2.3 Method of Solving
Documents stored into local databases will not
simply form a flat collection of unrelated
documents. As an example, a patient can have more
than one episode in different periods of time. It is
obvious that various documents are related to the
patient’s episodes, incidents, examinations, etc.
Thus, there is a need to group all these related
documents in a hierarchical tree structure. The
system has to implement a tree structure of
categories where each level has a different number
of fields that characterize the category. The fields
that characterize the first hierarchy level can be
demographic elements of patients while the fields
that characterize the second hierarchy level can be
elements that describe a specific episode (e.g.
incident, admission date, discharge date, final
diagnosis and so on). The leaves (documents) in this
hierarchy can also be characterized by a number of
fields. This set of fields forms a (document) profile.
Document Management and retrieval can be
conducting by giving values and constraints for the
various fields of the document. A feature of interest
is the support of both multiple-value (multi-row) and
single-value fields. Data types supported by the
system can include integer and real numbers, dates,
strings, lookup fields and multiple attribute (or
multi-column) fields. The combination of a multiple
attribute field that accepts multiple values derives
the ability to use two-dimensional tables in the
position of a single field. It must be possible to store
structured documents (e.g. PDF and XML
documents), other documents downloaded from the
Internet (HTML documents), etc.
These capabilities of FDB model and CUDL
language allow us to easily design and implement
hierarchically structured medical data, allowing also
support for future schema evolution. They also give
us the opportunity to design and implement the
integration structures for the correlation of
heterogeneous data (for importing data either from
“legacy” systems or from external files and other
resources).
3 STRUCTURING
HIERARCHICAL MEDICAL
DATA WITH THE CUDL
LANGUAGE
In this section we focus on a Hospital Information
System in order to clarify the concepts described in
the previous section. Information of interest could be
related to episodes or incidents (admission etc.) of
the patient to the hospital. For example, in each one
of the incidents the patient may need the care of
various doctors, and he may undergo some
operations. Certain physicians can participate in the
operations and certain (the same or others) attendant
physicians treat the patient. During the incident, the
patient may undergo Laboratorial or Radiological
Examinations on the same day in different hours or
in different days. In consequence the data we want
the HIS to hold for the various episodes could be the
following: patient’s code, social security institution
related information (e.g. code, name, rates for the
insured patients), data related to each incident of the
patient (e.g. code, admission date, discharge date),
data related to the doctors involved (e.g. attendant
physicians, surgeons), data for each operation that
took place and the description as well as the results
of the laboratorial examinations (e.g. laboratory,
test, date, results) during the incident. For each
patient we are also interested to keep demographic
data.
Figure 1 illustrates a part of the simplified
relational database schema of the integrated HIS
comprising of seven discrete objects (entities):
Patients, Doctors, Social Security Institutes,
Laboratorial Examinations (test), Radiological
Examinations (MRI, CT, ECG, etc), Diagnoses and
Operations. Diamonds (acting as relationships
between entities in the case of the well-known
Enhanced / Entity - Relationship model (Badia,
2004) are depicted as objects: Incidents, Lab
Examinations / Incident, Rad Examinations /
Incident, Doctors / Incident, Operations / Incident,
Doctors / Operation).
The FDB model is more compact and simpler.
As we can see in the examples of the following
subsection the same seven discrete entities are
involved but the model comprises by only one object
describing all the relationships between the entities.
Therefore, the CUDL language permits the
definition of more sophisticated relationships
(sophisticated diamonds or CUDL diamonds). In our
example, the whole set of the six relationships (see
the circle in figure 1) is replaced by a single
sophisticated relationship (a single CUDL diamond).
The rationale for this fact is that the underlying
(FDB) model can offer the possibility of having
repeatable values, sub-fields and a whole table in
place of a field (tag, in our terminology). Therefore,
we can easily include the attendant physicians, all
the laboratorial and radiological examinations that
took place in an incident, all the doctors that
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