This poster session reports the examination of user tasks in the context of domain specific vocabulary interoperability. Two vocabularies, Library of Congress Subject Headings and the Art and Architecture thesaurus, were selected for comparison using a single user task (Cross-vocabulary discovery). Analyzing the structure of the vocabularies in the context of this task found challenges associated with the differences in concept representation, differences in vocabulary structures and varying levels of specificity. The exploration found that the similarities in structure and semantics for these two vocabularies provide a solid foundation for both user-determined on demand and automatically derived interoperability in the context of the cross-vocabulary discovery task. The exploration of AAT and LCSH vocabularies also found that considering the impact on stakeholders (e.g., end users, vocabulary creators, vocabulary implementers) is important when considering how to design and implement vocabulary interoperability applications.