SOA, Web Services & BPEL - Tech Forum in Singapore

Recently, i gave a talk and BPEL demo to singapore partners for Oracle BPEL & SOA suites. Introducing them idea of SOA, BPEL and Web Services and how to make use of oracle technology in their applications.

SOA stands for service oriented architecture, it is a architecture model.

Talk about architecture, we need to understand basic building block of each application and system.

Like we build a real house, we use mortar and brick. Every application / system was built with business logic and process. Business process weaves all business logics into one application to achieve business goals. Process and logic weave seamlessly and hard coded into a monolithic application. Like we cook soup, we put all ingredients into water and hard for us to separate each out in the end, by which it reduce reusability of standard process and logics.

In traditional application, when people wanna change the process or integrated with other application / system, especially it is a heterogeneous platform or technology integration, that will be very hard and time-consuming.

For SOA applications, applications also build with process and so-called business logic (have been wrapped into self-contained services). Process and services are loosely coupled, people can easily add or remove services from process, not like traditional applications (process & logic fuse into one). Other than that, people can easily design & program the business process with a advanced IDE. Overall experience for process design and implementation will be a drag-and-drop exercise.

SOA process should be standard, easily extensible and composable. When build an SOA application, we start from building a portfolio of services , follow with well-defined business process to orchestrate services to achieve business goal. This is where BPEL comes in for business process implementation and web service for business service implementation.

Many people equate web services with Service-Oriented Architectures (SOA), but web services are just one element of SOA - they're about service invocation. SOA's scope is broader than just invocation. It's a complete software component architectural model, a way to organize, manage, deploy, discover, and expose software components, and to consume these over the Internet. From the software life-cycle perspective, in addition to the typical software development phases of design, development, and deployment, SOA defines web services-specific phases that include service publishing, discovery, binding and consumption, and management.

Note, SOA != web service+bpel

ESB vs BPEL

Both ESB and BPEL can be used for SOA implementation.

ESB (Enterprise Service Bus) implement messaging to enable services to be integrated in a message-based paradigm: both synchronous and asynchronous styles. ESB moves data via different adaptors (WebServices, FTP,File,JDBC etc) and protocols (HTTP,JMS) and enriches and transform data using XSL & domain value mapping lookups.

Oracle BPEL provides a comprehensive, standards-based and easy to use solution for creating, deploying, and managing cross-application business processes with both automated and human workflow steps.

ESB is good for routing messages to multiple destinations. It is also good for doing transformations that have little to no business rules. The footprint is much smaller and incurs minimal overhead therefore the performance is much better.

BPEL is used for bringing together multiple services. There is much more functionality and allows implementation of complex business logic.

• BPEL data transformations enrich and perform complex changes whereas ESB perform only simple transformations.
• BPEL can use Business rules, Human Workflow and Notifications, exception handling can be done in BPEL.

Use ESB when you want a really low cost solution, Only need connectivity, simple transformations and routing.

BPEL is primarily used for servies orchestration, data enrichment and human interaction.

Use BPEL+ESB when, You need to code complex business logic, integration with Workflow, complex transforms potentially involving the database or having long running processes which may or may not be stateful.

With an appropriately layered SOA architecture, one would look at ESB as a repository of services that BPEL orchestrates. At deployment time, this layered approach provides you the flexibility to dedicate servers to individual tiers (BPEL and ESB) and thereby maximize the resource usage for your particular use case.