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| Ecore->XSD->Ecore roundtrip [message #1072191] |
Mon, 22 July 2013 05:03  |
Eclipse User |
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Hi,
so after years of vanilla EMF modelling I'm finally forced to enter the world of XML Schema  , meh.
What I currently do is: Take my models that are defined already in Ecore, and use the XSD Export function on the genmodel to get corresponding XSD models. The first question here:
What is the difference between "Export XSD for Ecore" and "Export XSD for XMI"?
Once I exported the ecore to schema, can I just use XML/XMI resources, and the serialized result will automatically be a valid according to the schemas? I guess if the original model is defined in Ecore, there's no need to use ExtendedMetadata in order to serialize?
Now, out of curiosity, I take the XSD files and re-create the Ecore models from them to do a full roundtrip. If I compare the original Ecore models against those created from the Schemas, I can see the following differences:
- The wrapper datatypes for nillable elements
- ExtendedMetadata annotations
So now I don't know If I should use the original Ecore models to serialize/deserialize, or the ones created from re-importing the corresponding XML schemas? My guts feeling is that I can skip the re-import, since the wrapper types are not used, and the annotations should represent some sort of "default" but maybe I miss something?
Once I'm done I'd be happy to contribute at least to the wiki or so 
Thanks for comments,
Felix.
[Updated on: Mon, 22 July 2013 05:04] by Moderator |
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| Re: Ecore->XSD->Ecore roundtrip [message #1072206 is a reply to message #1072191] |
Mon, 22 July 2013 05:35  |
| Eclipse User |
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Felix,
Comments below.
On 22/07/2013 11:03 AM, Felix Dorner wrote:
> Hi,
>
> so after years of vanilla EMF modelling I'm finally forced to enter
> the world of XML Schema :|, meh.
>
> What I currently do is: Take my models that are defined already in
> Ecore, and use the XSD Export function on the genmodel to get
> corresponding XSD models. The first question here:
>
> What is the difference between "Export XSD for Ecore" and "Export XSD
> for XMI"?
XMI schemas are basically useless. They provide a schema that describes
an XMI serialization of your model, but that schema is of essentially no
value because you can't describe an XMI serialization with a schema that
does a reasonable amount of validation.
>
> Once I exported the schema, can I just use XML/XMI resources, and the
> serialized result will automatically be a valid according to the
> exported schema?
Yes, that's the idea. Another problem though is that XML Schema doesn't
support multiple inheritance so isn't general enough to describe all
Ecore models.
> I guess if the original model is defined in Ecore, there's no need to
> use ExtendedMetadata in order to serialize?
No.
>
> Now, out of curiosity, I take the XSD files and re-create the Ecore
> models from them to do a full roundtrip. If I compare the original
> Ecore models against those created from the Schemas, I can see the
> following differences:
>
> - The wrapper datatypes for nillable elements
I'd expect nillable elements only for things that already allow null,
i.e., for things that aren't primitives.
> - ExtendedMetadata annotations
>
> So now I don't know If I should use the original Ecore models to
> serialize/deserialize, or the ones created from re-importing the
> corresponding XML schemas?
The original.
> My guts feeling is that I can skip the re-import, since the wrapper
> types are not used, and the annotations should represent some sort of
> "default" but maybe I miss something?
You shouldn't need to reimport from the generated schema.
>
> Once I'm done I'd be happy to contribute at least to the wiki or so :)
>
> Thanks for comments,
> Felix.
>
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| Re: Ecore->XSD->Ecore roundtrip [message #1073683 is a reply to message #1072240] |
Thu, 25 July 2013 05:47 |
| Eclipse User |
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Hi Ed,
On 22/07/2013 13:14, Ed Merks wrote:
>>>> Once I exported the schema, can I just use XML/XMI resources, and the
>>>> serialized result will automatically be a valid according to the
>>>> exported schema?
>>> Yes, that's the idea. Another problem though is that XML Schema doesn't
>>> support multiple inheritance so isn't general enough to describe all
>>> Ecore models.
>>
>> But the exporter can still create schemas for such models right?
> Yes.
>> The information that cannot be expressed in XSD is attached by using
>> ecore:... attributes in the schema.
> That's right.
But it looks like for example an EAttribute that comes from a
"secondary" superclass is lost in the schema representation, I give a
trivial example:
Airport
- runways: EInt
Trainstation
- platforms: EInt
TrafficHub -> Airport, Trainstation
- closedOnWeekends: EBoolean
The schema exporter generates a complex type TrafficHub like this:
<xsd:complexType ecore:implements="test1:Trainstation" name="TransportHub">
<xsd:complexContent>
<xsd:extension base="test1:Airport">
<xsd:attribute ecore:unsettable="false" name="closedOnWeekends"
type="ecore:EBoolean"/>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
Aha Effect: The "platforms" attribute is missing from the TransportHub type.
When I now serialize a TrafficHub it will contain an attribute
"platforms" which is not allowed on a TrafficHub type according
to the schema, so a pure xml validator that uses the schema will report
the document invalid, and someone who wants to build tools around the
schema definition will miss important bits unless the ecore: attributes
are taken into account.
I guess that's what you meant with "Another problem.." above.
Thanks,
Felix
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| Re: Ecore->XSD->Ecore roundtrip [message #1074131 is a reply to message #1073683] |
Fri, 26 July 2013 03:08 |
| Eclipse User |
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Felix,
Comments below.
On 25/07/2013 11:47 AM, Felix Dorner wrote:
> Hi Ed,
>
> On 22/07/2013 13:14, Ed Merks wrote:
>>>>> Once I exported the schema, can I just use XML/XMI resources, and the
>>>>> serialized result will automatically be a valid according to the
>>>>> exported schema?
>>>> Yes, that's the idea. Another problem though is that XML Schema
>>>> doesn't
>>>> support multiple inheritance so isn't general enough to describe all
>>>> Ecore models.
>>>
>>> But the exporter can still create schemas for such models right?
>> Yes.
>>> The information that cannot be expressed in XSD is attached by using
>>> ecore:... attributes in the schema.
>> That's right.
>
> But it looks like for example an EAttribute that comes from a
> "secondary" superclass is lost in the schema representation, I give a
> trivial example:
>
> Airport
> - runways: EInt
>
> Trainstation
> - platforms: EInt
>
> TrafficHub -> Airport, Trainstation
> - closedOnWeekends: EBoolean
XML Schema can't support multiple inheritance so in the end, it's
impossible for the schema to represent what you're serialize. Even if
we copied all the super class structure, a TrafficHub instance wouldn't
be allowed to appear where a Trainstation instance is allowed to appear,
so the serialization still can't generally conform to this schema.
>
> The schema exporter generates a complex type TrafficHub like this:
>
> <xsd:complexType ecore:implements="test1:Trainstation"
> name="TransportHub">
> <xsd:complexContent>
> <xsd:extension base="test1:Airport">
> <xsd:attribute ecore:unsettable="false"
> name="closedOnWeekends" type="ecore:EBoolean"/>
> </xsd:extension>
> </xsd:complexContent>
> </xsd:complexType>
>
> Aha Effect: The "platforms" attribute is missing from the TransportHub
> type.
>
> When I now serialize a TrafficHub it will contain an attribute
> "platforms" which is not allowed on a TrafficHub type according
> to the schema, so a pure xml validator that uses the schema will
> report the document invalid, and someone who wants to build tools
> around the schema definition will miss important bits unless the
> ecore: attributes are taken into account.
So if you want something that works for pure XML Schema you have to
avoid things not supported by XML Schema, e.g., no multiple inheritance.
>
> I guess that's what you meant with "Another problem.." above.
Yes.
>
> Thanks,
> Felix
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