Specialization attributes in DITA can indeed have user-defined values, offering flexibility and customization to cater to specific requirements. These attributes are defined within the specialization DTD or schema and can accept values specified by content creators to provide domain-specific information.

Attributes are typically assigned values directly within DITA elements in the content. These user-defined values can vary based on the context and the specific details required for the specialized content. This ability to assign custom values to specialization attributes allows content creators to tailor content to the needs of their domain.

Example:

In a specialized DITA topic for software documentation, a specialization attribute like @platform can accept user-defined values to indicate the software platform. Content creators can assign values such as “Windows,” “Linux,” or “macOS” to this attribute within the topic to specify the target platform for the software being documented.

<software-feature platform="Windows">Description of a feature specific to the Windows platform.</software-feature>