Exchanging EPC Business Process Models with EPML.PDF

In this paper EPML is presented as an interchange format for EPC business process models. EPML builds on EPC syntax related work and is designed to be applicable as a serialisation format for EPC modelling tools. After a description of EPML in the large, examples are given to illustrate selected representational aspects including flat and hierarchical EPCs, business views, and graphical information. 1. Exchanging Business Process Models Today business process modelling is mainly used in two different contexts: business analysts use process models for documentation purposes, for process optimization and simulation; while information system analysts use them on the middleware tier in order to glue together heterogeneous systems. For both of these layers analysts have a variety of tools to choose from in order to support modelling of processes. In 2002 Gartner Research distinguishes 35 major vendors of such software [Ga02]. Heterogeneity of these tools causes huge interoperability problem in this context. A recent survey of DelphiGroup [De03] identifies the lack of a common and accepted interchange format for business process models as the major detriment for business process management. Event-Driven Process Chains (EPC) [KNS92] are a wide-spread method for business process modelling. SAP AG has been using them to express their SAP reference model [Ke99]. Motivated by the heterogeneity of business process modelling tools, a proposal for an interchange format for EPCs is in progress of development. It is called EPC Markup Language (EPML) [MN02, MN03b, MN03c]. The establishment of a standardized representation of business process models may be even more beneficial than in other domains of standardization, because it may be used in two different directions: horizontal interchange will simplify the integration of BPM tools of the same scope. Vertical interchange can leverage the integration of simulation engines, execution engines, and monitoring engines [Wf02]. Standardization might be a crucial step to close the engineering gap between business process modelling and implementation. This paper gives an overview over EPML. Section 2 introduces Event-driven Process Chains as a method to express business process models, their syntactical elements, and related research on EPC syntax. Section 3 presents EPML general design principles and XML design guidelines that have guided the specification. Section 4 explains how the syntax elements of EPML relate to each other and outlines why edge element lists are used to describe EPC process graphs in EPML. The Sections 5 to 8 introduce specific aspects of EPML by giving examples: Section 5 presents a simple EPC example and its EPML syntax representation; Section 6 shows how hierarchies of EPCs are expressed; Section 7 discusses how business perspectives can be included in an EPML file; and Section 8 shows which graphical information can be attached to a process element Section 9 concludes and lists future directions of research. 2. Event-Driven Process Chains (EPCs) Most of the formal contributions on EPCs have been focused on semantics, especially on the semantics of OR connectors. The translation of EPC process models to Petri Nets plays an important role in this context. Examples of this research can be found in Chen/Scheer [CS94], Langner/Schneider/Wehler [LSW98], van der Aalst [Aa99], Rittgen [Ri00], and Dehnert [De02]. A major point of discussion is the “non-locality” of join-connectors [ADK02]. This aspect has recently been formalized by Kindler [Ki03]. In this paper we will focus on EPC syntax referencing to based on the syntax definition of EPCs in [NR02]. Therefore we give a brief survey of syntax related work. In Keller/Nüttgens/Scheer the EPC is introduced [KNS92] to represent temporal and logical dependencies in business processes. Elements of EPCs may be of function type (active elements), event type (passive elements), or of one of the three connector types AND, OR, or XOR. These objects are linked via control flow arcs. Connectors may be split or join operators, starting either with function(s) or event(s). These four combinations are discussed for the three connectors resulting in twelve possibilities. ORSplit and XOR-Split are prohibited after events, due to the latter being unable to decide which following functions to choose. Based on practical experience with the SAP Reference model, process interfaces and hierarchical functions are introduced as additional element types of EPCs [KM94]. These two elements permit to link different EPC models: process interfaces can be used to refer from the end of a process to a following process, hierarchical functions allow to define macro-processes with the help of sub-processes. Keller [Ke99] and Rump [Ru99] provide a formal approach defining the EPC syntax. Based on this, Nüttgens/Rump [NR02] distinguish the concepts of a flat EPC Schema and a hierarchical EPC Schema. A flat EPC Schema is defined as a directed and coherent graph with cardinality and type constraints. A hierarchical EPC Schema is a set of flat or hierarchical EPC Schemata. Hierarchical EPC Schemata consist of flat EPC Schemata and a hierarchy relation linking either a function or a process interface to another EPC Schema. Fig. 1 shows a hierarchical EPC Schema consisting of two processes, which are linked via a hierarchical relation attached to the process interface “To Design Process”.