understanding semcor corpus structure h

I'm learning NLP. I currently playing with Word Sense Disambiguation. I'm planning to use the semcor corpus as training data but I have trouble understanding the xml structure. I tried googling but did not get any resource describing the content structure of semcor.

<s snum="1">
<wf cmd="ignore" pos="DT">The</wf>
<wf cmd="done" lemma="group" lexsn="1:03:00::" pn="group" pos="NNP" rdf="group" wnsn="1">Fulton_County_Grand_Jury</wf>
<wf cmd="done" lemma="say" lexsn="2:32:00::" pos="VB" wnsn="1">said</wf>
<wf cmd="done" lemma="friday" lexsn="1:28:00::" pos="NN" wnsn="1">Friday</wf>
<wf cmd="ignore" pos="DT">an</wf>
<wf cmd="done" lemma="investigation" lexsn="1:09:00::" pos="NN" wnsn="1">investigation</wf>
<wf cmd="ignore" pos="IN">of</wf>
<wf cmd="done" lemma="atlanta" lexsn="1:15:00::" pos="NN" wnsn="1">Atlanta</wf>
<wf cmd="ignore" pos="POS">'s</wf>
<wf cmd="done" lemma="recent" lexsn="5:00:00:past:00" pos="JJ" wnsn="2">recent</wf>
<wf cmd="done" lemma="primary_election" lexsn="1:04:00::" pos="NN" wnsn="1">primary_election</wf>
<wf cmd="done" lemma="produce" lexsn="2:39:01::" pos="VB" wnsn="4">produced</wf>
&l开发者_如何学运维t;punc>``</punc>
<wf cmd="ignore" pos="DT">no</wf>
<wf cmd="done" lemma="evidence" lexsn="1:09:00::" pos="NN" wnsn="1">evidence</wf>
<punc>''</punc>
<wf cmd="ignore" pos="IN">that</wf>
<wf cmd="ignore" pos="DT">any</wf>
<wf cmd="done" lemma="irregularity" lexsn="1:04:00::" pos="NN" wnsn="1">irregularities</wf>
<wf cmd="done" lemma="take_place" lexsn="2:30:00::" pos="VB" wnsn="1">took_place</wf>
<punc>.</punc>
</s>

• I'm assuming wnsn is 'word sense'. Is it correct?
• What does the attribute lexsn mean? How does it map to wordnet?
• What does the attribute pn refer to? (third line)
• How is the rdf attribute assigned? (again third line)
• In general, what are the possible attributes?

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The format is described in the "doc/cxtfile.txt" file in the SemCor 1.6 archive; for some reason, documentation is not included in later versions.