Developers of healthcare information systems are challenged by the difficulty of meeting the simultaneous goals of 1) capturing and electronically representing the broad array of data related to healthcare with sufficient expressibility to provide adequate documentation of the patient encounter, and 2) utilizing standardized coding and classification systems to facilitate linkages among computer-based systems. The evaluation studies to date have primarily focused on matching actual clinical data with terms in the recognized classification systems. These studies have provided evidence that the classification systems are relatively domain complete for categorizing patient problems and nursing interventions. Although several of the published criteria for evaluation relate to structure, it is noteworthy that this has not yet been a major focus of study in nursing. There are several areas of critical need that must be addressed. First, additional work is needed to develop and refine a standardized set of atomic-level terms relevant to nursing, including those for assessments, problems, and activities. Second, knowledge representations must be developed to support the building of complex concepts from atomic-level data.