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讲解CZ3005 Artificial Intelligence

CZ3005 Artificial Intelligence – Lab Assignment 2
Learning to Use Prolog as a Logic Programming Tool
1 Background: Wumpus World II
Environment: A finite grid world of size N ×M , where N,M are integer numbers greater than or equal to 6
(six). Outermost cells contain Walls1. A Wall can also appear elsewhere on the grid.
Agent and NPCs: The world is also populated by an Agent, a Wumpus, a set of Confundus Portals, and a set of
Coins. While the Agent is mobile, all other items remain fixed throughout the game and cannot co-inhabit a grid
cell.
Goal: The goal of the Agent is to find all coins that are accessible and return to the initial position.
Actions: The Agent has orientation, so that its movements are: Forward, TurnLeft, and TurnRight. The Agent
can also Pickup a gold coin if it is in the same cell as the Agent. The Agent can also shoot an arrow in the direction
it faces. The Agent has only one arrow.
Percepts: Prior to any movement, the Agent receives an vector of sensory indicators: Confounded, Stench,
Tingle, Glitter, Bump, Scream. All indicators are Off, except in the following situations:
? Confounded indicator is On at the start of the game and after the Agent stepped into a cell with a Confundus
Portal.
? Stench indicator is On in the cell next to one inhabited by the Wumpus.
? Tingle indicator is On in the cell next to one inhabited by a Confundus Portal.
? Glitter is On in the cell inhabited by a Coin.
? Bump is On if the Agent attempted an action Forward and the next cell in that direction contained a Wall.
? Scream indicator is On after the Agent shot an arrow and the Wumpus was in the direction of the shot.
Notice that the agent does not perceive its exact location on the grid.
Action Effects and Agent Capabilities: All actions taken by the Agent are deterministic in nature. The Agent
is capable of counting its steps and turns. Thus, the Agent is capable of orientation in space relatively to its initial
position and direction. The initial direction is termed Relative North. The direction to the left of Relative North is
Relative West, the direction to the right of Relative North is Relative East, and the direction opposite to Relative
North is termed Relative South. The initial position of the agent is the Origin with relative coordinates (0,0).
Actions have the following effects:
? Executing action Forward changes the position of the Agent. If the agent’s orientation is Relative North,
the second coordinate of its relative position will increase by 1: (x, y) → (x, y + 1). Executing Forward
in Relative South orientation will decrease the second relative coordinate: (x, y) → (x, y ? 1). Similarly,
executing Forward in Relative West (East) orientation will decrease (increase) the first relative coordinate.
Exceptions to the rule:
– The intended new location is inhabited by a Wall. In this case the relative location of the agent is not
changed.
1Notice that Walls are not between the cells, but within the cells completely filling them.
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– The intended new location is inhabited by a Confundus Portal. The Agent is randomly relocated to a
safe location in the Wumpus World. The relative position is reset to (0,0) and relative orientation is
reset to become the Relative North. All memory of previous steps and sensory readings is lost, except
the fact of existence of uncollected coins, whether the Wumpus is alive and whether the Agent has the
arrow.
– The intended new location is inhabited by the Wumpus. Game ends. Relative position reset occurs, as
with the case of stepping into a Confundus Portal, to prepare for a new game. All memory of previous
steps and sensory reading is lost without exceptions, the arrow is returned to the Agent.
? TurnLeft changes the Agent’s current orientation by 90 degrees counter-clockwise. E.g. if the Agent’s
current orientation is Relative East, then after executing TurnLeft the orientation will become Relative
North.
? TurnRight changes the Agent’s current orientation by 90 degrees clockwise. E.g., if the Agent’s current
orientation is Relative South, then after executing TurnRight the orientation will become Realative West.
? Pickup action removes a Coin, if present, from the current location of the Agent. Percepts change accord-
ingly.
? Shoot action removes the Wumpus from the world, if the Wumpus inhabits any of the cells ahead of the
agent.
2 The Assignment
In this assignment you will implement the Agent’s logic in a Prolog program. Your Prolog implementation will
allow the Agent to analyse the sensory data, navigate and map the current world. You will also implement a basic
Wumpus World Driver to test your (and other’s) Agent using PySWIP library.
2.1 The Agent
Your Proglog Agent program will implement the following terms:
? reborn/0 – implements Agent’s reset due to arriving into a cell inhabited by the Wumpus.
? move(A,L) – implement Agent’s reasoning response to executing action A and receiving sensory input L.
– Action constants are {shoot,moveforward,turnleft,turnright,pickup}
– Sensory input is a list of six indicators, one for each percept: Confounded, Stench, Tingle, Glitter,
Bump, Scream. In that order. Each indicator can have one of the two values {on, off}.
reposition(L) – implements Agent’s reset due to game start or arrival to a cell inhabited by a Confundus
Portal. The argument includes the initial sensory information. The format of L is the same as with the
move/2 function. Confundus indicator should be on.
Localisation and mapping.
– visited(X,Y), where X,Y are integers, returns true if the Agent has visited relative position (X,Y).
Otherwise it returns false.
– wumpus(X,Y), where X,Y are integers, returns true if the Agent knows (or reasons) that the Wumpus
may inhabit relative position (X,Y). Otherwise it returns false. Notice that there may be more than
one positions where true is returned. It is also possible that all positions return false, either because
there is no Wumpus or no relevant information exists.
– confundus(X,Y), where X, Y are integers, returns true if the Agent knows (or reasons) that a Confun-
dus Portal may inhabit relative position (X,Y). Otherwise false is returned.
– tingle(X,Y), where X, Y are integers, returns true if the Agent knows (or reasons that) it will experience
a Tingle indicator beging on at the relative position (X,Y). Otherwise, false is returned.
– glitter(X,Y), where X, Y are integers, returns true if the Agent knows (or reasons that) it will experi-
ence Glitter indicator being on at the relative position (X,Y). Otherwise false is returned. Notice that
this knowledge changes, once the Agent picks up the coin.
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– stench(X,Y), where X,Y are integers, returns true if the Agent knows it will experience Stench indi-
cator being on at the relative position (X,Y). Otherwise, false is returned. Notice that this knowledge
changes, once the Wumpus is killed.
– safe(X,Y), where X,Y are integers, returns true if the Agent knows or can reason that the relative
position (X,Y) contains neither a Wumpus nor a Confundus Portal.
– wall(X,Y), where X, Y are integers, returns true if the Agent knows or can reason that the relative
position (X,Y) contains a Wall.
explore(L) is true if the list L contains a sequence of actions that leads the Agent to inhabit a safe and
non-visited location.
– if there are no more safely accessible un-visited portions of the map left and there are no Coins on the
explored portion of the map, the explore(L) should return true on an action sequence that returns the
Agent to the relative Origin.
current(X,Y,D) is true if (X,Y) is the current relative position and D is the current relative orientation of the
Agent. Possible relative orientations are described by constants {rnorth,rwest,reast,rsouth}, and the relative
position consists of two integers.
hasarrow/0 returns true if the Agent has the arrow, and begins to return false after shoot action has been
executed by the Agent.
2.2 Wumpus World Driver
The Wumpus World Driver has to implement a map of size 7× 6 with the outer cells inhabited by Walls, and the
inner cells populated by at least one Coin, one Agent, one Wumpus and 3 (three) Confundus Portals. The initial
position and direction of the Agent can be random, but should be safe. All sensory input generated for the Agent
should refer to this map of the Wumpus World.
The Driver is to ask the Agent to reset (reborn/0 call), and then create a feedback loop with the Agent that
tests:
Correctness of Agent’s localisation and mapping abilities
– by asking the Agent to perform a test-sequence of actions
– using localisation and mapping terms to confirm that the Agent correctly represents its relative position
on its relative map.
Correctness of Agent’s sensory inference
– by asking the Agent to perform a test-sequence of (actions, observations)
– using localisation and mapping terms to confirm that the Agent correctly absorbed and interpreted its
sensory input
? Correctness of Agent’s memory management in response to stepping though a Confundus Portal.
– by feeding the Agent an (action,observation) sequence that creates a non-trivial map within the Agent’s
knowledge.
– ask the Agent to reset as if it stepped through a Confundus Portal (reposition/1 call)
– confirming that the knowledge base of the Agent has been correctly cleaned via the use of localisation
and mapping terms.
? Correctness of Agent’s exploration capabilities
– Repeatedly call explore(L), confirm the generated path correctness (safe and ends at a non-visited
location or Origin).
– Feed the exploration plan back to the Agent via a sequence of move(A,L) calls
– If the newly found cell contains a Coin, order the Agent to pick it up
– Confirm that the Agent returns and stays at the origin once there are no more safely accessible un-
visited parts of the map and all discovered coins have been collected.
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? Correctness of the Agent’s end-game reset in a manner similar to that of Confundus Portal reset.
Hint: Because you can always restart the Prolog, thus hard-resetting the Agent, you can run multiple Wumpus
World scenarios in each correctness test. This would make such a test more reliable and challenging. The posi-
tioning of NPCs and the Agent does not need to be purely random, thus creating a challenging exploration and
planning scenarios. You can also test the system by using empty or partially filled maps, where some NPCs are
missing.
2.2.1 Driver Printout:
Correctness (or lack-of) has to be demonstrated by a printout of the following:
Initial absolute map of the world depicted by an array of map cells. Rows correspond to the second coor-
dinate of the absolute position and the columns to the first coordinate of the absolute position. The map
begins at a new line of the printout and finishes by a newline.
Iteration of the following as many times as necessary
– Action sequence printout (e.g., ”moveforward, turnleft, moveforward, pickup”) finished by a newline
– Sequence of relative positioning maps that depict the complete knowledge of the agent, as the con-
sequence of applying the chosen action sequence. The relative Origin cell is always depicted at the
centre of the map. The sequence begins with the map of the initial knowledge before the first actions
is applied.
– Each map (except the initial knowledge map) is preceded by the percepts that were provided to the
Agent by the Driver as a sensory input after an action application. If a particular indicator is On, then
the full name of the indicator should be printed, otherwise the first letter of the indicator should be
printed. Dashes are used as the separators between indicators. E.g. ”Confounded-Stench-T-Glitter-B-
S” is printed, ending with a newline, to denote that Confounded, Stench and Glitter indicators are on,
while Tingle, Bump and Scream indicators are off, within the percept provided by the Driver to the
Agent.
2.2.2 Map format:
Map cells consist of 9 symbols forming a 3x3 square. Map cells are separated by a single space within a row of
the grid map and rows are separated by an new (empty) line. Let’s enumerate our symbols 1-9 within a single map
cell, like the following
1 2 3
4 5 6
7 8 9
. Then:
Symbol 1: Corresponds to the Confounded indicator of the sensory input in this map cell. If it is on, the symbol will
printout as ”%”, otherwise a dot will be printed
Symbol 2: Stench indicator. ”=” is printed if the indicator is on, and a dot will be printed otherwise.
Symbol 3: Tingle indicator. ”T” is printed if the indicator is on, and a dot otherwise.
Symbol 4: Prints ”?” if the cell contains the Agent or an NPC, otherwise prints as a single space.
Symbol 5: – Prints ”W” if the map cell is known or reasoned to (possibly) contain the Wumpus
– Prints ”O” if the map cell is known or reasoned to (possibly) contain a Confundus Portal
– Prints ”U” if the map cell is both: a) reasoned to possibly contain a Confundus Portal and b) reasoned
to possibly contain the Wumpus. Notice that no cell can factually contain both of those NPCs.
– Prints ”∧”,”<”,”>” or ”∨” to denote that the Agent inhabits the cell and faces, correspondingly,
(r)north, (r)west, (r)east or (r)south. The meaning of the direction is according to the map that is
being printed. Absolute in the actual Wumpus World map, and relative in the Agent’s localisation
map.
– Prints small ”s” for a non-visited safe map cell without the Agent inhabiting it
– Prints capital ”S” for a visited safe map cell without the Agent inhabiting it
– If none of the above, a single question mark, ”?”, is printed.
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Symbol 6: Prints ”?” if the cell contains the Agent or an NPC, otherwise prints as a single space.
Symbol 7: Glitter indicator. ”*” (star) is printed if the indicator is on and a dot otherwise.
Symbol 8: Bump indicator. ”B” is printed if the indicator is on and a dot otherwise.
Caution: Bump indicator is transitory. That is, it will appear only if the agent tried to go forward and
met a Wall.
Symbol 9: Scream indicator. ”@” is printed if the indicator is on and a dot otherwise.
Caution: Scream indicator is transitory. That is, it will appear only if the agent shot its Arrow and
the Wumpus was killed/removed.
Exclusion: If a map cell is inhabited by a (known) Wall, then all symbol are #
3 Marking Criteria
3.1 Agent capabilities (72 points)
Three different Driver implementations will be used to generate (and confirm) reports. Self-Driver, a ”friend”
Driver and a School chosen Driver.
Correctness of Agent’s localisation and mapping abilities.
12 points (4 per Driver that was run on the Agent).
Correctness of Agent’s sensory inference. 24 points (8 per Driver that was run on the Agent).
Correctness of Agent’s memory management in response to stepping though a Confundus Portal.
9 points (3 per Driver that was run on the Agent).
Correctness of Agent’s exploration capabilities
– Finding a safe path to a safe unexplored location. 12 points (4 per Driver that was run on the Agent)
– Confirmation of a return (and stay) path solution. 9 points (3 per Driver that was run on the Agent)
? Correctness of the end-game reset. 6 points (2 per Driver that was run on the Agent).
3.2 Driver capabilities (28 points)
Differentiation between the Absolute and Relative Map printouts. 3 points
Ability to test viable Agents. 5 points per Agent test (2 points for self-Agent, 2 points for ”friend” Agent”,
1 point for a School chosen Agent), totalling at 25 points for all tests.
4 Team Formation and Inter-Team Cooperation
You are required to form a team of up to 3 people to complete this project. A team with only a single person is
also allowed. For team size that is larger than one, you need to clearly state the contribution of each team member
in your solution report.
For the purposes of completing this Assignment you will need to exchange your Driver code with other teams.
However, this is done for test-run purposes only. Do not use someone else code as a clue/hint/inspiration – you
never konw where it will lead you.
You cannot exchange Agent code. If the ”A-team” needs a printout of their Driver running on the Agent of
the team ”FBI”, then the ”A-team” should send their A-Team-Driver to the team ”FBI”. The team ”FBI” will then
run the ”A-team-Driver” Driver on the ”FBI-Agent” and revert with the outcome.
5 Honour Code
If you use any existing code, libraries, etc. and consult any papers, books, online references, etc. for your project,
you must cite your sources in your report and clearly indicate which parts of the project are your contributions and
which parts were implemented by others. Using others’ code/ideas without acknowledgement will lead to failure
of your project. You should not even attempt to submit another team’s Driver code (partially or in its entirety) as
your own. Plagiarism testing tools are readily available and ruthless. You cannot exchange Agent code.
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6 Deliverables
You are required to produce:
1. A final report of no more than 5 pages. Name your report as -final-report.pdf.
2. Source codes for your project. Your source codes are to be submitted in .zip format. Name the zip file as
-final-code.zip.
The Agent code should be named -Agent.pl
The Driver code should be named -Driver.py
Friend Driver code should be named -Friend-Driver.py
Printout of Driver reports -testPrintout--.txt
– source is either ”Self” or ”Friend”. Thus, team ”Frodo” running their own Driver on a friendly
Agent should be named ”Frodo-testPrintout-Friend-Self.txt”.
The following is a suggested structure for the report:
1. Title, team members.
2. For each task, explain your approach, output, etc. In particular, explain how your printouts demonstrate
correctness. Enumerate maps within the reports when necessary.
3. Contribution: For teams with more than one person, please clearly state each team member’s contribution.
Separately mention the team who has provided you with the Friend Driver and the printout of Friend
Agent test. Each can come from a different team. So that you can ask for a Driver code from the “A-
Team” to run on your Agent, but ask the team “FBI” to give you the printout of your Driver running
on the FBI-Agent. Please notice again that only the Driver code can be exchanged.
4. Conclusion: What have you learned?
5. References: Please cite the sources you consulted in the report.

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