Redefinition Error

[Nikolaos Polyzotis <nxp@dcs.ed.ac.uk>]

I keep getting a redefinition error and I would really appreciate some
help.

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message = 
	{depend}dependence P.tpu id arrow id  |
	{insert} inserting P.tpu id  |
	{successfork} forking P.tpu forkinfo? ok activethreads	|
	{unsuccessfork} forking P.tpu forkinfo   not ok activethreads 	|
	{delay} delay P.tpu id colon [period]:int |
	{update} updating P.tpu id |
	{leave} leaving P.tpu id id;

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Error:Redefinition of ADependMessage.Id.

I don't show the rest of the grammar cause  i thought it's irrelevant.