Biomedical Engineering Reference
In-Depth Information
Figure 20.7
CDA data model
Data Item Value' column and the number of rows produced by
un-marshaling the CDA XML will prove to be a challenge for scalability
and a productivity hit for developers. It seems that to get the level of
fl exibility desired for longitudinal medical records sacrifi ces the very
reason for having a relational database!
An alternative design would be to store the entire clinical document
directly in the database. Many commercial relational databases provide
extensive XML support as a native data type. This allows easy storage,
intelligent search, and manipulation of XML using powerful and familiar
standards such as XPath and XQuery. MySQL does not support XML data
types natively, but does support some basic procedural functions to help
translate XML to and from the data model. When storing raw XML in
MySQL, the best option is storing it in the TEXT data type and manipulating
it with a programming language. Using the TEXT data type allows use of
MySQL's full-text search capabilities to fi nd specifi c content en masse.
However, this approach may cause issues with the accuracy of results
compared to a search mechanism that understands the differences between
the tags, the attributes, and the data. A better alternative for storing raw
XML would be a specialized database such as BaseX, or eXist-db. These
databases can be paired with MySQL such that the raw XML is stored in
an alternative location. However, an easier alternative is to skip the use of
a relational database altogether and use a NoSQL database instead.
20.6.1 A NoSQL approach
NoSQL databases offer signifi cant application development productivity
benefi ts due to the ease of access from an object-oriented development
environment and due to the lack of rigidity required in the defi nition of
the schema. Specifi cally, in clinical analytics, they offer the ability to store
longitudinal clinical documentation more effi ciently as the intersection of
many different EMR data models does not need to be pre-established.
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