SOS 2.0 Build InsertObservation: add gml:TimePeriod for phenomenonTime
Removed useless modifiers. In interfaces every method is public
Add new LaxValidationCase type to handle interelated cases incl. abstract types to provide some default implementations.
Move constants to XmlConstants; use new super class AbstractLaxValidation to reduce code duplication.
Use new DependentLaxValidationCase while filtering XmlErrors
Add new LaxValidationCase including validation of unknown substitution group.
Validate all requests before returning incl. bug fixes for found issues during validation