[Developers] Question about the backend software and data

[Shawn Simister]

Thanks for the feedback. I can see what you mean about the functional 
properties so I'll switch those over to cardinality restrictions. With 
respect to placing existential restrictions on certain properties, I 
don't think that that will be feasible for a couple of reasons.

First of all, I'm not aware of any such restrictions in the Freebase 
type system (although it might be nice to have them), so if I were to 
add these sorts of restrictions to ontologies there would be no 
guarantee that future RDF dumps of the Freebase data would actually 
conform to those ontologies.

Secondly, due to the fact that there are no explicit existential 
restrictions on any of the Freebase properties I would have to enter 
these restrictions by hand which is not easy given the growing number of 
types within Freebase. Even if someone where to model all these 
restrictions by hand, maintaining them over time as the types change 
would be a challenge.

One other issue that I have just noticed is that some domains have 
multiple types which have properties with the same names. For example, 
In the /measurement_unit domain, both DatedInteger and CountAsOfDate 
have a property named number. This causes a naming collision in some of 
the OWL ontologies. My first instinct was to simply merge the two 
properties into a single property which shares the domains and ranges of 
both properties.  The down side to this is that we would be making a 
naive assumption about the similarity of the properties being merged.

An alternate approach would be to model each Freebase type as a separate 
OWL file so that each type has a unique URI. I think that this approach 
is probably safer in the long run but I'd appreciate any input on what 
people think is a better design.

Shawn

Kavitha Srinivas wrote:
> Shawn
>   This is really very good.  I had a couple of suggestions:
> (a) Avoid usage of functional properties for integrity constraints and 
> use them instead for when you'd like to discover something.  For 
> instance, let's assume that you marriedTo is a functional property, so 
> that if the same person A is married to two people B and C then
> you want to infer B and C are the same person.
> (b) Another pattern you've used is to model domain and ranges for all 
> properties of a Person (e.g., Place of Birth, etc).  This is fine, but 
> I don't know if you want to capture the fact that any Person always 
> has a Place of Birth (but we may not necessarily know what that place 
> might be).  That is, Person can be modeled as an existential 
> restriction (exists.PlaceOfBirth{Location}).  This latter form of 
> modeling is a commonly adopted pattern in many large life sciences 
> ontologies.
>
> Kavitha
>
> On Oct 3, 2007, at 5:40 AM, Shawn Simister wrote:
>
>> I've just put together a first attempt at representing the Freebase 
>> type system as OWL ontologies. There's still some work to be done but 
>> I figured I'd give you guys an update and hopefully get some feedback 
>> on how I'm modeling these domains in OWL.
>>
>> You can download it at 
>> http://www.simister.ca/temp/freebase-owl-03-10-07.zip. The way that 
>> it's set up right now is one OWL ontology per file per Freebase 
>> domain. Let me know what you think.
>>
>> Shawn
>>
>> Kavitha Srinivas wrote:
>>> Not really, am in interested in modeling issues rather than a 
>>> specific domain.  Thanks!
>>> Kavitha
>>>
>>> On Sep 30, 2007, at 4:24 PM, Shawn Simister wrote:
>>>
>>>> I'm just putting together a new version of the ontology now which I 
>>>> will make available on my website. Is there a particular domain 
>>>> that you want to see? Right now I'm just focusing on the 67 or so 
>>>> main Freebase domains.
>>>>
>>>> Shawn
>>>>
>>>> Kavitha Srinivas wrote:
>>>>> Is Shawn's OWL ontology available somewhere?
>>>>> Kavitha
>>>>>
>>>>> On Sep 28, 2007, at 9:52 PM, John Giannandrea wrote:
>>>>>
>>>>>
>>>>>> Kirrily Robert wrote:
>>>>>>
>>>>>>> To me, RDF sounds like it meets those criteria.
>>>>>>>
>>>>>> I agree that an RDF dump of the data makes sense.
>>>>>> There are important details though, like how to represent
>>>>>> the schema.  Shawn Simister previously posted about
>>>>>> creating an OWL ontology from the freebase types, rather
>>>>>> than using RDF Schema, which seemed sensible.
>>>>>>
>>>>>> The key point was that Shawn was able to extract the data
>>>>>> and turn it into those formats, using HTTP, MQL and JSON.
>>>>>>
>>>>>> -jg
>>>>>>
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>>>>>
>>>>
>>>
>>
>
>