Potential BPMN-Spec conformance flaw: Link-Event-Definition target property is handled as an attribute

Describe the Bug

The target-property of a LinkEventDefinition is described as an xsd:element in the BPMN 2.0 Semantic-Schema. Therefore it should be a child node of the link event definition in a BPMN model.

In contrast bpmn-moddle defines a link event definition to include a property target which is marked as an attribute: Link-Event-Definition-Target property.

This results in serialized models violating the BPMN-Semantic-Schema mentioned above: The target-property will be serialized in an attribute of the LinkEventDefinition whereas the Schema requires it to be a child node.

Importing a valid model (including the target as a child node) results in the target property being removed from the link event definition entirely.

Steps to Reproduce

The described bug occurs in two “directions”:

Case A (Export/Serialization) - Setting the target property on a link event definition results in the value being set as attribute in a serialized model Case B (Import/Deserialization) - Importing a valid BPMN-model containing the target of a link event definition as a child node results in the property being removed

The bug can not be directly reproduced by the means of this repository, but rather using another library like bpmn-js using bpmn-moddle.

Github does not allow uploading XML or BPMN-files, therefore models have been uploaded in plaintext.

Case A:

If the target property of a link event definition is set programmatically an exported/serialized model will contain the target property as an attribute instead of a child node: see the attached file invalid-link-event-definitions.txt, Link-Event-Definition with ID ID14e6ec89-6434-4ef9-bdab-6784f8fee217.

Case B:

The attached file valid-link-event-definitions.txt contains a valid model according to the BPMN-Spec. Importing it by using bpmn-js (for example by using the bpmn-js demo) results in the target property being removed from the link event definition of the intermediate throw event. The demo also shows an import warning:

unparsable content <bpmn:target> detected line: 5 column: 8 nested error: unknown type <bpmn:Target>

Expected Behavior

In Case A, the serialized model should include the target property as a child node <bpmn:target>.

In Case B, the model should be imported without any warning and without the target property being removed.

Attached files valid-link-event-definitions.txt invalid-link-event-definitions.txt

[barmac]

@barmac We could also workaround it, as we often do (https://github.com/bpmn-io/bpmn-moddle/blob/master/tasks/transforms/transformBPMN.cjs#L47).

We could, but the linked file is already a ball of mud ^^

[nikku]

@barmac We could also workaround it, as we often do (https://github.com/bpmn-io/bpmn-moddle/blob/master/tasks/transforms/transformBPMN.cjs#L47).