COMP 4640 Intelligent & Interactive Systems Programs Supporting Model - Based Reflex Agents November 2008 Dr. Cheryl Seals

2 Simple reflex agents

Programs that support Model - based Reflex Agents Simple reflex agents select precepts based on the current percept ignoring the rest of the precept history Example: Beetle

4 Model-based reflex agents

Programs that support Model - based Reflex Agents Most systems are based on “condition- action” rules (i.e. situation-action rules, productions, or if-then rules) (e.g. If car-in-front is braking then initiate-braking p46) Model-Based Reflex Agents Most effective way to keep track of the part of the world it can’t see now. Most effective way to keep track of the part of the world it can’t see now. Maintain some internal state that depends on percept history and thereby reflects at least some of the unobserved aspects of the current state (e.g. using some type of variable). Maintain some internal state that depends on percept history and thereby reflects at least some of the unobserved aspects of the current state (e.g. using some type of variable).

Production Based Systems The production rule paradigm originated in the field of AI with the expert systems rule languages such as OPS5 (Brownston et al. 1985) condition  action An inference engine cycles through all the rules in the system matching the condition parts of the rules with data in working memory. Of all the rules that match (the candidate set), one is selected using some conflict resolution policy and this selected rule is fired, that is, its action part is executed. The action part may modify the working memory, possibly according to the matched data and the cycle continues until no more rules match. Rule based Rules have special ops: Rules have special ops: Fire, which causes a rule to be triggered Enable, which causes a rule to be activated Disable, which causes a rule to be deactivated Conflict resolution Break ties with Specification, Sequencing, Meta rules Break ties with Specification, Sequencing, Meta rules

Production Based Systems CLIPS (“C”Language Integration Production System) Production system developed at NASA’s Johnson space center. Production system developed at NASA’s Johnson space center.NASA’s Written in ANSI C instead of LISP Written in ANSI C instead of LISP CLIPS implements standard forward-chaining pattern- matching algorithm CLIPS implements standard forward-chaining pattern- matching algorithm CLIPS knowledge representation similar to OPS5 and ART systems. CLIPS knowledge representation similar to OPS5 and ART systems. Constructs Constructs simple string fact assertion & retraction Templates If-then rules (“productions”) Objects and instances NASA uses clips in the following projects Intelligent computer aided crew training, weather forecasting, shuttle space planning, shuttle diagnostics, Mission Control Center (telemetry data analysis and diagnostics), flight assistance and control Intelligent computer aided crew training, weather forecasting, shuttle space planning, shuttle diagnostics, Mission Control Center (telemetry data analysis and diagnostics), flight assistance and control ARTART commercial expert system has many of the same features as CLIPS ART

Agent Based Systems Systems to investigate Stagecast Creator TM ( Stagecast Creator TM ( Agentsheets TM ( Agentsheets TM (

End User Programming with agents Stagecast Study Report: We are attempting to create a cross-generational web based learning community for middle school students, teachers, and seniors. Learning community will design, construct, and discuss simulations of community issues. Summary of results of formative evaluation with students creating simulation projects. Proceedings of IEEE Visual Languages 2001, Rosson, Seals 2001; CHI 2001; DIS 2002; NSF Research: NSF ITR Proceedings of IEEE Visual Languages 2001, Rosson, Seals 2001; CHI 2001; DIS 2002; NSF Research: NSF ITR

Based on a movie metaphor Programming is facilitated by macro recorder to allow “programming by demonstration” Behaviors are represented as a set of as a set of productions or “if-then” rules Stagecast Creator

Procedure Participants: 10 middle school students Background survey Performed in usability testing lab study with “think aloud” protocol Recorded critical incidents Captured video, audio, and screen Subjective questionnaire, knowledge survey, retrospective interview

Visual Agent Programming Spatial context and visual appearance are required elements in a rule’s precondition Correct position and appearance are preconditions for rules If Precondition is satisfied, Then rule is fired. Characters may have many instantiations

Observations and Results Duration minutes Activity I Duration minutes Activity II Most students were successful in modifying simulations and adding new characters. Usability satisfaction Easy and fun to use Easy and fun to use Would like to use it in their classes Would like to use it in their classes But needed more exposure to feel confident But needed more exposure to feel confident No problems with drawing tools No problems with drawing tools Problems with tools for rule creation Problems with tools for rule creation

Issue Likely Cause Directing input to the wrong window Too many similar-looking windows Confused between rules and rule-actions lists Lists that look similar but have different meanings Select wrong icon Multiple similar icons Inability to find rules or other content in window Non-traditional method of scrolling Misunderstand spotlight and concept of stretching it Spotlight metaphor is not obvious or intuitive Stagecast Usability Problems

Practical metaphors for icons Bigger Icons Fewer layers of scaffolding Relation between internal variables and visual state of the simulation. Role of visual context in rules Rules must match exact visual context, most PBD system make rules to specific to be reused Rules must match exact visual context, most PBD system make rules to specific to be reused Visual Programming Challenges

End User Programming with agents AgentSheets Study Report: AgentSheets is a production based visual programming language where end users create with direct manipulation techniques Reports a study of teachers learning to build educational simulations as curricula aids. Summary of results of formative evaluation to design agent based production system for end user creation of educational simulations. Proceedings of IEEE Visual Languages 2002, Seals 2002.

Example Rule - left-hand specifies a “before” state - right-hand specifies one or more actions to take if state is confirmed - multiple rules are tested in order, first match fires

Empirical Study Results Need robust drawing tools Need robust drawing tools Objects should be important, not their spatial location Objects should be important, not their spatial location Flexible object size Flexible object size Support for import of objects Support for import of objects Allow incremental testing Allow incremental testing Increase the level of usability for novice programmers Increase the level of usability for novice programmers Platform independent implementation Platform independent implementation