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From Ole Ersoy <ole.er...@gmail.com>
Subject Re: [DAS OID GENERATION] Things that make you go hmmmm
Date Thu, 05 Apr 2007 04:16:11 GMT
Comments Inline

David Jencks wrote:
> I would prefer to see a solution that mapped java objects to existing 
> schemas
This will be supported.  The user just maps their SDO Metadata to
LDAP metadata in the configuration file.

The DAS only generates new LDAP metadata when the user wishes to skip
the mapping tasks.

>and perhaps has a way to generate schemas with oids,

For instance suppose I want to store schemas with my own
globally unique OIDs.  I just configure the DAS using my
PEN.

The DAS will automatically create the branches and use an ApacheDS
trigger to increment metadata OID numbers, or I could configure
the branches as well in case it is required for
synchronization / replication / etc.

The challenge with respect to the DAS generating OIDs is that
it has to know what the current OID incremental value needs to be.
Hopefully there is a simple LDAP standard way to discover that for 
servers that have yet to support triggers.  I know Hibernate supports
surrogate key generation, so that would be a good place to look and see 
how they did it.  Maybe they just scan the table column looking for
the maximum integer, and they start with that.  Our OID's are strings
though, so we'd need something a little more sophisticated.
  but it
> seems to me that autogeneration of something that is supposed to be 
> worldwide unique and meaningful may cause more difficulties than it solves.
> 
> For instance you'd need a way to reserve a unique PEN for each 
> installation on which you wanted to run this stuff.

Yes - Each Enterprise that wants to run it needs their own PEN, if they
want to guarantee global uniqueness, which they need when they
want to share metadata with other enterprises.  So I'll just put 
ApacheDS's PEN in as the configuration default, and we can add a note
in the users guide on "Global Uniqueness" requirements.
> 
> dunno, I'm kinda a beginner.
>
Good questions.  Do the answers sound ok?


> thanks
> david jencks
> 
Cheers,
- Ole
> 
> On Apr 4, 2007, at 4:22 PM, Ole Ersoy wrote:
> 
>> Yes - That's what I was hoping for - A trigger.
>>
>> Because the DAS could add some entries, and then
>> some other client, and then the DAS again.
>> So both clients would have to increment
>> the current OID number.
>>
>> I think it's a lot better to just make the server
>> responsible for this.
>>
>> Thanks,
>> - Ole
>>
>>
>>
>>
>>
>>
>> Emmanuel Lecharny wrote:
>>> Ole Ersoy a écrit :
>>>> Ah - That throws a fork wrench in my current planning.
>>>>
>>>> Can we change the specification so that we can have characters :-)
>>>>
>>>> OK - that brings up a different more serious question then.
>>>> Does ADS have the ability to assign an OID, sort of like
>>>> automatic surrogate key generation in RDBs?
>>>>
>>>> For instance I may wish to store an attributeType with the
>>>> following description:
>>>>
>>>> "org.tuscany.das.ldap.config.DASConfig.baseDN"
>>>>
>>>> Can ApacheDS assign the OID, thus freeing the DAS of that 
>>>> responsibility?
>>> Nope... OIDs are supposed to be unique, worldwide ! This may looks 
>>> like impossible to manage, but as you have you PEN, you can 
>>> workaround this problem. Just store somwhere in the server the 
>>> current number, or the last used number. You grab it, do your 
>>> homework (insert your objects), and store the incremented number.
>>> Otherwise, it could be interesting to add a trigger in the server to 
>>> auto-increment the OID after each insertion in a specific position 
>>> (this is something possible : we support triggers)
>>> SO you have options, but we should discuss them.
>>> The best thing you can do is to assume that ADS can assign OIDs, 
>>> whatever soltuion we will have to use to support this feature.
>>> Emmanuel
>>> ("If there is no solution, then the problem suddenly vanishes ...")
> 
> 

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