Business Visitor Visas (B-1)
Persons traveling from countries outside the U.S. who are not part of the U.S. Visa Waiver Program, are required to obtain a visa in order to travel to the United States. You are encouraged to begin the application process early. The U.S. State Department website indicates that if the purpose for your planned travel is to travel for a scientific, educational, or professional conference on specific dates, then a business visitor visa (B-1) would be the appropriate type of visa for your travel. Link to the State Department website for details and instructions: http://travel.state.gov/visa/temp/types/types_1262.html.
You may request an official letter of invitation to attend the 37th VLDB by contacting Arnd Christian König (email@example.com).