The openehr_extract Package

Items from an openEHR sytem included in an EHR Extract are always top-level objects (Composition, Directory, EHR_EXTRACT, PARTY, etc, and descendants) are expressed in the serialisable form of descendants of X_VERSIONED_OBJECT<T>. This type provides a standard interoperable way to serialise all or part of VERSIONED_OBJECTs for lossless transmission between systems, regardless of the likely implementation differences in versioning at each end. Accordingly, X_VERSIONED_OBJECT turns most functional properties of VERSIONED_OBJECT into data attributes. The two attributes of most interest are revision_history, which enables the optional inclusion of the complete revision history from the original VERSIONED_OBJECT, and versions, which allows any or all of the versions to be included form the original. The revision history can be requested on its own using by setting the includes_data flag of the version specification to False.

In most scenarios, versions will be included, and revision_history excluded. Each item in X_VERSIONED_OBJECT.versions consists of a wrapped copy of an ORIGINAL_VERSION from the corresponding VERSIONED_OBJECT object in the source system.

The overall structure of the openEHR EHR for a subject can be replicated with an archetyped Folder structure that creates the groupings of directory, compositions, ehr_access, and ehr_status that are found in an openEHR EHR. This use of folders is not mandatory, but is likely to be useful in most cases, and is the structure shown in Typical EHR Extract structure above.

Within the content an EHR Extract, wherever PARTICIPATION and PARTY_PROXY structures occur (for the latter, the PARTY_SELF and PARTY_IDENTIFIED descendants), they are preserved intact, for reasons of fidelity. However, the final 'pointer', i.e. the OBJECT_ID.value may be rewritten within the Extract to correctly refer to the intended demographic. A typical S_PARTICIPATION structure is illustrated at the bottom of Typical EHR Extract structure. In this figure, the OBJECT_ID.value has been rewritten to refer to the uid (11111111) of the first OPENEHR_CONTENT_ITEM object shown in the figure.