Re: SKOS modeling

Hi Alessandro


On Wed, 9 Nov 2016, at 15:36, Alessandro Seganti wrote:
> Hi everyone,
> after some years working with semantic technologies, I am still not
> 100% sure I understand what SKOS is used for.
>
> To my understanding, SKOS should be used to model relations between
> entities that are not certain so instead of modeling it as "is a" we
> say that it is "broader than" or things like this.
No, it's not about certainty. A SKOS concept may be an owl:Class in
which case a super-class would probably be a broader concept.

>
> If this is true, then I don't understand why I see many people
> building taxonomy trees using SKOS relations. Is there some confusion
> around or maybe I am missing something?
There are certainly many cases where you could use either SKOS or OWL or
use them together. The main difference is that OWL classes can have and
typically have instances while SKOS concepts cannot be instantiated
(unless they are also classes).

>
> Also could you give me an example where it is better to use SKOS than
> to use "is a" relationships?

If your data describes different individual dogs you might have various
classes for the different breeds of dogs, there probably are some sub-
class relations between those classes. Each individual dog is an
instance of one or several of those classes. If however your data is
about dog books, these books are obviously not an instance of a
particular breed of dog but may have a breed of dog as subject. In this
case you would better model the different dog breeds as skos:Concepts
rather than as owl:Classes.

So to summarize:
- if you want to categorize some resources use classes so that the
  resources can have meaningful types
- if you want to describe your thesaurus or want something a bit more
  formalized than tags to annotate your items (to say "this has to do
  with") use SKOS

Hope this helps.

Reto