COBA 2.0 Manual
Contents
1. 2 Press the revert button immediately to the right of the drop down list and 3 A dialog box with options Revert and Cancel will ask you to con firm the revert operation Either click option Revert to revert or click option Cancel to cancel the revert v Revert Confirmation Are you sure you want to revert to KB Snapshot 1 To revert the current EB IC list on the integrity constraints screen to a particular EB IC snapshot do the following steps 1 Select the number of the snapshot from the drop down list below the EB IC Snapshots list 2 Press the revert button immediately to the right of the drop down list and 3 A dialog box with options Revert and Cancel will ask you to con firm the revert operation Either click option Revert to revert or click option Cancel to cancel the revert To revert the current CB IC list on the integrity constraints screen to a particular CB IC snapshot do the following steps 1 Select the number of the snapshot from the drop down list below the CB IC Snapshots list 17 2 Press the revert button immediately to the right of the drop down list and 3 A dialog box with options Revert and Cancel will ask you to confirm the reversion Either click option Revert to revert or click option Cancel to cancel the reversion 4 Encoding Input in COBA Syntax To use COBA you must encode all your input sentences according to the COBA syntax COBA accepts almost all alphanumerical st2. Enter a senten Main Screen O Integrity Constraints ooo O History of Changes e Main Screen You will be presented with the main user interface through which you may 1 add sentences to or remove sentences from the knowledge base s the revision list and the contraction list 2 change the type of belief change the search algorithm for finding equivalence sets and the type of merging and 3 carry out parallel change on a belief change scenario and subsequently reject or commit a resultant knowledge base e Integrity Constraints You will be presented with the integrity constraints IC inter face through which you may add sentences to or remove sen tences from the entailment based IC list and the consisteny based IC list e History of Changes You will be presented with the history of changes interface through which you may revert to an older knowledge base snapshot as 10 well as view the log of changes made to the knowledge base list the entailment based IC list and the consistency based IC list 3 1 4 Help Menu File Settings Screen Help Enter a sentence About COBA COBA Manual COBA JavaDOCs e About COBA You will find information on the authors and implementers of COBA 2 0 in a dialog window e COBA Manual You will see the COBA 2 0 user manual in a new browser win dow This function is disabled if you are not running the COBA applet in a Web browser
3. e COBA JavaDOCs You will see the COBA 2 0 JavaDOCs in a new browser window This function is disabled if you are not running the COBA applet in a Web browser 3 2 The Main Screen The first screen is the main user interface through which you may 1 add sentences to or remove sentences from the knowledge base s the revision list and the contraction list 2 change the settings for the type of belief change the search algorithm for equivalence sets and the type of merging and 3 carry out parallel change on a belief change scenario and sub sequently reject or commit a resultant knowledge base 11 bd Applet Viewer cobaUl COBAApplet class onnan Applet File Settings Screen Help Enter a sentence Add to KB New Add for Revision Add for Contraction Knowledge Base s Sentences for Revision New Knowledge Base Preview defaut cnf Odnf Sentences for Contraction default ent dnf Reject Commit defaut Qenf Cant iy defaut Qf Odan Applet started The selected knowledge base KB is the one whose index appears at the top of the drop down list next to the Add to KB button on the main screen To add a sentence to the selected KB you may e either type a sentence into the entry field and press the Add to KB button e or append to the selected KB an input file of sentences by se lecting from the menu File gt
4. Append to KB Selected e or replace the KB list with an input file of sentences by selecting from the menu File gt New KB To add a sentence for revision you may e either type a sentence into the entry field and press the Add for Revision button or append to the revision list an input file of sentences by se lecting from the menu File gt Append to Revisor e or replace the revision list with an input file of sentences by selecting from the menu File gt New Revisor 12 To add a sentence for contraction you may e either type a sentence into the entry field and press the Add for Contraction button e or append to the contraction list an input file of sentences by selecting from the menu File gt Append to Contractor e or replace the contraction list with an input file of sentences by selecting from the menu File gt New Contractor If a sentence being added has a syntactic error the applet will display a red error message above the entry field and will not add the sentence Also if the default consistency check is on and a sentence being added is either inconsistent or mutually inconsistent with the selected KB the revision list or the contraction list it is being added to the applet will display a red error message above the entry field and will not add the sentence You may click the Default CNF and DNF buttons to view the sentences in a list in the default
5. CNF and DNF format respectively To remove a sentence from the selected KB the revision list or the contraction list click the sentence and press the x button in the lower right hand corner of the corresponding list To erase the entire KB list revision list or contraction list press the broom button in the lower right hand corner of the corresponding list A dialog box with options Erase and Cancel will ask you to confirm the erasure To specify the settings for computing the belief change scenario you may either use the Settings menu or click the toggle buttons near the bottom of the main screen This bottom panel will also display informative messages and instruc tions where appropriate Here are the steps you should follow to carry out a belief change 1 Once you have specified the settings and the belief change sce nario you want to compute press the Get Parallel Change button 2 If there are inconsistencies in a knowledge base the revision list or the EB IC list or if there are mutual inconsistencies between the revision list the EB IC list the contraction list and the CB IC list then a dialog box will notify you of all such inconsistencies Until you resolve all such inconsistencies and press the Get Parallel Change button again the belief change scenario will not be computed 3 Preview the proposed resultant KB s in the New Knowledge Base Preview list In the case of choice change there may be mo
6. confirmation dialog about your decision to replace the current sentences for revision You will then be asked to select an input file to import as the new sentences for revision e New Contractor If the contraction list is non empty you will be presented with a confirmation dialog about your decision to replace the current sentences for contraction You will then be asked to select an input file to import as the new sentences for contraction e New Entailment based IC If the EB IC list is non empty you will be presented with a confirmation dialog about your decision to replace the current EB IC s You will then be asked to select an input file to import as the new EB ICs e New Consistency based IC If the CB IC list is non empty you will be presented with a confirmation dialog about your decision to replace the current CB IC s You will then be asked to select an input file to import as the new CB ICs e Append to KB Selected You will be asked to select an input file to append to the selected knolwedge base KB In other words the sentences in the first KB in the input file will be added to the selected KB and the sentences in the second KB in the input file will be added to KB immediately after the selected KB and so on The indexing of the sentences in a knowledge base starts at 0 The indexing of knowledge bases starts at 0 The selected knowledge base is the one whose index appears at the top of the d
7. sentence should be listed on a separate line A single revisor will be constructed as a conjunction by taking each sentence as a conjunct The third argument Contraction_File is the path of the file containing the sentences for contraction Each line is interpreted as an independent con traction sentence Consequently while p amp q means that p amp q is to be q on two seperate lines means that both p and q are to be obliterated from the consequences of the resultant knowledge base obliterated from the consequences of the resultant knowledge base P listed 2 2 2 Using the COBA Command line Tool The COBA command line tool provides an interactive menu of tasks to perform 1 Specify the path of the KB input file You will be prompted for the path of the KB input file you want to load 2 Specify the path of the revision input file You will be prompted for the path of the revision input file you want to load 3 Specify the path of the contraction input file You will be prompted for the path of the contraction input file you want to load 4 Specify the path of the entailment based integrity constraints input file You will be prompted for the path of the entailment based integrity con straints input file you want to load 5 Specify the path of the consistency based integrity constraints input file You will be prompted for the path of the consistency based integrity con straints input file you wan
8. the broom button in the lower right hand corner of the CB IC list A dialog box with options Erase and Cancel will ask you to confirm the erasure 3 4 The History Screen The third and final screen presents three lists of older snapshots you may revert to You will find the log of changes for three lists 1 KB the removals replacements and changes committed 2 EB IC and 3 CB IC the removals and replacements made Each snapshot k captures the list contents immediately before change k is applied The numbering of the snapshots starts at 0 and continues in ascending order 15 File Settings Screen Help This page logs the history of changes made to three lists 1 KB the removals replacements and changes committed 2 EB IC and 3 CB IC the remova Each snapshot k records the list contents immediately before change k is applied KB Snapshots KB Change History EB IC Snapshots EI 0 Before Changes Changes to KB KB 0 Revisions none p Contractions none KE 1 EB ICs none p q CB ICs none 1 Before Removal 1 Removal from KB KB 0 KB 0 d p amp q amp p amp q p A Replacement of KB d File cs quests daphnel 1 e Before Replacement KB 0 Go to EB kal Go p amp q amp p H amp Q e CB IC Snapshots CI LEE MA Go to KB ed co tau Reven to Old KB a PT B Change ov Go to CB L_ i
9. 3 4 For each maximal set EQ create a belief change extension by a unnumbering in K every numbered atom p if p p EQ b replacing every numbered atom p with p if p p EQ Ky Ac Ko pA Gar Kyi A Ko pAqAnr ki A K2 pA aq Ar KAn Ko pA gr Kyi A K2 pA mq A r ki A K2 7p Anq A r Ky A K2 p q A gt r Kyi Ac Ke 5 The resultant knowledge base will simply be either the dis junction of all such belief change extensions for skeptical be lief change or one such belief change extension for choice belief change Skeptical Belief Change kK A K gt 2 T To try this example load the files example3 kb as the knowledge bases 24
10. COBA 2 0 Manual Daphne Liu lt daphnel sfu ca gt Sven Thiele lt sthiele rz uni potsdam de gt April 8 2005 1 Introduction COBA 2 0 is a Java implementation of the consistency based approach for be lief change invented by James P Delgrande and Torsten Schaub This approach presents a framework within which different operators for the revision con traction and merging of knowledge bases are defined With COBA you can construct any belief change scenario that entails a combination of merging re vision and contraction and compute the resultant knowledge base 2 Getting Started To compile and run COBA you need to have Java VM version 1 4 or higher installed on your machine 2 1 Compiling the Source Code Once you have the Java VM version 1 4 or higher installed simply download and unpack the archive coba2 tar gz You will find inside the unpacked archive several scripts readily available for compilation and execution purposes You may re configure the paths in the scripts for your local machine To recompile COBA you can use the included Makefile with two targets e make app to compile the command line version and build the JAR archive applet cobaapp jar to store the compiled command line version e make applet to compile the applet and build the JAR archive applet cobaUI jar to store the compiled applet version To run COBA you can either start the command line version with run_app KB_File or none Revisio or
11. Go To view a particular KB snapshot you may e either use the vertical scrolling bar that appears on the right hand side of the KB Snapshots list when there are more snap shots than can be displayed on one screen e or select its snapshot number from the drop down list below the KB Snapshots list To view a particular EB IC snapshot you may e either use the vertical scrolling bar that appears on the right hand side of the EB IC Snapshots list when there are more snapshots than can be displayed on one screen e or select its snapshot number from the drop down list below the EB IC Snapshots list 16 To view a particular CB IC snapshot you may e either use the vertical scrolling bar that appears on the right hand side of the CB IC Snapshots list when there are more snapshots than can be displayed on one screen e or select its snapshot number from the drop down list below the CB IC Snapshots list Selecting a snapshot number from a drop down list will cause the first line of the selected snapshot to be highlighted and displayed in the snapshots list above Similarly selecting a change number from a drop down list will cause the first line of the selected change to be highlighted and displayed in the change history list above To revert the current KB list on the main screen to a particular KB snapshot do the following steps 1 Select the number of the snapshot from the drop down list below the KB Snapshots list
12. IC button e or append to the list an input file of sentences by selecting from the menu File gt Append to Consistency based IC e or replace the list with an input file of sentences by selecting from the menu File gt New Consistency based IC If a sentence being added has a syntactic error the applet will display a red error message above the entry field and will not add the sentence Also if the default consistency check is on and a sentence being added is either inconsistent or mutually inconsistent with the list it is being added to the applet will display a red error message above the entry field and will not add the sentence You may click the Default CNF and DNF buttons to view the sentences in a list in the default CNF and DNF format respectively To remove an entailment based integrity constraint EB IC click the IC you want to remove and press the x button in the lower right hand corner of the EB IC list To erase the entire EB IC list press the broom button in the lower right hand corner of the EB IC list A dialog box with options Erase and Cancel will ask you to confirm the erasure Vv Clear All_ Confirmation D Are you sure you want to erase ALL the Entailment Based Integrity Constraints To remove a consistency based integrity constraint CB IC click the IC you want to remove and press the x button in the lower right hand corner of the CB IC list To erase the entire CB IC list press
13. changes made to the consistency based integrity constraints Exit You can terminate the applet and close the enclosing browser which displays the applet 3 1 2 Settings Menu File Settings Screen Help Ente Skeptical Change Choice Change E O AllDetEQ1 AllDetEQ2 la Default Merge v Projection Merge Consistency Check Skeptical Change You can click this item to change the type of belief change to skeptical change Choice Change You can click this item to change the type of belief change to choice change AllDetEQ1 You can click this item to change the search algorithm for find ing equivalence sets to AllDetEQ1 as described in the COBA paper by James Delgrande and Torsten Schaub AllDetEQ2 You can click this item to change the search algorithm for find ing equivalence sets to AllDetEQ2 which is more efficient as described in the COBA paper by James Delgrande and Torsten Schaub Default Merge You can click this item to change the type of merge to de fault basic merge Projection Merge You can click this item to change the type of merge to projection merge Consistency Check You can click this item to turn the default consistency check on or off A checked box indicates that the default consistency check is on which means that a consistency check will be performed automatically every time a sentence is added to the
14. f p p EQ and finally c conjoining this with the revisior a K e a pA 79 K a p A q 5 The resultant knowledge base will simply be either the dis junction of all such belief change extensions for skeptical be lief change or one such belief change extension for choice belief change Skeptical Belief Change KHa pA 7 qV p q To try this example load the files example1 kb as the knowledge base and examplel rev as the revision input file 5 2 Contraction Contraction is complementary to revision in that certain information is to be removed from the knowledge base This means the sentence we want removed from the knowledge base should not be a conse quence of the resulting knowledge base It is important to know that contracting a sentence does not necce sarily mean that the negation of this sentence is in the resulting knowledge base as that would simply be revising the knowledge base with the negated sentence The resulting knowledge base should have at least one model in which the contraction sentence is not true Given a knowledge base K pV q and a contraction sentence a pV q what should the resulting knowledge base look like The original knowledge base has only three models p q p q and p q and all are consistent with the contraction sentence Here a reason able extension could be a revision with the negation of the contraction sentence however we may lose too much o
15. f the original knowledge base because then the resulting knowledge base would have only mod els where the negation of the contraction sentence is true As you will see in the steps below COBA avoid this problem We will now show step by step how this contraction example is computed by COBA 1 Find the common atoms between the knowledge base and the contraction sentence CommonAtoms p q 2 Create a new knowledge base K by priming the common atoms in K K p vq 21 3 Find all maximal equivalence sets EQ p p p E CommonAtoms such that K U a U EQ is satisfiable EQ 4 For each maximal set EQ create a belief change extension by a unpriming in Kk every primed atom p if p p EQ b replacing every primed atom p with if p p EQ and finally c replacing all remaining primed atoms with T K a T 5 The resultant knowledge base will simply be either the dis junction of all such belief change extensions for skeptical be lief change or one such belief change extension for choice belief change In this case there is only one possible resulting knowledge base for skeptical change and for choice change K a T The resulting knowledge base has now three models p q p q and p q One model conflicts with the contraction sentence while the other two are the same as in the original knowledge base To try this example load the files example2 kb as the
16. files You may do so by e either running the default run_applet script with the policy file pol icy revision policy e or modifying the codeBase path and copying the policy in policy revision policy to your local java policy file See Sun s Web page at http java sun com j2se 1 4 2 docs guide security PolicyFiles html DefaultLocs for the default location of your java policy file 3 1 Using the Applet Menu The COBA applet has a menu bar of four items File Settings and Screen You will learn about each of these four menus in the following subsections 3 1 1 File Menu File Settings Screen Help New KB New Revisor New Contractor New Entailment based IC New Consistency based IC Ad for Revision Append to KB New Append to Revisor Append to Contractor Append to Entailment based IC Append to Consistencg based IC Sentences for Revisi Save KB As Save Revisor As Save Contractor As Save Entailment based IC As Save Consistency based IC As ac Save KB History As Save EB IC History As Save CB IC History As Teas e New KB If the KB list is non empty you will be presented with a confir mation dialog about your decision to replace the current knowl edge base s You will then be asked to select an input file to import as the new knowledge base s e Revisor If the revision list is non empty you will be presented with a
17. knowledge base and example2 con as the contraction input file 5 3 Merging The problem of merging knowledge bases with possibly conflicting pieces of information could arise if different sources such as sensor data or reports of multiple agents must be combined In contrast with revision and contraction one normally does not have the knowl edge that one source is preferred over the others Although the simplest solution would be to take the disjunction of all sources this may result in so much information loss that we may get a resulting knowledge base with too many models Rather we want to find a resulting knowledge base which only has the common models among the source knowledge bases Given a knowledge base 1 K p q r and a knowledge base 2 K apA7qA7r what should the resulting knowledge base look like COBA provides two different merge operators default basic merge and projection merge We will first show step by step how this merging example is com puted by COBA using default basic merge 1 Find the common atoms between the two knowledge bases CommonAtoms p q r 22 2 Create a new knowledge bases K by numbering the common atoms in K with i Ki p Aqg Ar K3 p Ang Aar 3 Find all maximal equivalence sets EQ p p p CommonAtoms such that UJK UN K U EQ is satisfiable BQ p p q r r EQ pap Pag rar 4 For each maximal set EQ create a belief change exte
18. mp a is a contradiction The conjunction of EB ICs is a contradiction Conflicting pairs of contraction sentences and revision sentences error message The contraction indexed 0 is inconsistent with the conjunction of revis Conflicting pairs of CB IC sentences and contraction sentences error message The contraction indexed 2 is inconsistent with the CB IC indexed 0 ind Conflicting pairs of CB IC sentences and revision sentences error message The CB IC indexed 1 is inconsistent with the conjunction of revisions Conflict between the conjunction of EB IC sentences and a CB IC sentence error message The CB IC indexed 3 is inconsistent with the conjunction of EB ICs ind Conflicting pairs of EB IC sentences and contraction sentences error message The contraction indexed 6 is inconsistent with the conjunction of EB IC 19 10 Conflict between the conjunction of revision sentences and the conjunction of EB IC sentences error message The conjunction of revisions is inconsistent with the conjunction of EE 5 The First Examples Now that you have got the program running let s start executing some belief change scenarios The subdirectory samples of the unzipped archive contains a col lection of sample test files In the following sections you will see several examples of how you can compute belief changes using COBA 5 1 Revision The problem of revision arises when for example an intelligent agent has t
19. n independent contraction sentence Consequently while p amp q means that p amp q is to be obliterated from the consequences of the resultant 18 knowledge base a listed on two seperate lines means that both p and q are to be obliterated from the consequences of the resultant knowledge base Entailment based integrity constraints EB IC input file Each sentence should be listed on a separate line A single EB IC will be constructed as a conjunction by taking each sentence as a conjunct Consistency based integrity constraints CB IC input file Each line is interpreted as an independent CB IC sentence As an example the following table shows the format of some valid input files KB_File samplekb Revision_File samplerev Contraction_File samplecont EBIC_Fi KB 1 q P a amp b c p amp qk amp r p q x amp Cy z KB qt s Special Cases of Belief Change Scenarios to Avoid The following special cases of belief change scenarios should be avoided 1 A tautolgy as a contraction sentence error message The contraction pt p is a tautology A contradiction as a CB IC sentence No error message sentence not added A contradiction as a revision sentence error message The revision akbk amp a is a contradiction The conjunction of revisions is inconsistent A contradiction as an EB IC sentence error message The EB IC akb a
20. nsion by a unnumbering in K every numbered atom p if p p EQ b replacing every numbered atom p with p if p p EQ and finally c conjoining the two unnumbered knowleledge bases with the disjunction of all source knowledge bases ki Ac Ko pAqAr Ky A Ko gt p A aq ar 5 The resultant knowledge base will simply be either the dis junction of all such belief change extensions for skeptical be lief change or one such belief change extension for choice belief change Skeptical Belief Change kK AK pAq Ar V ap 7qA71 The default basic merge operator at least retains as minimal in formation the disjunction of both sources In contrast the projection merge does not keep this information We will next show step by step how this merging example is com puted by COBA using projection merge 1 Find the common atoms between the two knowledge bases CommonAtoms p q r 2 Create new knowledge bases K by numbering the common atoms in K with i Ki p g Ar KZ op Ang Aar 3 Find all maximal equivalence sets EQ p p p Common Atoms such that J K U EQ is satisfiable EQ p p 4 r r EQ pl p q4 q r r EQ p p r r EQ pP p q r r EQ p 0 7 q r r EQ6 p p r r EQ pP p q r r EQs pP p q r r 2
21. o modify his or her belief s because he or she may have required more recent or preferred information The new information may con flict with the agent s older beliefs The ability to revise one s knowledge is essential for sound rea soning While an agent wants to incorporate the new information into their beliefs the agent also desires to 1 retain as much of his or her existing knowledge as consistently possible and 2 maintain a consistent set of beliefs Given a knowledge base K p q and a revision sentence a p V q what should the resulting knowledge base look like Simply conjoining the knowledge base with the revision sentence would violate consistency since pA q A p V 7q L On the other hand disjoining the two would still yield a model with p q true although the revision sentence states that either p or q must be false We will now show step by step how this revision example is com puted by COBA 1 Find the common atoms between the knowledge base and the revision sentence CommonAtoms p q 2 Create a new knowledge base K by priming the common atoms in K K Aa 3 Find all maximal equivalence sets EQ p p p E CommonAtoms such that K U a U EQ is satisfiable EQ p p EQ2 7 q 20 4 For each maximal set EQ create a belief change extension by a unpriming in Kk every primed atom p if p p EQ b replacing every primed atom p with p i
22. re than one resul tant KBs each one listed on a separate line 13 4 Either press either the Reject button if you wish to discard the proposed KB s and keep the current KB list or choose a proposed KB by clicking it and press the Commit button to replace the current KB list with the selected proposed KB 3 3 The Integrity Constraints Screen The second screen is the integrity constraints IC interface through which you may add sentences to or remove sentences from the entailment based EB IC list and the consistency based CB IC list File Settings Screen Help Enter an integrity constraint dC Add Entailment Based IC Add Consistency Based IC Entailment Based Integrity Constraints a amp b Consistency Based Integrity Constraints default Omt Cant D A defaut OQent Oant WwW Remove Selected Sentence To add an entailment based integrity constraint EB IC you may e either type a sentence into the entry field and press the Add Entailment Based IC button e or append to the list an input file of sentences by selecting from the menu File gt Append to Entailment based IC e or replace the list with an input file of sentences by selecting from the menu File gt New Entailment based IC 14 To add a consistency based integrity constraint CB IC you may e either type a sentence into the entry field and press the Add Consistency Based
23. rings for atom names The exceptions are the symbols in the following comma separated list apostrophe amp gt and Note that T and F stand for a tautology and a contradiction respec tively You can use the following connectives to express more complex formulas e A the negation of formula A A amp B the conjunction of formula A and formula B e A B the disjunction of formula A and B e A gt B formula A implies formula B e A B formula A is equivalent to formula B The syntax of the input sentences is strict A top level sentence with a connective operator amp and or gt implies or is equivalent to must be enclosed in parentheses Parentheses inside a sentence however are optional and are used only to enforce parsing preference For example a amp b c is a valid input sentence and is different from a amp b c whereas a top level sentence like a amp b is syntactically malformed 4 1 Encoding Input Files in COBA Syntax Formats of input files vary according to the type of list the sentences are added to e KB input file Each knowledge base should be preceded by a line KB without the double quotes each sentence should be listed on a separate line e Revision input file Each sentence should be listed on a separate line A single revisor will be constructed as a conjunction by taking each sentence as a conjunct e Contraction input file Each line is interpreted as a
24. rity constraints input file consistency based integrity constraints input file Set the type of change default skeptical change Set the equivalence set search algorithm default AllDetEQ2 Specify the type of merge default default merge Execute the belief change scenario 10 Exit COBA 2 0 Please select a task by entering its number Jf 3 Using the COBA Applet The applet version of COBA offers several additional and distinct advantages over the command line tool Specifically you may 1 add input from your local files or to type in the input yourself 2 view the history logs for the changes made to the knowledge base KB list the entailment based integrity constraints EB IC list and the consistency based integrity constraints CB IC list revert to an older KB EB IC or CB IC snapshot 4 save any list to an output file 5 view sentences in the default CNF or DNF format 6 turn off consistency checks on an entry and its mutual consistency with its list 7 reject or commit a resultant knowledge base 8 view the COBA user manual and JavaDocs in external browser windows if the applet is running in an html document You may start the COBA applet with the script run_applet The COBA applet needs your permission to read and create files on your local machine You must explicitly grant this permission to cobaUI jar if you wish to import files into the applet or save the applet output to
25. rop down list next to the Add to KB button on the main screen e Append to Revisor You will be asked to select an input file to append to current revision list e Append to Contractor You will be asked to select an input file to append to current contraction list e Append to Entailment based IC You will be asked to select an input file to append to current list of entailment based integrity constraints e Append to Consistency based IC You will be asked to select an input file to append to current list of consistency based integrity constraints Save gt You can save any one of the eight lists to the most recent file you last saved this list to If such a file does not already exist you will be prompted for the name of a new output file The output file format for any one of the three history lists is as follows 1 The snapshots before the changes in chronological order fol lowed by The line THE FOLLOWING ARE THE CORRESPOND ING CHANGES without the double quotes followed by The corresponding changes for the snapshots in chronological order KB You will save the current list of knowledge base s Revisor You will save the current revision list Contractor You will save the current contraction list Entailment based IC You will save the current list of entailment based integrity con straints Consistency based IC You will save the current list of consistency based integrit
26. selected KB the revision list or the entailment based integrity constraints list An unchecked box means that this default consistency check will not be performed automatically Perform Consistency Check gt This item is enabled once you have switched the default consistency check off The reason is that with default consistency check on a consistency check is automatically performed every time a sentence is added to the selected KB the revision list or the entailment based integrity constraints list e KB Selected If there is any inconsistencies or mutual inconsistencies in the selected knowledge base you will be advised of them in a dialog window The indexing of the sentences for the selected knowledge base starts at 0 The selected knowledge base is the one whose index appears at the top of the drop down list next to the Add to KB button on the main screen The indexing of knowledge bases starts at 0 e Revision List If there is any inconsistencies or mutual inconsistencies among the sentences in the revision list you will be advised of them in a dialog window The indexing of the sentences for revision starts at 0 e EB IC List If there is any inconsistencies or mutual inconsistencies among the entailment based integrity constraints you will be advised of them in a dialog window The indexing of the entailment based integrity constraints starts at 0 3 1 3 Screen Menu File Settings Screen Help
27. start the applet version with run_applet run_app is a script that starts the executable cobaapp jar the compiled command line version of COBA Please ensure that the path to java and the path to cobaapp jar are set correctly for your machine run_applet is a script that calls the appletviewer to start the JAR archive cobaUl jar the compiled applet version of COBA with the security policy policy revision policy Please ensure that the path to appletviewer and the path to cobaUI jar are set correctly for your machine 2 2 The COBA Command line Tool The command line version of COBA presents an interactive menu with which you can specify tasks to perform The default type of belief change is skeptical change the default type of merging basic merge and the default equivalence set search algorithm AllDetEQ2 2 2 1 Running the Command line Tool Script You may start the command line tool by running the script run_app with three arguments run_app KB_File or none Revision_File or none Contraction_File or none If any one of the three arguments is not used input none without the double quotes instead The first argument KB_File is the path of the file containing the sentences of the knowledge base s Each knowledge base should be preceded by a line KB without the double quotes each sentence should be listed on a separate line The second argument Revision_File is the path of the file containing the sentences for revision Each
28. t to load 10 Set the type of change default skeptical change You will be prompted for the belief change type skeptical change or choice change Set the equivalence set search algorithm default AllDetEQ2 You will be prompted for the search algorithm All DetEQ1 or AllDetEQ2 Specify the type of merge default default merge You will be prompted for the merge type default basic merge or projection merge Execute the belief change scenario You will see the resultant knowledge base s for the current belief change scenario Exit COBA 2 0 You will terminate and exit the COBA command line tool For tasks 1 5 and 9 you may see error messages if any input sentence is syntactically malformed or if there is an inconsistency error You should fix the error s and try to perform the task again To select a specific task from the menu simply enter its number at the prompt Terminal File Edit View Terminal Go Help bash 2 05b sh run_app usage java jar cobaapp jar KB_File Revisor_File Contractor_File bash 2 05b sh run_app temp kb txt none none Welcome to the COBA 2 0 Command Line Version The 1 2 3 4 5 6 7 8 9 COBA 2 0 Command Line Task Menu Specify the path of the Specify the path of the Specify the path of the Specify the path of the Specify the path of the KB input file revision input file contraction input file entailment based integ
29. y con straints KB History You will save the list of changes made to the knowledge base s EB IC History You will save the list of changes made to the entailment based integrity constraints CB IC History You will save the list of changes made to the consistency based integrity constraints All You will save all of the eight lists above Save As gt You will be prompted for the name of the output file to which you can save one of the eight lists The output file format for any one of the three history lists is as follows 1 The snapshots before the changes in chronological order fol lowed by 2 The line THE FOLLOWING ARE THE CORRESPOND ING CHANGES without the double quotes followed by 3 The corresponding changes for the snapshots in chronological order Save KB As You will save the current list of knowledge base s Save Revisor As You will save the current revision list Save Contractor As You will save the current contraction list Save Entailment based IC As You will save the current list of entailment based integrity con straints Save Consistency based IC As You will save the current list of consistency based integrity con straints Save KB History As You will save the list of changes made to the knowledge base s Save EB IC History As You will save the list of changes made to the entailment based integrity constraints Save CB IC History As You will save the list of
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