WSDL is a short form for Web Services Description Language, which is used to describe a Web service in terms of the messages that it creates and accepts. The WSDL document is an XML file that contains the interface schema for the Web service. It identifies the methods that are used during the exchange between a Web service consumer and a Web service provider. The following are the elements contained in the WSDL document:
• Types - Describe the variations of data types that are used to exchange messages between the user and the provider.
• Message - Describes the actual message or method call.
• portType - Describes the set of operations and each related message.
• binding - Describes the protocol details.
• service - Used to make groups a set of related ports together.

The UDDI directory has an advantage over a DISCO file, as it provides a single location where a client can find the Web services offered by different organizations.

You should use the < authorization > element to ensure that only authorized users access your Web service. This element allows or denies access to your Web service according to their role.

The EventLog class is used to access the Windows event logs from Windows services. Using EventLog, you can also customize Windows event logs that record information about important software and hardware events, such as the events of the .NET controls, keyboard, or other hardware devices.

The EventLog class allows you to read or write to event logs, delete logs, and create as well as delete event sources. You can use the EventLog class to create event logs while creating an event source. An event source can be used to write to only one event log at a particular time. However, it is possible to associate one event log to multiple sources.

The following are the ways to prevent your Web service from unauthorized access:
• Using encryption and message-based security.
• Using authentication and access controls for the Web service.