Home » Modeling » EMF » Insulating persisted data from changes to the Ecore model schema
| Insulating persisted data from changes to the Ecore model schema [message #767562] |
Sun, 18 December 2011 05:37  |
Eclipse User |
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Hi,
How can I re-use data that I've persisted earlier, using an older version of my Ecore model schema, after making changes, e.g addition of a new Ecore class and creating a new relationship?
For example, suppose that for the first version, I create a Library class and a Book class. I create the eclipse EMF plugin and create a new library project and add some books to the library.
For the second version, I add an Author class and model the relationship between the Book, Author and Library classes.
I've noticed that after I regenerate the new plugin, I am unable to right click on the Library model element and add a new Author.
I recall a while back that EMF was supposed to help insulate persisted data from changes in the model schema. I vaguely recall that it worked at the time.
But, when I try it now, it doesn't seem to work.
I'm using Eclipse-3.7 SR1 modeling tools SDK bundle on Mac OS X 10.7.2.
Elvis Dowson
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| Re: Insulating persisted data from changes to the Ecore model schema [message #767608 is a reply to message #767562] |
Sun, 18 December 2011 08:24  |
| Eclipse User |
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Elvis,
Comments below.
On 18/12/2011 11:37 AM, Elvis Dowson wrote:
> Hi,
> How can I re-use data that I've persisted earlier, using an older
> version of my Ecore model schema, after making changes, e.g addition
> of a new Ecore class and creating a new relationship?
Additions shouldn't be a problem.
>
> For example, suppose that for the first version, I create a Library
> class and a Book class. I create the eclipse EMF plugin and create a
> new library project and add some books to the library.
>
> For the second version, I add an Author class and model the
> relationship between the Book, Author and Library classes.
> I've noticed that after I regenerate the new plugin, I am unable to
> right click on the Library model element and add a new Author.
Did you add a containment reference? (Note if not, and you change it,
you'll still have to change the GenFeature property for Libraries
authors feature.)
>
> I recall a while back that EMF was supposed to help insulate persisted
> data from changes in the model schema. I vaguely recall that it
> worked at the time.
>
> But, when I try it now, it doesn't seem to work.
> I'm using Eclipse-3.7 SR1 modeling tools SDK bundle on Mac OS X 10.7.2.
>
> Elvis Dowson
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| Re: Insulating persisted data from changes to the Ecore model schema [message #767633 is a reply to message #767621] |
Sun, 18 December 2011 09:37 |
| Eclipse User |
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Hi Ed,
I tried it once again carefully, and it worked. I don't know what went wrong earlier.
The last time, I'd manually re-load the genmodel, this time around, I noticed that the genmodel was
always in sync with the changes made to the ecore diagram.
I've attached screenshots and the model project with this message. Its working fine now.
I've come across COPE (Coupled Evolution of Metamodels and Models) which takes things a bit further and allows you to build a migrator, to convert models if the meta-model changes.
While building this example, I changed the relationship between Book and Author from "has" to "written_by", and it automatically picked up the changes while loading an older version of the model, which had the "has" relationship.
So, to what extent does EMF actually insulate or preserve existing data, from changes to the meta-model / Ecore model schema?
Best regards,
Elvis Dowson
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| Re: Insulating persisted data from changes to the Ecore model schema [message #767656 is a reply to message #767633] |
Sun, 18 December 2011 10:55 |
| Eclipse User |
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Elvis,
As long as you only add things, but no renames or removes, you should be
fine. There are also options like OPTION_RECORD_UNKNOWN_FEATURES that
can help in cases where you really break the serialization.
On 18/12/2011 3:37 PM, Elvis Dowson wrote:
> Hi Ed,
> I tried it once again carefully, and it worked. I don't know what went wrong earlier.
>
> The last time, I'd manually re-load the genmodel, this time around, I noticed that the genmodel was
> always in sync with the changes made to the ecore diagram.
>
> I've attached screenshots and the model project with this message. Its working fine now.
>
> I've come across COPE (Coupled Evolution of Metamodels and Models) which takes things a bit further and allows you to build a migrator, to convert models if the meta-model changes.
>
> While building this example, I changed the relationship between Book and Author from "has" to "written_by", and it automatically picked up the changes while loading an older version of the model, which had the "has" relationship.
>
> So, to what extent does EMF actually insulate or preserve existing data, from changes to the meta-model / Ecore model schema?
>
> Best regards,
>
> Elvis Dowson
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