This is an issue about interoperability. It helps a lot to convince people of dmn-js if it is able to load DMN models from other vendors. It appears some items of the model below are in a location where dmn-js does not expect them, some may not actually be supported, but I would assume they are perfectly valid, coming from a competing vendor like kie/Trisotech. So I suspect dmn-js makes too many assumptions about the xml structure.
This model fails to load with numerous errors:
unparsable content <itemComponent> detected
line: 9
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 12
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 15
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 18
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 21
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 24
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 27
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 36
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 39
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 42
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <itemComponent> detected
line: 45
column: 2
nested error: unknown type <dmn:ItemComponent>
unparsable content <context> detected
line: 75
column: 2
nested error: unknown type <dmn:Context>
unparsable content <invocation> detected
line: 107
column: 5
nested error: unknown type <dmn:Invocation>
unparsable content <decisionTable> detected
line: 136
column: 6
nested error: unrecognized element <dmn:decisionTable>
unparsable content <context> detected
line: 246
column: 3
nested error: unknown type <dmn:Context>
unparsable content <literalExpression> detected
line: 326
column: 12
nested error: unrecognized element <dmn:literalExpression>