Sentence:  The basic principle governing case is:<br />(20) "The <WSD>Case</WSD> filter:"<br />A lexicalized NP must bear a <WSD>Case</WSD> feature in S-structure.<br />‘<WSD>Case</WSD>' with a capital C is here understood not as morphologically marked case, but as an abstract feature which will be present even in languages such as Swahili or Chinese which lack case marking on NPs (it is usually assumed however, that <WSD>Case</WSD> will be congruent with morphological case where the latter is present). 
Meaning of the word marked with <WSD> tags:  abstract feature of a noun phrase that determines its function in a sentence, such as a grammatical case and a position.