HealthVault data types are intended to be self-contained units of health information. The data types have distinct health items, such as medications, immunizations, and weight readings. This approach is characteristically different from relational data modeling in which the data is normalized and stored in distinct tables that have explicit relationships with each other. For example, in a relational model, medications may be expressed as separate medication name and medication dosage tables.
Often there is a need to represent relationships between individual health items. For example, a Medication is inherently related to Medication Fill. Medications are associated with a person’s profile as prescribed by a physician, and Medication Fill is used by a pharmacy to prescribe units of medications to a consumer as she consumes the prescribed medications.
The relationship between Medication and Medication Fill is expressed by related items. HealthVault offers related items as an inherent mechanism to link and associate data types. A related item is a special chunk of XML that resides in the common data of a health item. Relationships are usually described in the dependent item and link to the more independent one. For instance, to express the relationship between Medication Fill and Medication, one places related items in the Medication Fill type and points to the Medication type.
Another interesting use of related items is to link together a set of readings that are uploaded from a single device. For example, a device calculating body fat percentage and cholesterol can associate them through related items while uploading them. Because this association is done before uploading to HealthVault, a special unique identifier called a client ID can be used. Client IDs are usually unique identifiers associated to instances of HealthVault data types and are created by the client uploading the data.
One can take relationships even further and associate a set of medical images, medications, and conditions as a result of a particular health incident, maybe an accident. The Mayo Clinic Health Manager application provides a way to create a web of related HealthVault items.
Related items lie beyond the scope of this book, but the reader is encouraged to explore them and contribute interesting uses and examples at http://enablingprogrammableself.com.
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