Business Process Model and Notation (BPMN) 2.0 process models are used more and more, both in practice as in academia. Although academic research mainly focuses on sophisticated semantic checks and extensions there still exist problems in the basic usage of BPMN. This paper investigates issues in BPMN model serializations which arise as a result of the complexity and inconsistency of the standard document. We present a set of serialization constraints as a starting point for sophisticated compliance checks on serialized BPMN models. Furthermore, these constraints are used to perform an evaluation of current modeling tools. This evaluation reveals that the creation of standard compliant models is still a non-trivial endeavor.