AN INTEGRATED MODEL FOR THE TREATMENT OF TIME 
IN MT- SYSTEMS 
M. Meya J. Vidul 
Siemens CDS EUROTRA-E 
c/Luis Muntadas,5 Ctra. Vallvidriera, 25.27 
CORNELLA, 08940-BARCELONA 08017-BARCELONA 
Spain 
Abstract 
One of the ways to achieve a good translation of 
verbal forms is the morphosp~tactic approach, which consists 
in a function pairing the different morphological tenses 
that occur in a given language with the tenses of the other 
language. Complicated rules must be established to calculate 
the right pair for an expression, because of the amount of 
discrepancies that differmnt languages show with respect to 
each other. 
The way we have chosen to deal with this problem is, 
conversely, the projection of the different values coming 
from verbs (type, processivity, morftense, morfaspect, 
moodrequire~nent), from adverbs, prepositional phrases and 
temporal N~S (deixis, espect, iteration), and from 
subordinate conjunctions (aspect, moodrequirement). 
All this information permits to obtain a final value 
for aspect .~nd tense for the whole sentence, which later on 
i8 percolated, not only to the verb node, but also to the 
the rest of elements conveying information. 
Our proposal relies on the fact that tense/aspect 
calculation is relevant not only for a good translation of 
verbs, but also for a good translation of adverbs, PPs, 
temporal I~.~ and conjunctions, as we have intended to 
demonstrat~ ~n this paper. 
L Introduction 
'1~li~ article deals with a methodology to achieve the 
right t~s~lsiation of temporal expressions by giving account 
of the temporal reference and temporal relations in/ between 
sentences. The task to accomplish is to translate 
sy,%tactic marks into semantic values that decide/ reflect 
the aspectnal value of the sentences. 
Fo3:' o6r treatment of time and aspect we draw on the 
work of Eamp \[1979\] and Partee \[1984\] who have argued for 
taking statos and events as primitives and relations of 
precedanco ~md overlapping between them. The ordering 
relation ~t~n events is crucial for deciding about the 
aspect of the sentences involved. 
~hn presemt proposal presumes an analysis end a 
geme~ation t!omponent that deliver a set of S-trees whose 
leaves cor~:espond to words. The pre-terminals have 
morpbosynta¢:tic and ~elational information. As usual, 
features ar~J percolated and nodes get features assigned. 
~he time/ aspectual problem is dealt with under the 
perspect£~* of MT with the aim of sketching a system that 
can be i~lemented independently of the particular 
formalisms of different MT-systems. 
To outline a general model for the time/aspect 
calculation in MT we subsume a system with PSG rules that 
obtain some sentence structure with no regard to a specific 
grammar type; it could be an augmented PSG, as in METAL, or 
some kind of deep syntactic structure, as it is the case in 
Eurotra. 
The problem is the well known fact that translations 
of temporal expressions in NL does not involve a simple 
mapping of tenses and adverbials. We could just compare 
Spanish, rich ill aspect and tenses vs. German or English. 
That is, a MT dealing with Germanic and Romance languages is 
concerned with different parameters for each language; the 
whole practice in MT systems is to translate morphological 
tenses, and syntactical values into reference times that 
include events or stutes \[Partee 1984\]. 
Once the set of factors and values relevant for the 
specification oi! time, aspect, and mood has been defined, a 
calculation or unification in the form of rules fixes the 
values that must be generated in the target language. Such a 
system must "preserve" the same "semantic interpretation" 
for different language realisations, in order to be able to 
generate the right morphological tenses and periphrasis from 
language to language. 
2. Aktionsart 
Vendler's definition of Aktionsart \[1967\] relies on 
a classification of verbs into sentences. However, we start 
from verb primitives that are categorized (Verb Type) into: 
- stative : to be in love, stand, know.. 
- dynamic : w~ite, arrive, love,.. 
and we take an additional feature "Processive" to mark the 
differences between activities vs. accomplishment, 
ach£evement or quality/state vs. stance (R. Quirk 1985). 
The inherent type of these verb primitives is 
overridden during, the analysis by the morphological tense 
and by the syntactic functions, so that we finally obtain a 
437 
value for the Aktionsart of the whole phrase. 
- write (ancribir): VT = activity, Proc --yes 
(a durative verb) 
- send (enviar) : ~ : activity, Proc --no 
(a punctual verb) 
The original aktionsart of the verb, durative 
activit,y becomes an accomplishment in the sentence "I wrote 
a letter", In Spanish this information must be marked in 
order to choose the right past form. 
l \[escribio \[una caxta\]\] --> VT=activity & proc--no 
~-> tense=Indefinite Past 
\[escrib~a\] --> AKT=activity 
~-> tense=Imperfect 
3. Deixis 
The calculation of the time value, which is always 
expressed as a deictic value relating the speech time to the 
reference time, is obtained out of the deictic values of the 
morphological tenses together with the adverbials present in 
the sentence. For instance, the Spanish present tense has 
the value \[simultaneous and posterior\]. If it al~ears 
with a posterior adverbial, the final value is posterior. 
The deixis assigment in Spanish is reflected in table i. The 
left side is the assigmant in contexts with no temporal 
transposition; the right side shows the assigmant for tense 
transposition. The context for tense transposition is given 
for knowledge and diction verbs. 
Table 1 : Deictic assigmcnt to the tenses in Spanish 
No Tense Transposition I Tense T~ansposition 
.................................. I ........................ Tense Deixis i Deixia 
.................................. I ....................... Present simul, post ~ simul, post 
Past1 ( Inde finido) ant I ant 
Past2 (leper fento) ant I simul 
Future post l post 
Conditional ~ post ............................................................ 
Temporal modifiers can belong to different classes: 
1 - Adverbs: in this case the deictic value comes 
from the dictionary 
2 - PP: the deictic value comes fr~ the 
Preposition 
3 - l~: The deictin value is the result of two 
factors: 
a\] the demostrativas end 
b) the temporal type of the singular noun 
~'s when temporal desiguatora have the 
Deixia \[ant,post\]. When they appea~ with 
a plural definite a~ticle, this is an 
operator that overrides the original 
deixi8 values end yields the iterativa 
aspect. 
438 
i.e. : "el lunes "\[past, ante\] (="on 
monday"\]ve. "los lunes" liter| (on mondays) 
The delxis feature is the dianri~Linatlng factor 
to get the right transfer for "lunes". 
4 - Subordinate clauses : the deictic value of this 
adverbials is a calculus of the deictic value 
of the conjunction (if present), and that of 
the tense and of the mood, if present. 
There are two possible cases depending on the 
source language ( Germanic or Romance). For the 
first case, the axpectual value of the 
conjunction end the temporal value of the main 
clause select the mood of the subordinate 
clause. The deini8 value of the main clause i8 
copied onto the subordinate conjunction; this 
value decides about the 8ubjuntive ~squir~ent 
of the conjunction. Let's take the conjunction 
"till" (Eng.), "his" (Ge~.), "bests que" (Spa,.) 
that has no deictic value. If the main clause 
is in future, "till" gets the deixis "post", if 
it iS past than it' gets accordingly the deixis 
"ante". 
The interesting fact is that, according to the 
obtained deictic value the conjunctim~, selects 
the subjunctive requirement. When the 
conduction has assigned in the lexicon the 
com~itunt of subjunctive requirement, this 
value is the most relevant. For example: 
,~ I will\[pc}t\], work, t~ll\[post\]" you come" 
Traba\]ar~\[post\], hastaque\[deixis--~ost\] vengas" 
==> \[aubre~es\] 
"Er arbeitete\[ante\] hls\[ante\] mr kam" 
"Trabaj6 \[ante\] hasta que\[de~xis=ante\] 
lleg6\[ante\]" 
Taerefo~e the following general rule can be 
fomulated: 
Source Conjunction \[poSt\] => 
Tenge~Con~nct ion \[subr~ \] 
Again the deLv/s value also selects the right 
transfer of the conjunction. Here some examples 
for Spanish end German: 
.,..° .................. .,,°,0,...°° ...... 
cuando \[enb. ~\] ...... als 
cuando \[pest\] ..... werm 
~ando \[8imul\] ....... wnnn 
relent ras \[8imul, ante\] -- wahrend 
mientras \[post\] ..... solange 
seit \[ante\] ..... dase hace~ 
8eit \[post\] ...... desd~ hacxa 
.... . .... o.o ............. . .............. 
~x: "mientza8 el trabaja, ?o t~no el sol" 
"waehrend er arheitet, aonne\[Pres\] ich reich" 
• ~. 
"mient~u el t~abaje\[au~j.\], yo sere / \[Fur\] 
loll=." 
"anlange er arbsitet, bin \[Prns\] ich 
qlue~l£ch" 
4~ Aspect 
The a~pect.al calculus we propose relies on: 
- 'A) le~ical t~ of the verb pr~itives 
~!) mo~phologxcal tenses of the verb forms 
.- :~) the presence of t~pornl adverbials. 
~', d) the de~ee of definiteness of the sentence 
constituents 
Tht~ possible as~etual values are: \[inchoactive, 
dnrativo, tex~ative, perfective, retrospective, 
p~OSpecti~i\]. 
T~ lexical tipoloT\] was already mentioned: the Verb 
'~oe (~))?astute, and the Proceseive Feature. 
4.1 Calculus of the Aspect of the verb group 
~n order to cover all the aspectual meanings in 
Spanish ~e keep p~ogz~essivity as a value out of the aspectuel 
feature he,muse it does not appear in alternance with the 
othe~ valu~ss. ~ ~y to proceed in the calculation o£ the 
aspectual ~alue is the following: 
-t'irst: ~apture all the enpentual information 
coaain~ from the verb: 
- ~rb type & processivity feature 
-. verb fo~ (simple or with 
auxiliaries) 
-. second: the aspectual in formation of the 
adverbials. 
~n~ aspectual assig~ent to the tenses in Spanish is 
shown in table 2. 
Table 2: Aspect value~ for verbs in Spanish 
Source ~for~mtion Result'~ng Information 
J Verb fox~ process VRB-T~pelAspect Prog. 
................................................. J .................. 
I l 8~ple yes I durative no 
12 no Iperf., iter no 
J3 Aff~\[habsr\]÷V~\[lm~\] lretrospent, no 
14 ~\[a'~b~ deI+V~\[inf\] o Jretro.&~mm. no 
J5 ~x\[entarlT v~\[ger\] o Idurative yes 
16 AUX\[i%.~\] ~ V~ \[inf\] no star linchoactive no 
17 no d~ \[pro@ective no 18 
yes - Jinchoactive no 
19 A~\[ll~va~\]+ ~\[ger\] - - Iteminmtive yea 
j IOAUX \[Im~er \] +AUX \[~,~t ar\] +V~ - J retrospective ~en 
Ex: 
'7~abo de lloga~'! -~ ~i have just\[prox.\] arrived 
Zch bin gerade \[prox.\] gekonen 
"l,;st~ trebajando" ~ Ee in working\[dur, &prog. \] 
F.r arbeitet gerede \[prnx. \] 
The relevance of the presence/absence of the 
progresaivity can be shown when we translate into Greek. In 
this language the same aspect value generates different 
tenses according to presence or absence of progressivity. 
For instance, if aspect i8 retrospective and there is 
progressivity then the corresponding tense is Imperfect, hut 
if there is no presence of progressivity the corresponding 
tense for this aspect is Present perfect. 
The morphological tenses also imply monolingnal 
aspectual assignments. Here we will follow the proposal of 
F. van E~de. According to it, each language has a different 
distribution of aspectual features in tenses. However, here 
again we prefer to split up the mo~hological values 
according to two attributes : form end pro~fesivily 
form. 
4.2 Aspeetual value of adverbials 
Adverbs as well as prepositions and conjunot£ons have 
in the lexicon an aspectual value assig~ent. Temporal NP's 
as adverbials get the aspectual assigment from their 
dete~inents or quantifiers. Bare plurals or distributive 
quantifiera assign the value \[ iterativity\], while 
All-cuantifier8 furnish the NP with durativity, expressed in 
some languages as progressivity. 
"EE a~beitet den ganzen Tag ..... Esta trabajando todo el dla 
For instance, iterativity must be delivered from the 
source language in order to generate the right tense even for 
punctual verbs, e.g. : 
"un d~a I envio flores a Carmen" = 
"he once sent flowers to Carmen" vs. 
"envlaba cede d~a flore8 a Carmen"= 
"he sent to Carmen flowers every day" 
Deterniners/quentifiers have aspentual values as: 
un \[parr\]; cede \[ iter\]; todaa \[iter); todo/a \[dur\] 
So the transfer of "d~a" is "once" if we are 
concerned with a perfeative HP-adverbial. However the 
transfer of "d/a" e8 'day' when the aspeetual calculus has 
furnished the NP with the feature \[dnr\] or liter\]. 
In PP'a the final aspectual value is the result of 
the calculus of the aspect value of the preposition together 
with the daixis of the adverbial. For instance, the |~undary 
preposition "deeds" {since} with anterior adverbials yields a 
final terminative aspect, but with a posterior adverbial, or 
even with a anterior adverbial but together with another 
boundary expression (the final Point of the temporal} £t 
yields a perfective aspect. Examples: 
"dasda e.yer\[ente.\] t rabaja aq.~ ..... > teminati~ 
"dearie a~ora traDajard en EUROTRA" .... > perfective 
439 
"trabajo agu\[ desde el lunes hasta el jueves .... >perfective 
\[perf\] \[limitl--term\] \[limit 2--perf\] 
The resulting aspect value of this calculus must he 
attached to the preposition or adverb (overriding) the old 
values in order to get the right transfer. 
.... ...... 
en \[perf.\] --> in 
for\[perf.\] --> en 
for \[dur. \] --> durante 
In subordinate clauses the process is the same. As we 
have seen above the deixis of the calculus of the main clause 
must be attached to the conjunction. Thus, the calculus of 
the aspect of the main clause must be furnished to the 
conjunction in order to be able to get the right transfer of 
the conjunction and also for generating the right tense in 
the subordinate clause. 
Another important factor in the calculus of the aspect is 
the syntactic type of the constituents in the sentences. 
These determine the aspectual properties (Dowry). To 
illustrate it we take the examples of Dowry(1986) 
"John walked" -- Juan paseaba \[activity\] 
"John walked to the station" -- rue • la esteciotn \[achievment\] 
"John walked a mile" -- anduvo una mille \[accomplishment\] 
As we can appreciate, the Spanish sentences have a 
different lexical verb form for each of these aspectual 
differences. Up to now METAL have different transfers 
according to the different verb frames. Eurotra-Germany 
proposes to disambiguate in the Interface Structure by means 
of semantic feature bundles. Besides the constituency 
factors of the syntax, another important fact is the 
presence/absence of bare plurals for the objects: 
"lleva escribiando novelas tres a~os" -- 
"she has bean writing novels for 3 Years" 
"sie schreibt Romane seit 3 Jahren" vs. 
"He wrote a novel" -- "escribi~ una novela" 
\[Past~ per feotive\] 
"He wrote novels" --- "escribla novelas" 
\[Past, durative\] 
That means that the original verb value for 
prooessivity is cverriden according to the NP's that go with 
the verb. NP's with quantifiers assign the aspantual values 
so that punctual verbs express processes, or viceversa. 
5. Process for the calculus 
The calculus of time and aspect can be implemented either as: 
- a unification of features together with filters that 
catch or kill complex cases. (EUROTRA) 
- an assigment table gathering the possible TI~ and 
ASPECT configurations, and another table yielding 
the TENSE corresponding to each of the TIME/ASPECT 
configurations for the right target language 
generation. 
S \[deixis, aspect\] 
Verb-qro~ ~// ~ adverbials 
Sty" "-/" AUX {deixis, aspect, 
subj-requirament } 
Verb type deixis 
Processivity aspect 
Sub.Requir. progressivity 
The calculation process delivers a final value as a 
result which must be percolated to the S node. This process 
has the characteristic of a functional composition, provided 
that the different values can be considered as operators 
applied in a hierarchical order. The dominant value is the 
adverbial. 
\[Adv. (post) \[V (simul,post) \] \] ---> S (post) 
\[Adv. (term) \[V (perf, dur) \] \] ---> S (term) 
The calculus provides a value for S, and 
S-subclauses, but also for all the temporals implied so that 
they can be properly translated into morphological values, or 
into lexicalized forms. 
7. Summary 
In NL processing the calculus of Time and Aspect is a 
complex thing where almost all elements of the sentence are 
concerned. The dynamics of the aspect and deixis in Natural 
Language can be captured in the framework of a calculus of 
these. Same tables in this article give acquitance of this 
process. The originality of our proposal relies on the 
following aspects: 
- Unicity of criteria (the same features for all 
temporal categories) 
- Uminity of adverbial types (the same treatment for 
subordinated temporal clauses, for adverbs and PP's. 
- A strong interrelation of the aspectual modal and 
deictic values in the constituents of the sentence. 
440 
~ ~stach~t o~ the verb pzivacy for aspect in favor 
of ~ bi-di~ectloaal intez~elstion. That means, the 
v~b ea~ b~ correctly translated i~ the 
~nbjec~lobjec~ detez~acy is taken into account. 
'~b~e£o~e, the zlght tense and the right transfer 
fo~ the adverbials can be only guaerated in harmony 
~Ath the global calculated aspect and deixis. 

References

~. /~pp~lo : A e~apositional approach to the translation of 
h~,~pe~.~al expressio,~s in the Resents System. In Proceedings of 
th~ Colin~ ~986. Bonn. p.313-318 

E.Bach (1986) ~he algub~a of events. Linguistics and 
l~ld.loaphy, 9, 5~16 

D.S. ~'~e ~ ~.A Salt : Temporal I~elatlon8. To appear in 
Jou~ml fo~" S~mantics (Nij~egan) 

V. io Case~o Co Vet & Ch. Rchrer : lnyteractiou between 
Verbal Tenses and Temporal Adverbs in C~plex sentences; 
iu:T~o~al Structure in Sentence and Discourse (ed) Lo 
Caseio & Co Vet p. 229~249. 

}~o Pa~te~(l~84) k~eminal and Temporal ansphora", Linguistics 
a~id Philosophy, 7 (243-286) 

D~ Do~y T~e ef£ects Of aspectual class on the temporal 
~t~actu~e e! Discourse: Semantics Or Pragmatics, Linguisticu 
and Philoso~,hy, 9 (37-61) 

.~'.v~n Eynd~ '.~i~e a unified theory of tense, aspect and 
~ktion~z~. UnpuSlished. 1987 

~o~O~ne~ :~n~aetze zu einer inte~alan se~entischen ~eorie 
vo~, Tempus, Aspect ~md Aktionsart~. To appear in: (ed) V. 
~hlich ~nd ~. Vate~: Temporalsemantlk. Niemayer. Tuebingan. 
