Ian Holland's work at Northeastern University, College of Computer Science, was influential:

• He discovered the Law of Demeter (LoD), a foundational software engineering principle, which has become a household word among software developers. The LoD is a style rule that identifies bad coupling through a simple rule: Talk only to your friends. The LoD is covered in numerous books, including text books for undergradute students.

  The LoD is followed in many industrial systems. For example, at NASA, major systems which have used the LoD extensively include the Telemetry Delivery System (a real-time database begun in 1990), the Flight System Testbed, and Mars Pathfinder flight software (both begun in 1993).

  Ian Holland wrote his first conference paper on the LoD during his first year at Northeastern University. The paper was presented by Ian at the competitive OOPSLA conference which lead to a long collaboration with IBM first as a student at Northeastern and then as an IBM employee.

  The LoD has provided food for thought for several PhD projects. The work on Adaptive Programming is an attempt to follow the LoD and program in a structure-shy way. The work on Aspect-Oriented Programming is an attempt to refine the LoD: Talk only to your friends who share your concerns.

  The Law of Demeter was named after the Demeter project at the College of Computer and Information Science.

• Ian also collaborated with IBM researchers on a concept called "contracts". In his PhD thesis he developed contracts further to make them executable contracts. Ian's work on contracts was informative to the GOF (Gang Of Four: Gamma, Helm, Johnson, Vlissides)) and their design patterns, especially in the collaboration with Richard Helm. Those executable contracts also motivated work on aspectual collaborations that live in languages like Caesar (Technical University of Darmstadt) and Object Teams (Technical University of Berlin) and in Johan Ovlinger's Aspects and Modules.

In summary, Ian Holland's 5 years at Northeastern University have had an impressive impact on the software development community.

Ian Holland is now Vice President of Architecture and Systems Engineering at Kronos Incorporated in Chelmsford, MA.

April 2005, Karl Lieberherr