Efficient Transport Bindings for Web Service Messages

Although Web service technology is being used in more and more distributed systems, its areas of application are inherently limited by high latencies and high amounts of protocol overhead. For messaging in environments with user interaction, like Web platforms for business or multimedia applications, the response time of the whole system needs to be kept in tight boundaries. In other scenarios comprising mobile communication and battery-powered devices, bandwidth-efficient communication is imperative. In this chapter we address both of these issues. First we conduct a detailed latency analysis of different transport mechanisms for SOAP and then we thoroughly investigate their protocol overhead. For both aspects we present a theoretical analysis as well as experimental measurement results. We then will introduce a new transport binding called PURE that significantly reduces the protocol overhead while featuring low latency. Furthermore it enables interesting additional features such as point-to-multipoint communication via IP multicast and broadcast.

XWRAPComposer

We present a service-oriented architecture and a set of techniques for developing wrapper code generators, including the methodology of designing an effective wrapper program construction facility and a concrete implementation, called XWRAPComposer. Our wrapper generation framework has two unique design goals. First, we explicitly separate tasks of building wrappers that are specific to a Web service from the tasks that are repetitive for any service, thus the code can be generated as a wrapper library component and reused automatically by the wrapper generator system. Second, we use inductive learning algorithms that derive information flow and data extraction patterns by reasoning about sample pages or sample specifications. More importantly, we design a declarative rule-based script language for multi-page information extraction, encouraging a clean separation of the information extraction semantics from the information flow control and execution logic of wrapper programs. We implement these design principles with the development of the XWRAPComposer toolkit, which can semi-automatically generate WSDL-enabled wrapper programs. We illustrate the problems and challenges of multi-page data extraction in the context of bioinformatics applications and evaluate the design and development of XWRAPComposer through our experiences of integrating various BLAST services.

An SLA-Based Auction Pricing Method Supporting Web Services Provisioning

Applying auctions to Web services selection and invocation calls for examination due to the unique features of Web services, such as interoperable machine-to-machine interactions and re-enterable bargaining services. In this chapter we propose a formal model for Web services-based auctions. Examining the one-sided sealed auction type, we prove mathematically that service requestors’ risk preferences could lead to different pricing strategies for service providers towards higher profit. We argue that Service Level Agreement (SLA) documents can be used to analyze service requestors’ preferences. On top of WS-Agreement, we propose a basic service requestor risk preference elicitation algorithm, as well as a historical data-based service requestor risk preference prediction model. Guidelines are provided to iteratively approach the learning rate of the proposed risk preference prediction model. The methods and techniques presented in this chapter can be reused to investigate and examine more facades of services-oriented auctions, towards establishing a new research realm on comprehensive services-oriented auctions.

Efficient Encodings for Web Service Messages

A major drawback of using SOAP for application integration is its enormous demand for network bandwidth. Compared to classical approaches like Java-RMI and Corba, SOAP messages typically cause more than three times more network traffic. In this chapter we will explore compression strategies and give a detailed survey and evaluation of state-of-the-art binary encoding techniques for SOAP. We also introduce a new experimental concept for SOAP compression based on differential encoding, which makes use of the commonly available WSDL description of a SOAP Web service. We not only conduct a detailed evaluation of compression effectiveness, but also provide the results of execution time measurements.

Realizability Analysis of Top-Down Web Service Composition Specifications

A conversation protocol specifies the desired global behaviors of a Web service composition in a top-down fashion. Before implementing a conversation protocol, its realizability has to be determined—that is, can a bottom-up Web service composition be synthesized so that it generates exactly the same set of conversations as specified by the protocol? This chapter presents three sufficient conditions to restrict control flows of a conversation protocol for achieving realizability. The model is further extended to include data semantics of Web services into consideration. To overcome the state-space explosion problem, symbolic analysis techniques are used for improving the accuracy of analysis. The realizability analysis can effectively reduce the complexity of verifying Web services with asynchronous communication.

Model-Driven Semantic Web Services

The Semantic Web promises automated invocation, discovery, and composition of Web services by enhancing services with semantic descriptions. An upper ontology for Web services called OWL-S has been created to provide a mechanism for describing service semantics in a standard, well-defined manner. Unfortunately, the learning curve for semantically-rich description languages such as OWL-S can be steep, especially given the current state of tool support for the language. This chapter describes a suite of automated software tools that we have developed to facilitate the construction of OWL-S specifications. The tools operate in two stages. In the first stage, a Model Driven Architecture technique is used to generate an OWL-S description of a Web service from a UML model. This allows the developer to focus on creating a model of the Web service in a standard UML tool, leveraging existing knowledge. In the second stage, an interactive approach for generating groundings is used. This chapter describes both tools and demonstrates how the use of lightweight interactive tools facilitates creation of OWL-S specifications.

Dynamic, Flow Control-Based Information Management for Web Services

Information Flow Control (IFC) is a method of enforcing confidentiality by using labels, data structures for specifying security classifications. IFC is used in programming languages to monitor procedures in an attempt to detect and prevent information leakage. While it ensures greater security, IFC excessively restricts flow of information. This chapter presents a model of information flow control using semi-discretionary label structures. We propose a set of rules that not only increase the flexibility of IFC, but also define labels as a practical component of a security system. We propose a dynamic approach using a centralized model for dynamic label checking, and verify the proposed model using theoretical proofs.

Adaptive Search and Learning-Based Approaches for Automatic Web Service Composition

We investigate architectural properties required for supporting automatic service composition. First, composable service architecture will be described, based on modeling Web services as abstract machines supported by formally defined composition operators. Based on the proposed infrastructure, we introduce and analyze several options for achieving automatic service composition by treating it as a search problem. Namely, basic heuristic search, probabilistic, learning-based, decomposition, and bidirectional automatic composition mechanisms will be presented and compared. Finally, we discuss the impact and outlook for automatic composition.

NAM

Web Services is an emerging software technology that is based on the concept of software and data as a service. Binary and XML are two popular encoding/decoding mechanisms for network messages. A Web Service may employ a loss-less compression technique (e.g., Zip, XMill, etc.) in order to reduce message size prior to its transmission across the network, minimizing its transmission time. This saving might be outweighed by the overhead of compressing the output of a Web Service at a server and decompressing it at a client. The primary contribution of this paper is NAM, a middleware that strikes a compromise between these two factors in order to enhance response time. NAM decides when to compress data, based on the available client and server processor speeds and network characteristics. When compared with today’s common practice to transmit the output of a Web Service uncompressed always, our experimental results show NAM either provides similar or significantly improved response times (at times, more than 90% improvement) with Internet connections that offer bandwidths ranging from 80 to 100 Mbps.

A Framework Supporting Context-Aware Multimedia Web Services Delivery

As Web services become more and more popular, how to manage multimedia Web services provisioning and delivery remains challenging. This chapter presents a componentization model to support quality of service (QoS)-centered, context-aware multimedia Web services delivery, which seamlessly incorporates cutting-edge technologies relating to Web services. A multimedia Web service is divided into control flow and data flow, each being delivered via different infrastructures and channels. We also propose enhancements to Simple Object Access Protocol (SOAP) and Composite Capability/Preference Profiles (CC/PP) protocols to improve their flexibility to serve multimedia Web services. In addition, we present a set of experiments to show how our service-oriented componentization model can support efficient delivery and management of multimedia Web services.