The essence of workflow systems is workflow patterns. Languages based on Petri nets perform better when it comes to state-based workflow patterns. However, some patterns with complex semantic can not be described by Petri-net. It inspired us to develop a new Extended Petri-Net (EPNet). EPNet extends the Petri-Net through adding some new elements and the corresponding mechanisms. D element and C relation are introduced into EPNet for describing instance runtime data and complex relation of computing and communication. A task has three parts: entry function, body function and exit function. Soundness of an EPNet can be converted to the analysis of liveness and boundness of corresponding Petri-net. All workflow patterns can be directly described using EPNet. This paper investigates the issue and introduces a collection of workflow patterns formalizations, each with a sound formal definition and execution semantics. The formalizations can be used as a foundation for pattern-based workflow execution, reasoning, and simulation as well as a basis for future research on theoretical aspects of workflow.