[Platypuswiki-users] Re: [platypus] Unique identifier for a statement...

[Stefano C. <cam...@ya...>]

Laurian Gridinoc wrote:

>On Wed, 15 Sep 2004 07:16:15 +0200, Paolo Castagna 
>  
>
>>>>... we need an unique identifier for a statement
>>>>in the index and for reification.
>>>>  <subject uri> <predicate uri> <object uri>
>>>>Is there any problem if we use SHA1?
>>>>  sha1(<subject uri> <predicate uri> <object uri>)?
>>>>        
>>>>
>>>Very OK with me, I mentioned it in a discussion about reification:
>>>http://lists.w3.org/Archives/Public/www-rdf-interest/2004Aug/0194.html
>>>but no one argued back with me :(
>>>      
>>>
>>So, it's decided: we'll use SHA1 ;)
>>I don't know how to tell in english... but:
>>"chi tace acconsente" :)
>>    
>>
Ok, I have added the follow methods in MetaManager class:

/*
     *@return the Triple ID
     *
     */
    public static String getStmtId(final URI subject, final URI 
predicate, final URI object) throws NoSuchAlgorithmException {
        final String tbDigest = 
subject.toString()+predicate.toString()+object.toString();
        byte[] digest =  getDigest(tbDigest.getBytes());
        Base64 base = new Base64();
        byte[] encoded = base.encode(digest);
        final String result = new String(encoded);
        return result;   
    }
       
    private static byte[] getDigest(byte[] buffer) throws 
NoSuchAlgorithmException {
            MessageDigest md5 = MessageDigest.getInstance("SHA1");
            md5.update(buffer);
            return md5.digest();
    }

So, we can calculate the ID of triples (tbd: literals ).
I'd like thinking at the ID as a URI of the triple. In fact, this is 
what happen during the reification.
In Platypus, when we create a refication we put the new resource (the 
refified triple) in the namespcace "reifications", so the URI is 
something like this: reifications:_086yskjf (reification+_CRC(s,p,o)).
I consider this " reifications:_086yskjf" as the ID/URI of the triple, 
isn't it?

If a triple isn't reificated? what is it's ID/URI?
May be:
namespace:_SHA1 (subjURI, predicateURI, objectURI/Literal)

Or directly

SHA1 (subjURI, predicateURI, objectURI/Literal)

In my opinion we are creating a new RDF resource naming it, so it could 
be in a fixed "installation depending" namespace.

I need this ID, becouse I use it to "add" or "remove" triples from the 
Lucene index.

Any ideas?