Skip to content

serialization.md

Latest commit

 

History

History
72 lines (55 loc) · 3.29 KB

serialization.md

File metadata and controls

72 lines (55 loc) · 3.29 KB

Serialization

The following details some important Ethercis internals.

Composition Serialization

A Composition is traversed to identify each element/attribute which value has been changed. The change is specified by a boolean. The composition content (entry) is serialized into a json structure similar to the following:

{
  "openEHR-EHR-COMPOSITION.report.v1": {
    "openEHR-EHR-SECTION.history_rcp.v1": [
      {
        "openEHR-EHR-EVALUATION.reason_for_encounter.v1": [
          {
            "at0001": {
              "at0004": {
                "/name": "Question to MDT",
                "/value": {"value": "Increasing back pain"},
                "/$PATH$": "/content[openEHR-EHR-SECTION.history_rcp.v1]/items[openEHR-EHR-EVALUATION.reason_for_encounter.v1]/data[at0001]/items[at0004]",
                "/$CLASS$": "DvText"
              }
            }

An element is serialized with the following attributes:

  • name: the name as found in the composition
  • value: the element/attribute value formatted depending to the data type. The value depending on the type consists of a structured representation
  • the full path to this element/attribute: the path is used to assign values of element attributes in the composition. It is also used to set specialized indexes (example: partial index on diastolic BP from archetype blood pressure regardless of the current template).
  • A class name used to rebuild the data value object from the value structure

The template structure is projected into the json structure (it is a TreeMap), it allows using json specialized queries as discussed in PostgreSQL 9.4 json functions and operators

Queries

Querying in the DB involves mixing SQL and JSON functions and operators. For example, the following query selects the compositions id and entry where the SNELLEN visual acuity = '20/10' measured 28/08/2015 at around 7am :

select * from (
	select composition_id, entry.entry #>> '{openEHR-EHR-COMPOSITION.section_observation_test.v2,
	openEHR-EHR-SECTION.visual_acuity_simple_test.v1, 0,
		at0025, 0,
			openEHR-EHR-OBSERVATION.visual_acuity.v1, 0,
				at0001, [events],
					at0002, 0,
						/time, /value, value}' AS event_time from ethercis.ehr.entry

where template_id LIKE 'section observation test.oet'
	and entry.entry #>> '{openEHR-EHR-COMPOSITION.section_observation_test.v2,
openEHR-EHR-SECTION.visual_acuity_simple_test.v1, 0,
		at0025, 0,
			openEHR-EHR-OBSERVATION.visual_acuity.v1, 0,
				at0001, [events],
					at0002, 0,
						at0003,
							at0053,
								at0028, 0,
									at0009, 0,
						/value, /value, value}' = '20/10') SNELLEN

		where event_time LIKE '2015-08-28T07%';

NB. Whenever an array is used in the structure, an index should be specified unless a json array function is used to perform a transformation. For loop on array element is supported to perform queries on a set if required.

Assuming the REST API is used to perform the query, a resultset as follows is returned:

 "resultSet": [
    {
      "composition_id": "256dfcc1-5b0d-460f-b61f-17f96354460b",
      "event_time": "2015-08-28T07:50:34.394+07:00"
    }
  ]