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[sdw] What is the intended directionality of time:before and time:after? (#1241)

From: Wouter Beek via GitHub <sysbot+gh@w3.org>
Date: Wed, 20 Jan 2021 17:52:18 +0000
To: public-sdwig@w3.org
Message-ID: <issues.opened-790192567-1611165137-sysbot+gh@w3.org>
wouterbeek has just created a new issue for https://github.com/w3c/sdw:

== What is the intended directionality of time:before and time:after? ==
What is the intended directionality of `time:before` and `time:after`?

Suppose that I want to describe the two world wars as historic events, would assertion [1] be correct or assertion [2]?

```
[1] event:ww1 time:after event:ww2.
[2] event:ww2 time:after event:ww1.
```

Firstly, from the description for `time:after` the intended directionality is not unclear.  We do not learn the correspondence between `T1`/`T2` in the description and the subject/object positionality in triple usage, which is crucial:

> Gives directionality to time. If a temporal entity T1 is after another temporal entity T2, then the beginning of T1 is after the end of T2.

Secondly, the description of `time:before` does not provide any additional information over the description for `time:after`.  Since this description is completely symmetric with that of `time:after`, both directionalities are still possible:

> Gives directionality to time. If a temporal entity T1 is before another temporal entity T2, then the end of T1 is before the beginning of T2. Thus, "before" can be considered to be basic to instants and derived for intervals.

Finally, the value of `rdfs:label` [3] does not communicate the directionality either.  A label like [4] would be cleared for intended meaning [1], and label [5] would be clearer for intended meaning [2].

```
[3] "after"@en
[4] "has after"@en
[5] "is after"@en
```


Please view or discuss this issue at https://github.com/w3c/sdw/issues/1241 using your GitHub account


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