SOLUTIONS TO ISSUES DEPEND ON THE KNOWLEDGE REPRESENTATION
Frederick
B.
Tho~psoH
~li£orni~ Institute
o£ Technology
Pasadena,
C~,li?orni~
In orpQnizing This p~nel, our
Ch(tirmon, Bob Moore, expressed the view
thor too often discussion o? Hoturra'l
l,',nguage
occess To
dol'o
buses has focused
on
whot
p~rticulc~r
systems c~*n
or
cQnnot
do, ro'ther than on underlying issues. He
Then sd~irr4bly proceeded to orgonize the
prJnel nr. ound issues
r-qther th~n
systems.
In responding, I qttempted to ?rr.iMe
my
~'emr~rk~,
on
e,ach o? his five issues in r~

gener~l woy
that would not
reflec~
~y ,wn
pr4rochiul experience qnd interest, At one
point I thought th~.~t I h~d s,cceeded quite
well. Howe,.,er~ offer t~king a cleorer eyed
view~ it wqs
qpparent
thor
my
remarks
reflec~c;d
~ssumptions obout knowledge
representotion
theft
were
by no
Meons
univers~ol. This suggests ,a
sixth
issue
which I would like
~o r~omin~t,.,:
Are there
r'eolly
useful generolizNtions
~bou~ comput~Jtionr~l linguistic issues
th<~t c~r,e independer~t of r~ssumptions
concerning

knowledq,.~
r'epre.sentcition?
I will come back
'to
this sixth issue
q?ter discussing t'i~e ?ire cho-~.,n by our
Choir~or,.
I ~s~,e
@i
: A.q.ctreq~te_ F.~nc.t i
o ns qnd
~uon.!i.S.~.
F'irst~
let
us
csst
this issue in o
~omewhot di.fferent way, Irl m~.sny
d~tc, b~se
~:ituo.1io~s., there ,',r'e closes of
individuals olI of
whose
Me~bers shcire the
~.:oMs ot'~ributes ~and thus, ÷'rum the point
of view o.f the dr~'t~ bose~ ,ir~
.~.ndi~tJ,vuish,~ble. 'Thus there is no need
~o
~dd
,*II
of the~.~. ,

individuals Qs
~':.e. prw, o't(~
entities,
To use
Bob
Moore's
ex,a~ple., i? ,:z DEPARTMENT tile
h~
,.~ ~ield
Cur NUMPER"OF-EMPL.OYEES~ it strands To
r'~~,.~on th~L~' the pczr!icul~:~r [ndividu~.~Is ;~ho
~c~uolly existed in
the v,ar'ious
dep~r't~tHH~'~
would r~o~ be
s~ep,ar,~tely
r'~pr'e,>~:~,~ed
in
the.
dc~~obose
(for
uther'wise
there would be o redund,.~ncy whose
, :or1~J' :'~.;nc,./
would
be
h~r'd to police),
In
~u,-'h
:~i~u,:~io~s

we
need the. notion of ~'~
",~olleL'ti,~e," homely ~a
single
dr~tr~
b,ase
object ~'hot ~,.,l(e~
the;
pl~.'~c~,
of
ra number of
.ir~divid~.,r, ls
end which c,~r~
c,ar'ry their
cot~on ,~r!'r.Lbul'e~ together with one
,'~ddition,il item o? in~'ormotion,
nomely
~heir r~umber, Thus ~ DEPARTMENT could
h~ve ~s o single ~ember su,:h ~ collective
,.,f employees, indeed it could hove severQl
such collective MeMbers ond other
indiuidu~l
MeMbers ~s well. The procedure
thor is c~11ed when onswering "how Mony"
~nd "nu(~ber of" questions would know the
dif?eren(-e between subcl~s,~es, indiuidurJl
(~eMber~ r~nd collective ~embers~ it would
know to recurse on subclc~sses, ~.~dd one to
its coun'~ for individual MeMbers ond odd
the

indicoted'
number" to
its
count-for'
collec:tJve MeMbers. This ~ppe~rs To be
uni?ied ?r,~ework th,,t will h(1~d].e ,~11 of
the c:~s,e~ mentioned in Bob Moore's
stQtement
o?
Issue #I.
Issue '~2: .T,,iM,e, qnci T_e_p._s_e
I should like to split this issue into
two, The ?irst sub-issue is the problem of
hondling continuusly varying phenoMeno>
~.~uch ra,:,
1he MoveMent of ships~ the
chqnging
of
relotiv,.,
~zMount,:~ of
ingredients in che~ic~l reQc~ions~ or "the
percent completions o9 tnsks, Here it is
~pp(~rent thr~t
eoch instonce will
require s
~peci~lized procedure to hKLnflle
interpol,~tion. Ships cr~nnot s~il Qcross
Irjnd~
thus
~n interpolation procedure thor

produce~ the position of o ship on The
bdJsis
of
its
points o~' dep~u'tur~, ond
des'tinotJ, orl will need To know obout the
c0cAstlines
o?
conrinents~
Movements
to
cheMJ.c~l equilibriums. ~re not line~r~ t~sk
coMpletioNs depend on changing personnel
ossignf~ents. Just rls we coMputotionol
linguists
provide to our syste(,~ u~er the
(.opobili'¢y to introduce into his dotr~ b~se
system ~uch notion.'~
,a~
loc,=rions of"
port.~
end ship~, etc.> we Must ,also provide ~he
Met:ins by which he crarl define such
'.:ontinuously vr~ryir',~ p,ar(~meters r~s
position in such wqys th~.~t ~tpproprJ.ote
in~erpo],',tions c~zn be ~de. by ~he generol
system in con.junctioN with the p,lrtlculor
defini'tJon. For"
example,
'the

user
mr~y
de?ine~ "position o? X" in ter~ of
('.r~lcu]:'~%ions, perhops extensive> involvin 9
~he ,~ctu~.~l 9eo~etr'y of the ~eq~.
169
The second sub-issue on which
I
would
like. to coMmen~ concerns ~hose c~ses
where discrete
~ime
intervals provide rin
r.~dequ(l~(~, r, epresentr.~tion o@ "(he time
aspects relevr, nt to the da'tq bqse. In
*hese coses~ if` ~he
time inf`orf~tion
is
coMplete~
i,e,,
rictu(:l
st~Ir~lng
~nd ending
rimes of`
rill
events ripe
recorded
in ~he
d~tQ b,~se, the h~ndling o? time is rrither
strriightforwrird, However this c~se of"~en

does not ripply, Consider the ?allowing
e xQmp], e.
:
"The Ki~tyhriwk ~rrived in London Monday,
The Mriru will soil ?ram London Friday.
Will th~ Kitcyhowk ~nd Hrir'u h~ve been in
London ~t the s~e time?"
One is
teP~pted ~o
ollow the
computer
lo
give q
response: "Possibly,"
however
the introduction of` a three uolued logic
is Tr'qught with well known d~ngers of" its
own, A More protrricted response gets in
the way o~ clnuse [~bedding; how does one
hrind].e~
"Will
si~ips
thrit have been
in London
together
sriil
together?"
One
rins~er would
be:

"The Ki~i'.vh~.~wk rirrived IriF~t Mondc~y~
the Mor, u
will soil
next
Friday,
I~
they
will
hrive b~.en there
qt
the same
~iMe~
then
not
rill
ships ~hr~t were in
London together will sriil 1'ogether~ bu~
they
v:ould
be
the only exceptions,"
Choosing ~ relev~mt dic~gnosti,:
t,eessoge~ os obove., is o Mrijor r~nd
di£?icul't coMputotion,:~l liguis~c issue
(:~oing
w~],l
beyound questions
concerning
t iMe ~lII,J
*,ense,

Issue
%3 :
_~_~r.ULi.f,,.! i.]:Lg
~,p_xo ~u.esx
ions
This i~
a deep~
philosoph[c,ll
ques'~io,~. CoMput~,i. onol
linguists
hove
pr, ogrw:s~ed beyond tl'w. ,:onsiderqtion o?
~:~ing].e ~,.~'ntences,
r~nd
rire seeking
~o
,?ollow ~che 'focus of
,]
dirjlogu~. ~
(And
iden'ti.fy
'the
theme
o? ~
discourse,
This
is
ev~.r}~uqlly ,4n
infinite
regr'e,~ ultLMritely

invo].vi~g
cross
cul~'ur~l
brickgrounds,
~he
(perh~/ps
Mc, chiclvellion>
irlt,~.n~ o~ those
,.,,ha co~,trol ~he u'~e
oT o
particular
ctpplicr:~Lon;.
,:It,
Dv~: the
eng.i.neering
prob].ef~,
c~ le,~s'r ~
~he present eta're o£
• the
c~rt,, i~
:~Lapl~_:
whr, t
response
is
~os~
:Jse£u] "~.o
~'he use.r? Consider
kwo
possible
(n~swers ~o ,.'he Following question:

"Who ,.~on,.'~ges
ec~cl~
deportment?"
Ai:
"No single person M~nages ~ll o~
the depor~Ments,"
dept. A ~rin~ger
A
Unless ~here were ~n undue number o~"
dep~rtMents involved~ the second is
(.Ice, Ply prei~erred~ ?or
it ~uf`f`ices
"even
i?
the f`irst were intended,
I.
our own
experie.,ce, "e~ch" con usefully be
in'terpreted
,~s
coiling
~or ~,
l~b~.led list
,~s
onswer in
~l~ost oll coses, The
diff"icul¢ies of" being t~ore clever
ore
great
arid will o~°ten

result
in
coMbinqtori(ll explosion, I (~M
sur~.,
for o
]ong tJi~e
into
the future,
we will
be
seeking simple
solutions that (?.~) ore
respon,~,ive in
Mos~
c(~ses> (b) provide the
needed inforMr~eion~ even though redund~nt
Jn SOMe cGse~
rind
(c) M~ke c:lerir
the
Misinterpre~rition
in
the
£ew
c,~se where
this
rirjses, even though
these
solutions
May

violrite strict
linguistic
rinqlysis,
Issue
#4 :
~4e_.,r
vi.n~ ~.eM~n~ ic~.!_l y_
CoMp ke
X
In presenting i~his issue Io the prlnel~
Bob Moore used the ?ollowlng three
questions ris ~n example:
"Is
John Jones
(, child
oF
rln HIT
rll U MIIU ~- ? "
"Is one o£ John ~ones~s p~rsnts on HIT
(ll u~)n u.~ 9"
"Did e.i'~her poren~ o~" /ohn ]ones t~ttend
HIT?"
The
appqre.t problem is 'the
po.~sibilit~,, of" Multiple des(-rLptions~
o~'ten
involving
dispor'rite
words~
.For,

getting
~lt dril:t,
in
~he
datri h~se, In
(.JeBicjrlillg
our" systems)
we recognize two
tru~h~
which ~ppe,~r'
to
con,flick: (q)
the
v~lue o.F MiniMizing the reduhdrincy o£
.LnforMf~tion in the dqt(t b,1~e. (b) the
necessi-iy
o£ non-independent words
in the
vocobulr~ry,
In
our' own work~
,~s
Mo.~t o?
you know, we hove stressed the use
o?
definitions c~s
u Me~zns
of
,'Ich.i.eving o
synthe~i~ oF

'~-hese
*.wo princ:iples. I
recoMMe.d it to you u~ ri v~.r~ o~p.i~ul tool
in hondlino problems like Bob presents. We
illustrate
how Bob~s excLMpl~;
c,.~n
be
hr~ndled
:
"de'fini~ion'child:converse o~" parent
ve.rb:John ",;it~end"~ HITmJoh. is
' 'tud~.t,~
o?
HIT
dei'~inition:~lu~,r-'s'person who hod
been ~ student"
170
The
ubove
three questions then
ore
?.~n~1 y zed ~s:
"3"ohn )ones
is
(converse
o? parent)
o?
a
person

who
had been ~ student
of
HIT?"
"One of
~ohn
/ones's
parents
is a
person
who had been a student o-t HIT?"
"W~s
ei'ther parent o£ ~ohn ~ones
a
student of HIT?"
I do not wish to slur' over' the fact
that ~.=
definition Mech~.,nisM
~ust be
hifhly
:sophis~'~coted in i~s handling of f'ree
variables,, bu~ our ~xperience i~dic~*te.~
tha~ ~l'~s can be done quite
s~tisfac toril y.
Issue
#5:
Hu~ti-Fil#._~uer'ie_.s
This issue has been
stated
by Bob in

terms of G tr'~dixional Multiple file de=to
b,~se s'tructure, This issue h~s its
coun'ter'p~rt
in seM~intic
neT data.
base
structures discussed
in pr4per,~
on
k~ow].edge representation, Since we use
such q semantic net s~ructure
For,
our
data, le't me rephrase the issue in those
~erMs. In Dab's st~tteMerlt of the issue~ he
uses tl'~ example
of
the
SHIP
file and the
PORT .File; wl}ere the SHIP f.ile
h,~s fields
-For ho~,~¢ port, departure port and
destination port.
P,~,r'allelLnq
his
exa~p](:,
let
us consider ~h~ phrase:
"London

ship",
Suppose ~hr.~t (q)
there
w~s
ship n,~r~ed London, nnd (b) London was a
ho~e por~, port
of
depqrtur~
and
des'tir~o'~ion~ not necessarily o~" the same
ship, Then "London ship" is four ways
,~Mbifuous~ ~e~ning: (i)
the
ship London~
(2) London (ho~e port) ships, (3) l.ondon
(depr~r~-ur~z par-X) ~hips
~nd
(4) London
(destinq~ion port) ~hips, In this
for~ul~tion of
the
probleM~ ~II
is
easy~
insofar ~ the phr~s~;
"Londo,
ship" is
not
'.iisc~Mbigu~Ted
in

con'text~ the user is
informed
o?
the ~lMbiguous M~lrlincjs (Ind the
,~ssoci,:~'ted responses. The difficulty
urises
when There ar'~.
pos.~ibile
.i.nterpr,.'<'~'ations
?,~r~her (~field,
Fort
Collins is
n,.~.itl')er
,~
port
nor ~ ship~
however ~.he
headqunr'ters of
the
ABC
Sllippirt,# CoMpany
i~
there un,:l they own
~everol
ships.
Wh,~'t
?~r'e
we
~o ~e~n
by

"For"t
Collins
.~hip"?
The.~e ~u-e
pr'obleM~
tha't wer.e ?irs~ ~1'*:acked by
Quillicm, and
f
qM not ~ur'e ~'t~(~'t unyone I ~.~ c~dded
to
hi~
!=emii~ol ~r~r~ly':sj.s o£
lhe~,
In
our
own
work~
we
he*re
s~uppecJ
at "once
re~-1oved"
,.:onnec.'tJons.,
,:~ il].u~r~zTed by
the four-
w~,~y ,~mbiq,)ity
,Ibove.
Issue
~6:
Solution~ tO. Is~q.es_._D~.~.n

As
I look back on the abuv~ reMork~
t:oncerning Sob's
five
issues~ it becomes
~pparent
thr~t the u.~efulness
of
these
remarks
depends
on
The degree one is aware
of the
knowledge
representatLon that
underlie.s the solution suggested, For
ex~Mple~ in the case of the last
,Ls~ue,.
il ~
one only knew about traditional file
structures~ finding paths theft link fields
in More Than one file appears all
but
unsolvable, Even
if
one is accustomed to
semantic
net
structures~ the

viability of
finding connective pnth.~ is highl~
dependccn~ on the
existence of back links
between attributes and their ,~rgu~en~s and
values. Adding a definitional capability~
other
thun
simple abbreviqtions
~md
synonyf4s~ Burns on the
way free variables
ore handled
in
9ener~Jl
cmd on the
opporo.tus +'or binding theM) for example,
in processing the de+'inition:
"dei~]nition:are~:length times
width"
when applied ~o q class> say "areas of
;~hips", how does one ensure ~hat he will
ob rain
:
"lengTh(i) ~k width(i)
fop
i
=
I
to

number
of
ship~"
rather Thonl
"lengTh(i) ~ width(j)
?or i~j = i to nut.~ber o? ship =.?"
It coMe~ down to how variables qre
MainTained in The underlying knowledge
represen'tat ion,
One is £or'ced to conclude ~hat the
basis ~'or the integrcltion of the syntax
cu,d ~emonTics o? coMput,~tionr~l linguistic
systems
i~ -ccoMplished wh n
tile
d¢ci~4ion~ on knowledge r'epre~en~tiun ~r'e
Made, Di~Jcussions 0£ #ur
w:~rLous
sotut.En.n
to ~he J~sues of coMputaTional linguistics
can Meaningfully ~uke
pl<~ce
only in terM~
uf the,:,~ underlying knowledge
repr'eser~tot ions.
171