# Re: OWL-Time extensions for Era

From: Élie Roux <elie.roux@telecom-bretagne.eu>
Date: Wed, 15 Jul 2020 17:13:30 +0200
Message-ID: <CANfi1JhAwd9GPsu8JE=oRekiQhccnG05CujKkv3CJ1z_nDaakw@mail.gmail.com>

Cc: "Simon Cox (simon.cox@csiro.au)" <simon.cox@csiro.au>, Ted Guild <ted@w3.org>
```Dear Chris,

> I was slightly worried by the definition of Common Era as an unbound  interval. The original Allen Algebra of temporal intervals was only for finite intervals, but I think there has been substantial mathematical work to show that, generally, extension to allow left half-infinite, right half-infinite and fully infinite intervals would not cause any problems in practice.

That was a core issue in the design, thanks for raising it!

My understanding of the common use of the word "era" is that it
denotes a period of time (a temporal interval) that can be used as a
reference to assign numbers to years (year x or era Y). So if we
follow that, an era is both:
- a time:Interval (something that actually exists, and which
boundaries are known)
- a reference frame used to assign numbers to years

and the two concepts are conflated in one name (era). My initial idea
was to be prudent and to differentiate these two concepts, defining
time:Era only as the latter. So in my initial idea was that a resource
could be both a time:Era and a time:Interval.

Now, I think we could have something like:

time:Era rdfs:subClassOf time:Interval .

so that time:Eras are always intervals. Were you thinking of something
like that?

The reason I was uncertain about that is the following one:

I'm sure there are dates indicated in ancient documents that relate
semi-imaginary events in eras that we're not sure actually happened...
so how ok is it to encode an imaginary date or interval using
OWL-Time? To take an extreme example in a fictional world (Game of

ex:date1 a time:GeneralDateTimeDescription
time:year "0003" ;
time:era [ a time:Era ;
time:reignOf ex:AerysIITargaryen ;
] .

?

> Ted Guild could advise, but I think that the proposal is currently on your GitHub. Perhaps it should be in the W3C GitHub so that issues can be raised, discussed and resolved?

That would work for me

Best,
--
Elie
```
Received on Wednesday, 15 July 2020 15:13:55 UTC

This archive was generated by hypermail 2.4.0 : Thursday, 24 March 2022 20:31:03 UTC