Overall architecture

In Figure 1, it contains three major components, i.e., the front-end module, the middleware

module, and the back-end services including database servers. The front-end module

handles user interfaces via browsers. It establishes the user sessions as well as provides

services to validate users’ authentications, authorizations. The middleware module, i.e., HL7

Middleware Framework as indicated in the diagram, glues the front-end services and the

back-end facilities together. It provides communication and connectivity via SOA (Web

Services) mechanism. The HL7 embedded XML formatted data is implemented in the

framework for data exchanges among the modules. The back-end facilities support services

and database storage.

32 Web Intelligence and Intelligent Agents

Further detailed illustrations of the individual modules are provided as followings. In the

front-end module, for user friendly browsing interfaces, we adopt web based services. The

Portal Servers support the login process with the Single Sign on Service (SSOS) features

(Cheng et al., 2004). The servers construct dynamic web URL linkages (Weng et al., 2007),

direct to HIS components in the architecture. To enable the SSOS features, the authentication

and authorization component (Auth-WS) is introduced. During the HIS operations, any

validation needs to be verified through the Auth-WS. The Auth-WS integrates the Websession

Servers and Win-session Servers. The Web-session Servers interact with all other

servers in the architecture under the.NET web services environment. The Win-session

Servers are implemented as daemons (Window Services). All established conversations,

sessions are executed by the daemons including database access.

The Web User Interface (WebUI) Servers generate web-based pages for users’ interactive

activities. The State-session Servers store the user’s web session status variables for

analyzing user logic and validation.

In the middleware module, the ancillary Sub-systems provide the connectivity between the

WebUI Servers and HIS database (HIS DB) for HIS applications. The messages

communicated between the Sub-systems and WebUI Servers are exchanged via the HL7

Framework (Ko et al., 2006). The HL7 Framework is the Middleware Integration Engine of

the HIS architecture. It supports message management, routing, mapping, and database

access. Detailed information about the processing of each message is also automatically

logged by the Engine. Moreover, the Engine glues the medical systems (or applications)

together. The HL7 Middleware accesses HL7 message, embedded in XML format, over

Simple Object Access Protocol (SOAP). (Yang et al., 2006; Phan et al., 2007; HL7 Standard

v2.5, 2003)

A Dynamic Healthcare Portal Design and Enhancements 33

Fig. 1. NTUH HIS overall architecture

In order to achieve the data consistency, we introduce a Data Exchange Server that only

receives the message sending from the HL7 Middleware. While Data Exchange server

receiving messages, it will perform the data synchronization among patient demographic

data in HIS, patient radiology information orders to Outsourcing Systems, i.e., RIS

(Radiology Information System) database, or laboratory orders to LIS (Laboratory

Information System), i.e. Legacy HIS, database. This data exchange processing can ensure all

data in the systems, i.e., HIS and Outsourcing Systems, are updated and consistent as

indicated in the back-end facilities (Hsieh et al., 2006; Hsieh et al., 2007; Weng et al., 2006).

To increase the performance of the NTUH HIS, a cluster of identical servers are deployed

and dispatched dynamically by introducing Layer 4 and Layer 2 Switches. All the servers

are configured running under load balancing as well as failover modes to ensure the

system’s availability and concurrency. The firewalls are also installed to enhance the

security of the architecture.

4.2 Redirect scheme & Single sign on service