def _parse_common(tag):
    """Returns a tuple of (name, modifiers, dtype, kind)
    for the specified tag. Any missing attributes will have values of None.
    """
    if "modifiers" in tag.attrib:
        modifiers = re.split(",\s*", tag.attrib["modifiers"].strip())
        if "" in modifiers:
            modifiers.remove("")
    else:
        modifiers = None

    if "name" in tag.attrib:
        name = tag.attrib["name"]
    if "type" in tag.attrib:
        dtype = tag.attrib["type"]
    else:
        dtype = None
    if "kind" in tag.attrib:
        kind = tag.attrib["kind"]
    else:
        kind = None

    return (name, modifiers, dtype, kind)