A User Defined Type (UDT) is a complex type of Tag in Ignition that can be configured to easily control multiple instances. This type can hold multiple other basic types of tags (int, string, etc) as well as other UDTs. Changes made to the parent UDT will automatically be propagated to all children.
A User Source in Ignition is a group of users with their associated roles. Ignition uses a role-based security system, ie: each user may be assigned to various roles. Security policies are then defined in terms of these roles, rather than defined for specific users. This allows users to be reassigned, removed, and added without affecting the logic of the security policy. An Ignition Gateway may have many different user sources defined, each governing the security of different aspects of the Gateway. For example, logging into the Gateway configuration web interface might be governed by one user source, while the security for a project is governed by another.
User Datagram Protocol (UDP) is an alternate communications protocol to Transmission Control Protocol (TCP) and is used primarily for establishing low-latency and loss-tolerating connections between applications on the Internet. UDP is used by apps to deliver a faster stream of information by eliminating error-checking.
Uniform Resource Locator (URL) stands for Uniform Resource Locator. It is used to specify an address on the World Wide Web. URLs have the following format: protocol://hostname/other_information URLs most commonly refer to web pages (http), but they are also used for file transfer (ftp), email (mailto), database access, and other applications.