Re: defining the semantics of lists

From: Frans Knibbe <fjknibbe@gmail.com>
Date: Wed, 10 Jun 2020 20:07:58 +0200
To: semantic-web <semantic-web@w3.org>
```Hi all,

Perhaps a worthy example of using a list is defining geometric shapes by
using an array of coordinates. A very simple example would be a triangle
defined by the sequence (1,1) (2,3) (3,2) (1,1), with the numbers in
brackets being x,y values. In this list, completeness is important,
otherwise the described shape will be malformed or unclosed. Order is also
important: if the list elements are not reproduced in the right order, the
described shape will be malformed (in other words, the knowledge will not
be correctly represented). Next to that, if the shape is defined within a
reference framework, the sequence can be used to describe an area inside of
the triangle or outside of it. Common practice in Geographic Information
Systems (GIS) is to use the rotation in which the coordinates are connected
(clockwise or anti-clockwise) to indicate what is meant.

Greetings,
Frans

Op wo 10 jun. 2020 om 19:42 schreef Hugh Glaser <hugh@glasers.org>:

> Hi Thomas P,
>
> I had a feeling you didn't want to :-)
> Thanks for doing it.
> But as you probably expected, I agree with Thomas L - why on earth would
> you want to use a list for your unordered favourite colours?
> That would force you to decide on an ordering, and worse still the
> ordering might appear to have some meaning.
> Surely three simply triples is a much better representation of this
> knowledge?
>
> [And I know that hans.teijgeler@quicknet.nl said "For each of those you
> guys will undoubtedly invent some workaround, but that isn't good enough.".
> I don't think that is a workaround - it a correction of actually incorrect
> representation of the knowledge.]
>
> I am reminded of trying to program in languages with poor qualities for
> the representation of complex data structures (such as Lisp), where you end
> up squeezing everything into the same single structure - a list or perhaps
> an array.
>
> Massaging data structuring and deforming the data into your favourite
> construct is not a good way to go about programming, methinks.
>
> Have you got any better examples, perhaps?
>
> Best
> Hugh
>
> > On 8 Jun 2020, at 16:20, Thomas Passin <tpassin@tompassin.net> wrote:
> >
> > On 6/8/2020 10:26 AM, thomas lörtsch wrote:
> >>> On 8. Jun 2020, at 14:07, Hugh Glaser <hugh@glasers.org> wrote:
> >>>
> >>> Hi Thomas,
> > [snip]
> >
> >>> As a specific example of my problem, below you say: "I don’t see the
> pressing need for empty lists."
> >>> I think that means you have ideas of applications in mind - if you can
> expose those, please, that would be great.
> >> I didn’t for two reasons:
> >> - lists are such a fundamental concept that IMO examples rather cloud
> the view
> >> - my primary interest is to replace rdf:Lists with rdf:Collections and
> being able to close is what differentiates them on the semantic level
> >> But if you insist:
> >> - a list of my three favorite colors, unordered but finite.
> >
> > Not a list, so why try to make a list out of it?
> >
> >> - tables made from lists where it is important that each list (table
> row) has the same length
> >
> > If they are not the same length in the original set of triples, then you
> have to truncate them somehow.  If they are the same length, then you don't
> need to do anything special.  Either way, I don't see this as anything that
> needs list characteristics.  The list-ness of the data has nothing to do
> with how you fill a table with it.
> >
> >> And the application that I have always in mind is the contextualizing
> integrate-all-the-things that will finally bring love, peace and
> understanding to the world, ahem. But lists don’t play a very prominent
> role in that.
> >> Hope that helps
> >> Thomas
> >
> >
>
> --
> Hugh
> 023 8061 5652
>
>
>
```
Received on Wednesday, 10 June 2020 18:08:20 UTC

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