of enterprises, regional federations made up of
several local hospitals, healthcare providers, and
insurance provider supported communities
The key point in IHE XDS is the logical and
physically separation of the indexing information
used to retrieve documents from the actual content.
The document registry indexes documents, support
document search, and maintains a URI link back
where the document is stored in a document
repository. The basic XDS has been refined to
support special requirements for DICOM images,
structured laboratory reports, and HL7 CDA medical
summaries (CCD, 2009). The format of the used
metadata is largely based on HL7 Version 2 (Dolin
et al., 2001). Technically the XDS document registry
is a subset of the ebXML Registry standard
(ebXML, 2012), and documents are exchanged
using SOAP and HTTP (Singh and Huhns, 2005),
while SQL (Ullman and Widom, 1997) is used for
information retrieval in registries.
Although the IHE XDS has proven to be useful
and workable innovation, we argue that by
exploiting modern information technology we can
avoid many of the drawbacks of the IHE XDS. In
particular, we have addressed the following two
problems of the IHE XDS.
The main problem with ebXML registries is that
searches can only be based on the keywords and
folders. Although the keywords are taken from a
taxonomy only a very limited amount of semantics
can be provided (Dogac et al., 2007). Folders group
the related documents together (e.g., based on a
period of time, episode, or immunizations).
However, there are numerous cases where retrieving
predefined folders are not appropriate but rather
dynamic grouping of documents should be possible.
Another problem with the IHE XDS is that it
expects patients’ records to follow then when they
move from one affinity domain to another. The
problem here are twofold: First, moving records
between affinity domains is technically complicated
and error-prone due to the heterogeneities of affinity
domains. Second, due to the failed or missed
transmissions patients’ EHRs are incomplete.
We have designated a registry mechanism for
clinical documents that eliminates these drawbacks.
The expression power of document retrieval is
increased by introducing a specific OWL-ontology
(OWL, 2011), called Registry Ontology, for
document retrieval. It is derived from the class
diagram on which the Header of the HL7 CDA
documents (Boone, 2011) is based on. The primary
purpose of the CDA Header is to provide
unambiguous, structured metadata about the
document itself, which can be used in document
registers to classify, find and retrieve documents.
In our solution, the exchange of documents
between clinical affinity domains is eliminated by
retrieving all clinical documents from their original
sources. Such a feature can be carried out by the
Registry ontology and the Federated Queries
supported by SPARQL engines (SPARQL, 2008). A
useful feature of Federated Queries is that within a
query many registries can be accessed.
The rest of the paper is organized as follows.
First, in Section 2, we consider the basic
components of the IHE XDS architecture. In Section
3, we present the way the Registry Ontology is
derived. First, we give an overview of the HL7 RIM,
and the ways the RMIMs (Refined Message
Information Models) are derived from the RIM.
Then, we present the RMIM on which the Header of
the CDA documents is based on, and transform it
into OWL ontology (i.e., to Registry Ontology).
Further, in Section 4, based on the ontology we
present a SPARQL query which retrieves the URLs
of patients’ documents that are stored in two
repositories. Section 5 concludes the paper by
discussing our future work.
2 IHE XDS
2.1 IHE XDS Architecture
Integrating Healthcare Enterprise (IHE) was
established in 1999 by the Healthcare Information
Systems and Management Society (HIMSS) and the
radiological Society of North America (RSNA) to
improve the way healthcare computer systems share
information (IHE, 2005). It is not a standards
organization. Instead it promotes coordinated use of
existing standards to develop workflow solutions for
the healthcare enterprises. IHEs starting point was
radiology, where it developed profiles which specify
how to use DICOM and HL7 together, and later on it
has moved to cardiology, clinical laboratories, and
other specialities.
Another dimension of IHE’s work has been the
development of IT infrastructures standards for use
across departmental and institutional boundaries.
The IHE XDS profile is an example of this. Systems
designed in agreement with IHE profiles
communicate better with one another, and facilitate
efficient access to information.
The idea behind the IHE XDS is to build virtual
patient records on the fly from a variety of clinical
documents created by different healthcare
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