Tolog query questions

[Pierre Thibault]

Hello,

I am a newbie to Tolog.

I'm having some difficulties with Tolog. I am trying a query from Ontopia Tolog documentation:

select $A, count($B) from
  composed-by($A : composer, $B : opera)?

I am using Ontopia 5.3.0, the website itself, with the example file ItalianOpera.ltm and the query above returns no row at all.

But if I change the query by changing 'opera' to 'work':

select $A, count($B) from
  composed-by($A : composer, $B : work)?

then it returns:

A	B
Alfano, Franco	12
Puccini, Giacomo	12
Ponchielli, Amilcare	12
Montemezzi, Italo	8
Smareglia, Antonio	10
Franchetti, Alberto	10
Giordano, Umberto	13
Leoni, Franco	10
Leoncavallo, Ruggero	10
Cilèa, Francesco	7
Faccio, Franco	4
Boïto, Arrigo	2
Mascagni, Pietro	16
Catalani, Alfredo	5
Zandonai, Riccardo	13
Verdi, Giuseppe	28

The definition of composed-by is:

[composed-by = "Composed by"
             = "Composed" / composer
    @"http://psi.ontopedia.net/composed_by"]

and each time it used with "work":

composed-by( alfano : composer, cyrano-de-bergerac : work )

and "cyrano-de-bergerac" is an opera:

[cyrano-de-bergerac : opera = "Cyrano di Bergerac"
    @"http://psi.ontopedia.net/Cyrano_di_Bergerac"]

So why is the initial query for the tutorial returns no result?

The fix to me is:

select $A, count($B) from
  composed-by($A : composer, $B : work),
  instance-of($B, opera)?

It gives the same result. I guess all works are opera. Right?

But a problem here is that I don't know the type of the second end of "composed-by". And why would I need to know?

It does not make sense for me. Could someone explain?

[Dan Speck]

Pierre,

The composed-by association type has two roles: composer and work so you need to use those to find pairs of composers and works. If you want to only get the works that are operas you can narrow these results as follows:

select $A, count($B) from
  composed-by($A : composer, $B : work)
, instance-of($B, opera)
?

-dan

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[Pierre Thibault]

OK,

But why is the composer role only present in the definition?

[composed-by = "Composed by"
             = "Composed" / composer
    @"http://psi.ontopedia.net/composed_by"]

Why is "work" not present on the defintion?

[Dan Speck]

Pierre,

This LTM fragment:

[composed-by = "Composed by"
             = "Composed" / composer
    @"http://psi.ontopedia.net/composed_by"]

1. Defines a topic "Composed by" with item identifier "composed-by", subject identifier "http://psi.ontopedia.net/composed_by". The

= "Composed" / composer

assigns the name "Composed" with scope "composer" so that when viewing the association in, e.g., Omnigator, from the perspective of the "composer" you will see "Composed", otherwise you see "Composed by". This is really just a convention that Omnigator uses.

You really need to look at the topic map itself to see the role types in a given association type. If you export the ItalianOpera topic map in LTM format you will see:

...

/* -- AT: composed-by */
composed-by( alfano : composer, cyrano-de-bergerac : work )
composed-by( alfano : composer, don-juan-de-manara : work )
composed-by( alfano : composer, i-cavalieri-e-la-bella : work )
...

-dan