Features of the query editor:

• Queries are constructed incrementally by expanding concept descriptions. Concept instances are either selected from menus (for concepts in the knowledge base) or entered manually (useful for numerical values or other fields with unpredictable content, such as names).
• The query editor allows the construction of complex queries containing boolean operators (negation, union, intersection). For example, a diagnosis can be stated as "metastatic cancer of the lungs or of the breast but not with metastasis to the liver". This description is constructed by logically combining two cancer loci (lungs and breast) and one negated metastasis locus (liver).
• The interface allows the execution of incomplete queries. The result of a user selection over the feedback text is treated as an intermediate query, which is sent to the DBMS. In return, the DBMS will transmit to the interface a feedback answer. At this point, the feedback answer is a set of paired values representing the number of patient records that match the query and the percentage from the total number of records. There is also a further breakdown of patient records by sex, which was considered a good discriminatory feature. For example, for an intermediate query such as "Number of patients over the age of 60...", the feedback answer could be 100 records (20% of 500), 55 men (55%), 45 women (45%).
• As a further consistency checking mechanism, the interface provides an additional rendering of the query in running text
• Queries can be saved for later re-use, which is particularly useful for frequent users that formulate queries with little variance.
• The natural language interface is database-independent, since it does not require any knowledge of the database structure. The structure of the database is not only completely transparent to the user, but also to the interface developer: any changes at the database level don't require changes in the query editor.