XDS HE Architecture: Central vs Distributed Repository

Setting up an XDS Affinity Domain using IHE Components: This IBM Healthcare and Life Sciences document has some nice practical information on IHE XDS.

Here are two diagrams taken from this document showing a Centralized vs a Distributed repository architecture.

Centralized Repository: Note that the "Document Repository" object is contained within the "Infrastructure Provider" along side the "Document Registry".
Figure 1


Distributed Repository : Here the "Document Repository" is now contained within each hospital's infrastructure while the "Document Registry" still remains within the centrally located "Infrastructure Provider".


Figure 2

So what does this all mean ? By "Central Repository", I mean a central, single database that contains all the documents in the enterprise. The "Distributed Repository" implies multiple databases. These databases can be centrally located however , within a single data center. This would still be a "Distributed Repository" since each repository sits in its own database.

What is the advantage of this model ? You can best understand this by comparing it to "Google". When we perform a search in Google, the search term goes out to an index of terms within Google's infrastructure. This "index" in analogous to the "Document Registry". The index or registry contains links (or addresses) to the locations of the actual data. The actual data may reside at different servers throughout the world. This "Distributed Repository" model works the same way, and just like Google, it can scale infinitely.

Because of the scalability of this "Distributed Model", this model can be the basis of a "SaaS architecture" where there is a need to be able to scale to meet the needs of a rapidly growing user base.

Once again, please check out this IBM document for more information.

Also, here are some other useful IBM documents: Clinical Imaging Repositories, Solution Architecture for Clinical Data Management

Cross Enterprise Document Sharing: IHE XDS Integration

Microsoft IHE XDS Reference Implementation
I will be sharing information on Cross enterprise document sharing which is an important topic in the area of Health Information Exchanges and RHIOs. This model would equally apply to single organiziation document sharing as well.

Microsoft has recently released the IHE, XDS Reference implementation .

Roberto Ruggeri (a Senior Technical Strategist with Microsoft Worldwide Health) has an excellent introduction to IHE XDS on his blog.

Roborto writes:

"Integrating the Healthcare
Enterprise (IHE) is an organization
operating in the Health Information and Communication Technology area. The main
purpose of IHE is to create Interoperability Profiles that simplify integration
scenarios in healthcare."

"Arguably one of the most successful IHE profiles
is Cross-Enterprise Document Sharing or XDS. The profile focuses of the
publication, storage and retrieval of documents for the purpose of exchange
within a network of trusted participants (Affinity
Domain)."

IHE IT Infrastructure Technical Framework
Microsoft IHE, XDS Reference implementation

I found the presentations listed below useful for understanding IHE XDS basics concepts. It would be useful to review these documents before diving into Microsoft IHE, XDS Reference implementation .

IHE Canada, XDS Integration Profile, Technical Discussion

IHE XDS, Presentation by Jonathon L. Ellion MD (Heartlab): Very good , dynamic powerpoint introduction to IHE XDS

Leveraging IHE to Build RHIO Interoperability, Charles Parisot's (GE Healthcare) presentation discusses IHE issues as they relate to RHIOs

This article discusses a strategy for extending the IHE XDS for support of a federated architecture.
Enhancing IHE XDS for Federated Clinical Affinity Domain Support

Setting up an XDS Affinity Domain using IHE Components: This is an IBM Healthcare and Life Sciences document. It's a good practical guide to setting up a theoretical deployment. It addresses the architectural issues involved. Some of the points discussed are:

1. Patient Identity Cross Reference Manager

2. Security and Auditing

3. Physical and Logical Topology

4. Document Sharing Scenarios

HIE/RHIO Resources:

MA-SHARE Record Locator Service Technical Document
RHIO Reference Architecture Very good technical discussion of a RHIO architecture. Includes discussions on the use of BizTalk and data flow in a federated architecture model.