Copyright © 2014 Open Geospatial Consortium
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Error message
= One or more errors encountered in OCL constraint in class Installation : LengthValMeta ...
Detail message
= Linecolumns 6362: Unrecognized syntax [] encountered and ignored.
Detail message
= Linecolumns 6483: Identifier, literal or bracketed expression expected preceding operator
quot;=quot; token. Invalid assumed. Detail
message =
Linecolumns 6485‐502: Closing bracket expected preceding identifier quot;VoidNumValueReasonquot; token, assumed.
Detail message
= Linecolumns 6485‐502: Extra tokens following OCL expression ignored, starting with
identifier quot;VoidNumValueReasonquot;. Error
6.5.2 Identity comparisons between items of non-basic type
As it turned out it was necessary to provide support for equality comparisons on object- valued items. This had initially been ruled out, because it is hard to compile to XPath 1.0.
The following invariant expresses that the current feature of type SoundingMetadata requires that there is an associated HydroVertDimMeta object.
This would usually have been expressed by an invariant such as inv SoundingMetadata_ValidUse: hydroVertDimMeta-notEmpty
where hydroVertDimMeta points to the associated HydroVertDimMeta object. However, this hydroVertDimMeta role had been marked non-navigable in the model,
which disallows its use in the constraint. So this had to be re-formulated “from the other side” using the allInstances operation.
inv SoundingMetadata_ValidUse: HydroVertDimMeta.allInstances.soundingMetadata-existssm|sm=self
To do the translation of the sub-expression sm=self, equality comparisons had to be implemented also for objects. The implementation was added for comparison arguments,
which have identity such as FeatureTypes and results in the use of the XPath function
generate-idnode on the arguments. The function derives a unique string identifier from an element.
Note that this is an XSLT-extension to XPath and not a native XPath 1.0 one. This might lead to problems on Schematron implementations, which are not based on XSLT.
Comparisons between class instances, which do not carry identity such as DataTypes, are still refused in the Schematron code generation.
6.5.3 Inheritance of constraints
The implementation provided no support for inheriting constraints attached to the classes in the model, because it was not clear whether inheritance was indeed needed and how
constraints were supposed to override.
