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- the query language used to search and retrieve EHR data must be neutral to system design and implementation. In another words, regardless of the persistence data model/schema design of a particular EHR system, the query statements should be same for all EHR systems. This is the key requirement. It helps to achieve:
- users are able to write a query statement without knowing actual system design or data structure;
- the query statement is sharable within a system or across multiple systems;
- the query statement is reusable and future proof, which means that the query statement doesn't need to be changed whenever actual EHR system achitecture is changed or EHR system environment is changed.
- the query language is able to:
- express the queries used for a single EHR as well as for all a population of EHRs;
- express the queries used for retrieving an entire EHR, a clinical report, or fine-grained data within a clinical report or an entry;
- express the query criteria on both coarse-grained and fine-grained data items. For example, users can set query criteria on the name of the clinical report, or query criteria on a particular observation value (e.g. systolic blood pressure >= 140);
- express complicated query criteria. Some query criteria are very complicated. For example, this query scenario - Get the contact details of the women of child-bearing age who have not had a Pap smear in the past two years - is a population query, which has the criteria on gender, age, lab test name and date. It may also have criteria on terminology system, terminology id, data value, units etc.
- express the queries with logical time-based data rollback. This feature constrains the query to data that was available in the system within the specified time criteria. It allows the queries to be executed as though they were performed at a specified time.
- the query language is archetype-aware, i.e. enables the knowledge of location and type of data items as provided by archetypes (in the form of paths and type & other constraints) to be used when constructing queries.
- the query language is terminology-aware, i.e. can be used with terminology to retrieve items on the basis of coding.
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