ACM, New York. Different data types with vague predicates are required to allow for queries referring to arbitrary attributes of documents. Physical data independence helps in solving text search problems related to noun phrases, compound words and proper nouns. Logical data independence allows for different views on an IR database, thus implementing e.g. data security. Inheritance, especially on attributes, supports the creation of unified views on a set of IR databases.
Uncertain inference allows for query processing even on incompatible database schemas.