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From Peter Klügl <peter.klu...@averbis.com>
Subject Re: opinion on degree of backwards compatibility for Uima V3 experiment
Date Fri, 02 Sep 2016 13:27:33 GMT
Tested all formats, did not happen for a reasonable complex CAS.

Am 02.09.2016 um 15:26 schrieb Marshall Schor:
> Re: deserializing the same CAS twice shouldn't change the addresses;  if you
> have a case where it's doing that, I'll investigate (need a small test case...).
> -Marshall
> On 9/2/2016 5:36 AM, Peter Klügl wrote:
>> Same here.
>> It looks like that we are now also starting to use the address, and I am
>> also thinking of using it more in Ruta (internal indexing).
>> Btw, I did some simple experiments lately concerning the stability of
>> the addresses when using CasIOUtils. Can it happens that the addresses
>> change if you just deserialize the same CAs twice without serializing it
>> in between?
>> Best,
>> Peter
>> Am 01.09.2016 um 19:29 schrieb Richard Eckart de Castilho:
>>> FS IDs are IMHO a very useful thing. Providing out-of-band (i.e. out-of-type-system)
unique identifiers for feature structures facilitates handling them in e.g. in editors. We
use that quite a bit in WebAnno.
>>> In WebAnno, we do not rely on any heap arithmetics - an ID is just expected to
be a unique identifier. However, I could imagine cases where people might rely on the ID to
increment monotonically for new FSes.
>>> Most binary formats do not preserve the ID across a save/load cycle. However,
SERIALIZED and SERIALIZED_TSI *do* preserve the ID, and WebAnno makes used of that. It allows
to keep references to FSes without having to keep the CAS in memory all the time. 
>>> There should continue to be a V3 serialization format which preserves IDs across
a load/save cycle. 
>>> I do presently not see a case where a strong similarity between V2 and V3 IDs
would be important. It would be nice if deserializing a V2 SERIALIZED or SERIALIZED_TSI into
V3 would restore the V2 IDs - I expect it to be an easy thing to do.
>>> Cheers,
>>> -- Richard
>>>> On 01.09.2016, at 16:09, Marshall Schor <msa@schor.com> wrote:
>>>> UIMA V3 implementation includes in many places extra code (takes time / space)
>>>> whose goal is to make things look closer to version 2.  Some of this is for
>>>> interoperability with version 2 artifacts, like serialized forms.
>>>> An example: in v2, many serialization forms include "references" to other
>>>> Feature Structures (FSs), and for those, the encoding is the "address" in
>>>> heap of the FS.
>>>> In v3, there is no heap, but the FSs have "ids", which are (at the moment)
>>>> int which increments by 1.  This mis-matches the "address" in v2, so many
>>>> of the serialization code builds a map at serialization time from the v3
id's to
>>>> v2 "addresses", and uses the latter in the serialization form.
>>>> Currently, this is done for various binary serializations, so that these
can be
>>>> read back in by v2 code.
>>>> Currently, it's not done for JSON or XMI (and maybe XCAS - haven't checked).
>>>> the serialized forms for these differ between v2 and v3, in that the numbers
>>>> used to represent references to other FSs are different.
>>>> The deserialization code for XMI and JSON doesn't depend on these numbers
>>>> anything other than unique per FS, so there's no issue in deserializing.
>>>> the UIMA community may have built other things that depend on these identifiers
>>>> not changing. 
>>>> What's your opinion: should the XMI and JSON etc serialization in V3 be changed
>>>> to reproduce (approximately) the same reference numbers as v2?  I say
>>>> approximately, because other factors might affect these, such as the ordering
>>>> for things not in "ordered" indexes, etc. between v2 and v3.
>>>> -Marshall

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