Proceedings - Österreichische Gesellschaft für Artificial Intelligence

each soft restriction soft m set on an phrase ph i
is associated a number of slots num(soft m ) that
a candidate translation cannot claim if it does not
fulfil the condition.
Whenever a phrase P H 1 covered by a validated
candidate translation ct includes a phrase ph 1 ,
we consider that the translation of ph 1 should be
included by the second n-gram P H 2 also covered
by ct. We associate to such soft restriction
soft m a num(soft m ) = claims(ct, b n ). In
other words, if P H 1 includes ph 1 , we consider
that for claims(ct, b n ) slots of ph 1 its translation
should be included in P H 2 . For example if “la
bella casa” in Italian is validated as the translation
of “das schöne Haus” in German then, for any bitext
containing both, phrases included in “la bella
casa” should translate to phrases included in “das
schöne Haus” and vice-versa.
Also, whenever a phrase P H 1 covered by
a validated candidate translation ct is included
in a phrase ph 1 and slots(ph 1 , b n ) =
slots(P H 1 , b n ), we consider that the translation
of ph 1 should include the other phrase P H 2 covered
by ct. We associate to such soft condition
soft m a num(soft m ) = claims(ct, b n ). In
other words, if P H 1 is included in ph 1 and both
phrases have the same original number of slots
then P H 2 should be included by the translation
of ph 1 at least claims(ct, b n ) time(s). For example
if “bella” is validated as the Italian translation
of “schöne” in German then phrases including
“bella” and having the same number of slots
should translate into phrases including “schöne”
and vice-versa.
6.5.3 Combining restrictions and updating
the remaining candidate translations
Since we do not try to align phrases, combining
the restrictions violated by a candidate translation
must take into account that some restrictions may
apply on slots that overlap between one another.
Regarding strict restrictions, we can ensure that
two restrictions concern a set of slots that don’t
overlap even if we don’t explicitly affect a given
slot to a given strict restriction. For example, for
a phrase ph i with m + n slots in a given bitext
that is covered by two validated candidate translations
ct e and ct h , we can tell that m slots have
been locked by ct e and n slots by ct h and cannot
be claimed by other candidate translations without
stating explicitly which slot is locked by ct e
or ct h .
Whenever a soft restriction is involved, simply
adding the number of slots covered by the restrictions
would be incorrect because we cannot establish
if the restrictions violated do not overlap
on a same set of slots. For example, let’s consider
a bitext containing both one occurrence of
“la bella casa” in Italian and “das schöne Haus”
in German with only one occurrence of “bella”
and “schöne” in the whole bitext and two validated
candidate translations ct i and ct j that associate
“la bella” with “das schöne” and “bella casa”
with “schöne Haus”. A candidate translation ct k
that covers “bella” but does not associate it with
“schöne” would violate both soft restrictions set
by ct i and ct j . Simply adding the number of slots
covered by the soft restrictions set by ct i and ct j
would prohibit ct k to claims two slots when only
one is actually available. The same reasoning can
be extended to phrases having more than one slot
and to the combination soft and strict restrictions.
We thus look for the maximum number of slots
that a remaining candidate translation ct occurring
in a bitext b n and covering two phrases ph i
and ph j can claim. For each covered phrase ph,
we compute a value max soft(ph, ct, b n ) corresponding
to the maximum of the num(soft m )
values of the soft restrictions violated by ct for
covering ph in b n .
We then compute the value
sub claims(ph, ct, b n ) corresponding to the
number of slots originally available slots(ph, b n )
minus the maximum value between the number
of slots locked by strict restrictions locks(ph, b n )
and max soft(ph, ct, b n ),
sub claims(ph, ct, b n) =
slots(ph, b n) − max(locks(ph, b n), max soft(ph, ct, b n)).
Finally we update the claims(ct, b n ) value in a
similar manner as it has been first initialized
claims(th, b n) = min(sub claims(ph i, ct, b n),
sub claims(ph j, ct, b n))
It is important to note that generally only one
slot is available for most phrases in a bitext.
Therefore, conflicting with just one restriction in
a bitext, be it a strict or a soft, is enough for most
candidate translations to loose their occurrence.
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Proceedings of KONVENS 2012 (LexSem 2012 workshop), Vienna, September 21, 2012