[CSS21] First-Line Clarification

Hi,

I've been trying to understand First-Line but it seem ambiguous.

The specification says: "The :first-line pseudo-element applies special styles to the contents of the first formatted line of a paragraph", but it doesn't define what a paragraph is.  It later states that "The 'first formatted line' of an element may occur inside a block-level descendant in the same flow".  It seems like although most browsers (IE 8, Firefox, Chrome, Safari and Opera) define a paragraph to be the first formatted line of an element, but the specification leaves it up to the UA what a paragraph is. Is this by design or should the first-line pseudo-element always apply to the first formatted line of an element?

Thanks

Josh