(456a) Multilevel Control System Integration through An Ontological Chemical Flexible Infrastructure

An ontology, as a formal specification, is a body of formally represented knowledge based on conceptualizations, which are abstract, simplified views of the physical or procedural elements. These elements are part of a system that we wish to represent for some purpose and the relationships that hold among them [2, 3]. In the domain of the chemical engineering processes management, many different specialists work together. Disciplines like chemical engineering, chemistry, computers science, materials science, environmental engineering, mathematics and numerical methods, financial management, control, etc., are involved. Although each one of these disciplines uses a particular terminology, a precise common terminology does not exist (synonyms exists, some terms can be used in different disciplines with similar, but not identical meaning). Additionally, the terminology difficulty poses not only a problem which may originate mistakes associated to ?wrong understanding?; but is also associated to the ?lack of communication? often detected between professionals which should act in a coordinated way in their decision making. In this work, we describe the informatics system and the user interface used in the first prototype of the ontology (Flexpron: Flexible Process Ontology). Technical characteristics considered during the specification and development of the first prototype of the above mentioned ontology (Flexpron) and the preliminary results envisaged during its use are described. It is difficult to simultaneously achieve high degrees of usability and reusability: Specializing in one kind of task makes the ontology more useable for this particular task, but it also decreases the likelihood of its reusability; a highly abstract ontology, on the other hand, may be applicable to a wide variety of different tasks, but it is unlikely to prove very useful for any of these without extensive modification and detailing [1]. Flexpron models not only the terminology, but also the entire domain of chemical engineering processes, with a particular attention to the activity of control at different levels. So, on the one hand the ontology intends to resolve with eventual terminological confusions, since one of its commitments is to guarantee the consistency with respect to queries and assertions using the vocabulary defined in the ontology. Also, it relates the different mathematical models within the system, showing the correspondence that there exist among them. The aim of this action allows for the enrichment of models information for future decision making. On the other hand, reusing an ontology is far from being an automated process. It requires not only consideration of the ontology, but also of the tasks for which it is intended. The key for the presented ontology reusability is that it lies in the basis of the standard ANSI/ISA [5, 6, 7, 8, 9]. In general, this approach should facilitate building larger and better systems cheaply. It should also lead to a greater dissemination on these systems. The main objective established for development of this system was its capacity to integrate different perspectives (i.e., different hierarchical decision levels) and the mappings between them. In this sense flexpron contemplates the enterprise control system integration, where processes are categorized, the relationships between them are examined and imposed, and introduces the properties that aim at specify the aforementioned relationships are introduced. The informatics system allows the utilization of the ontology as a common model between actors, thus facilitating the communication and knowledge reuse among them. Even more, due to the existent lack of integration between the different control levels (Purdue Reference Model) [12] the ontology eases the decision support task [10, 11]. Flexpron supports different control activities by streamlining information gathering, data integration, model development and decision making, acting as a multilevel control system. So in the line of the current trends in electronics, computer science & artificial intelligence, Flexpron allows to improve the quality of the overall control decision making providing the technical capability to develop a multilevel decision making support. This information structure must become increasingly agile and integrated across the process functions. The ontological infrastructure has been built using Protege software [4], a tool for ontology editing and knowledge acquisition. Protege is aimed at assisting knowledge engineers and domain experts to perform knowledge-management tasks. One of the major advantages of the Protege architecture is that the system is constructed in an open source, modular fashion. Protege also generates an ontological model using OWL (Ontology Web Language). The OWL language has the expressive power needed to represent the different domains of the solution we want to explore. OWL format model can be implemented using a computer programming language such as Java or C++; coding of the ontology (OWL model) will allow the instantiation of classes' relations on objects with which the system is defined. Finally, the implementation of use case was used to encode the programming language which tells the class instances how to behave for better performance. Site, master and control recipes, distributed inside the Ontology representing a chemical flexible process, have been developed. These recipes contain a variety of information about available raw materials, processing requirements, the manufacturing of a single batch of a specific product, etc. Once this information has been created the schedule and lot sizing files are made available by the optimization algorithm which makes use of external elements (solvers). Facilitate inter-operation and communication between systems by providing a common terminology, promote the sharing of knowledge between systems at different levels and the development of friendly user interface as resource in the use of the ontology are shown. A Batch Pilot Plant (PROCEL) which is a basic environment for Open Simulation and Optimisation in a Real Time Environment package scenario is located at the laboratory facilities at the UPC Chemical Engineering Department. PROCEL brings an appropriate scenario to evaluate the ontology performance as well as study and develop new process strategies. This pilot plant has been used to test the proposed ontology and highlight its benefits.

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