MRML is short for Multimedia Retrieval Markup Language, which defines a protocol for querying a server for images based on their content. See http://www.mrml.net about MRML and the GNU Image Finding Tool (GIFT), an MRML server. . This package is part of KDE, as a component of the KDE graphics module. See the 'kde' and 'kdegraphics' packages for more information.
