Data Typing

The Common Desktop Environment provides a uniform user interface to the objects contained on the desktop. To do this, the desktop has a mechanism, called data typing, to determine an object's type using a set of criteria. The criteria includes properties potentially shared by file-based and buffer-based objects such as name pattern and content pattern. Other criteria are exclusive to files, and include path-name pattern and file permissions. Associated with every desktop type is an extensible set of attributes, including icon name, name template pattern, list of actions suitable for presentation to a user, equivalent type names for other type spaces (for example, MIME type), and a textual description of this type. The actions and data-types database stores data criteria and data attributes.

The Common Desktop Environment defines, and platform vendors supply, a set of desktop type definitions. Your application should augment the database with both proprietary and public data types at application installation time.

Information is extracted from the actions and data-types through a Common Desktop Environment library API. The data typing API matches an object's properties with the database type criteria to determine the object's desktop type. The matching algorithm uses a set of precedence rules to resolve conflicts.

The Common Desktop Environment type space is defined by the X/Open Common Desktop Environment standard and exists primarily to support desktop-oriented activities such as icon display and action association. The MIME type space is defined by the Internet Engineering Task Force and exists to deal with exchange of mail message parts. A ToolTalk media type space exists in order to match data with handlers, and is a subset of X selection target types defined by the X Consortium. Thus, to do a complete job of type definition, you have to define a Common Desktop Environment type, X selection target, and MIME type. For private Common Desktop Environment types, append the type name to an organization's name. This partitions the name space without need for centralized allocation of types. The Common Desktop Environment claims the Dt prefix, for Desktop.