The Soar 9 Tutorial
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The Soar 9 Tutorial John E. Laird University of Michigan August 27, 2008 Updated for Soar 9.0.0 (the Soar-RL Tutorial is currently a separate document from this six-part tutorial) 2 Acknowledgments This tutorial is the culmination of work by many people, and has been refined and expanded significantly over several years. Soar 8, based on Bob Wray's thesis work with contributions from Randy Jones and Mike vanLent, was a significant architectural departure from Soar 7. Eaters and TankSoar and the Soar Debugger have evolved with each version of Soar. Visual Soar significantly eases the development and debugging of Soar Productions. Below we recognize the individuals who have contributed to the Soar Tutorial: Soar 8: Randy Jones, Bob Wray, Karen Coulter Soar Debugger: Mazin Assanie, Doug Pearson Eaters: Randy Jones, Clare Bates Congdon, Scott Wallace, Jonathan Voigt Tanksoar: Mike vanLent, Mazin Assanie, John Duchi, Jonathan Voigt Visual Soar: Brad Jones, Brian Harleton, Andrew Nuxoll Documentation and other Tools: Karen Coulter, Clare Bates Congdon, Bob Marinier, Jonathan Voigt, Alex Roper, Taylor Lafrinere Soar Tutorial 3 Introduction This is a guide for learning to create software agents in Soar, version 8. It assumes no prior knowledge of Soar or computer programming. The goals of this document are: Introduce you to the basic operating principles of Soar. Teach you how to run Soar programs ...
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The Soar 9 Tutorial John E. Laird University of Michigan August 27, 2008 Updated for Soar 9.0.0 (the Soar-RL Tutorial is currently a separate document from this six-part tutorial)
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Acknowledgments
This tutorial is the culmination of work by many people, and has been refined and expanded significantly over several years. Soar 8, based on Bob Wray's thesis work with contributions from Randy Jones and Mike vanLent, was a significant architectural departure from Soar 7. Eaters and TankSoar and the Soar Debugger have evolved with each version of Soar. Visual Soar significantly eases the development and debugging of Soar Productions. Below we recognize the individuals who have contributed to the Soar Tutorial : Soar 8: Randy Jones, Bob Wray, Karen Coulter Soar Debugger: Mazin Assanie, Doug Pearson Eaters: Randy Jones, Clare Bates Congdon, Scott Wallace, Jonathan Voigt Tanksoar: Mike vanLent, Mazin Assanie, John Duchi, Jonathan Voigt Visual Soar: Brad Jones, Brian Harleton, Andrew Nuxoll Documentation and other Tools: Karen Coulter, Clare Bates Congdon, Bob Marinier, Jonathan Voigt, Alex Roper, Taylor Lafrinere
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Introduction This is a guide for learning to create software agents in Soar, version 8. It assumes no prior knowledge of Soar or computer programming. The goals of this document are: Introduce you to the basic operating principles of Soar. Teach you how to run Soar programs and understand what they do. Teach you how to write your own Soar programs. This is about the nuts and bolts of writing Soar programs, but not about the theory behind Soar. For that, you should read Chapter 3 of the Soar Manual or the Gentle Introduction to Soar: 2006 Update, http://ai.eecs.umich.edu/soar/sitemaker/docs/misc/GentleIntroduction -2006.pdf. This tutorial takes the form of a sequence of lessons. Each lesson introduces concepts one by one and gives you a chance to use them by creating Soar agents. Each lesson builds on the previous ones, so it is important to go through them in order. To make the best use of this tutorial, we recommend that you read the tutorial, do the exercises, run the programs, and write your own Soar agents. The programs are available as part of the standard Soar installation. Please use the most recent version. Although the tutorial is long, you should be able to work through it quickly. What is Soar? We call Soar a unified architecture for developing intelligent systems. That is, So ar provides the fixed computational structures in which knowledge can be encoded and used to produce action in pursuit of goals. In many ways, it is like a programming language, albeit a specialized one. It differs from other programming languages in that it has embedded in it a specific theory of the appropriate primitives underlying reasoning, learning, planning, and other capabilities that we hypothesize are necessary for intelligent behavior. Soar is not an attempt to create a general purpose programmin g language. You will undoubtedly discover that some computations are difficult or awkward to do in Soar (such as complex math) and they are more appropriately encoded in a programming language such as C, C++, or Java. Our hypothesis is that Soar is appropriate for building autonomous agents that use large bodies of knowledge to generate action in pursuit of goals . The tutorial comes in six parts. Part I introduces Soar using a simple puzzle task called the Water Jug to introduce the basic concepts of Soar. This is the classic type of toy problem that people in AI now rail against as being completely unrepresentative of real world problems. Maybe true, but it is simple and easy to understand. After working through Part I, you should be able to write simple Soar programs. Part II uses a Pacman like game called Eaters to introduce interaction with external environments. Part III uses a grid-based tank game called Tank-Soar and introducesSoar‟s subgoaling mechanism as it is used for task decomposition. Part IV uses Missionaries and Cannibals problems to further explore internal problem solving and search. Part V uses Missionaries and Cannibals along with the Water Jug to introduce look-ahead planning and learning. Finally, Part VI gives an overview of creating a more complex Soar system for playing Quake. Soar has its own editor, called VisualSoar, which we highly recommended for use in developing Soar programs. VisualSoar is part of the standard installation and is also available from the Soar homepage.
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Part I: Simple Soar Programs Throughout this tutorial, you will be writing and running Soar programs for simple tasks. In this part, you will be writing simple programs that do not use Soar subgoaling or chunking mechanisms. 1. Installing Soar Before reading further in the tutorial, you should install Soar and its associated software on your computer so that you can run the examples and exercises. Using your favorite browser, visit the Soar Getting Started page:tartng_settiar/g/uos.hdemuciek.rmatesi//p:tthed. Follow the directions on that page for installation. We recommend installing all of the Soar software so that you have a directory with the most recent release of Soar, the Eaters game, the TankSoar game, and VisualSoar. 2. Building a Simple Soar Agent Using Rules All of the knowledge in a Soar agent is represented as if-thenrules. In Soar, rules are calledproductions, and we will use the terms interchangeably. Rules are used to select a nd apply things calledoperators, and much of this tutorial will be describing how rules and operators fit together. But before we get to operators, we are going to learn about writing rules for a very simple agent– one that just prints “Hello World.”that we can run the programs youBefore we dive into rules, you will need to start up Soar so write. 2.1 Creating a Soar Agent and Using the Soar Debugger To start Soar, double click (or whatever is appropriate on your platform) on the Start Soar Debugger (Java) file in the folder where you installed Soar, or in Windows, click the Start button, select Programs, find Soar 8.6.2 and click Start Soar Debugger. After Soar has started, you will have a new window on your screen. This window is the Soar Debugger, which is shown below. This program will be used to run all of your Soar programs. Your version may look somewhat different, depending on the features added since this document was written.
Interaction window
Command Box
The large window to the left is called the Interaction window (above). During Soar execution, all debugging information and print statements will be displayed in the Interaction window. Just below the interaction window is the Command Box for typing in user commands. The windows on the right display information that you will find useful later.
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When the Soar Debugger starts, a default agent entitled „soar1‟ is created. The name of the agent can be seen on the title bar. The bottom of the window contains buttons for single stepping, running, or stopping an agent. When it is time to run your Soar programs, commands can either be entered by typing them into the command box, or b clickin the buttons
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2.2 Hello-World Rule: English The first Soar agent we will examineprints “Hello World”. In general, an operator should perform this type of activity, but in order to ease you slowly into Soar, we start with a single rule. Below is a simple rule written in English. hello-world: If I exist, then write “Hello World” and halt.Soar cannot directly interpret English, so youmust write rules in Soar‟s very stylized and precise language. A major component of the rest of this tutorial is teaching you that language. Soar works by testing the”if” parts of rules (“If I exist”). These ”if” partsare calledconditions. If all of the conditions of a rule are true in the current situation, the”then” parts, oractions, of the rule (“write „Hello World‟ and halt”) areexecuted, which usually involves making changes toworking memory,which holds all of the dynamic data structures in a Soar program. Executing the actions of a rule is calledfiringthe rule. To determine if the conditions are true, Soar compares them to data structures in working memory. Working memory defines the current situation, which for an agent consists of its perception of its world, results of intermediate calculations, active goals, and operators. The figure below shows a high level view of Soar. On the right are all of the underlying architectural processes that select operators, create states, learn new rule s, etc. These are all written in C and you will not be changing them at all (so don‟t worry if you don‟tknow C). In the upper center is the rule memory, which contains all of the rules. Rules encode the long-term knowledge in Soar and adding them is the way Soar is programmed–you do not change the way Soar creates states or learns, but you create rules. Working memory is where short-term information is stored and your rules will create and test structures in working memory. In contrast to C or Java, which have programs that are executed sequentially, Soar has rules that are matched and executed in parallel. C and Java have data structures, variables, etc. while Soar has working memory. While these other languages have a combination of local and global data, Soar has no local data–everything in working memory is global. Working memory consists of a graph structure of individualelementscreated by rules as well as from. The elements are sensors (not shown in the diagram), and the Soar architecture creates a limited set of working memory elements (the core part of states) automatically. Working memory is matched against rule memory to determine which rules will fire. When rules fire, the y can make changes to working memory, as well as performing simple actions such as printing messages in the interaction window.
Rule Memory
Working Memory
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Decision Making State Creation Learning …
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2.3 Loading and Running Hello-World Before going through the nitty-gritty of Soar syntax, let‟s see an example of Soar executing the hello-world rule. In order to execute the hello-world rule, it must be loaded from a file into Soar‟s rule memory. You can load in the rules from a file via the Interaction window by eitherclicking the “source” buttonor by using the File menu at the top left (you can also type the source command directly into the interaction window, but for that you need to know the path to the file) . To use the File menu, click on the toolbar as shown in the figure below.
nu The fo ow ng menu w pop up; se ec oa sourceClick on this me
Alternatively, click on the “source” button at the bottom of the interaction window. In both cases,a menu to select the file will pop up, such as below (your menu might have a different set of files available). You can navigate in this menu to get to the correct directory (<soardir>/SoarLibrary/Demos/) and then select the file you want to load (hello-world-rule.soar).
When rules are loaded into Soar, an “*” is prthe file has loaded, you will see theinted for each rule. When word “source” followed by the location of the file in the interaction window,
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At this point you can type run, or click on the run button in the bottom left of the interaction window. The first thing that happens is that Soar automatically creates the initial state, S1 (but this is not shown in the interaction window, but is shown in the window on the right where the state S1 is printed). All of working memory is organized as states, so even before any rules fire, a state is created. After the state is created the rule matches (details explainedlater) and it fires, performing its actions, printing “Hello World” and then halting.
Trace of run command being executed. “Hello World”printed out by rule followed by halt.
Soar always automatically creates a state (S1) for all data.
Start executing Soar by typing run in the command window or clicking on the run button.
Soar Tutorial
The “}” ends the rule.
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2.4 Hello-World Rule: Soar As stated earlier, Soar has a stylized and precise language for writing rules. Here is the Soar rule for hello-world. sp stands for “Soar The “{“ starts body of a rule. The name of the rule immediately follows the “{“. production” andThe name can include letters, numbers, “-“, and “*”. starts every rule. sp {hell -These are the then parts of the rule (actions). tThhei sr uilse t (hceo ifn dpitairot no)f. (stat --> (writ The --> separates(halt)} the if and then parts of the rule. Every rule starts with the symbol “sp”, which stands for “Soar production.” The remainder of the rule body is enclosed in curly braces: “{ and “}”. The body cothe rule name, followed by one or morensists of “ conditions (the“if” part), then the symbol “-->“, and then one or more actions (the “then”part). Below is a template for rules: sp {rule*name (condition) (condition) …… means additional conditions can follow. --> (action) (action… means additional actions can follow. …}The name of the rule can be any arbitrary combination of letters, numbers, dashes (“-“), and asterisks (“*”). The one exception is that a name cannot be a single letter followed by a numbersuch as S1 or O45. Soar reserves those names for its own purposes. The specific name is irrelevant to the operation of the rule, but you should always pick a name that is meaningful. Following the name, there must be at least one condition. A condition tests for the existence (or absence) of data in working memory. If all of the conditions match, then the rule will fire and all of the actions are per formed. Most actions create new working memory elements or remove existing working memory elements . Some actions create preferences for selecting operators (more on that later), while others perform functions such as writing text to the screen or halting as in hello-world. In the next several sections we will explore the structure of conditions and actions and explain what all of the special symbols, such as <s> and ^type, mean. Before doing that, we need to first look at the structure of working memory in more detail.
Soar Tutorial
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Stateidentifier Attribute Value
2.5 Working Memory Working memory contains all of a Soar agent‟s dynamic information about its world and its internal reasoning. It contains sensor data, intermediate calculations, current operators and goals. In Soar, all of working memory is organized as graph structures instates. Thus, every working memory element is connected directly or indirectly to a state symbol. For the first agents you will build, there will be a single state. Below is a simple example of what the structure of working memory might be like if the agent were representing that there were two blocks, one on top of the other, which is then on a table as shown in the figure below. ^nameAB1^colorblue^typeblock^block^onto ^nameBS1^blockB2^coloryellow^typeblocktable ^ontop Table^name^colorT1gray^typetableBelow is a graphic picture of the working memory structures that Soar creates automatically for every agent–so although not shown in the above figure,S1would have these additional structures. nil^suI2 ^io ^out -link Stateidentifier I1 ^in -link I3 Attributest state Value As a graph, there are nodes (or vertices) and links (or edges). The nodes, such asS1, B1, B2, A, and blue, are connected by links, such asblock, table, name, color,andsuperstate. Soar has two kinds of nodes:identifiersandconstants.The nodes that can have links emanating from them (they are non-terminal nodes), such asS1andB1, are calledidentifiers, while the others (they are terminal nodes), such asstate, blue, block,andnil,are calledconstants. In the example above,S1is the identifier for the state. All of the identifiers symbols are created automatically by Soar and consist of a single letter followed by a number. AlthoughI2andI3in the lower figure do not have any links emanating from them, they are identifiers and can have additional substructures added later. In contrast, the symbolstateis not an identifier and cannot have links emanating from it. The links are calledattributesin Soarand are prefaced by a “^”. Only identifiers have attributes. In the bottom figure, S1 has three attributes:superstate,io, andtype.I1has two: output-linkandinput-link.
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Working memory is actually built of individual elements which are triples of an identifier, an attribute, and value,node pointed to by the attributand where the value is that The value can be either a constant or e. an identifier. In the example above, the symbolsnil,I1,state,I2, andI3are allvalues. It is these triples that you add and delete when writing Soar programs. There are five working memory elements in the figure above: S1 ^superstate nil S1 ^io I1 S1 ^type state I1 ^output-link I2 I1 ^input-link I3 This is the minimal contents of working memory, and as your programs get larger and more complex, they will manipulate many more working memory elements. A collection of working memory elements that share the same first identifier is called anobject. For example, the three working memory elements that have S1 as their identifier are all part of the state object. The working memory elements that make up an object are calledaugmentations. Although we call them objects, they consist of the individual working memory elements that share the same identifier. Objects are usually written as a list of the augmentations surrounded by parentheses. The first item in the list is the identifier that is shared by all of the augmentations, followed by the pairs of attributes and values for each augmentation. The objects for the above working memory elements are: (S1 ^io I1 ^superstate nil ^type state) (I1 ^input-link I3 ^output-link I2) An individual augmentation can also be written in this form: (S1 ^type state) A working memory object usually represents something about the world, such as a block, a wall, a piece of food, or a cell on the board. The individual augmentations r epresent properties (such as color, size, or weight), or relations with other objects (such as on top of, behind, or inside). Soar can be used for many different tasks, and for each different task, working memory will contain descriptions of the task objects. The working memory elements for the blocks would be as follows: (s1 ^ b2 ^table t1) Apotn2bemao^Ak)ocyp^tbleb(blue^n1^colorkocbl^b1kocbl (b2 ^color yellow ^name B ^ontop t1 ^type block) (t1 ^color gray ^name Table ^type table) B Working memory usually also contains objects that are only conceptual things and do not have an identifiable physical existence, such as state s1, which organizes other o bjects, relations, and properties. The exact representation of objects is up to you, the designer of a Soar program. Soar does not require any declarations of the possible attributes and constants. In fact, some Soar programs generate new attributes and constant values as they execute. The Soar editing and development tool, VisualSoar, does require declarations for the structure of working memory elements, and those declarations are used to check for errors in your rules but they are not used by Soar when it is executing a program.
Soar Tutorial
