A Quality Evaluation Technique of RFID Middleware in Ubiquitous Computing

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1 A Quality Evaluation Technique of RFID Middleware in Ubiquitous Computing Gi oug, Oh, and Doo yeon, Kim and Sang il, Kim and Sung yul, Rhew Department of Computer Information, Kangwon Tourism College, Korea Ministry of Education & Human Resource Development, Seoul, Korea Department of Computer Science, Soongsil University, Korea Abstract With ubiquitous computing system, users can access information through a computer network at any time and in any place. The basic infrastructure of ubiquitous computing system is wireless network environment, and a RFID (Radio Frequency Identification) system is composed tags, readers, middleware, application services, etc. and uses networks. RFID middleware is system software that collects a large volume of raw data generated in RFID environment, filters the data, summarizes them into meaningful information and delivers the information to application services. RFID middleware links hardware to conventional middleware. Previous researches on RFID middleware have covered middleware from SUN, SAP, IBM, Microsoft, Oracle, etc. These products attach importance to different quality characteristics, and there have been few researches on the quality properties of RFID middleware. The present study examined functionality, reliability, usability, efficiency and portability among the quality characteristics of software in international standard ISO/IEC 9126 as well as the quality elements of standard RFID middleware of EPC Global, and based on them we extracted and analyzed items for evaluating the quality of RFID middleware in ubiquitous computing systems. Using the AHP (Analytic hierarchy process) that enables rational decision making by simplifying complicated problems, we evaluated the subjective characteristics of stakeholders in an objective way and proposed a selection method that evaluates quality using quality evaluation criteria. The proposed evaluation selection method is useful for developers who are going to develop RFID middleware in areas such as distribution and logistics to select RFID middleware suitable for their environment. 1. Introduction These days, shift to a new environmental and technological paradigm is in progress based on ubiquitous computing environment that enables users to access the network and process information freely in any place without consideration of computer or network environment. The maximized fusion and harmony of technologies is creating ubiquitous computing environment that minimizes collision and discontinuation [1]. RFID is being developed as an essential elemental technology for realizing sophisticated information technology in ubiquitous environment, and is spread to all social and cultural areas. RIFD is a technology to identify objects automatically using radio wave without human intervention. A tag containing an identification code is designed to respond to specific frequency, and if it enters the response range of a reader it sends information wirelessly and, receiving the information, middleware converts it and uses as CPU data [2]. According to the value chain of industries using RFID/USN technology, the software industry develops based on the hardware industry and into the service industry.in the value chain, if the quality of middleware is refined further, the connection between hardware and the service industry can be much easier [3]. Figure 1. RFID/USN Industry Value Chain In the present study, we examined the properties of software quality in international standard ISO/IEC 9126 such as functionality, reliability, usability, efficiency and portability and the quality factors of standard RFID middleware in EPCglobal, and in order

2 to build efficient RFID middleware from the results we derived items for evaluating the quality of RFID middleware in ubiquitous computing systems and analyzed the items. The analyzed quality factors were objectified further through excluding developers subjective and qualitative characteristics using the analytic hierarchical process of MCDM, and selected important quality factors in constructing middleware through a quantitative method. By selecting important quality factors, we can understand items to be considered seriously when selecting or developing RFID middleware and build more efficient middleware. In this paper, Chapter II presents related works, revising the quality factors of middleware and ISO/IEC 9126 and AHP of MCDM. Chapter III explains factors to be considered in selecting EPCglobal middleware and evaluation and Chapter IV evaluates of RFID middleware quality factors and analyzes their importance according to priority. Lastly, Chapter V draws conclusions and suggests future research. 2. Related Study RFID middleware Ordinary middleware is a program defined in the common application layer and software that shares hardware supporting applications and across applications, playing the role of organic connection between the reader layer that reads raw data and the application layer that utilize the data [4][5]. RFID middleware is system software that collects a large volume of raw data from heterogeneous RFID environments, filters them and summarizes into meaningful information, and delivers the information to application services, and middleware platform software that standardizes common functions necessary for the development of RFID applications and provides them as components [2]. The basic structure of middleware is as in Figure 2. The major basic functions of middleware are supporting the independency of the protocol of heterogeneous readers, managing data through realtime collection, filtering and summarizing, and interoperating with legacy system through being integrated with application programs. Other functions include process modeling, real-time execution and controlling, and middleware should have a structure of high scalability and availability. However, there are problems in interoperability due to lack of middleware standard, in real-time data processing, in integration with legacy systems, and in information protection [2][6][7]. Figure 2. RFID Middleware Structure Middleware has the purpose of describing the interface of application programming in network. Thus, middleware is software playing the role of a broker for data exchange among readers in existing information systems or among readers on the network. Thus, it supports connection between network and internal systems [4]. In EPCglobal network, Savant, which is an element of network software architecture, is software that processes and manages EPC events based on EPC data generated continuously, and middleware that captures and monitors EPC data and transmits the data. 2.2 ISO/IEC 9126 ISO/ICE 9126 is a standard quality model for evaluating software. Quality can be defined as fitness for purposes (Croz) or conformity with requirements. The quality model has 6 attributes and 26 subattributes for evaluating quality. Whether to have abilities to develop high-quality software is determined using models such as CMM and SPCE, but developed software is evaluated using ISO/ICE 9126, ISO/IEC 14598, etc. In this study, we evaluate quality by applying 5 out of the 6 attributes in ISO/IEC In Figure 3 showing the attributes of ISO/IEC 9126, efficiency is a set of software properties related to performance according to the quantity of resources used under given conditions, and portability is a set of properties for transporting software from an environment to another.

3 Figure 3. ISO/IEC 9126 Usability is a set of properties that are efforts to be made for using under explicit or implicit conditions and are evaluated by the results of use. Reliability is properties indicating safety that satisfies the performance level of software during the specified period, and functionality is a set of properties that realize given functions and particular contents, satisfying explicit or implicit requirements. Maintainability is efforts required to make particular corrections, namely, a set of properties to change and improve software in response to changing environment and to meet demands. The sub-attributes of each attribute are presented in Figure 3 [8][9]. 2.3 AHP (Analytic Hierarchy Process ) In this study, analytic hierarchy process (AHP), a method of making multiple decisions, is used to measure the importance of the quality factors of RFID middleware. AHP, a method that disintegrates a complicated decision making problem into understandable hierarchical structure and, based on the structure, makes decisions, satisfies the theorems of reciprocal, homogeneity, dependency and expectation. Alternative derivation is composed of 4 steps. The first step establishes a decision making hierarchy, the second step makes pairwise comparison among decision making factors in each level, the third step calculate the relative importance of decision making factors from the pairwise comparison matrix and measures consistency, and the last step integrates the hierarchical structure and prioritizes alternatives based on the structure. Figure 4 is the decision making structure of AHP. This is calculated through pairwise comparison, and participant decision makers investigate whether assigned values are consistent using a 9-point importance scale for pairwise comparison as in Table 1. Figure 4. Decision making structure of the AHP Table 1. Relative Importance for Pairwise Comparison Value Definition Description 1 Equal Moderate preferred Strongly preferred Very strongly preferred Two activities contribute equally to the objective Experience and judgment slightly favor one activity over another Experience and judgment strongly favor one activity over another An activity is strongly favored over another and its dominance demonstrated in practice The evidence favoring one activity over Extremely 9 another is of the highest degree possible of strongly preferred affirmation Used to represent compromise between the 2,4,6,8 Medium preferences listed above The consistency index indicating consistency is expressed as ( λ max n) CI =, and the consistency ratio ( n 1) is calculated using the consistency index to see if the index is valid. The consistency ratio is expressed as CI CR = *100%. It is considered consistent if the RI consistence ratio is within the range of 10%. Table 2 shows random index used in the consistency ratio. Table 2. Random Index size (n) RI As shown above, the relative weights of decision making factors are used together to get the overall ranks of alternatives calculated through the procedure above. The overall importance is expressed as k B i i= 2 C[ 1, k] = [10][11].

4 2.4 EPCglobal middleware and middleware quality factors MIT AutoID Center was founded in October 1999, and EPCglobal, a group for commercialization, was separated from the center in 2003 mainly centering on AutoID Laboratory, a research group based on MIT, UCC (Uniform Code Council) and EAN. Middleware should run in connection with existing legacy system ERP, control electronic devices fittingly to the operation of supply chain, and support the real-time Web service of the state of the supply chain. The architecture of EPCglobal network software is composed of readers, root ONS (Object Naming Service), local ONS, EPC IS (Information Service), EPC discovery service and EPC trust service. Figure 5 shows the architecture of EPCglobal middleware. The middleware describes the interface of application programming in EPCglobal network. Thus, it is software that defines services mediating data exchange among readers in existing information systems or readers on the network. Accordingly, the middleware supports connection between EPCglobal network and internal systems [4]. As for the quality factors of RFID middleware, [6][15] mentions scalability, integration, Suitability and interoperability, [12] privacy and security, and [5] scalability, integration, Simplicity and fault tolerance. [13] mentions heterogeneous system support, security, Suitability and interoperability, [14] scalability, integration and interoperability, [7] real-time system, collision avoidance, security, Suitability, interoperability and privacy, and [2] quick response, Simplicity, design and trust. Savant, which is an element of network software architecture, is software that processes and manages EPC events based on EPC data generated continuously, and middleware that captures and monitors EPC data and transmits the data. Figure 5. EPCglobal Middleware Architecture 3. Quality factor selection and evaluation 3.1 Quality factor selection The quality factors of RFID middleware are largely divided into those required to actual middleware and those emphasized by middleware developers. Figure 7. Mapping of RFID Middleware and ISO/IEC 9126 Quality Factors Figure 7 shows mapping between the quality factors of RFID middleware and those of ISO/IEC The higher category quality factors of ISO/IEC 9126 are efficiency, portability, usability, reliability, functionality, maintainability, and the sub-category include many quality factors. Because maintainability is relatively unimportant in developing and selecting middleware, it was excluded, and the other quality factors were selected. Efficiency was mapped to realtime and quick response between systems, portability to system scalability, integration and heterogeneous system support, and usability to collision avoidance and system design. Reliability was composed of usability, simple structure, fault tolerance, and trust. Functionality was composed of the appropriateness, interoperability, security and privacy of systems. 3.2 Quality factor evaluation using AHP Decision makers calculate the success factors and alternative factors of RFID middleware through pairwise comparison using AHP. Success factors and alternative factors are calculated stepwise by deriving the optimal factors used in the market. Decision making factors are composed of three parts in hierarchical structure. The top level sets the goal of the problem, and the middle level sets criteria for defining alternatives, and the bottom level derives alternative factors. Figure 8 shows the goals and factors of RFID middleware success factors and alternative selection factors. The value calculated for each factor shows which factor is most important in developing RFID middleware and, by emphasizing factors of a high value we can develop efficient middleware.

5 /3 1/ /2 1 1/6 1/ / Figure 8. Hierarchy Diagram of RFID Middleware Quality Success Factor and Alternative Factor Table 3 calculates the value of functionality, a subcategory quality factor of the success factor of RFID middleware, using pairwise comparison of AHP matrix. Table 3 Alternative Factor of Functionality 3.12 Security 3.13 Adaptation 3.14 Cooperation 3.15 Privacy /3 2 1/ /2 1/3 1 1/ /2 4 1 Table 4 Alternative Factor of Efficiency 3.1 Real Time 3.2 Quick Response Time /7 1 Table 5 Alternative Factor of Portability 3.3. Scalability 3.4 Integration 3.5 Heterogeneous System Support / /3 1 1/ Table 6 Alternative Factor of Usability 3.6 Design 3.7 Collision Avoid / Table 7 Alternative Factor of Reliability 3.8 Usability 3.9 Simplicity 3.10 Fault Tolerant 3.11 Trust If relative importance is calculated using the pairwise comparison matrix for functionality in Table 3, we can obtain results as in Table 8. If alternative factors are calculated repeatedly as in Table 4 through 7, the overall ranks of hierarchical structure alternatives are determined. Table 8. Importance of Functionality Alternative Factor 4. Evaluation of RFID middleware quality factors This study compared the quality factors of ISO/IEC 9126 and those of RFID middleware, identified important quality factors of RFID middleware through stakeholders, and measured their importance through a questionnaire survey. With the measured values, we calculated importance using AHP, a method of making multiple decisions. In this study, we derived and calculated five success factors and 15 alternative factors as important quality factors of RFID middleware. If alternative factors from Table 3 to 7 are calculated as in Table 8, the overall priority is determined. Thus when RFID middleware is developed or selected, if the most important quality factors are considered, we can develop or select more efficient middleware. Figure 9 is the result of calculation in Table 8 showing the importance of functionality, one of the quality factors of success factors. In the figure, consistency index is 0.03, which is less then 0.1, so considered consistent, and interoperability is most important among the calculated factors Sum Weight CR = Functionality Alternative Factor Security Suitability Cooperation Privacy Figure 9. Functionality Alternative Factor

6 Table 9 calculated overall importance and alternative factors, and the consistency index is Because the consistency index is below 0.1, it is considered consistent. According to Table 9, the most important success factor is functionality, and interoperability, which is the factor alternative to functionality, is most important. This is because RFID middleware processes a large volume of data from readers in the lower layer and interoperates with external systems such as SRM and ERP in the upper layer. Privacy is also an important factor because personal privacy is easily exposed in the course of processing FID tag data and such information should be not used for other purposes. Security is also an important factor for the safe processing of a large volume of data. Heterogeneous system support and real-time operation were also derived as important factors. Table 9. Importance of RFID Middleware Quality Success and Alternative Factor and Consistency Ratio Criteria Weight Alternative Weight Consistency Ratio Efficiency Portability Usability Reliability Functionality Real Time Quick Response Time Heterogeneous System Support Scalability Integration Design Collision Avoid Usability Simplicity Fault Tolerant Trust Security Suitability Cooperation Privacy Conclusions and future research The present study extracted success factors and alternative factors out of the quality factors of RFID middleware, and identified quality factors to be emphasized by stakeholders and decision makers. The importance of middleware quality factors was evaluated through considering and comparing the quality factors of ISO/IEC 9126, a method of software quality evaluation. The most important quality success factor was functionality, and portability and reliability were also found to be very important quality success factors. In addition, interoperability was identified as the most important alternative factor of functionality and privacy was also extracted as an important quality factor. The most important alternative factor of portability was heterogeneous system support, and an important alternative factor of reliability was fault tolerance. Important alternative factors of usability and efficiency were avoidance of collisions among systems and real-time systems, respectively. If requirements for important quality factors as identified above are satisfied, we can develop more efficient middleware or select more efficient RFID middleware. We need to make further research on the extraction of quality factors of general ubiquitous computing and the evaluation of ubiquitous computing environment based on the quality factors. References [1] Simon Schubiger-Banz, Beat Hirsbrunner A Model for Software Configuration in Ubiquitous Computing Environments Pervasive 2002, LNCS 2414, pp. 181~194 [2] 김영일, 김말희, 이용준, RFID 미들웨어기술동향및응용사례, 한국정보처리학회지, 제 12 권 5 호 [3] 박석지, 미래 RFID/USN 기술전망, IITA, [4] m [5] Bobby Burkett, php?manufacturers_id=&products_id=35, [6] Vlad Krotov, iddleware.ppt, University of Huston Bauer College of Business, Summer 2006 [7] Dave Weatherby, /Presentations /E PC-Global-eindhoven.pdf, Sep.9, 2004 [8] Software Engineering Product Quality-Part 1: Quality Model. ISO/IEC , June, 2001 [9] Software Engineering Product Quality-Part 2: Internal Metrics. ISO/IEC , June, 2001 [10] F.Della Croce, A. Tsoukias, and P. Moraitis. Why is difficult to make decisions under multiple criteria?. In B. Drabble, J. Koehler, and I. Refanidis, editors, Proceedings of the AIPS 2002 workshop on Planning and Scheduling with Multiple Criteria, pages 41-45, 2002 [11] Corner, J. L. and Buchanan, J. T. (1997) "Capturing decision maker preference: Experimental comparison of decision analysis and MCDM techniques", European Journal of Operational Research, vol. 98, no.1, pp [12] Ramaswamy Chandrmouli, Rick Kuhn, Susan Landau, Security Standards for the RFID Market, IEEE SECURITY & PRIVACY NOVEMBER/DECEMBER 2005, p [13] EPCglobal US, da.org/docs/ EPCglobal_kickoff.ppt, July, 30, 2004 [14] Michael Wohlwend, /rpsc/pdf/mic haelwohlwend.pdf [15] Christian Floerkemeier and Matthias Lampe RFID Middleware design-addressing application requirements and RFID constraints, ACM International Conference Proceeding Series; Vol. 121, 2005,