Angel Lagares Lemos

Web Service Composition: A Survey of Techniques and Tools

Web services are a consolidated reality of the modern Web with tremendous, increasing impact on everyday computing tasks. They turned the Web into the largest, most accepted, and most vivid distributed computing platform ever. Yet, the use and integration of Web services into composite services or applications, which is a highly sensible and conceptually non-trivial task, is still not unleashing its full magnitude of power. A consolidated analysis framework that advances the fundamental understanding of Web service composition building blocks in terms of concepts, models, languages, productivity support techniques, and tools is required. This framework is necessary to enable effective exploration, understanding, assessing, comparing, and selecting service composition models, languages, techniques, platforms, and tools. This article establishes such a framework and reviews the state of the art in service composition from an unprecedented, holistic perspective.

DataSheets: A Spreadsheet-Based Data-Flow Language

We are surrounded by data, a vast amount of data that has brought about an increasing need for combining and analyzing it in order to extract information and generate knowledge. A need not exclusive of big software companies with expert programmers; from scientists to bloggers, many end-user programmers currently demand data management tools to generate information according to their discretion. However, data is usually distributed among multiple sources, hence, it requires to be integrated, and unfortunately, this process is still available just for professional developers. In this paper we propose DataSheets, a novel approach to make the data-flow specification accessible and its representation comprehensible to end-user programmers. This approach consists of a spreadsheet-based data-flow language that has been tested and evaluated in a service-centric composition framework.

Service graph base: A unified graph-based platform for representing and manipulating service artifacts

The number of Web-Services publicly accessible through APIs have rapidly grown in recent years. Although, while these services are key in providing access to data as well as a variety of functionality, often their full potential remains yet to be fully exploited. Due to the different standards used to implement and expose Web services, it is usually cumbersome for developers to reuse them within third-party applications. In this paper, we present Service Graph Base, a unified graph-based platform for representing and manipulating service artifacts. It allows professional developers to add service knowledge to a graph base, which can be done either automatically or manually. By adopting the language-neutral RDF-based Graph Model and developing a uniformly-interfaced service editor for service native artifacts extraction, services are represented as RDF graphs in Service Graph Base. Once they are in the graph base, common SPARQL queries can be used to provide intelligent exploration over the base, thereby providing a unified approach regardless of the actual service type. In our work, we have harvested 4,925 Yahoo! pipes and 300 WSDLs for service artifacts extraction and service query. Experiments showed that 99.35% Yahoo! pipes and 100% WSDLs were successfully represented as RDF graphs.

Service Component Architecture (SCA)

In this chapter, we introduce a framework known as Service Component Architecture (SCA) that provides a technology-agnostic capability for composing applications from distributed services. Building a successful SOA solution in practice can be complex, due to the lack of standards and specifications, especially when integrating many different technology environments. This chapter explores techniques for adopting a consensus on how to describe an assembly of services, and how to implement and access them regardless of the technology.

Data Transformation Knowledge Reuse in Spreadsheet-Based Mashup Development Platform

Data transformation is a key task in mashup development (e.g., access to heterogeneous services, data flow). It is considered as a labour-intensive and error-prone process. The possibility of reusing previously specified mappings promises a significant reduction in manual and time-consuming transformation tasks, nevertheless its potential has not been fully realized in current approaches and systems. In this chapter, we study the problem of data transformation logic reuse in mashup development platforms. We formulate the problem and propose a solution that features novel reuse abstractions and techniques including spreadsheet templates, mapping generalization, and similarity join. Given a spreadsheet instance that is being mapped to the target schema, we recommend a list of mapping formulas that can be potentially reused for the instance. We implemented a prototype of the proposed solution and evaluated its performance via synthetic datasets.

Web Service Composition: Control Flows

In this chapter, we present BPEL and BPMN as two main languages of Web service composition. Both BPEL and BPMN allow the codification of control flow logic of a composite service. We will introduce the core syntax elements of the two languages and their usage examples. The lab activities will show how to build a simple BPEL service by composing other services to implement a home loan-processing scenario.

Web Service Composition: Overview

In this chapter, we introduce the motivation behind Web service composition technologies – going from an atomic to a composite service. In doing so, we discuss the two main paradigms of multiple service interactions: Web service orchestration and Web service choreography. In the rest of the book, we will focus on Web service orchestration as the main paradigm behind Web service composition techniques.

Web Services – Data Services

In this chapter, we explore the concept of data services. After clarifying the main concepts, we introduce key enabling technologies for building data services, namely XSLT and XQuery. These two XML-based languages are used to transform and query potentially heterogeneous data into well-understood standard XML documents. The lab exercises included at the end of this chapter will guide you to learn the basic syntax and usage scenarios of XSLT and XQuery.

Web Service Composition: Data Flows

In this chapter, we examine the data-flow aspects of Web service composition, which specifies how data is exchanged between services. The data-flow description encapsulates the data movement from one service to another and the transformations applied on this data. We introduce two different paradigms based on the message passing style, namely, blackboard and explicit data flow. We conclude the chapter with a discussion of Mashup applications as a way to implement data-flow oriented service composition.

Introduction to Service Oriented Architecture

In this chapter, we begin by understanding Service Oriented Architecture (SOA), its key values and goals too modern and evolving business ecosystems. We then describe the SOA architectural stack in reference to software application integration layers. This is followed by an introduction to service composition and data-flow techniques, including end-user mashups. This chapter also presents the overall goals, structure and organization of the rest of this book.