12.6 Conclusion

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In this chapter we discussed the design and implementation of the OAI, specifically focusing on the central role of XML on the structure of the system. After describing each of the components that make up the OAI and its relationship to the JEDMICS system, we described the use of XML as the means to submit requests and receive responses from the OAI and the consequences of making that decision. We covered in detail the design decisions we made in processing the XML input on its flow through the OAI, including structural validation through the use of DTDs, conversion into Java objects through the use of JAXB, and field validation by extending the JAXB-generated classes. We also discussed the conversion of the database data into XML, through the use of database-specific utilities, to generate the responses from the OAI and the development of an encoding mechanism for conversion of binary image data into XML. We closed the chapter by briefly reviewing some of the future directions we plan to take with the OAI. This includes the use of XSLT for filtering the XML documents returned to the clients, the use of Web Services for exporting the OAI functionality across JEDMICS sites, the need for a mass transfer capability for exchanging data across sites, and the use of messaging to move some of the processing that is currently synchronous into an asynchronous mode of operation.


Part IV: Applications of XML