The default extension attribute for a component looks like this (here an example for the component 'Period'): <xs:element name="periodExtension" type="D2LogicalModel:_ExtensionType" minOccurs="0" /> If there is a Level-B-Extension for the component Period, it will look like this (no error so far): <xs:element name="periodExtension" type="D2LogicalModel:_PeriodExtensionType" minOccurs="0" /> Of course there will be a complex type "_PeriodExtensionType" defined. But if you now deselect the Level-B-Extension in the DATEX-Tool (and keep Period selected), the result will be the same, that means there will be a pointer to "D2LogicalModel:_PeriodExtensionType", but this time the specific complex type is not defined anywhere (so the schema is invalid!). Solution: When deselecting a Level-B extension, the Tool must point to the default Extension class "D2LogicalModel:_ExtensionType". Alternatly, the specific extension type could be defined as an empty complex tyoe.
This is the same issue as issue #50.