Allan was LPD's (L. PeterDeutsch) sidekick (initially) and (later) boss. He worked on both PS and HPS, responsible for creating all the buggy parts. He was at ParcPlace 1986-1991, in charge of the Smalltalk product when it was changing its name all the freaking time.
This is a good place to mention that HPS stood for HighlyPortableSmalltalk.
After 1991, Allan lost his way and went into Internet security stuff. He moved to Tahoe in 1996 but recently was resurrected as Executive Director of CommerceNet? (http://www.commerce.net). You could try sending to him at ams at ieee.org.