The development of distributed computing and networking has provided the technological basis for remote access to data and applications. The development of different systems has increased the utility of these systems, but has not solved the problem of having a large number of applications interoperating with each other. The applications have not been built to be integrated, and therefore, they normally define different data formats, have their own communication protocols, and are developed on different platforms. Interoperability of distributed systems is still a challenge.
Nowadays it is important to allow interoperability of different types of information sources in a large company or community. Users and applications have a growing need to access and manipulate data from a wide variety of information sources. However, the data sources are generally created and administered independently, differing physically and logically. Other difficulties associated with such an environment include: heterogeneity and autonomy of database systems, conflict identification and resolution, semantic representation of data, location and identification of relevant information, access and unification of remote data, query processing, and easy evolution of the system.
An example of the above problem is found in the Food and Agriculture Organization of the United Nations (FAO). FAO is a specialized agency of the United Nations, which leads international efforts to defeat hunger. It helps developing countries modernize and expand agriculture, forestry and fisheries and ensure good nutrition for all. One of its most important functions is to collect, analyze and disseminate information to assist governments to fight hunger and achieve food security. Towards this effort FAO has established the World Agricultural Information Centre (WAICENT) for agricultural information management and dissemination.
Within the WAICENT framework, a large amount of data, represented in various distinct formats, in many different languages, and handled by several metadata structures, are generated every day and stored in different types of data sources. However, there are no standards for representing languages, metadata, and specific country information. People need to access and manipulate data distributed in the various sources from both inside and outside the organization. It is important to share data between systems quickly and easily, without requiring the systems to be tightly coupled. In simple terms, the existing systems need to "talk" to each other. Another main problem is related to the fact that within the organization the use of two different technologies (Microsoft ASP [5] and Java JSP/servlets [20]) is widespread and it is, therefore, very difficult to impose a single technology throughout the FAO.
In this paper we present an approach based on Web services [17] and eXtensible Markup Language (XML) [6] technology to allow interoperability of the different data sources in the FAO. It is a lightweight approach and is based on the use of an information bus to allow exchanged of data between various information sources implemented by using different technologies. The information bus supports multilingual access of data stored in various data sources, handles metadata in a generic way, and enables metadata to be used as exchange models throughout FAO. The approach also supports dynamic report generation. A prototype tool has been implemented to demonstrate and evaluate the approach.
The remaining of the paper is organized as follows. Section 2 describes the problem in the FAO that is being tackled by our approach. Section 3 presents some related work. Section 4 outlines the information bus and the dynamic report generation. Section 5 illustrates our work through examples. Section 6 discusses the implementation of our prototype and evaluation issues. Finally, section 7 summarizes our experience and suggests directions for future work.
