Intelligent Systems in the Knowledge Systems Laboratory at

Past Project: Guardian

The Guardian project was completed in 1996. This page contains references to some of the original Guardian materials and group members. A final list of all Guardian publications can be found on the AIS Publications page. The content of this page was last updated in 1996.

A Prototype Intelligent Agent for Monitoring Intensive-Care Patients

The Guardian project is part of the Adaptive Intelligent Systems project at the Knowledge Systems Laboratory, which in turn is part of the Computer Science Department at Stanford University. The project is performed in collaboration with the Laboratory for Human Performance in Anesthesia and the Anesthesia Simulator Center at the Palo Alto VA Hospital.


Guardian is based on the BB1 blackboard control architecture, and the system is under development in a laboratory environment using simulated and recorded patient data. Guardian has a number of advantages over existing real-time intelligent monitoring architectures. These include multiple reasoning skills, configuration of available knowledge and skills based on context, data reduction based on the availability of computational resources, and dynamic selection of reasoning skills under time pressure. Guardian is composed of a variety of software modules organized in two levels. At the lower level, Guardian has modules which perform data reduction and abstraction tasks. At the higher level, various reasoning skills exist and cooperate under the guidance of BB1. Domain knowledge bases for Guardian are based on a shared ontology for intelligent monitoring and control. These knowledge bases are available to any problem solving components that wish to use them.


The Guardian project addresses a wide range of problems in real-time intelligent monitoring and control, including:

  • Continuous acquisition and interpretation of patient data.
  • Construction of short- and long-term therapy plans and monitoring the execution of such plans.
  • Diagnosis and alarming of unexpected disorders and complications.
  • Agility in reaction to problems requiring immediate attention.
  • Explanation of physiologic and pathophysiologic phenomena.
  • Closed-loop control of therapeutic devices on demand.

Research Interests

We are studying intelligent agents for monitoring medical patients. We have concentrated so far on a class of intensive care patients. However, we anticipate broadening our scope to include support for self-monitoring by certain ambulatory care patients with ongoing monitoring needs. Our research interests include: dynamic run-time configuration of appropriate reasoning methods and knowledge components, context-relevant selective perception, and situation assessment, planning, and plan monitoring in a dynamic environment. Guardian incorporates the BB1 software architecture.

A block diagram of Guardian
The BB1 software architecture
David Gaba's Guardian page

Guardian Project Members (as of October, 1996)


The full list of Guardian publications can be found on the AIS Publications page.

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