Elsevier

Decision Support Systems

Volume 42, Issue 3, December 2006, Pages 1959-1973
Decision Support Systems

An adaptive coordination framework for fast atomic multi-business transactions using web services

https://doi.org/10.1016/j.dss.2006.05.004Get rights and content

Abstract

Web services are emerging as an effective means for carrying out automated transactions between multiple business parties. While there are several specific protocols that have been discussed to address the problem of coordinating web services-enabled business transactions, we consider the tentative hold protocol (THP) that allows the placement of tentative holds on business resources prior to actual transactions in order to provide increased flexibility in coordination. In this paper, we present a formal coordination framework for applying THP in conjunction with two phase commit protocol to the problem in which service providers independently manage resources and clients seek to acquire the resources from multiple providers as a single atomic transaction. The proposed framework facilitates the performance optimization of THP through effective parameterization with the notion of overhold size and hold duration. Subsequently, a detailed analysis is carried out to obtain an efficient method that can optimize the performance by adaptively determining the hold duration. The simulation results show that the proposed adaptive approach yields a significant improvement over other non-adaptive policies.

Introduction

Currently significant efforts are being invested in application integration, enabling business processes of different companies to interact and form complex multi-party processes. In particular, as web services are becoming the predominant technology for facilitating business-to-business (B2B) collaboration, there are increasing needs for the enhanced transaction models that can effectively support complex, multi-party business interactions based on web services. Although efficient and reliable, the traditional transaction models that require fine-grained control of locking and close trust are not directly applicable for open, loosely coupled computing environments consisting of autonomous and heterogenous services [21]. In a web service based B2B environment, transactions are often complex, involve multiple autonomous parties, span many independent organizations, and may have long duration [17].

There are a number of emerging specifications that seek to address the requirements of such web service based collaborative business transactions. These specifications define a flexible and extensible framework for the coordination of loosely-coupled web services by use of a predefined set of transaction semantics, and they also suggest new notions of transactions that relax some of the ACID properties [1] of conventional transaction processing [6].

Business Transaction Protocol (BTP) [15], a committee specification of the Organization for the Advancement of Structured Information Standards (OASIS), is proposed to support interactions that cross application and administrative boundaries, requiring extended transactional support beyond the ACID properties. It is based on two phase commit (2PC) [1] for short duration interactions called atoms, which can be further aggregated into larger non-ACID transactions called cohesions [12]. More recently, Web Services Transaction (WS-Transaction) proposed by IBM and Microsoft [4] provides specifications for atomic transactions in a trusted domain that uses 2PC, and for business activities using compensating transactions. It also defines an XML-based protocol for multiple transaction processing platforms to interoperate.

Taking a slightly different approach to the problem, Tentative Hold Protocol (THP) [19], published as a W3C (World Wide Web Consortium) note, attempts to define a building block that can work with other technologies in order to facilitate the automated coordination of multi-business interactions as well as the creation of new opportunities to leverage the web services to improve business efficiencies. THP is an open, loosely coupled, messaging-based framework for the exchange of tentative commitments between businesses prior to actual transaction [19]. It addresses more semantic issues than low-level transactional mechanisms by providing a standard means for trading partners to place tentative holds for business resources.

In this protocol, it is possible that multiple clients can place tentative holds on the same item prior to sale, and whenever one client completes the purchase of the item, the other clients may receive notifications that their holds are not valid any more. Hence, the clients have the ability to request tentative holds on the resources they want to acquire as a single coordinated purchase, verifying availability before completing the transaction. On the other hand, the resource providers may grant non-blocking reservations on their products, retaining control of their resources, while allowing the clients greater flexibility in coordinating their acquisitions.

When combined with existing multi-business transaction coordination methods such as custom applications, compensating transactions, and 2PC, THP can provide several significant benefits. In particular, as claimed in [22], introducing a tentative hold phase to long-running collaborative business applications that employ 2PC protocol for ensuring atomicity of multi-transactions can overcome the limitations of the pure 2PC. THP allows clients to tentatively obtain resources for long time periods before entering the prepare phase of a 2PC transaction, enabling the possibility that the clients make tentative commitments to the terms of a contract and make all decisions without actually requiring the resource provider to lock such resources for the duration. Accordingly, it can shorten the required 2PC lock duration by reducing the time spent on the prepare phase while at the same time it will also facilitate minimizing the time required for business applications to successfully complete their multi-transactions. The result of a simulation study that shows the performance improvement achieved by adding THP to 2PC in a generalized resource allocation environment that allows co-allocation of arbitrary number of resources as well as alternative resource co-allocation schemes can be found in our earlier work [18].

In this paper, we consider the problem in which businesses independently manage and expose their resources through web services and client applications seek to acquire resources from them as a single atomic web service transaction [11]. In such circumstances, the clients are competing for finitely available resources, and it is not guaranteed that the required resources are always available. Moreover, the client should be able to achieve all-or-nothing semantics for the entire end-to-end transaction: if some of the transactions for resource acquisition are not successful, the entire transaction must be canceled. This problem is getting increasing attention in many real-world application contexts [5], [9], [3], including an e-commerce application that seeks to identify the best combination of many small orders from several businesses for making a purchase [22], a travel web service that interacts with flight, hotel, and car rental services [16], and a supply chain management application that carries out conversational transactions via the web services of suppliers and shippers [7].

Coordination of this kind of multi-business transactions could be carried out through the human intervention or the creation of a custom application that is aware of the inter-dependencies among the transactions. However, the increasing complexity of multi-business interactions driven by the technologies for automated discovery and integration of web services makes it necessary to flexibly automate the coordination in order to increase the business efficiency and agility [20]. Indeed the THP's key contribution is the flexibility it provides with the notion of tentative holds whose life expectancy can be explicitly defined. It can enhance the flexibility by providing targeted customer service in the granting of holds, specifying greater or less hold expiration periods for a given hold request, and allowing notification to clients when another client reserves some resource [22]. Yet, presently the problem of determining whether or not a particular tentative hold requested by a client should be granted and for how long still remains unexplored.

Motivated by this, the objective of this paper is to address the issue of optimizing the performance of THP to realize its full potential when it is used in conjunction with 2PC for the problem outlined above. The starting point for our discussion is the observation that THP can be effectively characterized in terms of two parameters, namely overhold size and hold duration, each of which respectively represents the number of holds that can be placed on a single available resource, and the time period during which a granted hold is valid. As will be detailed in the next section, these parameters represent the resource provider's commitment to the service level, and may vary according to the specific provider. Furthermore, the proposed parameterization provides a basis for constructing Petri net-based [23], [24] formal behavioral models of clients and resource providers that are participating in the multi-transactions spanning organizational boundaries.

The proposed THP characterization also provides a framework where one can seek to minimize the time required for clients to successfully complete their multi-transactions. Specifically, two different cases depending on the value of the overhold size are taken into consideration. In the first case, we examine the case in which the overhold size is finite, and propose computational methods to adaptively determine the hold duration that can lead to overall reduced transaction completion time. In the second case in which the overhold size is infinite, we show the result that the performance is indifferent to the individual resource provider's decision on the hold duration. The proposed method assumes that each provider is autonomous and fully decentralized, and does not require any single party controlling all the resources needed for a transaction. Therefore, it is anticipated that the proposed framework will facilitate more efficient multi-party business transactions, resulting in faster transaction, higher resource utilization, and better customer satisfaction in e-business.

The paper is organized as follows: the next section presents a characterization of THP based on the overhold size and hold duration, and then introduces Petri net-based models to define formal models of the participants' behavior considered in the paper. Subsequently, Section 3 describes the methods that compute the hold duration for two different cases: Section 1 for finite overhold case and Section 2 for infinite overhold. In Section 4, we demonstrate the efficacy of the proposed approach through the simulation experimentation. Finally, Section 5 concludes the paper by pointing out some future research work.

Section snippets

Characterization of tentative hold protocol

In web services computing, services are platform and network independent operations that clients or other services invoke [14]. The distributed system model considered in this paper consists of a set of service provider processes S = {s1, …, sm} that expose their resources as web services, and a set of client processes C = {c1, …, cn}, each of which seeks to acquire a set of resources from the providers, denoted by Rj  2S, such that Rj  ∅, j = 1, …, n. Service provider si, i = 1, …, m manages resources

Analytical models for computing hold duration

In this section, formal analysis for computing the hold duration is carried out in detail. In Section 3.1, we first consider the finite overhold case and propose a novel method to adaptively compute the hold duration based on the local information available to individual service provider. Then, Section 3.2 considers the infinite overhold case, and shows that the average time for clients to complete their atomic multi-transactions is indifferent to the length of hold duration.

Experimental results

Simulation analysis results are given in this section to demonstrate the performance of the THP + 2PC protocol with the proposed adaptive policy for computing hold durations. We consider an experimentation scenario in which e-tailers sell the commodity products through the web services. Clients purchase the products from multiple e-tailers to make assembled products, and seek to purchase these items as a single atomic transaction. E-tailers, on the other hand, are assumed to start their business

Conclusion

The recent advent of web services has opened up the possibility of automating multi-business transactions that span across the organizational boundaries. While there are several specific protocols that have been discussed to address the problem of coordinating web service enabled business transactions, this paper considered the tentative hold protocol that allows the placement of tentative holds on business resources prior to actual transactions in an attempt to provide increased flexibility in

Acknowledgements

This work was supported by the Korea Research Foundation Grant (KRF-2004-003-D00482).

Jonghun Park received B.S. and M.S. degrees in industrial engineering from Seoul National University (SNU), Seoul, Korea, in 1990 and 1992, respectively, and Ph.D. degree in industrial and systems engineering with a minor in computer science from Georgia Institute of Technology, Atlanta, GA, in 2000. He is currently an Assistant Professor at Department of Industrial Engineering of SNU. Before joining SNU, he was with School of Information Sciences and Technology at Pennsylvania State

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    Jonghun Park received B.S. and M.S. degrees in industrial engineering from Seoul National University (SNU), Seoul, Korea, in 1990 and 1992, respectively, and Ph.D. degree in industrial and systems engineering with a minor in computer science from Georgia Institute of Technology, Atlanta, GA, in 2000. He is currently an Assistant Professor at Department of Industrial Engineering of SNU. Before joining SNU, he was with School of Information Sciences and Technology at Pennsylvania State University, University Park, PA, and with Department of Industrial Engineering at KAIST, Daejeon, Korea, both as an Assistant Professor. His research interests include Internet services, entertainment computing, and mobile services.

    Ki-Seok Choi received B.S. and M.S. degrees in industrial engineering, respectively from Seoul National University, Seoul, Korea, in 1991, and from KAIST, Daejeon, Korea, in 1993, and Ph.D. degree in industrial and systems engineering from Georgia Institute of Technology, Atlanta, GA, in 2003. He is currently an Assistant Professor at Department of Industrial Information and Systems Engineering, Hankuk University of Foreign Studies, Korea. Previously he worked at Electronics and Telecommunication Research Institute and Samsung Data Systems. His research interests are in telecommunication networks and quality of services.

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