[protege-owl] necessary vs necessary and sufficient

classic Classic list List threaded Threaded
5 messages Options
Reply | Threaded
Open this post in threaded view
|

[protege-owl] necessary vs necessary and sufficient

Hugo Ferreira
Hi All,

I am trying to understand what it means for a class to have "necessary"
or "necessary and sufficient" conditions. I have read the article
entitled "OWL Pizzas: A practical Experience of Teaching OWL-DL: Common
Errors & Common Patterns" but still cannot understand this.

Can anyone point me to text that explains this in very simply terms? I
am specifically interested in knowing what implications this has in
concept modeling and inference results.

TIA,
Hugo Ferreira.
-------------------------------------------------------------------------
To unsubscribe go to http://protege.stanford.edu/community/subscribe.html

Reply | Threaded
Open this post in threaded view
|

[protege-owl] Re: necessary vs necessary and sufficient

Ulrike Sattler
Hi Hugo,

assume I define

"OldCat"

as cats of old age (and it doesn't really matter how exactly I do this).

If this is a "necessary" definition and somebody gives me an instance  
of OldCat, then I will know that this cat is of old age.
I.e. this "necessary definition" corresponds to an implication from  
OldCat to cats of old age.

If this is a "necessary and sufficient" definition and somebody gives  
me an instance of OldCat, then I will know that this cat is of old  
age.  Moreover, if somebody gives me a cat that is of old age, then I  
can conclude that this is an instance of OldCat.
I.e., this "necessary and sufficient" definition corresponds to a bi-
implication between OldCat and cats of old age.

Cheers, Uli

On 29 May 2006, at 15:01, Hugo Ferreira wrote:

> Hi All,
>
> I am trying to understand what it means for a class to have  
> "necessary" or "necessary and sufficient" conditions. I have read  
> the article entitled "OWL Pizzas: A practical Experience of  
> Teaching OWL-DL: Common Errors & Common Patterns" but still cannot  
> understand this.
>
> Can anyone point me to text that explains this in very simply  
> terms? I am specifically interested in knowing what implications  
> this has in concept modeling and inference results.
>
> TIA,
> Hugo Ferreira.
> ----------------------------------------------------------------------
> ---
> To unsubscribe go to http://protege.stanford.edu/community/ 
> subscribe.html
>

-------------------------------------------------------------------------
To unsubscribe go to http://protege.stanford.edu/community/subscribe.html

Reply | Threaded
Open this post in threaded view
|

[protege-owl] Re: necessary vs necessary and sufficient

Hugo Ferreira
Hi,

Ulrike Sattler wrote:

> Hi Hugo,
>
> assume I define
>
> "OldCat"
>
> as cats of old age (and it doesn't really matter how exactly I do this).
>
> If this is a "necessary" definition and somebody gives me an instance  
> of OldCat, then I will know that this cat is of old age.
> I.e. this "necessary definition" corresponds to an implication from  
> OldCat to cats of old age.
>
> If this is a "necessary and sufficient" definition and somebody gives  
> me an instance of OldCat, then I will know that this cat is of old  
> age.  Moreover, if somebody gives me a cat that is of old age, then I  
> can conclude that this is an instance of OldCat.
> I.e., this "necessary and sufficient" definition corresponds to a bi-
> implication between OldCat and cats of old age.
>

I think I have it. Just to check:
a) I define the class Cat with property age
b) I define the class Old-cat with the restriction that any cat with
"age>5" is an old cat
c) I define an instance subClass(Bobby,Cat) and assign it the age
property a value of "6"

If I use the "necessary & sufficient" restriction in (b) then I can say
that Bobby is not just a cat, he is an Old-cat.

If I use "necessary" restriction in (b) then I can only say that Bobby
is a 6 year old cat. So if I query the reasoner to "compute all
individuals for class Old-cat" I get nothing.

Correct?

Thank you,
Hugo Ferreira.


> Cheers, Uli
>
> On 29 May 2006, at 15:01, Hugo Ferreira wrote:
>
>> Hi All,
>>
>> I am trying to understand what it means for a class to have  
>> "necessary" or "necessary and sufficient" conditions. I have read  the
>> article entitled "OWL Pizzas: A practical Experience of  Teaching
>> OWL-DL: Common Errors & Common Patterns" but still cannot  understand
>> this.
>>
>> Can anyone point me to text that explains this in very simply  terms?
>> I am specifically interested in knowing what implications  this has in
>> concept modeling and inference results.
>>
>> TIA,
>> Hugo Ferreira.
>> ----------------------------------------------------------------------
>> ---
>> To unsubscribe go to http://protege.stanford.edu/community/ 
>> subscribe.html
>>
>
> -------------------------------------------------------------------------
> To unsubscribe go to http://protege.stanford.edu/community/subscribe.html
>
>

-------------------------------------------------------------------------
To unsubscribe go to http://protege.stanford.edu/community/subscribe.html

Reply | Threaded
Open this post in threaded view
|

[protege-owl] Re: necessary vs necessary and sufficient

Ulrike Sattler
On 29 May 2006, at 16:00, Hugo Ferreira wrote:

> Hi,
>
> Ulrike Sattler wrote:
>> Hi Hugo,
>> assume I define
>> "OldCat"
>> as cats of old age (and it doesn't really matter how exactly I do  
>> this).
>> If this is a "necessary" definition and somebody gives me an  
>> instance  of OldCat, then I will know that this cat is of old age.
>> I.e. this "necessary definition" corresponds to an implication  
>> from  OldCat to cats of old age.
>> If this is a "necessary and sufficient" definition and somebody  
>> gives  me an instance of OldCat, then I will know that this cat is  
>> of old  age.  Moreover, if somebody gives me a cat that is of old  
>> age, then I  can conclude that this is an instance of OldCat.
>> I.e., this "necessary and sufficient" definition corresponds to a  
>> bi- implication between OldCat and cats of old age.
>
> I think I have it. Just to check:
> a) I define the class Cat with property age
> b) I define the class Old-cat with the restriction that any cat  
> with "age>5" is an old cat
> c) I define an instance subClass(Bobby,Cat) and assign it the age  
> property a value of "6"
>

ok, apart from the fact that Bobby is an *instance* of Cat (or you  
could have a subclass "veryOldCat")

> If I use the "necessary & sufficient" restriction in (b) then I can  
> say that Bobby is not just a cat, he is an Old-cat.
>
> If I use "necessary" restriction in (b) then I can only say that  
> Bobby is a 6 year old cat. So if I query the reasoner to "compute  
> all individuals for class Old-cat" I get nothing.
>
> Correct?
>

yes, correct!

> Thank you,
> Hugo Ferreira.
>
>
>> Cheers, Uli
>> On 29 May 2006, at 15:01, Hugo Ferreira wrote:
>>> Hi All,
>>>
>>> I am trying to understand what it means for a class to have  
>>> "necessary" or "necessary and sufficient" conditions. I have  
>>> read  the article entitled "OWL Pizzas: A practical Experience  
>>> of  Teaching OWL-DL: Common Errors & Common Patterns" but still  
>>> cannot  understand this.
>>>
>>> Can anyone point me to text that explains this in very simply  
>>> terms? I am specifically interested in knowing what implications  
>>> this has in concept modeling and inference results.
>>>
>>> TIA,
>>> Hugo Ferreira.
>>> --------------------------------------------------------------------
>>> -- ---
>>> To unsubscribe go to http://protege.stanford.edu/community/ 
>>> subscribe.html
>>>
>> ---------------------------------------------------------------------
>> ----
>> To unsubscribe go to http://protege.stanford.edu/community/ 
>> subscribe.html
>
> ----------------------------------------------------------------------
> ---
> To unsubscribe go to http://protege.stanford.edu/community/ 
> subscribe.html
>

-------------------------------------------------------------------------
To unsubscribe go to http://protege.stanford.edu/community/subscribe.html

Reply | Threaded
Open this post in threaded view
|

[protege-owl] Re: necessary vs necessary and sufficient

Hugo Ferreira
Hello,

Ulrike Sattler wrote:

> On 29 May 2006, at 16:00, Hugo Ferreira wrote:
>
>> Hi,
>>
>> Ulrike Sattler wrote:
>>
>>> Hi Hugo,
>>> assume I define
>>> "OldCat"
>>> as cats of old age (and it doesn't really matter how exactly I do  
>>> this).
>>> If this is a "necessary" definition and somebody gives me an  
>>> instance  of OldCat, then I will know that this cat is of old age.
>>> I.e. this "necessary definition" corresponds to an implication  from  
>>> OldCat to cats of old age.
>>> If this is a "necessary and sufficient" definition and somebody  
>>> gives  me an instance of OldCat, then I will know that this cat is  
>>> of old  age.  Moreover, if somebody gives me a cat that is of old  
>>> age, then I  can conclude that this is an instance of OldCat.
>>> I.e., this "necessary and sufficient" definition corresponds to a  
>>> bi- implication between OldCat and cats of old age.
>>
>>
>> I think I have it. Just to check:
>> a) I define the class Cat with property age
>> b) I define the class Old-cat with the restriction that any cat  with
>> "age>5" is an old cat
>> c) I define an instance subClass(Bobby,Cat) and assign it the age  
>> property a value of "6"
>>
>
> ok, apart from the fact that Bobby is an *instance* of Cat (or you  
> could have a subclass "veryOldCat")
>

Oops. That's what I meant: Bobby is an instance of Cat.

>> If I use the "necessary & sufficient" restriction in (b) then I can  
>> say that Bobby is not just a cat, he is an Old-cat.
>>
>> If I use "necessary" restriction in (b) then I can only say that  
>> Bobby is a 6 year old cat. So if I query the reasoner to "compute  all
>> individuals for class Old-cat" I get nothing.
>>
>> Correct?
>>
>
> yes, correct!
>

Thank you very much. Appreciate it.

Regards,
Hugo Ferreira.


>> Thank you,
>> Hugo Ferreira.
>>
>>
>>> Cheers, Uli
>>> On 29 May 2006, at 15:01, Hugo Ferreira wrote:
>>>
>>>> Hi All,
>>>>
>>>> I am trying to understand what it means for a class to have  
>>>> "necessary" or "necessary and sufficient" conditions. I have  read  
>>>> the article entitled "OWL Pizzas: A practical Experience  of  
>>>> Teaching OWL-DL: Common Errors & Common Patterns" but still  cannot  
>>>> understand this.
>>>>
>>>> Can anyone point me to text that explains this in very simply  
>>>> terms? I am specifically interested in knowing what implications  
>>>> this has in concept modeling and inference results.
>>>>
>>>> TIA,
>>>> Hugo Ferreira.
>>>> --------------------------------------------------------------------
>>>> -- ---
>>>> To unsubscribe go to http://protege.stanford.edu/community/ 
>>>> subscribe.html
>>>>
>>> ---------------------------------------------------------------------
>>> ----
>>> To unsubscribe go to http://protege.stanford.edu/community/ 
>>> subscribe.html
>>
>>
>> ----------------------------------------------------------------------
>> ---
>> To unsubscribe go to http://protege.stanford.edu/community/ 
>> subscribe.html
>>
>
> -------------------------------------------------------------------------
> To unsubscribe go to http://protege.stanford.edu/community/subscribe.html
>
>

-------------------------------------------------------------------------
To unsubscribe go to http://protege.stanford.edu/community/subscribe.html