oship-dev team mailing list archive

[Eduardo César <xcesar@xxxxxxxxx>]

Hi all,

Thank you Sergio and Luciana for the answers. I did a little research in the
web about the subject of circular references in python and there seems to be
a consensus between various developers about the non triviality of this
particular problem in the python language.
As far as I know, the python language lacks a support for circular
references, and there is no guarantee that we can implement them by standard
ways. Perhaps a clever hack would be the answer we need, but I don't really
know how to do this. In this matter, I would like to see more about what the
Zope/Grok and python experts have to say and perhaps we can come up with a
solution.

Cheers
Eduardo

2010/3/13 Luciana Tricai Cavalini <lutricav@xxxxxxxxx>

>  Hi all,
>
> Let me try to say something about what I've heard from Tim about this
> "circular importing" problem.
> The fact is that, so far, no Zope application development had to deal with
> such a complex hierarchy as the implementation of the openEHR
> specifications.
> Tim has discussed it over and over again on the Zope and Grok developer's
> lists and they often told him that OSHIP was "overengeneered".
> This is a lack of understanding about the specific complexity of healthcare
> information, and especially how multilevel modeling has to be implemented
> for healthcare, which is the best (only?) way to deal with the complexity of
> healthcare information.
> Despite the fact that ZODB solves the persistence problems that all other
> openEHR implementations seems to struggle with, fact is that nodoby in the
> planet have ever implemented something so complex in Zope/Grok as OSHIP, as
> far as we know.
> Thus, dealing with those "circular import" problems is still work in
> progress for us.
> So, yes, Sergio, as far as I know, the current configuration is the only
> solution Tim found.
> I am not sure about how detailed this whole circular import problem and its
> solution is described in the OSHIP developer's guide, but we need to take a
> look.
> We have Zope/Grok experts in the project now; this is something that I
> think they could contribute to. I am sure Tim would appreciate that. Not to
> mention the improvement to the project as a whole.
>
> Cheers, Luciana.
>
>
> Sergio Miranda Freire escreveu:
>
>  Hi Eduardo,
>
>
>
> Ever since Oship began, Tim has been complaining about this kind of
> problem. In the first versions, he had arranged all classes in separated
> directories and files, according to its package structure. Later for reasons
> that I ignore he has moved to the current configuration. He had to change
> the schema of some attributes in order to avoid the problem you have just
> mentioned. In this case, parent in IEvent is defined as being an IObjectRef.
> Possibly this may happen somewhere else. This was the solution Tim found. I
> don´t know if there is an alternative. Maybe it is another case to go into
> the implementation guide.
>
>
>
> Cheers,
>
>
>
> Sergio
>
>
>
> *De:* oship-dev-bounces+sergio=lampada.uerj.br@xxxxxxxxxxxxxxxxxxx [
> mailto:oship-dev-bounces+sergio=lampada.uerj.br@xxxxxxxxxxxxxxxxxxx<oship-dev-bounces+sergio=lampada.uerj.br@xxxxxxxxxxxxxxxxxxx>]
> *Em nome de *Eduardo César
> *Enviada em:* sábado, 6 de março de 2010 01:44
> *Para:* OSHIP-Dev
> *Assunto:* [Oship-dev] Egg and chicken
>
>
>
> Hi,
>
> In datastructures.py, in the class IEvent, the attribute "parent" needs to
> be defined as of type "IHistory".
> But there is a catch because the class IHistory has some attributes that
> are of type IEvent.
>
> If I try to define "parent" with the correct type, the interpreter
> complains that IHistory is not defined yet. If I exchange the order of the
> classes, the interpreter complains that IEvent is not defined. Right now,
> "parent" is defined of being of another type, for things to work.
>
> I am wondering how I can solve this... someone has any hints?
>
> Cheers
> Eduardo
>
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