Harvest generates a content summary for each information object it gathers, and places these summaries into an attribute-value pair record format called the Summary Object Interchange Format (SOIF).
SOIF provides a means of bracketing collections of summary objects, allowing Harvest Brokers to retrieve SOIF content summaries for many objects in a single, efficient compressed stream. Harvest Brokers provide support for querying SOIF data using structured attribute-value queries and many other types of queries, as discussed in "Help for Broker Queries".
More information about SOIF is available in the Harvest User's Manual and RFC 2655.