Limitations
Things That Work
- Class constants corresponding to string enumeration constraints
- Simple and complex type definitions
- List and union datatypes
- Constraints on (simple) datatypes (e.g., minInclusive, length)
- Model groups and attribute groups
- Complex content models (all, sequence, choice); minOccurs and maxOccurs
- Abstract types, xsi:type,
substitution groups
- Nillable elements with xsi:nil
- Namespace qualified attributes and elements
- Documentation annotations present in the schema are converted to Python
docstrings in the generated bindings.
- Pattern constraints (as long as the simple type derives from something
that is represented as a Python string)
Things That Don’t Work
...but could someday
- The ability to use templates to customize binding generation was promised
in the vision document. That has not yet been done, though it should be
fairly straightforward.
- Identity constraints (“key”, “unique”, “keyref”) are stored in the content
model, but are not used.
- Wildcard elements are
supported in the sense that classes that enable them in the content model
provide access to unrecognized values through the
complexTypeDefinition.wildcardElements method.
Where the type of the node is recognized, it is converted to a Python
binding instance; otherwise, the xml DOM instance is stored. Neither the
namespace constraint nor process contents attributes of the wildcard are
applied.
- Wildcard attributes are supported
in the same sense as wildcard elements: no constraints are checked, and
all are aggregated into the
complexTypeDefinition.wildcardAttributeMap.
Values are uninterpreted Unicode strings.
...and probably never will
- When generating a DOM instance from a binding instance, the resulting
document should validate against the schema, but the order of elements
within it may be different from the original order of creation. For an
example of this, see
tests/test-mg-choice:TestMGChoice.testMultichoiceOrderImportant.
See also
complexTypeDefinition._validatedChildren for a
work-around.
- The redefine directive
is not supported.
Things That Mostly Work, But They’re Ugly
- The duration type is based
on the Python datetime.timedelta class, which works reasonably well
for small deltas but does not handle month and year deltas. The PyXB
version records that information, but the timedelta functionality
(adding/substracting from datetime instances) does not incorporate
that portion of the delta. Negative durations also may not work properly.
Intended Near-Term Enhancements