Drakoulis Martakos

Supplier selection in electronic marketplaces using satisficing and fuzzy AHP

Supplier selection is a critical and demanding task for companies that participate in electronic marketplaces to find suppliers and to execute electronically their transactions. This paper is aimed to suggest a fresh approach for decision support enabling effective supplier selection processes in electronic marketplaces. We introduce an evaluation method with two stages: initial screening of the suppliers through the enforcement of hard constraints on the selection criteria and final supplier evaluation through the application of a modified variant of the Fuzzy Preference Programming (FPP) method. The proposed method alleviates the information overload effect that is inherent in the environment of electronic marketplaces, facilitates an easier elicitation of user preferences through the reduction of necessary user input (i.e. pairwise comparisons) and reduces computational complexity, in terms of the number of linear programs to be solved, in comparison with the original FPP method. The FPP method is adopted and modified accordingly in order to tackle the issue of inconsistency/uncertainty of human preference models. Our approach is demonstrated with the example of a hypothetical metal manufacturing company that finds and selects suppliers in the environment of an electronic marketplace.

Trust and relationship building in electronic commerce

In e‐commerce, trust becomes an essential prerequisite for customer relationship building. Drawn from established theoretical work on trust and relationship marketing, a model is proposed aiming to help in highlighting the differences between traditional and e‐commerce and to facilitate thinking as to how trust can be built in virtual environments. Conceptualized in the context of an electronic servicescape, the model helps to demonstrate how agent and virtual reality technologies can facilitate the expressiveness required for the formation of trust through iterative interaction with promises being made, enabled and fulfilled.

A utility-based fuzzy TOPSIS method for energy efficient network selection in heterogeneous wireless networks

Mobile terminals in 4G heterogeneous wireless networks continuously undergo horizontal and vertical handovers. In order for a mobile terminal to be connected to a network in the best possible way in terms of QoS performance and energy consumption, access network selection as the main decision within the handover process is obviously crucial. This paper presents a novel method that takes into account user preferences, network conditions, QoS and energy consumption requirements in order to select the optimal network which achieves the best balance between performance and energy consumption. The proposed network selection method incorporates the use of parameterized utility functions in order to model diverse QoS elasticities of different applications, and adopts different energy consumption metrics for real-time and non-real-time applications. User preferences are easily configured for different application and situation contexts through the use of linguistic assessments and their representation as triangular fuzzy numbers. The aggregation of multiple criteria for the calculation of the overall rating of the networks is performed through the use of the Fuzzy Set Representation TOPSIS method that resolves the issue of inconsistency related to conflicting decision criteria and is modified through the use of the employed utility functions for the elimination of the ranking abnormality problem. Finally, simulations are conducted in order to demonstrate how the proposed method would work and confirm its suitability and effectiveness.

Revisiting public information management for effective e‐government services

Governments are employing modern information and communication technologies to serve society better. Raising the effectiveness and quality of government services is not only a matter of new technologies; it also involves clear vision and objectives as well as a sound business strategy. Information systems need to support internal work within a government’s boundaries, serve customers through digital interfaces and leverage digital relationships among social partners. To implement such systems, preparatory work is required in both organization and technology. A new public information management philosophy underlies this significant revamping of the value propositions made to customers. The ongoing enrichment of the Greek Ministry’s of Finance e‐services follows an ICDT‐like business logic. A key factor of all these advances is the re‐orientation of information systems for customer‐centric service.

In-depth analysis and simulation study of an innovative fuzzy approach for ranking alternatives in multiple attribute decision making problems based on TOPSIS

In this paper, an innovative fuzzy approach for ranking alternatives in multiple attribute decision making problems based on TOPSIS is presented in-depth and studied through simulation comparison with the original method. The TOPSIS method provides the principle of compromise that the chosen alternative should have the shortest distance from the ideal solution and, simultaneously, the farthest distance from the negative ideal solution. However, the TOPSIS method does not always produce results in harmony with this principle due to an oversimplified definition of its aggregation function which does not grasp the contradictory nature of the principles formulation. Our approach addresses this issue through the introduction of a fuzzy set representation of the closeness to the ideal and to the negative ideal solution for the definition of the aggregation function which is modeled as the membership function of the intersection of two fuzzy sets. This model enables a parameterization of the method according to the risk attitude of the decision maker. Thus, a class of methods is formulated whose different instances correspond to different risk attitudes of the decision makers. In order to define some clear advises for decision makers facilitating a proper parameterization of the method, a comparative analysis of the proposed class of methods with the original TOPSIS method is performed according to well defined simulation techniques. The results of the simulation experiment show on the one hand that there is no direct correspondence between the proposed class of methods and TOPSIS, and on the other hand that it is adequate to distinguish three instances that correspond respectively to risk-averse, risk-neutral and risk-seeking decision makers. Finally, a numerical example pertaining to the problem of service provider selection is presented to illustrate the application of the proposed class of methods and its functioning.

An approach and model for assessing the business value of e-banking distribution channels: evaluation as communication

The reluctance of information systems practitioners to adopt recommendations of evaluation methods and techniques is a sobering realization. One possible explanation is that they do not accommodate changing perceptions of what constitutes system-derived business value whose assessment requires richer evaluation approaches than mono-dimensional cost-benefit analyses. This paper reports a study that was undertaken in a bank faced with the challenge of assessing the value of its main e-banking channel in operation. Arguing that the evaluation of an information system should be seen as a form of communication, we describe the approach and evaluation model that was created and applied. The model employs five different perspectives each having its own set of metrics. These can be used to assess the business value along two viewpoints: (a) the internal view, where the channel is considered as a resource whose utilization must be maximized; and (b) the external view, where the channel as an interface to the banks customer base should enable and support customer relationship management.

Quantified PQoS assessment based on fast estimation of the spatial and temporal activity level

This paper presents a novel method for fast and quantified estimation of the Perceived Quality of Service (PQoS) for MPEG-4 video content, encoded at constant bit-rates. Taking into account the instant PQoS variation due to the Spatial and Temporal (S–T) activity within a given MPEG-4 encoded content, this paper introduces the Mean PQoS (MPQoS) as a function of the video encoding rate and the picture resolution, and exploits it as a metric for objective video quality assessment. The validity of this metric is assessed by comparing PQoS experimental curves to the theoretical benefit functions vs. allocated resources. Based on the proposed metric, and taking into account the qualitative similarity between theoretical and experimental curves, the paper presents a prototype method for pre-encoding PQoS assessment based on the fast estimation of the S–T activity level of a video signal.

What Is Trust in E-Government? A Proposed Typology

Trust in e-government is of vital importance for the effective adoption and use of electronic public services. Understanding the concept of trust and the different types it involves in the e-government context is a key challenge for both research and practice. Aiming to address this need, this paper proposes a parsimonious yet comprehensive typology of trust in e-government. Trust in e-government is analyzed into seven different types conceptualized around the different targets they are related to. Each trust type is further delineated into its composing dimensions and the approach by which it can enabled. The paper continues to present an example of the practical applicability of the proposed typology by showing how the identified types of trust have been addressed in an online taxation portal.

Evaluation of video quality based on objectively estimated metric

Multimedia applications and especially encoded video services, are expected to play a major role in the 3rd generation (3G) and beyond mobile communication systems. Given that future service providers are expected to provide video applications at various price and quality levels, quick and economically affordable methods for preparing/encoding the offering media at various qualities are necessary to be developed. This paper presents a method for objective evaluation of the perceived quality of MPEG-4 video content, based on a quantification of subjective assessments. Showing that subjectively derived perceived quality of service (PQoS) vs. bit rate curves can be successfully approximated by a group of exponential functions, the proposed method exploits a simple objective metric, which is obtained from the mean frame rate vs. bit rate curves of an encoded clip. The validity of this metric is assessed by comparing subjectively derived PQoS results to the corresponding ones, which come from the proposed objective method, showing that the proposed technique provides satisfactory PQoS estimation.

An XML-based, 3-tier scheme for integrating heterogeneous information sources to the WWW

The phenomenal growth that the WWW currently experiences necessitates the integration of various types of information sources to its platform. We present an open, extensible multi-agent architecture, which is based on standards like XML, for the efficient retrieval of information from RDBMSs and HTML document collections. We also specify a series of protocols for achieving the synergy between a number of server- and client-side components.