UDDI, Discovery and Web Services Registries

Introduction To facilitate e-commerce, companies needed a way to locate one another and exchange information electronically Organizations responded by creating their own methods of publishing business-related data on the Web and offering third parties access to the data. – inefficient, difficult and time-consuming

Introduction IBM, Microsoft and Ariba developed Universal Description, Discovery and Integration (UDDI) to address the problem – A specification that defines registries in which businesses can publish information about themselves and the services they provide. Service consumers can use UDDI registries to locate general and technical information about various service provid­ers. Consumers can initiate business transactions, form partnerships and purchase services

Web Services Registries Web services registries – Repositories containing documents that describe business data – Provide features such as search capabilities and programmatic access to remote applications – E.g., Find the best Web service for credit card payments

Discovery The process of locating Web services through registries Two categories – Direct discovery The process of obtaining data from a registry maintained by the service provider Improves the likelihood that data is accurate – The organization providing the information also operates the Web service

Discovery – Indirect discovery Obtains data through a third-party registry Data might not be as accurate – because service providers might not update information in third­party registries as frequently When performing indirect discovery, organizations must pose the question: How often do third-party registries interact with service providers to ensure that the data is still accurate?

SOAP, UDDI and WSDL Technologies enable communication among applications in a manner that is independent of specific programming languages, operating systems and hardware platforms – SOAP provides a communication mechanism between Web services and other applications – WSDL offers a uniform method of describing Web services to other programs – UDDI enables the creation of searchable Web services registries

Web Services Architecture

Universal Description, Discovery and Integration (UDDI) In September 2000, the UDDI project - led by IBM, Microsoft and Ariba - released Version 1.0 of the UDDI specification Defines a framework for centralized registries that facilitate the storage, discovery and exchange of information about business­es and their Web services In June 2001, the UDDI project released a beta specification of UDDI Version 2.0 – Offers advanced searching capabilities – Increases the global scope of UDDI registries E.g., provide company and product descriptions in various languages

Operator Nodes and Registrars Operator node - an organization that hosts an implementation of the UDDI Business Registry (UBR) Four operator nodes - Hewlett-Packard, IBM, Microsoft and SAP - host beta implementations of the UBR that adhere to the UDDI Version 2.0 Two operator nodes - IBM and Microsoft - host implementations of the UBR that adhere to the UDDI Version 1.0.

Operator Nodes and Registrars Replication – the process of updating records so that all instances of those records are identical – operator nodes synchronize their data at least every 12 hours “Register once, publish everywhere" principle – A company needs to register with only one operator node to be listed in the UBR – Information contained in one registry is replicated in the other registries when a company registers with one operator node (known as a custodian), the company's data appears in the other three registries, as well

Operator Nodes and Registrars A company can update its information only through its custodian – Because the UDDI Version 2.0 API Specification does not provide a protocol for reconciling disparate or duplicate data

Advantages of Registering Registering in the UBR offers advantages to both service providers and service consumers For service providers, – the UBR is an effective method of advertising Web services Global visibility Helps service providers expand their markets For service consumers, – the UBR saves time and simplifies the process of using Web services Integrate applications with remote services more quickly and efficiently Do not have to spend time locating service-related information

Advantages of Registering The UBR also can reduce costs for service providers and service consumers – Service providers can advertise their businesses and services for free – Service consumers can locate compatible Web services for free

Role of UDDI in Web Services Vendors often compare the UBR' s structure to that of a phone book – The components of the UBR's phone-book structure - white pages, yellow pages and green pages. White pages – Contain general information about a company Such as its name, address, contact informa­tion and identifiers.

Role of UDDI in Web Services Yellow pages – divide companies into various categories on the basis of their products or services – E.g., a software company might be categorized under computer software or software engineering – Allow registry users to search for companies or services that fit a particular category (such as sales, travel or books)

Role of UDDI in Web Services Green pages – Contain technical information about a company's products, services and Web services – This data allows a service client to bind (i.e., establish a communication channel) to a Web service, because the information defines how to invoke the service.

UDDI Registries UDDI can be supported on both public and private registries Public registry – E.g., the UDDI Business Registry (UBR) – Can be accessed by individuals or businesses Private registries – Restrict access to services – Impose additional security measures to safeguard against unautho­rized access

UDDI Business Registry Contains information about companies and their technical capabilities Allows service providers to organize and describe Web services in a central location Service consumers can browse this registry to find information about businesses and Web services To post information in the UBR, businesses need to register with the UDDI project

UDDI Business Registry The UBR usually is referred to as a Public Cloud – The "UDDI Business Registry" consists of several registries owned and maintained by public operator nodes Data entered in one registry is replicated in the other registries. – The replication of data is guaranteed, Because the operator nodes are governed by the Operator's Council – A committee that consists of the current operator nodes – Governs the UDDI specifications and quality-of-service (QoS) issues

Private Registries Limit access to Web services. Restricting access to services can reduce concerns regarding service-level agreements and security Implemented by organizations that are uncomfortable exposing services in a public forum – Access to which is restricted to certain parties – E.g., the employees, partners and affiliates of a particular company

Private Registries Companies are adopting private registries more quickly than public registries – Partly because most organizations want to experiment with Web services by deploying them internally before offering publicly accessible Web services. – Organizations can use private registries to locate services offered by their own departments or by their partners

Limitations of UDDI Although UODI facilitates the discovery of Web services, there are certain limitations to UODI and UDDI registries. The most significant limitation of UDDI is the immaturity of the UDDI specification – No "official" organization is controlling its development – The specification may change significantly in future versions – Data reliability E.g., UBR does not indicate when data was last updated or checked for accuracy

Limitations of UDDI UDDI registries describe Web services, but do not evaluate them – QoS? – E.g., Service consumers might want to know the following: How often can I access a certain Web service? Will the Web service "crash" if numerous companies use it simultaneously? Does the service provider offer technical support? If so, what is the turnaround time for resolving issues?