We have defined an XML Schema for Xaal. To make the language more modular, we have separated the schema to several XML Schema documents. The relationship between these documents is illustrated in the Figure below. This kind of modularity makes it possible to more easily change or reuse some parts of this language in other languages. These modules specify parts of the language as described in the following.

• xaal.xsd - The main schema document that specifies the root element and combines all the other modules.
• xaal-metadata.xsd - Defines the metadata that can be included in a Xaal document.
• xaal-graphical-animation.xsd - Defines the graphical primitive animation operations.
• xaal-graphics.xsd - Defines the graphical primitives available in Xaal.
• xaal-animation.xsd - Combines the animation operations allowed in Xaal and defines how to group these operations.
• xaal-animation-common.xsd - Defines common animation properties, such as timing.
• xaal-datatypes.xsd - Defines data types used in Xaal.
• xaal-common.xsd - Defines some common types used by several other schema modules.
• xaal-structure-animation.xsd - Defines the data structure operations available.
• xaal-structures.xsd - Defines the data structures available in Xaal.
• xaal-interaction.xsd - Defines the interactive questions available in Xaal.