The top-level node, Sign, is completely unspecified and has the null value. At the Word node, information about inflectional neutralisation and constraints on the interpretation mapping is specified. For reasons which cannot be argued here, the default interpretation for HEAD SURF is the null value.
Sign:
<> == .
Word:
<> == Sign
<plur surf phon> == Morphophon:<Interpretation>
<surf phon> == Morphophon:<Interpretation>
<plur surf graph orth> == Morphograph:<Interpretation>
<surf graph orth> == Morphograph:<Interpretation>
<surf> == Interpretation
<plur surf> == Interpretation
<mean> == Interpretation
<plur mean> == Interpretation
<plain> == Interpretation
<plain plur mean> == <plain mean>
<operator sing> == "<operator>"
<operator plur> == "<operator>"
<operator plain mean> == "<operator mean>"
<operator mean> == OF
<sing> == <>
<modi sing> == "<modi>"
<modi plur> == "<modi>"
<head plur> == "<head>"
<head surf> ==
<head mean> == <indiv "<mean indiv>">
<indiv exists> == APPLICATION
<indiv mass> == some
<indiv> == one
<head plur mean> == more_than_one
Noun:
<> == Word
<cat surf> == noun
<plain sing> == <plain>
<plain plur> == <plain sing>
<head plur surf graph> == #+ s
<head plur surf> == #+ /Z .
Noun_compound:
<> == Noun
<cat morph> == compound
<plain operator> == "<operator>"
<operator surf> == #.
Noun_derivation:
<> == Noun
<cat morph> == derivation
<operator surf> == +.