FINDING WEB SERVICES

The third mechanism to be discussed is the universal description, discovery, and integration (UDDI) registry. Once we have created a message making use of a format known as WSDL and we have a way of sending the message, the next step is to provide a way that other people are aware that the message exists. The message could be a service that provides a list of prices for a business, or it could be a list of stock quotes for the day. Whatever the message is people need to find out about that service. This is accomplished via the UDDI registry. The UDDI registry is established by an industry consortium to create and implement a directory of Web services, just like in the case of a telephone directory. The UDDI registry accepts information describing a business, including the Web services it offers, and allows interested parties to perform online searches and download the information.

If you want to find the telephone number and address of someone, you can look it up in a telephone directory. Similarly, if you want to interact with a business’s Web service to check stock availability before placing an order, check for hotel accommodation, car rental or flight information for travel reservations, you need to be able to find and contact the business’s Web service.

If you do not know the business’s name or if you would like to compare several

suppliers, the problem becomes more complex and the need for a generic search would arise. The UDDI registry provides such a mechanism and is therefore important to the ultimate success of Web services.

Figure 3.8 below illustrates the public UDDI service hosted by IBM, Microsoft, SAP, HP, and potentially others. Each company provides a publicly accessible database

containing business registry data, posted via SOAP requests to one of the company’s data centers and replicated to the others. SOAP requests query the results of the posted updates to find information about businesses to be contacted, including other information about a business’s Web services.

Figure 3.8 – The Public UDDI Service

The databases on the previous page are called operator sites. UDDI makes use of SOAP API’s to interact with one or more of the sites. The operators do not charge for the basic UDDI service. Business data can contain pointers to Web services interface specifications, such as WSDL.

3.5.1 The UDDI Organization

The UDDI began as a collaboration among Microsoft, IBM, and Ariba to promote the adoption and use of Web services standard (5). These companies founded UDDI.org and they invited other organizations to join the organization. Ground rules were set, initial specifications and requirements were defined and the work was distributed among the various organizations.

The three original founders were the original operators. HP joined them later on and replaced Ariba as a registry host site. SAP has now joined the other operators. At the moment the UDDI operator costs are being covered by IBM, Microsoft, HP and SAP. As UDDI grows and becomes more popular the cost issues will be addressed.

SOAP Requests UDDI.org IBM SAP Others HP Micro soft

3.5.1.1 How Does The UDDI Work?

The way in which the public UDDI registry works is very similar to that of the Internet domain name service (DNS). Businesses register with any of the hosts (IBM, Microsoft, SAP or HP), and the information they provide will be placed into the database at that host site. At regular intervals, normally every night, the other sites are updated or replicated with the information. This ensures that each site has its own version of the database and that the databases are kept in sync. When the business needs to update its information, it needs to return to its host site where the data was originally placed and execute the update function.

3.5.1.2 Security And UDDI

Security is obviously a concern for UDDI.org members. Once a business has been approved/authorized for registration to the UDDI.org, they will be given an authorization token that allows the business to log onto the UDDI site and to store or to update data. Authorization to update the registry is handled by the operators individually.

3.5.1.3 Other UDDI Concerns

Another primary concern other than security is the quality or validity of the data. It is important to ascertain that each business that has been registered is a legitimate business. Each operator needs to ensure that the businesses being registered are who they say they are. The operators need to ensure that UDDI.org remains an organization that would attract people to the Web services.

3.5.1.4 Information Categories

Once a business has been registered and the business has their authorization token and the operators have evaluated whether or not the business is a legitimate one, the

information that a business can place into a database would fall under one of the following categories:

(a) White pages contain the business’s name, address, contact information, web site name and other relevant information;

(b) Yellow pages would describe the type of business, it’s location and products, industry type and business ID;

(c) Green pages provide technical information about business services such as how to interact with them, business process definitions and so on;

(d) There would be a pointer to the business’s WSDL file, if such a file exists (this is a new category and is Internet specific);

To summarize, the UDDI provides a structure for companies to register their Web services.

WSDL, SOAP and UDDI cover the basics of Web services. These basics are often not enough and other mechanisms/tools are needed to ensure that Web services operates as efficiently as possible.