Interoperability is "the ability to exchange and use information, usually in a large and heterogeneous network ..." (wordnet.princeton.edu/perl/webwn).
Many people expect medical data to be as easy to exchange as financial data or travel reservations. Unfortunately, medical data is much more complicated. The process of exchanging data is further complicated by the fact that the actual data stored in the various Electronic Health Records (EHR) software systems uses different codes to mean the same thing. One system might use a number, 10520, to represent a blood type such as O+ while a computer system in another hospital uses just stores the text "O+". This makes it difficult for two healthcare providers to exchange anything but reports which have translated the codes back into text understandable by a human.
International data standards, standardized reference terminologies and message standards are foundations of interoperability. The raw data has to mean something specific to the party which receives it. There are thousands of different kinds of HL7 messages which can be sent to share patient encounters or lab results and accomplish various clinical goals. Or a doctor may be sending a prescription to a pharmacy to be filled. But the raw data inside the message must be understandable to the party who receives it. Hence standard codes for all of the drug names must be compiled and maintained.
Before these HL7 messages can be consumed by an Electronic Healthcare System, the various parts of the message must be very specifically defined and agreed upon by the sender and the receiver. Part of the design work which goes into implementing a clinical message is to describe the business processes and use cases which define the clinical process. Every individual aspect of the work done by healthcare providers to take care of patients with any type of disease or preventive care can modeled. HL7 is an organization dedicated to creating standards for the structure of each clinical message type.
Founded over 50 years ago, HL7 works to allow anyone in the world to exchange medical data. Many countries are cooperating to make these international standards a reality.
Along with the clinical data, the security layers are transported. These govern who is allowed to see the data in the EHR record, and when and how could that be overridden in an emergency. Roles and responsibilities are defined for each user. A VERY complex dance is orchestrated to run through who can see and or change information and under which circumstances this can occur. 'Need to know' protocols are invoked much like in a defense agency to protect patient privacy and safety.
80% of the challenge of interoperability is the establishment of practical and implementable data standards. The other 20% includes healthcare policy, human languages, and legal problems. This is a technical challenge which must be solved in an international arena with international standards so the effort and costs can be spread out between various countries. Canada, the U. K., Australia, Japan, Brazil, Italy, and Germany are already dedicated to data standards. Galen Mulrooney, Exec. V.P. J P Systems
The ideal state of healthcare interoperability would be that of healthcare providers being able to send data to each other as easily as banks can now. The real state is that of a budget driven lack of cooperation to agree on a "standard" standard. Software vendors are a part of the puzzle.