We have discussed the importance of shared vocabularies in electronic health record  systems and interoperability, but this is not enough. In order to successfully build interfaces between EHR systems, we need to understand them in functional terms, and we need to understand how those requirements are realized in actual systems. Unfortunately, different products have been developed to meet different business goals, and often have different priorities.a Fortunately, healthcare has a long history, and there are familiar procedures that are more or less standard. Examples include admitting a patient, writing a prescription or a lab order, entering progress notes, patient education, and so forth. To be successful, an EHR system will need to be as familiar and useable as possible. It can succeed best by…