Hi Bertrand,

I believe this is unchartered territory.
It is (usually?) safe to assume that the persistence state written by Oak 
version X can be read and modified by version Y if Y > X.
However: version Y might introduce new features or perform changes on the 
state’s format, etc. When such a change is introduced it is not considered that 
version X might still operate on the same state.
For many values of X and Y your setup would probably work in practice. But to 
my knowledge there is no formal way to find out which values of X and Y are 
safe - at least so far. 

Michael




On 28/07/16 10:45, "Bertrand Delacretaz" <[email protected]> wrote:

>Hi,
>
>On Thu, Jul 28, 2016 at 10:23 AM, Stefan Egli <[email protected]> wrote:
>>...we could introduce a concept of
>> 'compatibility levels' which are a set of features/behaviours that a
>> particular oak version has and that application code relies upon....
>
>Good timing, I have a related question about multiple client apps
>connecting to the same Oak backend.
>
>Say I have to Java apps A and B which use the same Oak/Mongo/BlobStore
>configuration, are there defined requirements as to the Oak library
>versions or other settings that A and B use?
>
>Do they need to use the exact same versions of the Oak bundles, and
>are violations to that or to other compatibility requirements
>detected?
>
>-Bertrand

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