Cover: AI@50--We Are Golden, by James Gary, New York, New York. What Do We Know About Knowledge? Send all submissions to AI Magazine, AAAI, 445 Burgess Drive, Menlo Park, CA 94025-3442. Electronic submissions should be submitted using the web-based submissions form. Submissions information is available at aimagazine.org. Although no particular style is required for submissions, electronic submissions must be in PDF form. Authors whose work is accepted for publication, will be required to revise their work to conform reasonably to AI Magazine styles. If an article is accepted for publication, a new electronic copy will also be required. Although AI Ma ga zine generally grants great deference to an author's work the Magazine retains the right to determine the final published form of every article. Calendar items should be posted electronically (at least one month prior to the event or deadline). News items should be sent to the News Editor, AI Magazine, 445 Burgess Drive, Menlo Park, CA 94025-3442. Please do not send news releases via either email or fax, and do not send news releases to any of the other editors. Web-based job postings can be made using the job bank submissions form at aimagazine.org. Replacement copies (for current issue only) are available upon written request and a check for $10.00. Back issues are also available (cost may differ). Send replacement or back order requests to AAAI. Microform copies are available from ProQuest Information and Learning, 300 North Zeeb Road, Ann Arbor, MI 48106.

De Groot was going on a year long trip to the U.S. and the highlight of his journey was a visit to Herb Simon and Allen Newell. I met Allen for the first time when I came for a two semester long visit to Carnegie Mellon University in 1968. This encounter was a distinct factor in my later decision to join the faculty at Carnegie Mellon University. I interacted with Allen much more closely when I became department head in 1979. He was for me a mentor and a sounding board for ideas I wanted to pursue for computer science at Carnegie Mellon University. I enjoyed working with many good friends on the faculty, but Allen was really special. Many of us will remember him for his evenhanded treatment of all students at the Black Friday meetings. He would never pursue his own agenda, he would always look for the merit of a student's work and not whether the rules were violated. He was a staunch defender of the rule that replaces all rules, which says that the only thing that counts is whether or ...

I am pleased to present this issue, most of which is devoted to a single subject-Spatial Reasoning. Our guest editor is Avi Kak, of Purdue University. Avi called me in the Summer of 1987, very enthused about a workshop he had recently attended. The idea of a "theme issue" on spatial reasoning sounded like a winner to me. I asked Avi to take the responsibility for selecting and editing the articles, and he agreed.

Technical Program Registration The Fifth National Conference on Artificial Intelligence will be held 13-17 July 1987 in Seattle, Washington. AAAI-87's Technical Program will present outstanding research papers in AI. These papers will be divided into those emphasizing basic research and those emphasizing applied research. Basic research papers will stress the computational principles underlying cognition and perception in man and machine. Applied research papers will highlight pragmatic issues that arise in applying these computational principles.

(ISAIM 2008).

Summer calendar of AI events.

(MDAI 2007).

What Do We Know About Knowledge? Cover: AI@50--We Are Golden, by James Gary, New York, New York. Please contact AAAI for such permission. Electronic submissions should be submitted using the web-based submissions form. Submissions information is available at aimagazine.org.

(MDAI 2007).

Distributed Sensor Networks (DSN) Computers and Advanced Technology Symposium. Paper submission is required by November 8, 2006.