Re: [Virtuoso-users] [Dbpedia-discussion] Text Searching in Virtuoso / 2 questions

[Yrjänä R. <gh...@zo...>]

Aldo Bucchi wrote:
> Yrjänä,
>
>   
>>> String literals in predicates is not a very common practicality in
>>> RDF. We only have full-text indexing on object values.
>>>       
>> Hmm. Sorry for being sarcastic here. Subject and predicate values cannot
>> be literals in RDF statements. Just to be clear.
>>     
>
> YOU ARE RIGHT and for all formal purposes the latter holds true.
>
>   

> However, bear in mind that when you get to the actual implementation
> of these models it becomes evident that such design decision (
> specially not allowing literals on the subject ) is questionable.
> In fact there has been an ongoing discussion about whether to allow
> this in a future version of RDF.
>   
Indeed: this is the current formal definition as per W3C documentation 
and may be subject to change. Albeit I am partially aware of the 
argument for allowing literals in subject position, I've seen none for 
allowing them in the predicate position.

I also wanted to publicly apologise Marvin for my rather stupid 
sarcastic remark in the first reply, as it goes against the philosophy 
and purpose of mailing lists such as these. We're all here to learn, 
after all :)

> SPARQL grammar, for example, allows literals on subject positions. And
> all my RDF implementations allow it with looks to a future change in
> the spec. I bet most DB implementors, such as OpenLink, have left the
> door open too at a deeper level.
>
> The restriction is not at all that obvious ;)
>
> Anyway. Just to give you some context on why someone might refer to
> this as something that is not "common" instead of not "possible".
>
>   
I thank you for that insight.

Best regards,

Yrjänä

> Best,
> A
>
>
> On Mon, Dec 1, 2008 at 12:14 PM, Yrjänä Rankka <gh...@zo...> wrote:
>   
>> Yrjänä Rankka wrote:
>>     
>>> Marvin Lugair wrote:
>>>       
>>>> Hi all!
>>>> This is more for the virtuoso folks but still cc-ing dbpedia.
>>>>
>>>> Please give us some input if you can answer these questions:
>>>> I am trying text search in virtuos from isql against a locally loaded
>>>> dbpedia.
>>>>
>>>>
>>>> *QUESTION ONE*
>>>> Why does bif:contains return faster than REGEX search, and why are
>>>> they returning a different number of counted rows? The search string
>>>> is not the real string but it does not change the question. Which
>>>> should we use?
>>>>
>>>>
>>>>         
>>> Marvin,
>>>
>>> Actually question one seems to be two questions
>>>
>>> 1. bif:contains uses Virtuoso's full-text indexing capability which is
>>> a much faster method than comparing each ?o using regex pattern.
>>> 2. regex filter and bif:contains have different pattern syntax and
>>> thus have different matches.
>>>
>>>       
>>>> (1) searching with with regex
>>>>
>>>> SQL>  sparql select count(*) where { ?s ?p ?o . FILTER regex(?o ,
>>>> "searchstring", "i")};
>>>> callret-0
>>>> INTEGER
>>>> _____________________________________________________________________________
>>>>
>>>>
>>>> 4344
>>>> 1 Rows. -- 3895755 msec.
>>>>
>>>>
>>>>
>>>>
>>>> (2) searching with bif:contains
>>>>
>>>> SQL> sparql select count(*) where {?s ?p ?o. ?o bif:contains
>>>> "searchstring"};
>>>> callret-0
>>>> INTEGER
>>>> _______________________________________________________________________________
>>>>
>>>>
>>>> 20737
>>>> 1 Rows. -- 208426 msec.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *Question 2*
>>>> Why can't I search a property or subject?
>>>>
>>>> SQL>  sparql select count(*) where {?s ?p ?o. ?p bif:contains
>>>> "searchstring"};
>>>> *** Error 37000: [Virtuoso Driver][Virtuoso Server]SQ074: Line 1:
>>>> SP031: SPARQL compiler: The group does not contain triple pattern
>>>> with '$p' object before bif:contains() predicate
>>>> at line 1 of Top-Level:
>>>>  sparql select count(*) where {?s ?p ?o. ?p bif:contains "searchstring"}
>>>>
>>>>
>>>>         
>>> String literals in predicates is not a very common practicality in
>>> RDF. We only have full-text indexing on object values.
>>>       
>> Hmm. Sorry for being sarcastic here. Subject and predicate values cannot
>> be literals in RDF statements. Just to be clear.
>>
>> Yrjänä
>>
>>
>>     
>>> Please see
>>> http://docs.openlinksw.com/virtuoso/rdfsparqlrulefulltext.html for
>>> more info.
>>>
>>> Yrjänä
>>>       
>>>>
>>>> THANKS!
>>>> Marv
>>>>
>>>>
>>>>
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>>>>         
>>>       
>> --
>> Yrjänä Rankka (gh...@zo...)
>> Grand Praetor of Excruciations - ZONK.NET Propaganda HQ
>> ZONK.NET - Advancing the Thermal Death of the Multiverse Since 1998
>>
>>
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>>     
>
>
>
>   


-- 
Yrjänä Rankka (gh...@zo...)
Grand Praetor of Excruciations - ZONK.NET Propaganda HQ 
ZONK.NET - Advancing the Thermal Death of the Multiverse Since 1998