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Introduction

UDDI is most commonly used in four types of topologies:

• The UDDI Business Registry
  A network of public UDDI registries on the Internet.
  
• The UDDI E-marketplace
  UDDI Registry dedicated to a given industry sector.
  
• The UDDI Private node
  UDDI Registry on the intranet used to provide UDDI functionality to corporate users.
  
• The UDDI Extranet node
  UDDI Registry on the extranet to provide UDDI functionality to business partners.

The UDDI Business Registry (UBR)

IBM, Microsoft, SAP and NTT Communications are running public UDDI sites. For example, the public UDDI registry of IBM is located on the Internet at the uddi.ibm.com URL. Any company can register in these UDDI instances information on their services or look up for services provided by other companies.

An important characteristic of the UDDI registries of IBM, Microsoft, SAP and NTT Communications is that their data are replicated over each other. Conceptually, these registries can then be considered as a single system built from multiple nodes. This network of UDDI registries is called the "UDDI Business Registry" (UBR), and is also known as the "Public Cloud".

In principle, any company can become a member of the UDDI Business Registry by setting up a public UDDI registry and making it participate to the UBR replication process. In order to ensure an acceptable level of service, however, such company would have to comply with a rather long list of requirements defined in the UDDI Operator Specification. Among the topics covered by the UDDI Operator Specification are the UUID1 generation algorithms, the XML data validation, the backup and recovery systems, the policies for data replication, etc.

The UDDI e-marketplace

E-marketplaces are focused on a particular business topic, such as the paper or travel business. The UDDI e-marketplace is an implementation of electronic marketplace based on UDDI. Two aspects of UDDI are particularly relevant to e-marketplaces: its categorization architecture and its ability to register technical specifications to access services.

Categorization:

Without proper classification and categorization, large content cannot be managed effectively and browsing through it may be very difficult. Classical e-marketplaces typically develop and manage their own proprietary structure for categorization. The UDDI e-marketplace, on the other hand, takes benefit of the flexible UDDI architecture for categorization. UDDI not only adopts all the well-known taxonomical architectures such as NAICS2 or UNSPSC3, but it also allows new taxonomical architectures to be registered.

Technical specifications registration:

In order for automated business to business interactions to become mainstream within a given industry, common business processes need to be identified and agreed upon. Several initiatives are currently on the way. For example, the Open Travel Alliance4 (OTA) provides a forum where all sectors of the travel industry work together to create unified and integrated information exchange specifications. The technical specification of these business processes can be registered within an UDDI registry thanks to the notion of technical model (tModel).

The UDDI private node

Companies are showing an increasing interest for UDDI private nodes. The UDDI private nodes sit on the corporate intranet, typically behind the firewall. They are typically not accessible from the Internet, or in a restricted fashion, and the data they contain is not replicated in the UDDI Business Registry. Private operator nodes can define the access rules for their nodes on a finer-grain level, or follow the same access model as the UDDI Business Registry. A grouping of UDDI private nodes replicated over each other can be created within the company.

UDDI private nodes contain entries for Web services provided by other departments or groups within the organization. For example, a data processing centre could publish a set of Web services to access back-end functionality and catalogue information. These Web services could be used by the Webmasters to build on-line systems. Typically, standards will be established within the enterprise and the technical models used will correspond to the technology standards in use.

The UDDI extranet node

The UDDI extranet node is intended to be used by partner companies. It lists Web services that can be accessed by companies with which a business relationship has been established. The UDDI extranet node only exposes its query API to authorized companies, the publishing API is kept private and is used by the UDDI extranet operator for the administration of the UDDI node.

Companies can lookup the UDDI extranet nodes of their partners and copy the Web services definitions in their own private nodes. As business relationships are formed and dissolved, the entries in the UDDI private node will be updated. Applications can then be written that bind to the business partners's Web services. As interactions only occur between well-identified service providers, business or technical rules can even be established that govern how an application binds to Web services at runtime. For example, bulk orders may be preferably treated by a given business partner while more modest orders may be treated by another one.