Sentence:  Class guessers for the Xerox tagger assign potential POS [part-of-speech] tags to unknown words according to a <WSD>surface analysis</WSD> of the word form. In addition to the common practice of mapping POS tags according to the words' suffixes, this implementation makes use of the case of the initial letter of a word, which is highly significant for POS assignment in German. 
Meaning of the word marked with <WSD> tags:  Any valid analysis of a word's morphology regardless of whether it represents its etymology in the strict sense of that word (that is, the historical origin); for example, the word (biology) has a surface analysis of (nocat=1) although it was not coined as the combination of those (combining forms) (in fact predating them). The word can validly be viewed as an example of words ending in the suffix (-ology) even though it was not coined as one (whereas many analogous but newer words were thus coined, such as (immunology)).