MARIA (Model-based lAnguage foR Interactive Applications) is a universal, declarative, multiple abstraction level, XML-based user interface markup language for modelling interactive applications in ubiquitous environments. MARIA one of the languages that has been submitted for standardization at W3C. Abstract User Interface The MARIA Abstract User Interface (AUI) level describes a UI only through the semantics of the interaction, without referring to a particular device capability, interaction modality or implementation technology. An AUI is composed by various Presentations that groups model elements presented to the user at once. The model elements are of two types: Interactor or InteractorComposition. The former represents every type of user interaction object, the latter groups together elements that have a logical relationship. According to its semantics an interactor belongs to one of the following subtypes: Selection. Allows the user to select one or more values among the elements of a predefined list. According to the number of values that can be selected, the interactor can be a Single Choice or a Multiple Choice. Edit. Allows the user to manually edit the object represented by the interactor, which can be text (TextEdit), a number (NumericalEdit), a position (PositionEdit) or a generic object (ObjectEdit). Control. Allows the user to switch between presentations (Navigator) or to activate UI functionalities (Activator). OnlyOutput. Represents information that is submitted to the user, not affected by user actions. It can be a text a Description that represents different types of media, an Alarm, a Feedback or a generic Object. The different types of interactor-compositions are: Grouping: a generic group of interactor elements. Relation: a group where two or more elements are related to each other. CompositeDescription: represents a group aimed to present contents through a mixture of Description and Navigator elements. Repeater which is used to repeat the content according to data retrieved from a generic data source MARIA allows describing not only the presentation aspects but also the interactive behaviour. For this purpose it has various features: Data Model: the description of the data types bound with elements of the interface. At runtime, modifying the state of an interactor will change also the value of the bound data element and vice versa, in order to describe dynamic UI changes (correlation between UI elements, conditional layout, conditional connections between presentations, input values format etc.). The data model is defined using the standard XML Schema Definition constructs. Generic Back End. The interface definition contains