23 Questions
What was the main reason for rejecting symbolic approaches to building agents?
They were not suitable for time-constrained environments.
What is the common theme among alternative approaches to agency?
The rejection of symbolic representations.
Why is intelligent behaviour seen as linked to the environment an agent occupies?
Because the environment influences the agent's decision-making process.
What is the term used to describe AI systems that emerge from the interaction of various simpler behaviours?
Reactive systems.
What is the main characteristic of situated approaches to agency?
The agent's actual situation in its environment.
Why are alternative approaches to agency often referred to as 'reactive'?
Because they simply react to their environment without reasoning.
What is the main difference between symbolic and alternative approaches to agency?
The focus on decision-making versus the focus on interaction with the environment.
What is the common goal of alternative approaches to agency?
To create AI systems that can operate in time-constrained environments.
The subsumption architecture is arguably the best-known ______ agent architecture.
reactive
Rodney Brooks is one of the most vocal and influential critics of the ______ approach to agency.
symbolic
According to Brooks, intelligent behaviour can be generated without explicit ______ of the kind that symbolic AI proposes.
representations
Brooks identifies two key ideas that have informed his research, including ______ and embodiment.
situatedness
The subsumption architecture realizes an agent's decision-making through a set of ______ behaviours.
task-accomplishing
In Brooks's implementation, the behaviour modules are ______ state machines.
finite
The task-accomplishing modules are assumed to include no complex ______ representations.
symbolic
Intelligence is 'in the eye of the ______' - it is not an innate, isolated property.
beholder
In many implementations, these behaviours are implemented as rules of the form situation- ______,
action
Brooks proposed arranging the modules into a ______ hierarchy, with the behaviours arranged into layers.
subsumption
Lower layers in the herarchy are able to ______ higher layers.
inhibit
The idea is that higher layers represent more abstract ______.
behaviours
A behaviour is a pair (c,a), where c G P is a set of ______ called the condition, and a E A is an action.
percepts
A behaviour (c,a) will fire when the environment is in state s E S if and only if see(s) E ______.
c
Let Beh = ((c,a) I c E P and a E A) be the set of all such ______.
rules
Study Notes
Limitations of Symbolic/Logical Approaches
- Researchers questioned and rejected the assumptions of symbolic/logical approaches to building agents due to their limitations in operating in time-constrained environments.
- Minor changes to the symbolic approach, such as weakening the logical representation language, were deemed insufficient to overcome these limitations.
Alternative Approaches to Agency
- In the mid-to-late 1980s, researchers began exploring alternatives to the symbolic AI paradigm.
- Common themes among these approaches include:
- Rejection of symbolic representations and decision-making based on syntactic manipulation of representations.
- Intelligent, rational behavior is seen as inherently linked to the environment an agent occupies.
- Intelligent behavior emerges from the interaction of various simpler behaviors.
Characterization of Alternative Approaches
- Alternative approaches to agency are sometimes referred to as:
- Behavioral (developing and combining individual behaviors).
- Situated (agents situated in an environment, rather than being disembodied from it).
- Reactive (systems reacting to an environment without reasoning about it).
Subsumption Architecture
- Developed by Rodney Brooks, a prominent critic of the symbolic approach to agency
- Brooks' three key theses:
- Intelligent behavior can be generated without explicit representations of the kind that symbolic AI proposes
- Intelligent behavior can be generated without explicit abstract reasoning of the kind that symbolic AI proposes
- Intelligence is an emergent property of certain complex systems
- Brooks' two key ideas:
- Situatedness and embodiment: 'Real' intelligence is situated in the world, not in disembodied systems
- Intelligence and emergence: 'Intelligent' behavior arises as a result of an agent's interaction with its environment
Defining Characteristics of Subsumption Architecture
- An agent's decision-making is realized through a set of task-accomplishing behaviors
- Each behavior is an individual action function that continually takes perceptual input and maps it to an action to perform
- Behavior modules are assumed to include no complex symbolic representations and do no symbolic reasoning
- Behaviors are often implemented as rules of the form situation-action, which simply map perceptual input directly to actions
Subsumption Hierarchy
- Many behaviors can 'fire' simultaneously, requiring a mechanism to choose between the different actions selected
- Behaviors are arranged into a subsumption hierarchy, with lower layers able to inhibit higher layers
- Higher layers represent more abstract behaviors, with lower layers having higher priority
Formal Model of Subsumption Architecture
- The see function represents the agent's perceptual ability and remains unchanged
- Decision function action is realized through a set of behaviors, together with an inhibition relation holding between these behaviors
- A behavior is a pair (c,a), where c is a set of percepts called the condition, and a is an action
- A behavior (c,a) will fire when the environment is in state s if and only if see(s) belongs to c
This quiz explores the limitations of symbolic and logical approaches to building agents, and the need for a new approach to operate in time-constrained environments.
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