Validating CPACS via Python's lxml library

[ArneBachmannDLR]

I just came across a kind of funny error when validating a CPACS 2.1 file via our CPACS validator webservice:

CPACS document is invalid for schema version 3.1: "Element 'cpacsVersion': [facet 'enumeration'] The value '2.1' is not an element of the set {'3.09999990463257e+00'}."
CPACS document is invalid for schema version 3.2: "Element 'cpacsVersion': [facet 'enumeration'] The value '2.1' is not an element of the set {'3.20000004768372e+00'}."

So it seems that the lxml parser really interprets the string 3.1 and 3.2 in the respective schema documents as floats and thus cannot compare them to the cpacsVersion which is e.g. 2.1.

One cause could be that cpacsVersion is a stringBaseType but receives a restriction to xsd:float with enum values that cannot be represented in binary.
Applies to headerType and updateType.

On the other hand, if lxml knows the expted enum type, it should equally convert the value of the CPACS file to float before comparing, so it may be a bug in lxml.

[codingpoets]

Is cpacsVersion really a stringBaseType? It seems to be a simpleType.

I would suggest making it a stringBaseType which would allow versions such as 3.3-beta1 to be used for beta releases. Otherwise cpacs files using a beta version can be confused with the final release.

[MarAlder]

With CPACS 3.4 it was restricted to xsd:string to account for patch versions (e.g, 3.3.1) (DLR-SC/tigl#830).

<xsd:element name="cpacsVersion" minOccurs="0">
    <xsd:annotation>
        <xsd:documentation>CPACS version that the dataset is valid to. The element is optional, since data sets
            can be valid for several CPACS versions. However, we strongly recommend to assign data sets to a
            specific CPACS version as far as possible, especially since some tools and libraries (e.g. TiGL)
            require this specification.
        </xsd:documentation>
    </xsd:annotation>
    <xsd:simpleType>
        <xsd:restriction base="xsd:string">
            <xsd:enumeration value="3.4"/>
        </xsd:restriction>
    </xsd:simpleType>
</xsd:element>