Needed to verify if the following static validation is in place. The bug i noticed was I had an OnEvent referring to an
operation whose message has a part. But the onEvent itself didn't define the message. The validation didn't ERR on that. 
While it should ERR on that, I wanted to make sure that we don't ERR on the following which is acceptable by the BPEL
spec. (refer the spec's static analysis section)

SA00047
One-way invocation requires only the inputVariable (or its equivalent <toPart> elements) since a response is not
expected as part of the operation (see section 10.4. Providing Web Service Operations – Receive and Reply ).
Request-response invocation requires both an inputVariable (or its equivalent <toPart> elements) and an outputVariable
(or its equivalent <fromPart> elements). If a WSDL message definition does not contain any parts, then the associated
attributes variable, inputVariable or outputVariable, MAY be omitted,and the <fromParts> or <toParts> construct MUST
be omitted.	Section 10.3
Section 10.4
Section 10.4
Section 11.5
Section 12.7

SA00048
When the optional inputVariable and outputVariable attributes are being used in an <invoke> activity, the variables
referenced by inputVariable and outputVariable MUST be messageType variables whose QName matches the QName of the input
and output message type used in the operation, respectively, except as follows: if the WSDL operation used in an
<invoke> activity uses a message containing exactly one part which itself is defined using an element, then a variable
of the same element type as used to define the part MAY be referenced by the inputVariable and outputVariable
attributes respectively.	Section 10.3