Composing RESTful Services andCollaborative WorkflowsA Light Weight Approach

Author(s): Rosenberg, F (Rosenberg, Florian); Curbera, F (Curbera, Francisco);Duftler, MJ (Duftler, Matthew J.); Khalaf, R (Khalaf, Rania)

Source: IEEE INTERNET COMPUTING Volume: 12 Issue: 5 Pages: 24-31DOI: 10.1109/MIC.2008.98Published: SEP-OCT 2008

Web of Science Categories: Computer Science, Software EngineeringResearch Areas: Computer ScienceTimes Cited: 20 (from Web of Science)Cited References: 7

Abstract

• The use of RESTful Web services (based onHTTP) can integrate easily into applicationslike mashups

• In order to compose RESTful services intoWeb-scale workflows, using Bite as a lightcomposition language to accomplish the taskby describing both the control and data flow

Introduction

• Increasing adoption of SOA paradigm

• Limits of Web services model consists of twocontention points:

– The complexity

– Lack of alignment with the Web’s acceptedarchitectural principles

• The Representational State Transfer (REST)model is introduced

Introduction

• In REST, the main architectural concept is theinformation resource, and the principalinteraction mode lets clients retrieverepresentations of those resources

• The article addresses the complementaryproblem:

– How the service paradigm and SOA’s servicecomposition model can benefit mainstream Webapplications

Introduction

• Explore the potential benefits of process-oriented composition for Web scenarios

• Focus on design principles and applications ofthe process-oriented composition model ofBite language, derived by aligning SOA processcomposition principles with REST architecturalrequirements

Bite Overview

• Allow web applications can seamlesslycombine:

– RESTful services

– Simple human interaction

– Collaboration services

– Back-end services

The Bite Approach

• Requirements and Design Goals:

– Atom life-cycle model

– Light weight process model

– Scripting approach

– Language extensibility

– Web and human integration

The Bite Approach

• Basic Model and Language:

– Comprise a flat graph containing actions and linksbetween them

– Use while activity to allow containing of otheractivities

– Encodes graph execution logic in conditionaltransition links between activities and supportserror handling via special error links to an error-handling activity

The Bite Approach

• Basic Model and Language:

– Bite’s core activities consist of:

• Basic HTTP communication primitives

• Utility activities

• Control helpers

– A Bite flow both uses external services in its flowlogic and exposes itself as a service

– Each flow instance can define multiple receiveactivities corresponding to multiple entry points.

The Bite Approach

• Flow Example

The Bite Approach

• Bite Extensibility

– Creating Bite extension activities and registeringthem with Bite engine

– Creating an extension activity lets developers implement the core extension logic with minimal overhead for reading and evaluating the extension’s syntax

The Bite Approach

• Executing Scripts

– Executing script code in the flow facilitates certaintasks (for example, calculation or accessing someback-end system)

The Bite Approach

• UI Integration and Rendering Capabilities

– Enables a user interface (UI) integration becauseall entry points in a flow are accessible via URLs.

– Provides HTML rendering capabilities usingvarious template languages to render HTTP repliesor emails from a flow

Collaborative Flows in Bite