["subclasses"]
        for s in sc:
            if not c["class"] in classes:
                classes[c["class"]] = {}

            classes[c["class"]][s["subclass"]] = (c["name"], s["name"])

    return classes