Pml in Application – an Example of Integral Sheet Metal Design with Higher Order Bifurcations

Processes are very important for the success within many business fields. They define the proper application of methods, technologies, tools, and company structures in order to reach business goals. Not only manufacturing processes have to be defined from the start point to their end, also other processes like product development processes need a proper description to gain success. For example in automotive industries complex product development processes are necessary and defined prior to product development. Over the last decades several product modeling languages have been developed moving to object oriented modeling languages, such as UML, but the used process modeling languages are still procedural. The paradigm shift caused by object oriented description within product modeling languages has to be transferred to process modeling languages. This paper describes an object oriented approach for process modeling, referred to as PML and its application to a complex product development and production process for integrated sheet metal design of higher order bifurcations. Using UML as a starting point an object oriented process modeling method is differentiated. The basic concepts which are needed for process modeling are put into an object oriented context and are explained. The paper gives an outlook, what can be achieved by the new approach. INTRODUCTION As the tendency of enterprises to collaborate growths steadily, industry faces new challenges managing business processes, product development processes, manufacturing processes and much more. Furthermore, discipline spanning product development processes are increasing, e. g. desired mechatronical products are in the need for knowledge from mechanical, electrical as well as software engineers. Humanists and economists also play a huge role in modern product development processes. Each individual discipline has its own, well-defined and specific processes, which typically are based on well-tried methodologies. These process descriptions are very powerful within the traditional discipline or the original enterprise, they were invented in. On the other side, they lack for flexibility, due to the reason that most existing process descriptions are based on a procedural approach. These are not powerful enough to meet requirements of describing cross collaboration. A short example is given to illustrate the problem. Fig. 1: Conventional and algorithm-based design process Integral sheet metal products with higher order bifurcations represent an innovative product genus of sheet metal products. Product development for integral sheet metal products of higher order bifurcations requires a novel kind of development process utilizing knowledge of several disciplines like mechanical engineering, applied mathematics and material science. This new approach of product development is called algorithm-based product development and does not fit into the traditional VDI 2221 process (Fig. 1). The conventional product development process of VDI 2221 reflects the human thinking processes in product development. Following this conventional product development approach, the designer 1 Copyright © 2008 by ASME begins his work by means of assumptions and first solution ideas, based on his former design experience. This solution is further intuitively refined and iteratively changed until an adequately suitable solution based on the designer’s subjective assessment has been created. Concluding, a successful product is dependent on its developer’s heuristic capabilities [4]. The potency of human mind is to draw coherent conclusions even on the basis of vague or fragmentary information chunks. Then again, humans only have limited cognitive resources. These facts, combined with the non-existence of basic examples for such products humans could orient on, make it impossible for specialized applications to realize the product development process in the conventional way. Taking everything into account, the need for a new scientific approach in the development process was affirmed and the algorithm-based approach was established. The new algorithm-based product development approach does not rely on individual knowledge and subjective experience, but ideally generates complete and palpable solutions systematically. Still there is no proper description for this kind of flexible processes. To meet all these needs a new process modeling language is developed and demands the following requirements: • Support of hierarchical structures. • Support of flexible interpretation of a defined process without getting incompatible – support of generalization and specification. • Robust process definition for flexible proceeding sequences of activities without losing process comparability – support of interchangeability of processes. • Support of different integration scenarios and levels without changing process description at any time.— support of flexibility of processes. • Easy to learn and read – audience of those process definitions are very broad. This paper proves the sustainability and performance of a recently developed process modeling language means by the application to a complex product generation process example. A conclusion closes this paper. BENCHMARK OF EXISTING PROCESS MODELING LANGUAGES In this chapter some existing process modeling languages are covered. It is briefly described why they do not meet the requirements of modern process definitions. For an in depth analysis and further particular details we refer to [13]. IDEF0 / SADT and Event Driven Process Chains (EPC) are procedural process modeling languages and support modeling processes with different levels of details. Both process modeling languages lack for transparency and clarity if they are applied to complex processes. Moreover, they are not very flexible regarding changes to the proceeding sequence of activities. [1], [2], [3], [4] The Unified Modeling Language (UML) offers an all spanning modeling language. Regarding data and information model the language is object oriented. If UML is utilized to describe processes, UML reveals several disadvantages. UML is not an object oriented language for process modeling, because processes are still modeled procedural. Each activity is seen as an object. Relations between activities still base on logical states. Processes defined with UML are not very flexible regarding changes in the proceeding sequence of activities. [5], [6], [7] Business Process Modeling Notation (BPMN) representation of processes is quite similar to the UML activity diagram. It is a standardized graphical notation for drawing business processes in a workflow. Processes are defined as a sequence of activities in swim lanes. Again it is a state based connection between object oriented activities. Therefore the evaluation result upon BPMN is similar to the UML verdict. The Integrated Enterprise Modeling as a refinement of SADT enables users to generate views on the complete enterprise, not only on its processes. [9], [2] Processes are still in a SADT kind of style. Due to its retaining on logical sequence of activities it has no real advantage in modeling flexible processes. It still lacks a powerful support of process flexibility. The Process Specification Language (PSL) basically is an ontology for describing processes. As PSL’s objective is to serve as an Interlingua for integrating several process-related applications without formal and graphical constructs, it is therefore not capable for process modeling. [10] The Semantic Object Model (SOM) methodology allows flexible and robust process modeling, based on the division of an enterprise model into several model layers, each of them describing a business system from a specific point of view. Within the process model the activity objects are connected with events. In comparison, SOM is most progressive regarding the definition of relations, but its constructs are difficult to understand due to the complex, integrated approach. The modeling languages still describe relations on state based, proceeding sequences of activities. Taken together these results evoke the need for a new process modeling language facing the requirements of the paradigm change. BASICS OF PML A new approach for a process modeling language will be introduced in this chapter, which uses object oriented techniques and hence meets all requirements. This approach uses the well known and widely used modeling language UML, that applies object oriented techniques to obtain modularization, reuse, flexibility and easy maintaining, among others, in the field of software and system modeling. UML is a technology that has a wide acceptance by users, developers and managers. Ongoing developments on the basis of UML, like SysML, prove the sustainability of the UML metamodel. Thus UML is a good starting point for the development of an object oriented process modeling language. 2 Copyright © 2008 by ASME Fig. 2 shows the definition of an UML class diagram including class name, attributes and methods. The class itself is time invariant as it is a generic description of the content of the context. But the instance of a class, an object, is time variant, because it holds characteristic values that can be checked to given times and can change over time. This means, the values can change, but the general structure of an object (number and kind of attributes) can not change.