Custom metadata elements (or specialization) in DITA can be reused across multiple DITA projects to ensure consistency and efficiency in managing metadata. This practice involves creating a shared metadata framework that can be employed across various projects, reducing redundancy and streamlining metadata management.

Specialization allows organizations to define and use their unique metadata attributes or elements to meet specific content management needs. Reusing custom metadata elements across multiple DITA projects offers:

• Consistency: By defining a consistent set of metadata elements, organizations can ensure that the same metadata structure is used across various projects. This consistency aids in standardizing metadata values and their interpretation.
• Efficiency: Reusing custom metadata elements eliminates the need to recreate metadata structures for each project. This saves time and effort in metadata design and implementation.
• Interoperability: Standardized metadata structures enhance interoperability between different projects, tools, and systems. This facilitates content exchange and integration.
• Maintenance: When updates or changes are needed to metadata elements, making modifications to a shared framework ensures that the changes are reflected uniformly across all projects using those elements.
• Documentation: Custom metadata elements and their intended usage can be documented in a central location, making it easier for content creators and project stakeholders to understand and apply them consistently.

Example:

A multinational corporation produces a range of technical documentation, including user manuals, product specifications, and training materials. They want to ensure consistent metadata management across all their documentation projects.

The corporation decides to create a shared custom metadata framework that includes elements like <product-name>, <document-version>, <audience-type>, and <publication-date>:

        <metadata-framework>
            <custom-metadata>
                <product-name></product-name>
                <document-version></document-version>
                <audience-type></audience-type>
                <publication-date></publication-date>
            </custom-metadata>
        </metadata-framework>
    

This framework becomes a standard for all their DITA projects. In each project, these custom metadata elements are reused to describe product names, document versions, target audience types, and publication dates. As a result, metadata consistency is maintained across all projects, and updates to these metadata elements can be applied universally when needed.