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\noindent{\Large\bf WORDS~FOR ~TIME}
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{\large\it  David S. Br\'{e}e }\\
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{\it Computer Science Department, Manchester University, \\
Oxford Road, Manchester, M13 9PL, U. K.\\
e-mail: bree@cs.man.ac.uk\\}
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\abstract{
Taxonomies of the temporal subordinating conjunctions and 
prepositions in English, Dutch 
and German are presented. These high frequency words are highly 
ambiguous. So a good taxonomy is of 
practical importance for computerized Natural Language understanding or 
translation system. 

It is also of psychological importance. By examining the taxonomies that 
we have developed for 
different languages, we see that certain features are common across 
languages, for example before and after, 
and their equivalents in other languages can qualify any type of temporal 
point or interval. Other features 
are idiosyncratic. For instance, in English {\it night} is treated differently 
from the other parts of the day: {\it in the 
morning/at night}. The extent of the idiosyncratic features is a sure 
indication of associative learning that 
must take place during language acquisition. However all is not ruleless. 
This agrees with a theory of the 
mind as a hybrid system capable of learning and using not only 
regularities but also a large number of 
individual associations. }

\section{Introduction}

Linguists have long been interested in lexical semantics. However, it is 
only recently that an interest in the 
non-content words - the function words - has grown (Zelinsky, in press). 
The spatial prepositions have 
attracted considerable interest. We have already looked at the use of 
prepositions of inference and cause 
(Br\'{e}�e, Smit \& Schotel, 1984). In this paper I would like to look at the 
temporal use of prepositions and 
subordination conjunctions, which I will call 'temporals' for short. As 
with the spatial use of prepositions, 
temporals show similarities, but also idiosyncratic differences across 
languages. One of our tasks is to 
distinguish between these by comparing the meanings of temporals in 
several different languages. We have 
already analysed (Br\'{e}�e \& Smit, 1987) and compared (Br\'{e}�e, Smit \& van
Werkhoven, 1990) English and Dutch temporals. We have also analysed the German temporals 
(Durrell \& 
Br\'{e}�e, in press). Here we use this 
last work to revise the previous analysis of English and Dutch. The 
result is a uniform analysis of the 
temporals in all three languages.

Our general approach is to build a 'selection tree.' This is similar to a 
decision tree, being a graph, with 
a root node and leaf nodes. The leaf nodes indicate the temporal word to 
be used in a particular context. The 
other nodes indicate questions about the context. The possible answers to 
these questions are indicated on 
the links emanating from nodes and directing the selection process to a 
further question or to a particular 
temporal at a leaf node. These selection trees can also be used in 
natural language understanding. The path 
back from a particular temporal leads along various links which indicate 
the context which the temporal 
requires. This context can be considered to be the 'meaning' of the 
temporal. 

The questions that are posed in our selection trees centre on the 
temporal relationship between the time 
of the event or state (which we call a 'stevent') in the matrix and 
sub-clauses. This time is usually a time 
located on the ordinal time axis, being either a point in time or a 
period of time. But it may also be a pure 
time duration, for example 5 minutes, not located on the time axis. With 
pure durations, there is a similar 
distinction, that between the duration of the main stevent and the 
duration from the Time of Discourse to 
the beginning or ending of the main stevent. It has turned out that the 
separation of durative from non-
durative uses considerably simplifies the selection trees. In language 
generation this separation is clearly no 
problem; in comprehension there could be a problem, but as it is always 
clear whether the temporal phrase 
is a pure duration of time or an actual location on the time axis, the 
appropriate selection tree can be 
consulted.

A distinction is also made between a stevent filling the whole of a 
period or just occurring at some 
point or sub-period within that period.

A major distinction is that between the sub-stevent directly setting the 
time at which the matrix stevent 
occurs versus setting one end of a period in which it occurs. In the 
latter case the other end is often the 
Time of Discourse (ToD). The ToD may be either the here and now, or a 
past or a future time. Another 
concept that is required is that of a semi-range. A semi range is either 
the time from the Big Bang up to a 
particular time point or the time from a point up to Eternity.

Finally a distinction is made between the sub being a clause or a phrase. 
It is interesting that for the 
choice of a temporal this frequently makes no difference; either a 
temporal can be used both as a preposition 
and as a conjunction, for example {\it after}, or the preposition can be turned 
into a conjunction by adding some 
standard suffix equivalent to {\it that} in English, for example {\it na +dat} in 
Dutch. These are enough distinctions 
to go on with.

\section{Pure Duratives}

The first way to specify a temporal attribute of a stevent is to indicate 
its duration without directly 
specifying the whereabouts on the time axis the duration occurs. Examples 
of pure time durations are: a 
moment, five minutes, a year. Each of the three languages under 
consideration has a half dozen or so 
prepositions for doing this. We will look in detail first at the English 
prepositions. Then we will note the 
differences that both Dutch and German have from English. 

\subsection{ENGLISH DURATIVE PREPOSITIONS}

The prepositions taking a pure durative phrase fall into three major 
categories. The basic use is to give the 
duration of the main stevent. This duration itself may be linked to the 
Time of Discourse (ToD). A second 
use is not to give the duration of the matrix stevent but rather the 
duration of the time interval between 
such events. Lastly the sub-phrase can be used to place the time of the 
matrix stevent on the time axis 
through linking its time of occurrence with the ToD. The sub-phrase then 
gives the time duration from the 
ToD to a second time point; the preposition relates the time of the 
matrix stevent to this second time 
point. We now examine the three main categories of the use of temporal 
prepositions with a pure durative 
in English - see Figure~\ref{figure:englishd}.

\begin{figure}
\centering
  \noindent\psfig{figure=fig1.ps}
\caption{Selection tree for English durative use of temporals}
\label{figure:englishd}
\end{figure}

When the sub-phrase is used to indicate the duration of the main stevent, 
the preposition depends on the 
nature of the main stevent. If it is an accomplishment, the English 
preposition to be used is {\it in}. If it is an 
activity or a state, then {\it for} is used. For example
\begin{squote}
The coach can reach St Malo in three hours.\\
We sat in the coach for three hours. 
\end{squote}

The second use is to fix the cycle time of the matrix 'stevent'. In 
English no preposition is required, but 
rather the adjective {\it every},  for example
\begin{squote}
A train leaves Paris for Rennes every hour.
\end{squote}

Finally there are four uses of the sub-phrase to relate the time of 
occurrence (as opposed to the duration) 
of the matrix stevent to the ToD. Two uses fix the time at a specific 
time point either before or after the 
ToD, for example 
\begin{squote}
The train had left an hour before. {\tt (this is to say at ToD - 1 hour)} \\
The train leaves in an hour. 	{\tt (this is to say at ToD + 1 hour)}
\end{squote}
The other two uses indicate the semi-range of time in which the matrix 
stevent is to occur. The secondary 
time point is always fixed later than the ToD and the matrix stevent is 
to fall either earlier or later than this 
point, for example 
\begin{squote}
The train will leave within an hour. {\tt (this is to say at a time < ToD + 1 hour)}\\ 
You can come back after an hour. {\tt (this is to say at a time > ToD + 1 hour)}
\end{squote}
There is one complication in English. When the time of the matrix stevent 
is being placed at a point earlier 
than the ToD by the duration of the sub-phrase, then the choice of 
preposition depends on whether the ToD 
is also the time of speech, this is to say the here and now. If it is 
then ... {\it ago} is used rather than ... {\it before}, 
compare: 
\begin{squote}
John rushed into the station, but the train had already left 5 minutes 
before. \\
"You just missed it. The train left 5 minutes ago."
\end{squote}

Note that there is an ambiguity in the English temporal prepositions used 
with a pure duration: in is 
used to indicate the duration of an accomplishment but also to indicate 
the time span after the ToD at 
which the matrix stevent will occur, for example 
\begin{squote}
John will present his paper in 20 minutes.
\end{squote}
can mean either that John will take 20 minutes to present his paper or 
that he will start his presentation 20 
minutes from now. It is necessary to decide in which way English {\it in} plus 
a durative is being used. How 
this should be done is still an open question.

This completes our description of the English temporals used with a 
purely durative phrase. We turn 
now to the differences that Dutch and German durative temporals have from 
their English counterparts. 

\begin{figure}
\centering
  \noindent\psfig{figure=fig2.ps}
\caption{Selection tree for Dutch and German durative use of temporals}
\label{figure:dutgd}
\end{figure}
                                             
\subsection{THE DUTCH DURATIVES}

The durative use of temporal prepositions in Dutch is similar to that in 
English - see Figure~\ref{figure:dutgd}. There are 
two differences, one minor the other major. The minor differences is that 
in Dutch there is no distinction 
that parallels that between {\it ... before} and {\it ... ago}. When the time of the 
matrix stevent is being set to a time 
earlier than the ToD by the duration in the sub-phrase, then the Dutch 
use ... {\it geleden}, irrespective of 
whether or not the ToD is the here and now.

The major difference is that where English uses {\it for} Dutch has three 
alternatives: \# (no preposition), {\it al, nog}. 
Normally when the duration of a matrix stevent which is an activity 
or a state is being set, then no 
preposition is used in Dutch, for example 
\begin{squote}
We will stay in St Malo five days.	{\tt (no preposition)}
\end{squote}
When the matrix activity or state is to be attached to the time axis at 
the ToD, then a preposition is used, 
the choice depending on whether the matrix activity or state is to begin 
or end at the ToD,  for example
\begin{squote}
We have been in St Malo for four days.	(al 4 dagen)\\
We will remain in St Malo for another day.	(nog een dag))
\end{squote}

As far as machine translation is concerned, the only problem arises in 
translating English {\it for} into Dutch 
{\it al, nog} or no preposition.

\subsection{THE GERMAN DURATIVES}

The German use of temporal prepositions with a duration in the sub-phrase 
parallels that of the Dutch use. 
The actual prepositions are of course different - see Figure~\ref{figure:dutgd}. There are 
two minor points to be made. 

While in German the use of the sub-phrase to indicate the cycle time of 
the matrix stevent is again 
indicated by an adjective with the accusative case as in Dutch, a 
different adjective is used for singular 
({\it jeden})  versus plural ({\it alle}) nouns. The other minor difference is that 
there are two prepositions in German 
to indicate that the matrix stevent occurs at a time later than the ToD 
plus the duration of the sub-phrase, 
corresponding to {\it within} in English: 
{\it innerhalb} and {\it binnen}. Usually 
{\it innerhalb} is used, but in more formal 
registers {\it binnen} may be used.

\subsection{IN SUMMARY}

There is little difference between the three languages in the use of 
temporal prepositions together with a 
time duration to indicate either the duration of the matrix stevent or 
its cycle time or when it occurred in 
relation to the ToD. All three systems are rather neat with only one or 
two idiosyncrasies. When we turn to 
the non-durative use of temporal prepositions, this simplicity will no 
longer be found. 

\section{Non-duratives}

In the non-durative use of temporals the sub-phrase specifies a time 
point or period on the time axis, 
compare {\it ... in a month} (durative) {\it ... in October} (non-durative). In this 
section we will look first at the non-
durative use of English temporals (see Figure~\ref{figure:engnd}), and then at their Dutch 
and German counterparts.

The major distinction in the non-durative use is between the sub-stevent 
being used to indicate the time 
of the matrix stevent versus indicating one (or more) end(s) of a time 
period in which the matrix stevent 
falls. This corresponds to the distinction in the durative use between 
indicating the time of the matrix 
stevent in relation to a time point some distance from the ToD versus the 
duration of the matrix stevent 
itself. There is no equivalent in the non-durative use of temporals that 
corresponds with the use to indicate 
the cycle time of the matrix stevent.

\begin{figure}
\centering
  \noindent\psfig{figure=fig3.ps}
\caption{Selection tree for English non-durative use of temporals}
\label{figure:engnd}
\end{figure}
                                                     
\subsection{INDICATING THE TIME OF OCCURRENCE OF THE MATRIX STEVENT}

When the sub-stevent is being used to indicate the time of occurrence of 
the matrix stevent, there are two 
major cases: the sub-stevent is used to indicate a point in time or a 
period in time. Typical points in time 
are clock times and non-durative actions such as exploding, dying etc. 
Typical durations are months, years 
and states such as "being at a workshop". This distinction is not always 
to be found in the nature of the 
sub-stevent itself. An explosion is usually considered to be a point in 
time, but if one is interested in the 
sequence of events during an explosion then an explosion is regarded as a 
period (and hence during is used 
in English). On the other hand a millenia, while usually a period of 
time, can be regarded from a geological 
point of view as a point in time. Even longer periods can be regarded as 
points in time, in for example 
\begin{squote}
When the dinosaurs ruled the earth, there was a balanced ecology.
\end{squote}
an interest is being expressed in the conditions pertaining at a certain 
time in contrast to another time. 
Compare this with an interest in the goings on in the same time period: 
\begin{squote}
While the dinosaurs ruled the earth, mammals didn't stand a chance.
\end{squote}
In English the two temporal conjunctions that are used for time point and 
time periods are when and while 
respectively. The contrast between them can be seen for example in 
\begin{squote}
When (*while) John reached the footlights, he looked up.\\
While (*when) the minutes ticked by, we held our breaths.
\end{squote}

The situation is not so simple when it comes to the temporal prepositions 
as opposed to the 
conjunctions. The English preposition used to indicate a time point is 
simply {\it at}, for example at {\it 5 o'clock, 
at high tide, at the beginning of the day}. However, to indicate a time 
period in which the matrix stevent is 
to occur there is a choice between {\it during} and {\it in}. There most 
probably are no criteria for choosing between 
these two prepositions common across different speakers in English. 
However, there is one necessary 
condition for permitting the use of {\it in} rather than {\it during}: the 
sub-stevent must not be able to be given a 
non-temporal interpretation. If the sub-stevent can be given a 
non-temporal interpretation, then {\it in} may not 
be used. For example 
\begin{squote}
The King fell asleep in the opera.
\end{squote}
would mean that the King was a character in the opera. If he was part of 
the audience, then one would have 
to say:
\begin{squote} 
The King fell asleep during the opera.
\end{squote}

In addition a distinction can be made concerning whether or not the 
matrix stevent lasts for only a part 
of or for the whole of the period of the sub-stevent. If it is definitely 
to last for the whole of the period 
(which means that it cannot be an accomplishment) then English use {\it for}. 

This completes the description of the use of English temporals to 
indicate the time point or period of 
the matrix stevent in general. However, there are two special cases for 
indicating the time of the matrix 
stevent. The first is common to many languages. When the sub-stevent is a 
day then a special preposition 
is used. In English this is {\it on}, for example 
\begin{squote}
We arrived (on) Monday.
\end{squote}
It should be noted that the {\it on} is not required with days; no preposition 
may be used. No preposition is also 
used for indefinite moments in the past, for example 
\begin{squote}
One day we found him hiding under the bed.
\end{squote}
{\it On} is also used for a qualified part of a day; although not for an 
unqualified part of a day: 
\begin{squote}
You can see the isle of Jersey on a fine morning. \\
You can see the isle of Jersey *on a morning.
\end{squote}

The other special case for English is that when the sub-stevent is an 
ongoing activity then the 
conjunction {\it as} may be used instead of {\it when} or {\it while}, for example 
\begin{squote}
As we walked down the drive, we could see over the park to the hills 
beyond.
\end{squote}
The criteria for choosing as rather than {\it when} or {\it while} are not clear. 
Following David Palliser in the 
"Quincunx", I favour 'ongoing activity' as the criterion. 
This completes the overview of the use of a temporal sub-stevent to fix 
the time of the matrix stevent 
directly. We turn now to its use to fix the ends of its time duration.

\subsection{INDICATING AN END OF THE TIME PERIOD IN WHICH THE MATRIX STEVENT 
OCCURS}

When the sub-stevent is being used to fix one end of the time period in 
which the matrix stevent is to fall, 
the question arises: what is going to fix the other end? There are two 
alternatives, the first is that the other 
end is open or fixed by default to the ToD. The other is that the 
sub-stevent is in fact a double stevent, 
fixing both ends of the matrix stevent.

When the other end is open or fixed by the ToD there are two situations: 
either the sub-stevent is used 
to mark the beginning of the time period in which the matrix stevent 
occurs, or to mark its end. In both 
cases the other end can be open, so that a semi-range is indicated (or 
set to the ToD by default). When it is 
left open as a semi-range, then English uses {\it after} or {\it before}, for example 
\begin{squote}
After we left Paris, we were quiet for a while. \\
Before we arrived at St Malo, everybody had introduced themselves. 
\end{squote}
If the ToD marks the other end of the time duration, then {\it since} and 
{\it until/by} are used, for example 
Since we left Paris, not a word has been said. 
\begin{squote}
Please remain seated until the plane comes to a complete halt. \\
By the time we reach St Malo, everyone will have introduced themselves!
\end{squote}

The distinction between {\it after} and {\it since} is that with after the actual 
period during which the matrix 
stevent occurs or may occur is open, as long as it is later than the 
sub-stevent, whereas with {\it since} it must 
occur earlier than the ToD. Similarly the distinction between {\it before} and 
{\it until/by} is that with {\it before} the 
matrix stevent can occur in any time earlier than the sub-stevent, 
whereas with {\it until/by}  it must occur later 
than the ToD.

There is an asymmetry between {\it since} and {\it until} (Br\'{e}�e, 1985).
 With {\it since} 
the matrix stevent may occur at 
any time during the period from the sub-stevent to the ToD or it may 
occupy the whole of this period. In 
contrast, {\it until} may be used only if the matrix stevent is to occupy the 
whole of the period from the ToD to 
the sub-stevent. If it is to occur only at some point in this period, 
then {\it by} must be used, compare: 
\begin{squote}
John has been in great spirits since we got here. \\
John will be in great spirits until we leave / by tonight. \\
John has phoned home once since we got here. \\
John will phone home once *until we leave / by tonight.\\
\end{squote}
With {\it until} the matrix stevent must last for the whole of the period, so 
it cannot be an accomplishment; 
with {\it by} it can. If {\it by} is used with an activity or state then this does 
not already hold at the ToD, whereas 
with {\it until} it does.

We turn now to the situation in which there is a double sub-stevent, 
fixing both ends of the matrix 
stevent. Here again there are two alternatives, corresponding to the 
difference between {\it until} and {\it by}. If the 
matrix stevent is to occur for the whole of the period between the two 
sub-stevents, then {\it from ... to}  is 
used, for example 
\begin{squote}
Lights will be out from 10 in the evening to 7 in the morning.
\end{squote}

Note that {\it until} may be used instead of {\it to}. In such cases the default of 
the ToD normally assumed for 
{\it until} is overridden. If the matrix stevent is to occur at some point in 
the time period or only for some of 
the time period, then {\it between ... and}  is used, for example 
\begin{squote}
 You may go out once between 10 in the evening and 7 in the morning.
\end{squote}

This completes the description of the use of the sub-stevent to fix the 
ends of the time period of the 
matrix stevent. There are no ambiguities. The only 'surprise' is that 
{\it since} and {\it until} are not symmetric with 
respect to temporal order.

\subsection{THE DUTCH NON-DURATIVES}

Having completely described the use of non-duratives in English, we will 
describe their use in Dutch by 
pointing out the contrasts with English. We begin with the 'top half' of 
Figure~\ref{figure:dutchnd}, showing the selection of 
Dutch temporals for non-durative use. When a conjunction is needed, this 
is to say when the sub-stevent is 
expressed by a clause, then there are several differences between Dutch 
and English. In the first place, there 
is no equivalent to the English {\it as}. Temporal {\it as} is almost always 
translated into Dutch by {\it toen} or {\it terwijl}. 
To choose between these two, the simplest rule is to replace {\it as} by {\it when}
or by {\it while} in the original 
English. This can always be done, and usually only one of the two is 
appropriate in the context, for 
example 
\begin{squote}
As (while/*when) we were eating, we discussed the issue. \\
As (when/*while) I left, I felt a weight had been taken from my 
shoulders.
\end{squote}
For the rest, the 'top half' of the figure is more complex for Dutch than 
for English.

In the first place, when the sub-stevent indicates a time point and a 
clause is needed, then Dutch must 
choose between {\it toen}, {\it als} or {\it wanneer} whereas English makes do with {\it when}. 
The choice is based on the 
timing of the matrix stevent. If this is a one-off event in the past, 
then {\it toen} is used. In all other cases, this 
is to say for events in the present and the future and for repeat events 
and regularities, then {\it als} or  {\it wanneer} 
are used. The van Dale Dutch dictionary also permits {\it als} to be used for 
one-off events in the past. However 
this use is not frequent in modern Dutch, if it is used at all nowadays.

To fix the time of the matrix stevent at a point three prepositions, {\it om, 
met} and {\it aan}, are available in 
Dutch instead of the single {\it at} in English. {\it Om} is used only with clock 
times. For religious feasts the Dutch 
use {\it met} (literal translation in English being {\it with}!). {\it Aan} is used in a 
few expressions, for example {\it at the 
beginning/end}. {\it Aan} in its spatial sense is used to indicate something 
hanging on a surface, for example a 
painting on the wall, as opposed to on top of a surface, for example a 
book on a table; here {\it aan} is used for 
a time at either end of a time period rather than in the middle. {\it In} would 
be used for the middle of the day. 

There are a couple of other occasions in which {\it at} is used in English 
which are given different 
translations in Dutch. {\it At night} is translated by {\it 's nachts}. The Dutch 
treat the night as any other part of the 
day, such as the morning, whereas the English do not. For them night is 
treated as a point in time, {\it at 
night}, whereas other parts of the day are treated as periods of time, {\it in 
the morning} etc. The other occasion 
in which {\it at} is not translated by {\it om, met} or {\it aan} is for natural events 
such as: {\it at high tide, at sunrise}. For 
these events the Dutch use {\it bij}, a preposition which is used for 
sub-stevents that are causally linked to the 
main stevent.

Turning now to the placing of the matrix stevent in a time period rather 
than at a point in time, the 
choice of preposition is again more complex in Dutch. This is 
particularly the case when the sub-stevent is 
not a temporal term, this is to say where {\it during} is required. In Dutch 
{\it tijdens} is normally used. However if 
the sub-stevent is a simple action then either {\it bij} or {\it onder} may be used. 
{\it Bij} (also used for natural events, see 
above) is used when there is some causal connection between the sub and 
matrix stevents. If there is no 
causal connection, then {\it onder} is used, for example 
\begin{squote}
During my morning exercises, I would ...          {\tt (bij)} \\
During the meal, he would tell us stories of the war.	{\tt (onder)}
\end{squote}

There is also a complication when the stevent is a temporal term and {\it in}
would be used in English. Dutch also uses {\it in}, 
but if the sub-stevent is a part of a day, for 
example morning, evening, night, or the 
two main seasons, winter and summer, then it usually uses {\it 's} ({\it 's} is short 
for {\it des}, the old genitive of the 
definite article in Dutch). For the minor seasons, spring and autumn, 
this option is not available. We have 
here moved from the level of general to language-specific rules.

\begin{figure}
\centering
  \noindent\psfig{figure=fig4.ps}
\caption{Selection tree for Dutch non-durative use of temporals}
\label{figure:dutchnd}
\end{figure}

\begin{figure}
\centering
  \noindent\psfig{figure=fig5.ps}
\caption{Selection tree for German non-durative use of temporals}
\label{figure:germannd}
\end{figure}

Turning to the lower half of Figure~\ref{figure:dutchnd}, we will note the few differences 
from the English when the sub-
stevent sets one end of the time period in which the matrix stevent is to 
occur. The first is that whereas the 
English prepositions {\it after, before, since} and {\it until} can also be used as 
conjunctions, their Dutch 
counterparts (with the exception of {\it sinds}) have to have {\it dat} (that) added 
as a suffix to make them into 
conjunctions. If {\it -dien} is added to these prepositions as a suffix, then 
they are deicitic, in the same way as 
{\it afterwards}.

The second difference is that the Dutch equivalent to {\it by, tegen}, 
literally means {\it against} which is reflected 
in its use. {\it Tegen} is appropriate with clock times but not in expressions 
such as {\it by the time} in which case 
{\it toen} (when) is used,  for example
\begin{squote}
We'll be there by 5 o'clock.				(tegen)\\
John had left by the time we got there.		(toen)
\end{squote}
The other difference is that when the sub-stevent is to mark the end 
point of matrix stevent that is negative, 
either explicitly or implicitly,  for example 
\begin{squote}
It was a long time before I saw what he was getting at.
\end{squote}
{\it eer} may be used instead of {\it voor} when the matrix contains a negative.

To summarize, the main differences between Dutch and English in the 
non-durative use of temporals are 
that:

\begin{itemize} 
\begin{itemize} 
\item	there is no equivalent for the English {\it as} to indicate that the matrix 
stevent is taking place at the 
same time as an ongoing activity; a choice has to be made to use either 
{\it toen} (when) or {\it terwijl} 
(while); 
\item	the point of time at which the matrix stevent occurs may be introduced 
by {\it toen} or {\it als/wanneer} 
depending on whether the ToD is in the past or not; 
\item	there are three prepositions for a time point, corresponding to {\it at}: {\it om} 
for clock times, {\it met} for 
religious feasts and {\it aan} for beginnings and ends; 
\item	there are three prepositions {\it tijdens, bij, onder} to indicate that the 
matrix stevent occurred in a time 
period, distinguished by whether or not the sub-stevent is an action and, 
if so, whether or not it is 
causally related to the matrix stevent; 
\item	a special construction, {\it 's}, is used for parts of days and the major 
seasons.
\end{itemize}
\end{itemize}

\subsection{THE GERMAN NON-DURATIVES}

Once again the German selection tree is similar to the Dutch (see Figure 
5). There are a few differences to 
be noted. First, when a clause is being used to indicate the point of 
occurrence of the matrix stevent, then 
{\it wie, als} or {\it wenn} is used in German. But note that German {\it als} is used when 
the matrix stevent is one-off in 
the past, whereas Dutch {\it als} is used when it is not! The equivalent to 
Dutch {\it als/wanneer} is {\it wenn} in 
German. The equivalent to Dutch {\it toen} is either {\it als} or {\it wie} in German. {\it Wie}
is used with the historic present.

Second, whereas both Dutch {\it aan} and German {\it an} are used with "the 
beginning/end" {\it an} is also used with a 
day or a part of a day. In Dutch a day either takes no preposition or {\it op}; 
a part of a day is treated like a 
period and takes {\it 's} or {\it in}. In German the distinction between {\it in} and {\it 's} 
does not exist. However, there is a 
means for indicating that the matrix stevent lasts for the whole of the 
period of the sub-stevent, namely by 
using no preposition and the accusative case.

Thirdly the preposition {\it zu} in German is not only used with religious 
feasts (compare {\it met} in Dutch) but 
also with phrases containing the words for time: {\it Zeit, Stunde}. These 
'time' phrases may also be used with 
{\it in}, indicating that they may be considered either as points (with {\it zu}) or 
periods (with {\it in}).

Fourthly, there is no German equivalent of the Dutch {\it onder} to indicate 
that there is no causal relation 
between the sub-action and the matrix stevent.

In the 'lower' half, of Figure~\ref{figure:germannd} we see a close correspondence with the 
Dutch. Note that whereas the 
Dutch make a conjunction from a preposition by adding {\it -dat}, the German 
generally adds {\it -dem}, with the 
exception of {\it be+vor}. The only other difference is that in German there is 
no correspondence to the {\it until/by} 
or {\it tot/tegen} distinction. In both the durative and the non-durative 
pointers to the time period following the 
ToD, German uses {\it bis}.

\subsection{IN SUMMARY}

The non-durative temporals can be divided in two main groups, those that 
fix the time of the matrix stevent 
to be that of the sub-stevent and those that fix one or both ends of a 
time period in which the matrix 
stevent falls. In the former case, the time of the matrix stevent is 
fixed at either a point or a period. In 
addition days of the week are given a special treatment. In these cases 
prepositions and conjunctions are 
different words. Both Dutch and German have more such temporals than 
English. They typically have 
different conjunctions for time points, depending on whether the 
situation is a one-off event in the past or 
not. Also they have special prepositions for time points, depending on 
the kind of point that is being 
picked out by the preposition: clock time, religious feast, beginning/end 
etc. In addition both Dutch and 
German have a finer distinction for prepositions indicating a time 
duration than does English.

As for the prepositions, and the conjunctions made from them, that 
indicate the ends of the time period 
in which the main stevent takes place, there is a primary distinction 
between those prepositions that take a 
single and those that take a double phrase, the later enabling both ends 
of the matrix stevent to be 
explicitly fixed. When only one end is fixed, the other end may be left 
either open or fixed at the ToD.

\section{Conclusion}

After considerable adjustment to the selection trees as they were 
originally proposed, it seems that this 
method of representing the use of temporal prepositions and conjunctions 
has settled down. It can now be 
used to quickly pinpoint the temporals that are idiosyncratic to any 
other European language. Examination 
of the criteria by which the temporals are selected reveals that there 
are very basic concepts, such as: 

\begin{itemize}
\begin{itemize}

\item	pure duration versus on the time axis;
\item	fixing the time of occurrence or the length of time of the matrix 
stevent;
\item	pointing to a time point or period;
\item	locating the matrix time as earlier than or later than the sub-stevent 
time;
\item	in those cases where one end of the time period is fixed, indicating 
whether the other end is open 
or fixed by default at the Time of Discourse;
\item	in those cases where a time period is involved, indicating whether or 
not the matrix stevent occurs 
somewhere in that period or for the whole of the period;
\item	sometimes an indication of a regular co-occurrence or a one-off 
situation;
\item	a special treatment for days and sometimes for parts of days, religious 
feasts etc.
\end{itemize}
\end{itemize}

In addition to these regular features that occurred in all three of the 
languages, there are points peculiar to 
an individual language. For instance, the use of {\it 's} with {\it winter} and 
{\it summer} but for {\it spring} and {\it autumn} in 
Dutch. There are a few of these in all three languages and there is no 
reason to doubt that they will occur in 
other languages that are examined.

So what we find is a basic system that is likely to be reflected in the 
use of temporals in all languages, 
or at least all European languages, together with a few language-specific 
points. Preliminary work with 
French supports this. Extension to other European languages is planned.


\section{References}

\begin{description}
\item Br\'{e}�e, D.S. (1985) The durative temporal subordinating conjunctions:
 {\it since} and {\it until}.  {\it Journal of Semantics},  {\bf 4}, 1-46.
Br\'{e}�e, D.S .\& R.A. Smit (1987) Temporal relations
{\it Journal of Semantics}, {\it 5},  345-383.
\item Br\'{e}�e, D.S., R.A. Smit \& H.P. Schotel (1984) Generation and
 comprehension of Dutch subordinating conjunctions by computer. 
In T. O'Shea, ed., {\it Proceedings of the 6th 
European Conference on Artificial 
Intelligence}. Amsterdam; Elsevier,  205-208.
\item Br\'{e}�e, D.S., R.A. Smit \& J.P. van Werkhoven (1990)
 Translating temporal prepositions between Dutch 
and English. {\it Journal of Semantics}, {\bf 7(1)}, 1-51.
\item Durrell, M. \& D.S. Br\'{e}�e (in press) German temporal
 prepositions from an 
English perspective. In Zelinsky, C. ed., {\it The Semantics of 
prepositions in natural language processing}. Berlin; Mouton de 
Gruyter.
\item Zelinsky, C., ed. (in press) {\it The Semantics of prepositions 
in natural language processing}. Berlin; Mouton de Gruyter.
\end{description}
\end{document}
