Re: [Boost-users] [serialization] skipping data

From: Joel de Guzman (joel_at_[hidden])
Date: 2006-07-11 09:38:51

Peter Dimov wrote:
> Joel de Guzman wrote:
>> Peter Dimov wrote:
>>> Joel de Guzman wrote:
>>>> Peter Dimov wrote:
>>>>
>>>>> I can't help but wonder: if some parts of your v1 format are so
>>>>> completely redundant as to allow you to reconstruct the original
>>>>> data even if you skip them, what was the point of writing them in
>>>>> the first place?
>>>> Here's one scenario (I'm sure there are others): Your class uses a
>>>> 3rd party library called Y. Later, you decide to replace it with
>>>> a better engine using a library called Z.
>>> Still not getting it. Do you have an example?
>> That was the example ;)... Ok let me see if I can clarify...
>> With version 1 you have a class A with this structure:
>>
>>     class A { W, w, X x; Y rep; };
>>
>> Now with version 2, you want to use a new engine to replace Y:
>>
>>     class A { W, w, X x; Z rep; };
>>
>> Z is so different from Y that it does not need any of its data.
>> It is also plausible that W,X,Y and Z get some data from other
>> external sources. So, in effect, Z starts with a default data and
>> gets filled as the app runs.
> 
> Right. What I was saying is that if the pair (w, x) is all you need to 
> reconstruct an A, then there is no need to store the Y part (except 
> short-term convenience). 

Good point! Maybe I ought to review the situation. It might be
that what's actually needed in this case is a converter from Y
to Z.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net