Probably the best known examples of enumerations as strings are in CSS. CSS values are lower cased with hyphens for a multi-word-value. We should use that for inspiration.

This property has some parallels with the CSS [clear](http://www.w3.org/TR/CSS2/visuren.html#propdef-clear) property. Can the values be:

    "none"
    "back"
    "front"
    "both"