A web PACS architecture based on WADO service of DICOM standard
G. KOUTELAKIS, G. TRIANTAFYLLOU, G. MANDELLOS, M. KOUKIAS, D. LYMPEROPOULOS
The implementation of the Web PACS architecture is based on Oracle Web based services and applications platform, called Oracle 9i Application Server and is implemented based on a three-tier architecture (figure 1). The database tier comprises of databases that include data, metadata and enterprise management rules. In our system this tier includes all databases concerning the DICOM information. The user is not in direct contact with the data storage level. Every user has to retrieve the required data through the middle tier. This method is used to preserve data security and integrity. The end-user has no knowledge of the underlining processes cooperating in order to render data to him. The server tier (or the middle tier) includes the solutions of the Application Server Oracle9iAS that concern formalized application and Web services. The server processes the service requests coming from the client tier. The service of a client tier request may demand access or change of the database tier data. The middle tier is the most important and complicated tier of this architecture. It provides the technology for Web application development. The middle tier of Oracle9iAS consists of Application Server and Infrastructure Server. The client tier comprises the different kind of clients and it includes Web browsers, Web services and back-office applications. The clients request services on the server tier using different networks and telecommunication protocols. The front-end interface of the applications appears on this tier, providing the end-user with all necessary information to fulfill the desired tasks .The Application Server creates an expandable, secure and embedded platform middle tier, which it allows Web content provision, Web application support and communication with back-office applications. It improves the performance, scalability, and availability of frequently used Web sites that run on the Oracle9i platform. By storing frequently accessed URLs in memory, Oracle9iAS Web Cache eliminates the need of repeatedly process requests for those URLs on the Web server. Furthermore, HTTP server (part of Application Server), based on Apache Web technology, handles the http requests . The Application Server uses the J2EE platform offering various advantages, because it supports: (a) JSP (Java Server Page), (b) Java servlets, (c) Enterprise JavaBeans (JVB) . The existence of the Infrastructure Server is prerequisite for many of the Oracle9iAS Application Server Layer parts. There is a database inside the Infrastructure Server, which contains the whole of data and metadata that support all the individual parts of Oracle9iAS .

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