[Echempp-devel] segment classes and Factory (and XML)

[<ber...@t-...>]

Hi,
I thought a bit more about the problem of `outside' storage of segments 
(and possibly other classes) and reading of such storage.
In principle, we want to `save' and `load' information in a textual way.
I suggest that we call the corresponding functions like that.
Then, we have two problems which have to be solved:
(1) which techniques will allow us to generate an object of the desired 
type when loading information?
I think that Alexandresu's Factory template will help us a lot. Among 
other things, this template implements a function which generates an 
object of a certain type, when the type is coded by an ID of type say 
int (or better: char *). Thus, each type which is desired to be 
generated has its distinct ID (for example, each segment type must be 
coded into something exactly denoting its type). This object (concrete 
product of the factory) is returned as a pointer to its base class 
(abstract product). The ID code is stored in the file. Hopefully, this 
procedure will do. We will have to add some functions to each segment 
type, but that should be possible.
I'm afraid that I will have to do a similar thing for the Quantities 
library, because similar information is needed for the various quantity 
parameters `inside' the segment. And this brings us to the next question:
(2) what do we want to save and in which format?
Here, I recommend (taking up some earlier discussion with Kai) to use 
some XML extension, say `echemML' or `echeML'. I don't know too much 
about XML, but what I read tells me that this should give us a 
structured way to store and retrieve information. There are even C++ 
parser classes which read XML code and generate a parse tree from it
(see: http://www.grinninglizard.com/tinyxml/index.html). I have, 
however, no idea how complicated it is to implement something like that.
Best regards
Bernd

-- 
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Bernd Speiser
Institut f"ur Organische Chemie
Auf der Morgenstelle 18
D-72076 T"ubingen
Germany
phone: +49-7071-2976205 (office) +49-7071-2976242 (laboratory)
fax:   +49-7071-295518
e-mail: ber...@un...
Internet: http://www.uni-tuebingen.de/speiser
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