Mediating and Metasearching on the Internet.

摘要: The Internet emerges as the largest database. Increasingly, users want to issue complex queries across sources obtain data they require. However, finding relevant information and querying them manually is problematic: there are numerous sources, vary in type of objects contain interface present their users. Some text documents support simple query models where a just list keywords. Other more structured provide interfaces style relational languages. Furthermore, have fuse results by merging information, removing redundancies, ranking answer appropriate order, so on. Since it tedious contact several heterogeneous can benefit from metasearchers mediators, which services that with virtual integrated view sources. Users access using unified offers location, model, transparency, i.e., illusion single database do not be aware location Although applications might directly through wrappers, mediators offer an world, related same entity has been fused together, redundancies eliminated, inconsistencies removed. architecture virtually identical (Figure 1). Wrappers export common model each source’s data. also interface. After receiving query, wrapper translates into source-specific or command, hence giving transparency user. Then, underlying source format. To evaluate user over multiple databases, both will typically perform three main tasks: