...
Question: How would that be done technically? Does System A send a text file containing the necessary information structured in dADL or a derived XML-format to system B?
Answer: Technically this is done in a transport protocol agreed by the two communicating systems. It can be XML or dADL.
Question: How would Paul be identified in the transmitted data file?
Answer: According to the EHR_EXTRACT http://www.openehr.org/releases/1.0.2/architecture/rm/ehr_extract_im.pdf
Question: Is there an example for a file like that available somewhere to get an practical insight how it works?
Answer: see above.
Question: In the exchanged file the used archetypes are listed but not defined. Does that mean that the receiving system is able to correctly interpret the received data only if it has access to the same archetypes the sending system has used when creating the file?
Answer: Yes, especially in case of decision support systems. (A pure reporting of the received data might be possible without having access to the used archetypes.)
Question: Back to our example: System B receives blood pressure measurements from system A. In system B there are two possibilities to store (and display) blood pressure measurements (either within the 'encounter' composition or within the 'vital signs' composition). How does system B decide where to store and display the received data?
Answer:
The received data should be represented as is. That is the data should be presented using the blood pressue archetype. For read-only purpose, the data will not be saved in the receiving system. But if for any reason, the data have to be saved, it should probably be saved in a special composition, e.g. recevied EHR_EXTRACT composition to indicate that the data were not originated from the current system.
Question: It might be easy in the example as the structure of the EHR of system B is similar to the structure of system A - but what about openEHR based EHR systems with a completely different structure?
Answer:
...
Question: How will system A manage that (e.g. the composition 'vital signs' might not be available in system A)? (Would be all blood pressure measurements mapped to the existing structure in system A? Would system A be able to create a list of ALL blood pressure measurements created during the hospitalization?)
Answer:
In any openEHR system, if one particular archetype isn't avialable for interpreting the exchanged data, some basic way of presenting the data using the semantics from the openEHR Reference Model should be used. The RM is the structure of any openEHR-based EHR system.
Question: If system A will be able to receive all blood pressure measurements created during the hospitalization correctly, would it later be (within system A) possible to distinguish those measurements which were initially saved using the 'vital signs' composition and those using the 'encounter' composition?
Answer:
The id of the template that is used to create the data will be preseved in the RM instances when data are saved. However it is not required to have the original composition (most likely a template) to interpret the data semantics correctly. A well modelled archetype can be safely reusable across different clinical context.