Introduction to Web Services and SOA

Study Notes

SOA is a collection of services that can communicate with each other
Services are what is connected together, typically web services
Communication is facilitated through interface agreements and internet protocols
SOA is built on concepts similar to RPC (Remote Procedure Call), like RMI (Remote Method Invocation), CORBA (Common Object Request Broker Architecture), and DCOM (Distributed-Component Object Model)

SOA is an architectural style focused on achieving "loose coupling" between interacting services via communication protocols
It is an internet-native distributed computing model
"Service-oriented" supports dynamic service description, publication, discovery, and usage

Web services are loosely coupled, contracted components that communicate through XML-based interfaces
Loosely coupled means web services and their invoking programs can be independently changed
Contracted means that a web service's behavior, its input/output parameters, and bindings are publically available
Components are encapsulated code with hidden internal implementations
XML is a human-readable, text-based format, firewall friendly and self-describing

SOAP (Simple Object Access Protocol) is a messaging framework for transferring information between peers over the web
It uses XML for decentralized and distirbuted communication
WSDL (Web Service Description Language) is an XML-based way to describe and express the interface of a web service
UDDI (Universal Description Discovery and Integration) is a repository for WSDL documents.

Business motivation for SOA includes:
- Broad intra and inter operability
- Future e-business interoperability via the internet
- These requirements lead to high IT complexity and costs, and demand for quicker response
Benefits of SOA:
- Reduced costs by leveraging existing legacy services
- Incremental revenue by assembling existing services
- Integrated value chains for e-business collaborations
- Highly dynamic and distributed applications
- Achieve “just in time” integration

Goals of SOA include:
- Software reuse and integration
Challenges from the previous generation of RPC models, such as RMI, CORBA, and DCOM, include:
- Single-vendors, non-interoperable solutions
- Binary, non-readable protocols
- Tightly coupled systems only
SOA aims to solve these problems

The Web Services Interoperability (WSI) Organization aims to:
- Ensure web services interoperate across platforms, applications, and programing languages
- Accelerate web services deployment by setting standards
- Provide guidance, tools, samples, and best practices
- Facilitate discussion and meetings

E-business is the marriage of traditional supply chain management with the internet
Includes:
- E-commerce (B2C, C2C): direct transactions and point-of-sale
- E-procurement (B2B): processes by which a manufacturer obtains products from suppliers
- E-collaboration (B2B): information sharing and collaborative planning