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References: Verb Vocabulary Design and the ADL Verb Registry

  1. Controlled Vocabulary - Wikipedia - Foundational article on why curated vocabularies (versus free-text tags) are the prerequisite for cross-system analytics. Maps directly onto why xAPI verbs must be IRIs from a known registry.

  2. Resource Description Framework - Wikipedia - RDF's subject-predicate-object triple is the conceptual ancestor of xAPI's actor-verb-object. Reading this clarifies why xAPI verbs are IRIs and why semantic interoperability is achievable.

  3. Semantic Versioning - Wikipedia - The major.minor.patch model that vocabulary profile maintainers must apply when evolving custom verb sets without breaking existing analytics queries.

  4. Designing Data-Intensive Applications - Martin Kleppmann - O'Reilly Media - Chapters on schema evolution and forward/backward compatibility translate directly to vocabulary design — what happens when one team's attempted becomes another team's tried.

  5. Learning Analytics: From Research to Practice (2nd Edition) - Larusson and White (Editors) - Springer - Multiple chapters discuss the consequences of inconsistent verb vocabularies on cohort comparison, the analytics problem this chapter is teaching readers to prevent.

  6. ADL Verb Vocabulary Registry - ADL / Tin Can - The canonical registry of community-vetted verbs, complete with definitions, related activity types, and example usage. The reference this chapter teaches readers to consult before inventing anything.

  7. ADL xAPI Verbs - ADL Initiative - The original ADL-published verb namespace (http://adlnet.gov/expapi/verbs/...) that includes experienced, attempted, passed, completed, failed, and other foundational verbs.

  8. xAPI Profile Server - ADL Initiative - The official server hosting community xAPI profiles, including verb concepts, activity types, and Statement Templates. Where a custom verb profile ultimately gets published.

  9. cmi5 Specification — Defined Verbs - AICC / ADL - Worked example of a constrained vocabulary profile: cmi5 defines exactly nine verbs for LMS-launched content. A model for how to draw a tight vocabulary boundary.

  10. xAPI.com — Choosing Verbs - Rustici Software - Practical advice on selecting verbs that maximize cross-platform analytics value, including the real-world cost of vocabulary fragmentation.