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This manual is for GNU Aris, the logical proof program.
Copyright (C) 2013 Ian Dunn
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
This manual is for GNU Aris, the logical proof program.
This is edition 1.3, for
aris version 2.2
|• Introduction:||Overview of Aris.|
|• Terms:||Terms used in this manual.|
|• Options:||The command-line options used for Aris.|
|• Basic Usage:||A quick walkthrough of Aris usage.|
|• Menu Options:||The keyboard shortcuts used in Aris.|
|• Rules Index:||The logical rules used in Aris.|
|• Customization:||Customizing GNU Aris.|
|• Submission:||Submitting proofs for grading.|
|• Sequence Logic:||An overview of Sequence Logic.|
|• Interoperability:||An explanation of interoperability.|
This manual is for GNU Aris, a sequential proof program, designed to assist anyone interested in solving logical proofs. Aris supports both propositional and predicate logic, as well as Boolean algebra and arithmetical logic in the form of abstract sequences. It uses a predefined set of both inference and equivalence rules, however gives the user options to use older proofs as lemmas, including Isabelle’s Isar proofs.
A biconditional is a connective that connects two sentences, denoted by ‘<->’. A biconditional claims that ‘sentence a if and only if sentence b’ is a new sentence. A biconditional can be inserted in Aris using the key combination CTRL+5 (see Other Key Shortcuts).
A conclusion is a sentence that is derived from a combination of other sentences and a rule. A focused conclusion will be highlighted in cyan. A conclusion has a set of references associated with it, which are highlighted in violet. Both of these colors can be changed using customization (see Customization).
A conditional is a connective that connects two sentences, denoted by ‘→’. A conditional claims that ‘if sentence a, then sentence b’ is a new sentence. A conditional can be inserted in Aris using the key combination CTRL+4 (see Other Key Shortcuts).
A conjunction is a connective that connects two or more sentences, denoted by ‘^’. A conjunction claims that ‘sentence a and sentence b’ is a new sentence. A conjunction can be inserted in Aris using the key combination CTRL+7 (see Other Key Shortcuts).
A connective is a logical symbol that connects one or more sentences. The connectives used in system PSI are conjuction (‘^’), disjunction (‘v’), negation, (‘~’), conditional (‘→’), and biconditional (‘<->’). In addition, system PSI recognizes the one-place connectives of the tautology (‘T’) and the contradiction (‘!’).
A contradiction is a zero-place connective that stands on its own, denoted by ‘!’. A contradiction represents something that is always false. A contradiction is only used with the boolean rules (see Boolean Rules), and can be inserted using the key combination CTRL+6.
A disjunction is a connective that connects two or more sentences, denoted by ‘v’. A disjunction claims that ‘sentence a or sentence b’ is a new sentence. A disjunction can be inserted in Aris using the key combination CTRL+\ (see Other Key Shortcuts).
To evaluate a sentence means different things depending on the type of sentence. At the very least, evaluation checks the sentence for text errors, i.e. mis-matched parenthesis, etc. Evaluating a conclusion checks that the sentence’s text logically follows from the given references and its rule. Evaluating a goal means checking the corresponding proof for a sentence with this exact same text. To evaluate a sentence use the key combination CTRL+E (see Proof Windows).
An evaluation value is the value that appears to the right of a sentence’s text entry. It can either be a square, a light green check, an X, an X polygon, a pointer box, or a dark green check icon. The square means that the sentence is awaiting evaluation. The light gren check means that either the conclusion logically follows from its references and rule, or that the goal has been found in the corresponding proof. In the case of premises, this means that the premise has no syntactic errors. The red X means that either the conclusion does not logically follow from its references and rule, or that the goal has not been found in the corresponding proof. The X polygon means that there is a text error with this sentence. The green check means that one of the conclusion’s references has a text error. The pointer box means that the conclusion is missing a rule.
An existential is a quantifier that precedes the rest of sentence, denoted by ‘3’. An existential claims that ‘there exists at least on item that has property property P’ is a new sentence, assuming that ‘P’ is a valid predicate. An existential quantifier can be inserted into Aris using the key combination CTRL+3.
A function symbol maps one object to another object. These are always lower case. Examples of a function symbol is seqlog’s ‘z’ and ‘s’ symbols (see Sequence Logic).
A goal is a sentence that the user is looking to meet in a certain proof. The goal window contains all of these sentences, and can be toggled by the key combination CTRL+L (see Proof Windows). When a sentence in the proof matches a goal, the proof sentence’s line number is highlighted in red, while the goal’s line number is changed to match the proof sentence’s line number.
A negation is a connective that is inserted in front of a sentence, denoted by ‘~’. A neagion claims that the opposite of the negation is true. A negation can be inserted into Aris using the key combination CTRL+` (see Other Key Shortcuts).
A null object is an object, denoted by ‘nil’. In Aris it resembles a null byte, ‘\0’, and represents an undefined object in a sequence. A null object can be inserted by using the key combination CTRL+..
A predicate is a type of logical symbol that denotes a property of or relation between one or more objects. These always begin with capital letters, and generally use prefix notation. Exceptions of this are the identity predicate (‘=’), the less than predicate (‘<’), and the element of predicate.
A premise is a sentence that is given. A premise has no rule associated with it, nor does it have an evaluation value, unless there is an error in it. Any variables introduced in a premise are not considered arbitrary.
A proof is a set of sentences, beginning with a set of premises and ending with a set of conclusions, that the user is trying to derive something from. The proof window is the main window that appears when the user opens up a proof.
A quantifier is a type of logical symbol that claims something about the amount, or quantity, of an object that holds a specific property. The quantifiers used in system PSI are the universal (‘V’), and the existential (‘3’).
A reference is a sentence that is being used to derive a conclusion. A reference is highlighted in violet, and can be added or removed from the current sentence by holding down CTRL, and left-clicking on the desired reference.
The rules in Aris are a combination of inference rules, equivalence rules, and predicate rules that the user can use to derive sentences. The rules window (also referred to as the rules tablet) is shared amongst all of the proofs in Aris. It can be toggled by the key combination CTRL+R (see Proof Windows) from any proof window. For the list of rules, Rules Index.
A sentence is a line in Aris. A sentence always consists of a text entry, a line number, and an evaluation value.
A proof within a proof. To begin a subproof in Aris, use the key combination CTRL+B, and to exit one, use the key combination CTRL+D.
A tautology is a zero-place connective that stands on its own, denoted by ‘T’. A tautology represents something that is always true. A tautology is only used with the boolean rules (see Boolean Rules), and can be inserted using the key combination CTRL+1.
A universal is a quantifier that precedes the rest of sentence, denoted by ‘V’. A universal claims that ‘for all items, they have property P’ is a new sentence, assuming that ‘P’ is a valid predicate. A universal quantifier can be inserted into Aris using the key combination CTRL+2.
A variable represents an object within a proof. A variable is introduced when it is first used. If the line that it is introduced in is a premise, the start of a subproof, or a line using existential instantiation (see ei), then it is not considered arbitrary. Otherwise, it is. Only the variables from lines that can be selected from the current line are taken into account when processing it. This means that after a subproof is ended, then lines after it don’t worry about variables introduced within it.
Use VARIABLE as a known variable in evaluation mode. Prepend an ’*’ to specifiy that the variable is arbitrary.
Start Aris in boolean mode.
Use CONCLUSION as a conclusion in evaluation mode. This flag can only be specified once.
Run Aris in evaluation mode. This means that no GUI will be loaded.
Evaluate FILE if running Aris in evaluation mode, otherwise load FILE in Aris. This flag can be specified multiple times.
Grades a file specified by the file flag. This flag is ignored if used more than once.
List the rules available in Aris, and exit.
Use PREMISE as a premise in evalution mode. This flag can be specified multiple times.
Use RULE as a rule in evaluation mode. This flag can only be specified once.
Simply check the correctness of TEXT in evaluation mode.
Run Aris verbosely, printing status and error messages.
Convert FILE to a LaTeX proof file in evaluation mode.
Print the version of Aris and exit.
Print a help message and exit.
This chapter describes the basic usage of GNU Aris.
|• Startup:||When the program is started.|
|• Connectives:||Using connectives.|
|• Adding:||Adding sentences to the proof.|
|• Selecting:||Selecting sentences.|
|• Syntax:||The syntax that Aris uses.|
When Aris is loaded up, you will see a few things. You will see the rules window and a proof window. The rules window contains the different rules. A rule will not be selected if a premise is in focus.
The initial layout of Aris is a single sentence. From left to right, the items of a sentence are: its line number, its text entry, its evaluation value, and its rule. The rule will not be initially visible, since no rule has been selected. In addition, premises do not have rules, and thus the rule will not appear.
Aris has several connectives (see Connectives) When the keyboard command for the desired connective is activated, the desired connective will be inserted at the current cursor point, overwriting selected text.
For example, pressing Ctrl+7 inserts a conjunction. This is the character that looks like an upside-down ‘v’. This is also called a ‘logical and’.
Hitting Ctrl+J adds a conclusion to the proof. A conlusion is always added after the current line, or, if the line is a premise, then the conclusion is added after the last premise. If the current line is a conclusion, then it is highlighted in cyan.
Hitting Ctrl+P adds a premise to the proof. A premise will always be added after the last premise.
Pressing Ctrl+B adds a subproof to the proof. When in a subproof, a conclusion will always be added within the subproof. The first line of a subproof does not require a rule, but instead acts as a premise. Pressing Ctrl+D ends the current subproof. This creates a new conclusion just after the subproof.
To undo a command, simply press Ctrl+Z. This will undo the last text modification, insertion, or deletion. In the case of several insertions or several deletions, undo will undo all of them. To undo an undo, press Ctrl+Y, or redo.
Holing CTRL, and left-clicking on a sentence will select a sentence as a reference sentence. The current line’s reference sentences are highlighted in violet. Only a line before the current line can be selected as a reference. In addition, if the sentence is in a different subproof than the current line, then the sentence can not be selected as a reference. Each rule requires a specific amount of references (see Rules Index).
Holding SHIFT and left-clicking on a sentence will select the sentence. The sentence will be highlighted in red-orange. Multiple sentences can be selected this way, however when another action is taken, all of them will be de-selected. Pressing CTRL+K will kill (cut) the selected lines, and CTRL+G will copy the selected lines. If no lines are selected, then the current line will be used.
Aris expects a certain form of syntax. Most of the connectives are infix, which means that they are placed in between their arguments. The negation is one exception to this.
Aris expects that all predicates start with an uppercase character. Aris also expects that all function symbols begin with a lower case character. After this, Aris will except any combination of upper case letters, lower case letters, numbers, or ‘_’.
To assist in understanding the proofs, Aris also allows for comments in sentences. To make a comment, simply insert a ‘;’. Aris will ignore everything after a ‘;’ when evaluating a sentence. This way, plaintext can be written into sentences.
The main GUIs for Aris all have menu bars. Each of the three types of GUIs have different menu bars, and the options for each of these are described in this section.
|• Proof Windows:||The window for proofs.|
|• Rules Table:||The rules table that floats around.|
|• Other Key Shortcuts:||Miscellaneous keyboard shortcuts|
The keyboard shortcuts here (with the exception of the connectives) can be changed using customization See Customization. The shortcuts listed here are the default shortcuts for Aris.
These are the menu options for the main proof windows. Each one can be assigned a key command.
Start a new proof. A new window is opened for this proof.
Open an existing proof in a new window.
Save the current proof.
Save the current proof under a different name.
Export the current proof to a LaTeX file.
Close the current proof.
Exit Aris. But since logic is so much fun, I doubt you’ll ever want to use this one.
Insert a new premise at the end of the other premises.
Insert a new conclusion after the current line if it is a conclusion, or at the start of the conclusions if it is a premise.
Begin a new subproof after the current line if it is a conclusion, or at the start of the conclusions if it is a premise. This is unavailable in boolean mode, since subproofs can’t be used.
End the current subproof, if there is one. Otherwise, this doesn’t do anything. This is unavailable in boolean mode, since subproofs can’t be used.
Undo the last modification to the current proof. On a new file, this does nothing.
Undo an undo operation. If no undo has been made, then this does nothing.
Copy the current line.
Kill, or cut, the current line. This removes the line from the proof.
Insert the copied/killed line.
Evaluate the logical validity of the current line.
Evaluate the logical validity of the current proof. This evaluates each line of the proof.
Toggle the goal window for the current proof.
Toggle boolean mode for the current proof See Boolean Rules.
Import another proof into this one. This will merge the premises of the other proof into the current one, and insert the goals of the other proof as conclusions. In addition, it sets the conclusions’ references as the premises, and sets them all to use the lemma rule see lm.
Toggle the rules window.
Change the font size to small (8pt).
Change the font size to medium (12pt).
Change the font size to large (16pt).
Change the font size to a custom size. This menu option opens a dialog box with a numerical entry.
Display Aris help. This is the only key command that cannot be modified.
Displays information about GNU Aris.
These are the commands for the rules window. Many of them are the same as for the main proof window.
Start a new proof. A new window is opened for this proof.
Open an existing proof in a new window.
Submits all open proofs for grading. There is more on this in the Submission session in this manual See Submission.
Change the font size to small (8pt).
Change the font size to medium (12pt).
Change the font size to large (16pt).
Change the font size to a custom size. This menu option opens a dialog box with a numerical entry.
Display Aris help. This is the only key command that cannot be modified.
Opens the customization dialog. For more information on this, see See Customization.
Displays information about GNU Aris.
These are the keyboard shortcuts for each of the connectives. Unlike most of the other keyboard shortcuts, these cannot be modified.
Insert a conjunction (‘^’) into Aris.
Insert a disjunction (‘v’) into Aris.
Insert a negation (‘-’) into Aris.
Insert a conditional (‘→’) into Aris.
Insert a biconditional (‘<->’) into Aris.
Insert a universal (‘V’) into Aris.
Insert an existential (‘3’) into Aris.
Insert a tautology (‘T’) into Aris.
Insert a contradiction (‘!’) into Aris.
Insert an ’element of’ predicate into Aris.
Insert a null object (‘nil’) into Aris.
The rules are divided into five categories: Inference, Equivalence, Predicate, Boolean, and Miscellaneous.
|• Inference Rules:||Rules that work on basic logic.|
|• Equivalence Rules:||Rules that work on sentence parts.|
|• Predicate Rules:||Rules that work with predicates and quantifiers.|
|• Boolean Rules:||Rules that handle Boolean Algebra|
|• Miscellaneous Rules:||Rules that don’t fit in anywhere else.|
The premises of any of these rules can be in any order.
|• mp:||Modus Ponens|
|• hs:||Hypothetical Syllogism|
|• ds:||Disjunctive Syllogism|
|• ex:||Excluded Middle|
|• cd:||Constructive Dilemma|
One of the basic rules of logic, modus ponens say that ‘if P happens, then Q must happen. P happened, so Q must happen’.
For example, if it is known that ‘If the dog begins to bark, then someone is at the door’, and it is also known that ‘the dog has begun to bark’, then modus ponens says that ‘someone must be at the door’.
Modus Ponens requires exactly two references.
What addition says is that something is already known, so it must be true that that something or something else, or something else, etc. must also be true.
For example, if it is known that ‘The sky is blue’, then addition says that it can be inferred that ‘The sky is blue, or the sky is yellow, or the sky is pink’, since only one of those statements has to be true.
Addition requires exactly one reference.
Simplification says that if it is known that P and Q and R, etc. is known to be true, then P is true.
For instance, if it is known that ‘It is cloudy, and it is raining’, then simplification allows the inference of ‘It is cloudy’ and ‘It is raining’.
Simplification requires exactly one reference.
What conjunction is saying is the exact opposite of simplification. If P is known, and Q is known, and R is know, etc. then P and Q and R, etc. is also known.
Take for example, that it is known that ‘I don't like green eggs and ham’, and ‘I would not eat them in a house’, and ‘I would not eat them with a mouse’. Conjunction allows us to infer that ‘I don't like green egss and ham, and I would not eat them in a house, and I would not eat them with a mouse.’.
Conjunction requires at least two references.
Also referred to as the chain rule, hypothetical syllogism states that if one knows that ’if P then Q’, and ’if R then S’, then one can infer ’if P then S’. For example, if it is known ‘if it is raining, then it is cloudy’, and ‘if it is cloudy, then it is not sunny’, and ‘if it is not sunny, then it is cold’, then hypothetical syllogism allows us to infer that ‘if it is raining, then it is cold’. This works with any number of conditional statements, as long as they all follow this pattern.
Hypothetical Syllogism requires at least two references.
Disjunctive syllogism is commonly used when disjunctions are present. It claims that if one knows that ’P or Q or R’, and ’P is false’, and ’R is false’, then Q must be true. This works with any number of disjuncts.
A law of logic, excluded middle asserts that something is either true, or it is not true.
Excluded middle requires zero references.
Constructive Dilemma requires at least three references.
Equivalence rules operate on any valid part of the sentence, and work both ways. Each equivalence rule requires one reference.
|• dn:||Double Negation|
|• Recursion:||Recursion in the equivalence rules|
Implication uses the definition of the conditional. It is also valid to claim something such as ~(~P v Q) v (~R v S) <=> (P → Q) → (R → S), because implication is recursive.
A note to users, typically association is used as P ^ (Q ^ R) <=> (P ^ Q) ^ R. While Aris will allow you to prove that this is equivalent, association allows the removal of one pair of parentheses at a time. (P ^ Q) ^ (R ^ S) <=> P ^ Q ^ R ^ S is also valid in Aris, because association allows recursion, but only when removing several sets of parentheses or adding several sets of parentheses.
Just like addition and multiplication, conjunctions and disjunctions are commutative. This of course means that ‘I would like some pie and I would like some cake’ is the same as saying ‘I would like some cake and I would like some pie’.
Idempotence claims that ‘I like blue and I like blue’ is the same as saying ‘I like blue’.
Equivalence uses the definition of the biconditional. Claiming that ‘P if and only if Q’ is exactly the same as claiming ‘if P then Q’ and ‘if Q then P’. Equivalence is the only rule that works with biconditionals explicitly, and is thus used any time a biconditional is seen.
You probably learned in english class that saying ‘I would not like to disagree’ is the same thing as saying ‘I would like to agree’. That’s what double negation claims.
This is one of the few equivalence rules that deals with conditionals.
Also called absorption. This rule can be used in Boolean mode.
For the convenience of the user, the equivalence rules work recursively. For example
This is an example of using implication recursively. Recursion only works if the rule is being used the same way. For example, removing multiple parentheses with association is fine, however adding and removing parentheses with association is not.
Commutatvitity and idempotence work differently than the others when it comes to recursion. If commutativity is applied to a connective, then no parts of that connective, or parts of those parts, and so on, can be used in commutativity. However, other parts from the sentence can be rearranged. The same goes for idempotence.
The predicate rules are the rules that work specifically with predicate logic.
|• ug:||Universal Generalization|
|• ui:||Universal Instantiation|
|• eg:||Existential Generalization|
|• ei:||Existential Instantiation|
|• bv:||Bound Variable|
|• nq:||Null Quantifier|
|• fv:||Free Variable|
Universal Generalization claims that if a property ‘P’ is true for some arbitrary object, then it is true for all objects. A symbol is arbitrary if nothing is known about, or rather if it was not introduced through a premise or using existential instantiation. Variables
Universal Generalization uses exactly one reference.
Universal Generalization claims that if a property ‘P’ is true for all objects, then it must be true for an object ‘a’.
Universal Generalization uses exactly one reference.
Existential Generalization claims that if ‘P’ is true for some object, then there exists an object for which ‘P’ is true.
Existential Generalization uses exactly one reference.
Existential Instantiation claims that if there exists an object for which property ‘P’ is true, then it can be claimed that some unused object has this property. In this case, ‘a’ becomes a placeholder for the object. Variables
Existential Instantiation uses exactly one reference.
Bound Variable allows the user to substitute any bound variable for another bound variable, given that the second bound variable does not appear anywhere in the scope of the quantifier of the first bound variable. For example, if it is known that Vx(Vy(P(x) ^ P(y))), an invalid use of bound variable would be to state that Vx(Vx(P(x) ^ P(x))).
As an equivalence rule, bound variable uses only one reference, and can work on any part of the sentence.
If a quantifier’s bound variable does not appear in its scope, then the quantifier is said to be null, and can be removed using Null Quantifier.
As an equivalence rule, null quantifier can be used on any part of the sentence, and only uses one reference.
The Prenex Laws are used to move quantifiers to the start of the sentence.
Prenex uses only one reference, and, being an equivalence rule, can be used on any part of the sentence.
Identity asserts that any variable is identical to itself.
Identity does not use any references.
Free Variable allows the user to substitute a free variable for another free variable, given that the two are identical.
Free Variable uses exactly two references.
Aris can be set to use ’boolean mode’, a mode used for boolean algebra. In boolean mode, only equivalence rules that handle negations, conjunctions, or disjunctions and boolean rules can be used. In standard mode, the boolean rules can still be used, however.
|• bi:||Boolean Identity|
|• bn:||Boolean Negation|
|• bd:||Boolean Dominance|
|• sn:||Symbol Negation|
Boolean Identity claims that the conjunction of a sentence with a tautology is logically equivalent to the sentence. It also claims that the disjunction of a sentence an a contradiction is logically equivalent to the sentence.
Boolean Negation claims that the conjunction of a setentence and its contradiction is a contradiction, and the disjunction of a sentence and its negation is a tautology.
Boolean Dominance claims that the conjunction of a sentence and a contradiction is logically equivalent to a contradiction. It also claims that the disjunction of a sentence and a tautology is logically equivalent to a tautology.
Symbol Negation claims that a tautology is the opposite of a contradiction.
This handy little rule allows one to use proofs one has already done. The premises don’t have to match exactly, but they must be of the same form. Aris will check for each symbol it recognizes (connectives, quantifiers, parentheses, comma, and identity). These symbols must match exactly. Aris will then check that the sentences match the correct form, or rather that they appear in the correct order.
For example, if you already did a proof of the form:
And want to reuse it, then your reference sentences must be in the form ‘A’ <-> ‘B’, and ‘A’. In general, they do not have to be in that order, however. Then, your conclusion must be the second half of the biconditional.
This is where Isar interoperability comes in. Instead of selecting a previous Aris proof, a .thy file can be used. Aris will attempt to translate it into a form that it can use, using most of the keywords as references, and the lemmas and theorems as goals. These are the sentences that can be proved. For more information, see Isabelle/Isar.
Given a subproof with premise ’P’ and conclusion (the LAST sentence) ’Q’, one can infer from subproof ’P → Q’. In some circles, this is called conditional introduction.
This introduces a new sequence given a function. The sequence introduced this way must not have been used, and the final argument of the given function must be the bound variable of the sentence.
This rule is how Aris implements mathematical induction. ‘P(z(x))’ is the base case, and the inductive step is ‘P(x)’ → ‘P(s(x))’.
GNU Aris can be customized using the customization dialog, or manually through the customization file. The customization dialog can be accessed through the rules table, under ’Help’.
|• Dialog:||The customization dialog.|
|• Config File:||The customization file format.|
When the dialog appears, there are several tabs. These are explained as follows:
This tab allows the user to customize the keyboard shortcuts that Aris uses with the proof and rules table menus. Each entry corresponds to a menu item. The only option that can not be edited is the ’Contents’ menu keyboard shortcut.
This tab allows the user to customize the keyboard shortcuts that Aris uses with the goal menus.
This tab allows the user to customize the display settings. Included in here are the font size presets, which will be set to the indicated size when activated; the default font size, which Aris will be in when loaded; and the color preferences, which will change the colors that Aris hilights different objects in.
This tab allows the user to set preferences specific to the grade server. The two options here are for the IP address of the grading server, and the password used to authenticate into the server. (see Submission)
For a description of the format of key commands, see Config File.
The config file uses s-expressions to store the customization file. It is stored under the home directory, and called ‘.aris’. There are several key words that it recognizes:
Assigns menu ‘cmd’ to keyboard shortcut ‘key’. The keyboard shortcuts are all in the same format, which is either s or c, a plus sign, then a letter. A c before the letter means ‘Hold control, and press the key’, and s means the same except with the shift key.
Assigns ‘size’ to font type ‘type’. The ‘type’ key word can be either ‘Small’, which means set the small font preset, ‘Medium’, which means set the medium font preset, ‘Large’, which means set the large font preset, or ‘Default’, which means set the font size that Aris loads up with intially.
Assigns ‘color’ to color preference ‘type’. The ‘color’ key word is in hexidecimal.
This allows customization of the grade server’s information (see Submission). The two options for ‘key’ are ‘ip’ and ‘pass’. The ‘ip’ key sets the grade server’s IP address, and the ‘pass’ sets up the password GNU Aris will use for authentication.
GNU Aris allows users to submit their proofs to a grading server, which allows instructors to use Aris in their classes. Aris submits proofs through FTP, and allows users to indicate an email for themselves and an optional email for their instructors.
Submission allows for all open proofs to be submitted. This is done by specifying a problem designation (‘11.10’, ‘nats’, etc.). Only those that have designations are submitted. The designation is changed by editing the text box next to each file name in the submission dialog box.
Grading runs by checking the correctness of the entire proof. It is the responsibility of the grading server to confirm that the proof is the correct proof.
When the files are submitted, Aris submits them to the server, along with a directive file. The directive file will be named ‘USER.directive’, where ‘USER’ is the base name of the email address specified. The files submitted will be renamed to be ‘BASE-USER.tle’, where ‘BASE’ is the original basename of the file. This prevents filename conflicts on the FTP server. The grading server will then run Aris in grade mode (see Options), and use the email provided to email the results back to the user. If the user specified an instructor’s email address, then Aris will CC the instructor.
Sample scripts are included with GNU Aris. These are the files ‘doc/collect.sh’ and ‘doc/collect.el’. The grade server would run ‘collect.sh’, which will call GNU Emacs in batch mode while loading ‘collect.el’. It is ‘collect.el’ that handles the emails.
Sequence Logic, often abbreviated ’seqlog’, is an alternative arithmetical representation system from the standard Peano Axioms in First-Order Logic. Seqlog’s original purpose was allowing more natural definition of recursive functions in FOL.
Seqlog uses the symbols ’s’ (the sucessor function), ’z’ (the zero function), ’v’ (the value function), and ’\0’ (null object).
|• Axioms:||The axioms used by seqlog.|
|• Induction:||An overview of the induction scheme.|
Sequence Logic, often abbreviated ’seqlog’, uses the following six axioms:
The first axiom states that no sucessor is the zero object, or, to put it differently, that the zero object is the first object. The second axiom states that no two different objects have the same sucessor. Using these two axioms, a ’Universal Sequence’ can be defined, in a way similar to how the Peano Axioms define the natural numbers. The third axiom is the definition of a sequence, stating that the value under a given sequence ’S’ of every object ’x’ can be determined by a function. The rule ’sq’ introduces such a sequence (see sq). The fourth axiom defines the nil object. This is a lot like ‘NULL’ in C, or ‘nil’ in lisp.
The natural numbers are defined as a sequence. For example, Vx(x = nat → VyVz(v(nat,y) = v(nat,z) → y = z) ^ Vy(~v(nat,y) = \0)). This will define an infinite sequence (2nd part), that is one-to-one (1st part). Then, to define zero, one simply states Vx(v(nat,z(x)) = 0). This means that the zero’th element of the ‘nat’ sequence is the object ‘0’.
Mathematical induction requires a base case, and an inductive step. In Aris, this is used in conjunction with seqlog. For seqlog, the induction scheme is:
In addition to everything else Aris can do, Aris can also use other proofs from other systems with the lemma rule (see lm).
|• Isabelle/Isar:||The proof system Isar.|
Aris will scan an Isar proof, which is a proof done using Isabelle, and look for certain keywords. This is still being tested, and doesn’t work fully yet. This section will be updated as more of this is implemented.
|• fun:||The ’fun’ keyword.|
|• type_synonym:||The ’type_synonym’ keyword.|
|• lemma/theorem:||The ’lemma’ keyword.|
|• case:||The ’case’ keyword.|
|• primrec:||The ’primrec’ keyword.|
|• definition:||The ’definiton’ keyword.|
|• datatype:||The ’datatype’ keyword.|
|• class:||The ’class’ keyword.|
|• instance:||The ’instance’ keyword.|
|• other:||Everything else.|
Standard definition of a function in seqlog.
Lemmas and theorems are treated the same. Lemmas end up as the goals of the proofs that Aris creates, and are the actual sentences that can be deduced. It takes the ’if-then’ form of each lemma.