Toward more expressive contracts

The principles of Design by Contract form the basis of the Eiffel approach and account for a good deal of its appeal. The design has proved its value, and Eiffel programmers enjoy it. But the time may have come to revisit the trade-off and see how much more we could express with contracts - how close we could come to the goal of full specification without losing the simplicity and self evidence of the classic Eiffel mechanism. This article explores recent progress, resulting from work in several areas: 1. a language development: a new "agent" language mechanism with a new variant (inline agents); 2. new Eiffel library work, especially around EiffelBase, an open-source framework covering the fundamental data structures and algorithms; and 3. progress in the Trusted Components project 4 aimed at building a rich set of high-quality reusable components for the industry