What Are Web Services?

The quick answer is: Web services are a distributed computing architecture. Only this particular architecture makes use of loosely coupled applications, as opposed to tightly coupled applications, to enable applications to communicate. This tightly coupled concept radically affects how information systems will work in the future a theme that will be explored in depth in this book.

The longer answer is that Web services pertain to:

1. How data is presented/shared using a content/format approach called "XML" eXtensible Markup Language. Most information is shared on the Internet today using a language called HTML. HTML is great for displaying (presenting) text and graphics but XML tells cooperating application programs what the data is (a name, address, phone number, etc.) and thus enables developers to control, display, share, and manipulate data (rather than presenting data graphics and static information).

2. How applications find services and share information and data across diverse systems environments, using Web services registries and templates/interfaces known as:

   • Universal Description, Discovery, and Integration (UDDI) a "registry standard" that allows applications to be listed and located;

   • WSDL (Web Services Description Language) a "template" that allows applications to describe to other applications the rules for interfacing and interacting;

   • SOAP (Simple Object Access Protocol) a programmatic interface that enables applications to bind together and commence program-to-program communications.

3. How communications take place over a common network (the Internet) using HTTP protocol as the transport.

Sidebar 0-1
Quick Definitions

Protocol In this book a protocol is a way that applications can "talk" to each other. Protocols can be established ways to send and receive data over a network, or they can be tacit agreements between applications on what procedures should be observed when sharing information (for instance, how one application should respond to the request of another application for data or information).

Registry A registry is simply a place where an application program can "register" characteristics about itself (how to communicate with it, or what it does, etc.). The word "directory" is often used synonymously with "registry," but directories provide somewhat different functions, such as user account or configuration information, and are less often used as repositories for application information characteristics.

It is important to know what protocols are and what they do in order to understand how Web services are able to share information with other applications on disparate systems. Further, it is important to understand the "registry" concept because registries will play a crucial role in helping Web services applications find each other and work with each other in the future.

"Web services" refers alsoto what the aforementioned standards do they enable certain applications to provide computational, messaging, or transactional services for other applications, regardless of the platform, operating system, or programming language the originating application is running on.