The problem of generating reasonable natural language-like responses to queries formulated in nonnavigational query languages with logical data independence is addressed. An extended ER model, the Entity-Relationship-Involvement model, is defined which assists in providing a greater degree of logical data independence and the generation of natural language explanations of a query processor's interpretation of a query. These are accomplished with the addition of the concept of an involvement to the model. Based on involvement definitions in a formally defined data definition language, DDL, an innovative strategy for generating explanations is outlined and exemplified. In the conclusion, possible extensions to the approach are given.

The query inference problem is to translate a sentence of a query language into an unambiguous representation of a query. A query is represented as an expression over a set of query trees. A metric is introduced for measuring the complexity of a query and also a proposal that a sentence be translated into the least complex query which “satisfies” the sentence. This method of query inference can be used to resolve ambiguous sentences and leads to easier formulation of sentences.

Abstract Minimum isolated failure immune networks are shown to be 2–trees. Further, subgraphs of 2‐trees are shown to be exactly those graphs which contain no subgraph homeomorphic to the four‐vertex complete graph. Together, these two characterizations yield a linear time algorithm for adding lines to a network to produce a minimum isolated failure immune network, whenever this is possible. This same algorithm, in conjunction with a linear time Steiner tree algorithm for 2‐tress, yields a linear time Steiner tree algorithm for partial 2‐tress. This contrasts with the known NP‐completeness of the Steiner tree problem for planar graphs.

A characterization of an end user and a discussion of an end-user facility are presented. A language for aiding the data-base administrator in designing forms for user's of an end-user facility is described in a tutorial manner. The paper concludes with an outline of work related to the form's approach and other types of user-oriented query language facilities.