Technology

Technology

It is important to look at Web services from a technology standpoint and explore some of the fundamental concepts before moving on to the business scenarios to which Web services can be applied. This should help to add clarity to the concept among the mass of confusing acronyms which do little to explain what exactly Web services are really all about and how they can enable new forms of business value.

The conceptual model behind Web services is a service-oriented view of business applications composed of a service provider, a service user, and a service registry. In the physical world, each of these elements is generally software running on a computer server or collection of servers in a data center. In order for the service user to dynamically search for and discover the software services of the service provider, the service registry is used as a metarepository for information about the published service. A metarepository is a database that contains "metadata," which are basically information about information, or a pointer to the real data. The service registry therefore serves as a machine-searchable database for published services similiar to a Yellow Pages telephone book. It's important to note that this database is primarily intended to be searched via machine, although most registries also provide a browser-based interface for manual searches. Figure 2-3 shows the conceptual model for service providers, service users, and service registries.

Figure 2-3. Web Services Conceptual Model. Source: Adapted from Hewlett-Packard Web Site.

In the conceptual model, the service provider publishes component services to the service registry. Note that it is the description of the service, or its metadata, that is published to the registry and not the actual software component itself. These component services can be simple or complex units of business applications, business processes, computing resources or information, all expressed via software. Hewlett-Packard defines Web services as any asset available over the Internet to complete a task, solve a problem, or conduct a transaction, so the scope of what constitutes a Web service is very broad.

The service user, again a software application, locates required services within the service registry and then connects directly to the service provider, another software application, in order to execute the desired services. The service user can execute the service of the provider as a standalone unit of work, that is, a complete application, business process, computing resource, or piece of information, or it can combine other services from the same or other service providers in order to execute a more complex, composite unit of work. This conceptual model is very powerful; it describes a mechanism for the business to become a virtual enterprise. Enterprises can provide services which they want to maintain as core competencies and consume services which they want to outsource and acquire from the outside.

Additionally, there is no limit to the number of partners that can be integrated in this manner. Any end-to-end business process can be composed of discrete services from many service providers. With this knowledge of the conceptual model behind Web services, business users can start to think about which business processes they would like to either publish or subscribe to and what kind of value may be charged or paid in exchange for these services.

Web services registries, which serve as the directory or Yellow Pages for Web services, can be either public or private. Private registries are strictly controlled and are typically operated by corporations within their corporate firewall. The private registries are used to integrate with both external and internal services located within both private or public registries.

An example of a service registry is the Hewlett-Packard UDDI Business Registry. This is a private registry that companies can use to create and manage their own ecosystem of Web services. Companies can expose services to the public or they can make some or all of their Web services private and accessible only to selected business partners. When registering, companies enter basic contact information such as name and email address together with their company name, country, and Web page address. Once registered, companies can manage their account in terms of profile and password, search for businesses by name, and publish various services for others to discover and utilize.

The main theme behind Web services is that businesses are now able to use the Internet to publish business functionality and not just content. Other businesses can then search for and access this business functionality, giving them a way to tap inside another business and to execute real-life transactions within the back-end systems of that business. Since the transactions are machine to machine in nature, with minimal human interaction, there needs to be considerable planning in terms of what functionality is published and how this functionality is to be secured and audited. Businesses will also need to understand usage patterns and be able to charge for certain business functions that provide value to employees, customers, and business partners. The Web services infrastructure will therefore need to evolve from the basic communication mechanisms between Web services components that we have just discussed to support a variety of management and monitoring services around this core functionality.