The Holiday Web Service has support for two different modes of communication.
The first way is through the REST architecture. The holiday application supports the RESTful scheme and allows parameters for the web methods to be passed in through the url. An example of this, is if you wanted to get the closest holiday to 2012-01-10 you would query the service by going to the url: https://www.hawaii.edu/its/ws/holiday/rest/closest?date=2012-01-10
The second way is through the use of a WSDL. A client application can be quickly setup by using wsdl2java which utilizes the wsdl that is setup by the holiday application.