A hybrid ontology approach for integration of obsolescence information

Abstract

Information sharing among distributed obsolescence management systems is a challenge because of the heterogeneity of data (data with different forms and representations). Indeed, this is the main hurdle that exists for current tools managing product obsolescence. This paper presents a hybrid ontology approach for the integration of obsolescence information that combines a global ontology that provides a shared vocabulary for the specification of the semantics of obsolescence domain knowledge, along with local ontologies that describe structures of multiple data sources distributed in various obsolescence management tools. A procedure is provided for mapping local ontologies to the global ontology by quantifying relationships between classes and identifying groups of classes with a clustering method. Ontologies and rules of identifying relationships are realized with OWL (Web Ontology Language) and SWRL (Semantic Web Rule Language). With the application of the hybrid ontology approach, a unified view of data is provided to support decision making for efficient obsolescence management and a structure where new sources of information can be easily added with little modification in the future.

Introduction

Obsolescence is an emerging issue in the past decade caused by fast moving technologies which cause high-tech components to have shortened life cycles. Newer and better technologies are being introduced frequently, rendering components obsolete. Yet, custom low volume products and systems such as ships, submarines and aircraft can be manufactured and in use for decades. During such a long time period, obsolescence of components often emerges before the systems are even fielded and recurs throughout the support life. For example, in a surface ship sonar system, over 70% of the parts are obsolete before the system is installed (Singh & Sandborn, 2006). As obsolescence brings serious consequences including high maintenance costs and much waste, it has drawn greater attention in recent years. Many tools have been developed for managing obsolescence: Diminishing Manufacturing Sources and Material Shortage (DMSMS) Knowledge Sharing Portal (KSP) of the Department of Defense (DoD), Component Obsolescence and Reuse Tool (CORT) of Raytheon, Q-Star of QinetiQ, and so on. These tools can report current obsolescence status of components, forecast obsolescence risk, and enable the identification of possible alternative components. However, current obsolescence management tools are predominately populated by a set of data that are not integrated with each other, complete, consistent in the information provided, or even contain consistent definitions of the quantities tracked and achieved. Data conflicts are more common than data agreement (Sandborn et al., 2011). Heterogeneity of data, data with different representations and sources, is the main problem existing in current obsolescence management tools.

The heterogeneity of data is a common phenomenon in distributed information sources and is growing with the development of computer and information technologies that have created a huge amount of data and information (Kashyap and Sheth, 1997, Kim and Seo, 1991). In general, heterogeneity problems can be divided into three categories, including syntax heterogeneity, structure heterogeneity, and semantics heterogeneity (Stuckenschmidt & van Harmelen, 2005), where

• Syntax heterogeneity is related to data format heterogeneity.

• Structure heterogeneity is related to homonyms, synonyms or different attributes in database tables.

• Semantics heterogeneity is related to intended meanings of terms in a special context or application.

In obsolescence management tools, an example of syntax heterogeneity is the format of a component’s obsolescence date that is month, date, year in Tool A, but mm/dd/yy in Tool B. An example of structure heterogeneity is a component’s original equipment manufacturer (OEM) information and introduction date that are in the same data table in Tool A, but in separate data tables in Tool B. An example of semantic heterogeneity is how components in Tool A but parts in Tool B are used to represent the items that build up the product. In order to prevent errors resulting from the heterogeneity of the data, to ensure data consistency across different tools and to utilize all of the data to efficiently support obsolescence management, knowledge integration and sharing of obsolescence information is required.

Research related to information integration can be traced back to the 1990s. Madhavaram, Ali, and Zhou (1996) proposed a general model of a Heterogeneous Distributed Database System (HDDBS) for database integration. This initial work was a valuable start, but was limited to an abstract, prototype model describing the problem in general. Other integration approaches have since been developed for various applications. For example, Bellatreche, Dung, Pierra, and Hondjack (2006) developed an ontology-driven integration approach to integrate electronic catalogs within engineering databases; Chen (2010) proposed a systematic approach to develop a knowledge integration and sharing mechanism for collaborative molding product design and process development. There is also progress with information integration in other specific application domains (Abiteboul et al., 2002, Omelayenko and Fensel, 2001; etc.). Unfortunately, these approaches are not suitable for the needs of obsolescence information management.

This paper develops a hybrid ontology approach for information integration in the domain of obsolescence. In Section 2, types of ontology-based integration approaches are compared and the hybrid ontology approach is described. To apply the approach, ontology representation for obsolescence information is introduced in Section 3. Section 4 provides the overview of the hybrid ontology integration approach. The details of the approach are provided in Section 5, while the details of the ontological framework and rules for the approach are provided in Section 6. A case study to demonstrate the application of the hybrid ontology approach for information integration for more efficient obsolescence management at reduced cost is provided in Section 7. Section 8 provides conclusions and future work.