Nurses prepare a summary of patient information that they consult and update throughout the shift. This document is believed to be integral to cognition, working memory, and decision-making. While serving as a key support to nursing practice, this summary also represents risks to patient safety. Characterized as a PCCAT, or Personally Created Cognitive Artifact, studies of this document in the context of nursing practice have not been reported. The absence of reported research, the importance of the document to nurse cognition and practice, and related safety risks prompted the research that this paper discusses. A taxonomy was developed through the analysis and coding of 151 PCCATs. Further analysis and mapping provided an ontology of the PCCAT. Content differences were noted between nursing units and among nurses. This may reflect differences in unit-based culture and/or differences in the patient complexity. The interaction between culture and perceived complexity of practice is one of the great difficulties in generating automated information systems for clinical practice settings. This paper is part of a larger research protocol that explores meta-level knowledge structures and revision to the understanding of the granularity of nursing knowledge. Development of a taxonomy and ontology of the nurse PCCAT, an important component of the larger research protocol, is described in this paper.