By default, Harvest uses the Glimpse index/search subsystem. However, Harvest defines a flexible indexing interface, to allow Broker administrators to use different index/search subsystems to accommodate domain-specific requirements. For example, it might be useful to provide a relational database back-end, or a Latent Semantic Indexing [9] back-end.
At present we distribute code to support an interface to both the free and the
commercial WAIS index/search engines, Glimpse, and
Nebula [6] 
.
Below we discuss how to use WAIS instead of Glimpse in the Broker, and provide some brief discussion of how to integrate a new index/search engine into the Broker.