Search Middleware and the Simple Digital Library Interoperability Protocol

Introduction The development of novel information applications is reaching an impasse. HTML forms for searching the Web are fine for traditional, form-based interfaces to information. But what if we wish to develop more intuitive interfaces that reach across multiple information sources, or are more specialized for particular sources? For example, we might want to enter queries about human body parts by having the user point to the respective spot on the screen image of a body, or we might wish to combine a molecular layout tool with searches over a database of chemical compounds. These are examples where potentially elaborate applications must be written to mediate between the user and the information source, even if advanced HTML features or JavaScript are used in the user interface itself. A similar need for application support arises when small handheld information devices are used to access backend information sources. Standard Web browsers are frequently inadequate for t