getting domain and range from Object Property

[PiotrB]

Hi,
I have serached along the forum for the answer, but cannot find it. My question is obvious: how do I get information about domain and range of Object Property. In Object Property of onto there are two private members: _range and _domain, however thay are empty whilst example owl file (dummy.owl) I am reading has set these properties. Here is my code:

#load the file
pth = "file:///dummy.owl"
onto = get_ontology(pth)
onto.load(only_local=True)
#try to access range and domain of specyfic object property
print(onto.r1._range)

The questions are:
1. how do I get range and domain of Object Property?
2. How do I easily find all Object Properties of a given class (e.g. onto.r1) for particular object class (e.g. onto.t1)?



dummy.owl

[PiotrB]

Hi,

This seems like a basic question. does nobody know the answer for it? Or maybe I don't understand how it should work. Please help.

[PiotrB]

Ok,
I have discovered some strange behaviour:
if I load this simple owl example (dummy.owl from posts above) it has only 1 singe object property called r1 i.e. onto.r1.
1. At first onto.r1._domain is None
2. I call onto.r1.domain (without underscore) and not onto.r1._domain is not empty anymore.

how is it possible if onto.r1 does not have a method called "domain"?

the same situation is with range.

Can anyone explain that?

[Jiba]

Hello,

You can get ranges and domains with the "range" and "domain" attribute (without _) of ObjectProperties.
The "_range" and "_domain" are attributes used for caching the value of range and domain. Owlready do not load ranges and domains until they are asked for, hence the need for a cache.  "_range" and "_domain" shoul dnot be used directly.


Regarding your second question, you may use .get_class_properties() to get the properties of a class, but it returns only properties that are necessarily present (i.e. with a "some" constraint).

If you want to obtain all possible properties (but not necessarily present), you can simply test all properties, as follows:

def get_possible_class_properties(Class):
    for prop in default_world.properties():
        if not prop.domain: yield prop
        else:
            for domain in prop.domain:
                if not issubclass(Class, domain): break
            else:
                yield prop
                   
print(list(get_possible_class_properties(onto.t1)))

Jiba

[Bart]

Hi Jiba, this doesn't seem to catch all properties. I have tried to handle multi-class domains (e.g. Or'd) and lists (Class.domain.Classes, Class.domain[0].Classes), but these are not catching the domains I am looking for.

What am I missing?
Thanks

Jiba wrote

Hello,

You can get ranges and domains with the "range" and "domain" attribute (without _) of ObjectProperties.
The "_range" and "_domain" are attributes used for caching the value of range and domain. Owlready do not load ranges and domains until they are asked for, hence the need for a cache.  "_range" and "_domain" shoul dnot be used directly.


Regarding your second question, you may use .get_class_properties() to get the properties of a class, but it returns only properties that are necessarily present (i.e. with a "some" constraint).

If you want to obtain all possible properties (but not necessarily present), you can simply test all properties, as follows:

def get_possible_class_properties(Class):
    for prop in default_world.properties():
        if not prop.domain: yield prop
        else:
            for domain in prop.domain:
                if not issubclass(Class, domain): break
            else:
                yield prop
                   
print(list(get_possible_class_properties(onto.t1)))

Jiba

[Jiba]

Hi,

I need more information for helping you. What is exactly the domains you are looking for ? Could you give me an example ?

Jiba