1. A surveillance system implementing an architecture and process to support real-time abnormal behavior assessment operations in a distributed scalable sensor network, the system comprising: an automated behavior model builder generating behavior models from sensor data; a plurality of abnormal behavior scoring engines operating concurrently to generate abnormal behavior assessment models by scoring the behavior models; and an execution performance manager performing fast switching of behavior models for said abnormal behavior scoring engines, wherein said execution performance manager performs detection of abnormal behavior score distribution characteristic deviation by comparing a current abnormal behavior assessment model to a pre-recorded abnormal behavior assessment model, and selects a pre-recorded behavior model for said abnormal behavior scoring engines when the deviation exceeds a predetermined threshold.