[Cuis-dev] ODB options

[Hilaire Fernandes]

Le 17/12/2024 à 09:00, H. Hirzel a écrit :
>
>     The educator model[1] is straightforward to persist with reference
>     stream
>
>
> But it could also just just a number of  CSV files. A dynabook app 
> part managing planning schedules, task and time tables well is an app 
> in its own right which is will be welcomed by teachers. There are 
> situations where  each student has his or her own schedule. Also 
> general information is available in table format [3]  A user will have 
> more trust in the app if he or she sees that the information is stored 
> in a directory with subdirectories with CSV data

CSV is used to import/export time table, times slots or students. But 
you can't get everything on CSV,  for example the task  object in top of 
time/date/slot related attributes also contains a document object, which 
is handwritten notes.

task


>     but it is more complicated with the knowledge model[2] where each
>     document should be saved in its own refstream file and loaded at
>     demand, otherwise the whole model (educator+knowledge) may become
>     too big and slow to save/load. Imagine the activity of a teacher
>     or a learner along one school year, a lot of documents will be
>     produced.
>
> I understand that teachers and students produce dynabook documents and 
> exchange them. That means that a format for exchanging these documents 
> is needed. Probably a binary one but not necessarily. Or a combination 
> of it. MS Powerpoint and LOImpress also have  pages/sildes and use 
> various data formats. This format then is also the one to be used for 
> persistence.

Document will be a mixture of PlacedMorphs inserted in a common 
substrate, the Document Page. Using a save-format foreigner to the 
Smalltalk objects involved in a Document will be too much work for me

>     I play a bit with DiskProxy so that document referenced in the
>     educator model are saved as that, but I suspect it ends all the
>     document model are still load at once. Document are a mix of view,
>     model and presenter so it makes a lot, and it is not easy to
>     control how far in the tree of objects the persistence goes, then
>     other problems arise at realod, like disconnected object.
>
> Would it be possible to de-couple persistence needs?
> Do the views need to be persisted? See recent discussion on this list 
> about recreating morphs from source code, i.e. getting the source code 
> for a morph tree and then using it to rebuild it.

The handwritten notes are views, etc. If you don't save the views, then 
you have to design a model you can rebuild the views from. Saving the 
objects, as it was done in Squeak with project, is more straightforward. 
Trouble only come if your object definition changes, but there are some 
strategy for that kind of scenario.


-- 
http://mamot.fr/@drgeo
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