The initial step in building the MSE ontology is to find common concepts for VE knowledge sharing in the global supply chain design and operational management of the global manu- facturing system. This common concept enables a semantic translation to be made from one information source into another; Stuckenschmidt and van Harmelen (2004) call it a bridge concept. They also point out that top-level classifications or taxonomies that subsume every
other possible concept are mainly used to find the bridge concept to enable the definition of all terms to be translated. The common concepts of a manufacturing system in the MSE ontology have been well defined, containing the manufacturing taxonomy and axioms of basic manufacturing concepts, properties of concepts, relationships, and constraints between different enterprises’ MSE applications. Figure 13 illustrates the basic elements of the MSE abstract classes’ structure and the relationships between classes, using the ontology editor tool, Protégé OWL Plugin (http://protege.stanford.edu/plugins/owl/) and its visualization ontology Plugin, Jambalaya (http://www.thechiselgroup.org/~chisel/projects/jambalaya/
jambalaya.html).
The top-level taxonomy of the MSE ontology model has been captured in seven key base classes, project, flow, virtual enterprise, enterprise, resource, process, and strategy, using the knowledge and experiences of published manufacturing system information models (Harding & Yu, 1999; Kosanke, Roland, & Nell, 2003; Molina & Bell, 1999).
The Project class provides the trigger for the formation and operation of a VE MSE process.
The definition of the Project class is used to represent the business objects, that is, documents, contracts, or a program that flows through the manufacturing systems and processes. The relationships of the Project class, Flow class, and Process class for executing a new order flow for a VE project is represented in Figure 13. Each instance of the Project class travels along one or more flows (instances of the Flow class) that connect independent processes or activities into a system with a purpose.
The MSE ontology model enables the moderator to operate within an E-SCM which has been designed to support manufacturing system collaborative design and engineering within a VE environment. Therefore, the MSE ontology model encompasses several independent companies assembled into a temporary consortium of partners and services for one or a
Building.Stage The.purpose,.scope.and.
common.concepts. identification Definition.of.Class Definition.of.Property
Ontology.Implementation
Manipulating.Stage Semantic. Match(SM)
Maintaining.Stage Ontology.Manager Ontology.
Editor
Metadata.
Generator
SM SM Enterprise..A
Ontology Enterprise.B Ontology SM
SM
VE2.MSE Ontology
SM Refinement
Finding.Property.Values Generation.of.Classification
VE1.MSE. Ontology
Enterprise..C
Ontology Enterprise.. D
Ontology
Figure 12. The steps of engineering the MSE ontology model for VE knowledge sharing
limited number of specific projects in order to pursue a market opportunity and to achieve competitive advantage since individual companies concentrate on their own core competen- cies (Prahalad & Hamel, 1990)]. Therefore, the virtual enterprise class has been defined, and this is an aggregation of enterprise classes. Each enterprise class object is concerned with the representation of capabilities and information in any specific company within the VE system, since the processes, resources, and strategies are arranged into different enterprises related to their individual business objectives and function.
The relationships between resource class, process class, and strategy class are interacting in the MSE ontology model. The resource class describes mechanisms that enable a pro- cess to be performed. The process class are business functions or activities necessary for the operation of the enterprise. The strategy class is used to describe not only the business strategy but also the efficient production or manufacturing strategies. The processes can be measured and controlled through links to strategies, and resources can also be effectively allocated through links from processes to strategies.
The MSE ontology model has been encoded in resource description framework (RDF), RDF schema, and Web Ontology Language (OWL), which is the W3C standard semantic mark-up language for publishing, sharing, and reuse of semantic data on the World Wide Web. The top-level classifications of the MSE metadata shown in Figure 13 are all abstract classes, so each represents a hierarchy of subclasses that are classified according to their main character- istics. Each class has properties that may be thought of as attributes of the class and can also represent relationships between classes. For example, properties such as uses resource, used in process, apply, and controls, and so forth, represent inter-relationships between resource, process, and strategy classes, as shown in Figure 13. Further details of classes, subclasses hierarchy, and properties of the MSE metadata can be found in Lin (2004).
Figure 13. Top-level taxonomy of manufacturing system in the MSE ontology model
Metadata plays a central role in information processing in general and in information sharing in particular. In addition, the expressiveness of the OWL primitives is made available not only in the taxonomy and axioms to define the classification, but also in the constructions to state equality between classes and between properties. These provide the mediate service for enhancing information integration within an inter-enterprise community; an example of semantic match manipulation using OWL primitives will be illustrated later in the next section.