ESTA - OVERVIEW

1. ESTA - OVERVIEW • ESTA – Expert System for Text Animation • ESTA can be used to create an expert system for any subject area by building the knowledge base in that domain. ESTA + Knowledge Base = Expert System

2. System interface External Programs Working memory Knowledge Base Explanation Facility Inference Engine Developer’s interface User Interface Knowledge Engineer User

3. Overview • ESTA is a rule based system that has the facilities for • Knowledge base • Inference engine • Graphic user interface • Graphic developer interface • Explanation • Uncertain reasoning • Debugging • interface to system programs

4. Knowledge base • The knowledge base in ESTA is represented by two distinct kind of objects: • Sections • Parameters

5. KnowledgeBase - Sections • Each section describes both how to decide whether any advice should be given to the expert system user, and to which section ESTA should go next. • Consultation begins with the start section. • All knowledge bases in ESTA must begin with a section called start. • Sections can be modified from the section tree. • Updates are dynamically reflected on the section tree.

7. Parameters • Parameters are variables which determine the flow of control between the sections. • Example – car.kb • section start : 'main section‘ • if (problem='starting_problem') do starting_problem • if (problem='overheating') do overheating • if (problem='smell_of_gasoline') do smell_of_gasoline • if (problem='vibration') do vibration • do other • /* An alternative is to write : do_section_of problem */

8. Parameters Sections and parameters within a knowledge base can be listed. Parameters that are not yet assigned a value appears with a ? Mark.

9. Section List of car.kb alternative_transport : Investigation of other transport possibilities another_battery : start the car using another battery bad_idling_section : the engine idles badly bad_running : the engine runs badly battery_dead : the battery is dead brakes : problems with the brakes electrical : check the electrical system gasoline_help : what to do when there is no gasoline on the car horn_problem : problems with the horn lack_of_power_section: the engine feels lacking in power light_problem : problems with the lights other : other problems not dealt with in the start section overheating : the engine gets overheated push_start : push-start the car recharge : recharge the battery smell_of_gasoline : the car smells of gasoline start : main section starting_problem: starting problems vibration : vibrations in the car wet_weather: the weather is wet wiper_motor: problems with a wiper moto

10. Parameter list of car.kb acceleration_noise : there is a noise during acceleration( ? ) another_battery : you can use another battery( ? ) bad_idling : the engine is idling badly( ? ) battery_dead : the battery is dead( ? ) brake_long_travel : the brake has a long travel( ? ) brake_nonoperative : the brakes do not work at all( ? ) brake_otherproblem : the brakes have unclassified problems( ? ) brake_poor : stopping ability is poor( ? ) brake_spongy : the brakes feel spongy( ? ) brake_springy : the brakes feel springy( ? ) brake_veer : car veers to one side when the brakes are applied( ? ) car : the kind of car( ? ) close_to_fueltank : you are close to a gasoline station( ? ) engine_vibration : the engine vibrates excessively( ? ) gasoline_can : you have a spare can with gasoline( ? ) gasoline_ok : there is gasoline in the car( ? ) horn_badnoise : the horn is not working properly( ? )

11. Knowledge Representation Knowledge representation in ESTA is based on the following items: • Parameters • Sections • Title

12. Knowledge Representation Numbers Numbers are either integers or decimal numbers/ Examples: 12 45 234.54 -898.7e3 Strings Strings are a sequence of characters between two single quotes. ‘This is a string.’ Symbols Comparison symbols: < > <> <= >= = Arithmetic operators: * - + / Other symbols : () .. , . /* */

13. Knowledge Representation Comments Comments are enclosed within /* */ Expresions There are three types of expressions in ESTA Text expression Number expression Boolean expression

14. Text Expressions • Text expressions can be used in the explanation field, in the question field, or in the text rules of parameter declerations. • In sections text expressions are used as advice. • The & character can be used to insert new lines into the text. • The text functions are: • concat(X,Y) returns the string X concatenated with Y • startstr(N,X) returns the first N characters from the string X • endstr(N,X) returns the last N characters from the string X

15. Text Expressions • startstr(1, name_of_day) = ‘t’ /* days starting with ‘t’ are accepted*/ • ‘The favorite food of the ’ animal ‘is’ favorite_food ‘.’ (The above string is composed of strings and values of parameters.)

16. Number Expressions Number expressions are used in the rule fields of a number parameter declaration, or in boolean expressions. The usual operators are: • + addition • - subtraction • * multiplication • / division Functions • ESTA includes a full range of mathematical functions Examples Salary – tax 5 * 8 / x – 7 + y (sqrt(cos(x)*cos(x)+sin(x)*sin(x)) + 3) / 2

17. Boolean Expressions • Boolean expressions guide the logic of ESTA’s dialog They consist of : • boolean parameters • comparisons between number expressions • comparisons between strings • compound boolean expressions • A boolean parameter may evaluate to true, false or unknown • Examples • number_of_days_required / 7 < weeks_required • has_retired or is_unwell • date_of_birth < 1960 and owns_a_car

18. Parameters • Parameters are like variables which determine the flow between the sections. • A parameter can be any of the following four types: • boolean parameter • text parameter • number parameter • category parameter • Any parameter can obtain a value in one of the following ways: • From an answer to a question • As a result of applying some rules • An assignment resulting from an assign action

19. Parameters The Decleration Field parameter <parameter-name> [:]<description text> The description text is used to generate replies when a user ask HOW a certain value was established or WHY a certain piece of advice was given. For boolean parameters ESTA phrase is: THE OBJECTIVE IS TO FIND OUT WHETHER <DESCRIPTION TEXT> For number, text or catagory parameters, ESTA phrase is: THE OBJECTIVE IS TO ESTABLISH THE VALUE OF <DESCRIPTION TEXT>

20. Parameters The Decleration Field parameter owns_car ‘you own a car’ type boolean ESTA will generate THE OBJECTIVE IS TO FIND OUT WHETHER YOU OWN A CAR

21. Parameters The Explanation Field • Text in the explanation field is reflected to the user upon ‘explain the question’ request parameter marital_status ‘the people are married’ type category explanation ‘Marital status is determined by whether’ & ‘there exists a marriage certificate for’ & name ‘and’ name_of_partner ‘ or not’ options married, unmarried. question ‘What is the marital status of’ name ‘?’

22. Parameters The Question Field • The question field is used when the value of a parameter is to be determined by an answer to a question. • If the question text is omitted, ESTA will generate a default text for the question, based on the description text of the decleration field and type of the parameter. • For boolean parameters the default question text is: IS IT TRUE THAT <DESCRIPTION TEXT> • For text, category and number: WHAT IS THE VALUE OF <DESCRIPTION TEXT>

23. Parameters The Rules Field • The rules field is used when a parameter’s value should be determined by rules and not by a question • Examples rules ‘blue’ if frequency < 1000, ‘orange’ if frequency >= 1000 and frequency < 2000, ‘red’ if frequency > 2000 and frequency < 3000, ‘invisible’.

24. Parameters The Picture Field The picture field is used to specify a picture that will be shown during the consultation. The picture can be specified by the name of the picture from the picture database or the name of a parameter. picture ‘cars’ /* cars is a picture name from the pictures db. */ picture car /* car is a parameter name */

25. Boolean Parameter parameter wet_weather ‘the weather is wet’ type boolean explanation ‘It has been raining within the last few days or it is foggy’ question ‘Is the weather wet?’ • If the question is not provided ESTA will generate it as: IS IT TRUE THAT THE WEATHER IS WET?

26. Number Parameter parameter height_cm ‘your height in cm’ type number range 100 250 question ‘What is your height in cm?’ ESTA verifies if the input is a number and if range is given further validates if the number is within the range.

27. Text Parameter parameter name ‘the name of the user’ type text question ‘What is your name?’ Category Parameter parameter car ‘the kind of car’ type category explanataion ‘Identify your car with one of the listed types’ option ambulance, policecar, sedan, van. question ‘Which kind of car do you have?’ picture ‘cars’

28. Sections The actions that can be defined within a section are: advice assign call chain do exit stop

29. Sections section start : ‘the first section to be executed’ if car_color = ‘red’ (advice ‘your car is red, try to sell it to the fire brigade’, call sound(200, 100)) if car_color <> ‘red’ and car_color <> ‘blue’ advice ‘Your car is not one of our favourite colors!’ advice ‘That’’s all folks!’ parameter car_color ‘the color of the car’ type text question ‘What is the color of your car?’

30. Sections Assign The assign action is used to assign values to parameters. Examples section start ‘a very short section to illustrate assign’ assign n := 7 + 8 / 2 advice ‘evaluation of 7 + 8 / 2 gives’ n assign n := (7 + 8) / 2 advice ‘evaluation of (7 + 8) / 2 gives’ n ‘as / has higher priority than +.’ & ‘Notice that the parameter changed the value’ parameter n ‘n’ type number

31. Sections Chain The chain action enables ESTA to consult new knowledge bases Example section start : 'Start section in the demo knowledge base' if esta = 'information'(call display('uk_inf.txt'),chain '') if esta = 'car' chain 'car.kb' if esta = 'sanocor' chain 'sanocor.kb‘

32. Sections parameter esta : '' type category explanation 'You can choose to get information about ESTA or to consult a knowledge base.' options information - 'Information about ESTA', car - 'Knowledge base about cars', sanocor - 'Knowledge base about health'. /* rules */ question 'Choose a subject to explore.' picture 'estademo'

33. Sections Do The do action transfers control to another section. Example section start : ‘first section to be executed’ if answer = ‘yes’ (do positive_section, do next_section) if answer = ‘no' do negative_section

34. Sections Do_section_of section start : 'main section' do_section_of problem parameter problem : 'the problem with your car' type category explanation 'Identify the problem with your car as closely as you can. Only those listed are dealt with in this knowledge base.' options starting_problem - 'starting problems' overheating- 'the engine gets overheated' smell_of_gasoline - 'the car smells of gasoline' bad_running- 'the engine runs badly' brakes- 'the brakes' vibration- 'excessive vibrations' wiper_motor- 'the wiper motors' light_problem- 'the lights' horn_problem- 'a faulty horn'. question 'What is the problem with your ' car ' ?' picture car

35. Sections Exit The exit action terminate consultation with the current knowledge base Stop The stop action may be used to optimize rules written in a section. Execution of a stop action indicates that no more actions are to be executed in the containing section.

36. Sections Call The call action is used to call one of the built in procedures in ESTA. call clear_all() – clears all the parameter values in the current knowledge base call clear_value (<parameter_name>) clears a particular parameter value in the current knowledge base display(<filename>) displays the content of a text file in a window on the screen Examples call display(‘inform.txt’) call display(‘c:\\info\\inform.txt’)

37. Sections Call Hyperadvice enables to activate a specific node in a Windows helpfile.The node is shown as a topic in the Windows hypertext help system. Example section brakes 'problems with the brakes' if brake_long_travel call hyperadvice('hypercar.hlp',8) if brake_poor call hyperadvice('hypercar.hlp',13) if brake_veer call hyperadvice('hypercar.hlp',14) if brake_spongy call hyperadvice('hypercar.hlp',17) if brake_springy call hyperadvice('hypercar.hlp',15) if brake_nonoperative call hyperadvice('hypercar.hlp',16) if brake_otherproblem (advice 'This is a difficult problem, but perhaps one of the following is the cause: Maybe the shoes are installed incorrectly with do to leading and trailing ends Broken shoe return spring. Try to find the answer in the car manual', call hyperadvice('hypercar.hlp',5))

38. Sections Call Restore_values restores the ESTA parameters to settings previously saved in a data file. This procedure is used in combination with chaining to other knowledge bases or communicating with external programs called within ESTA. Example call restore_values (‘c:\\esta\\setup.dat’) Save_values(<filename>) saves in a datafile the settings of all parameters currently bound to a value. Example call save_values (‘c:\\esta\\setup.dat’)

39. Sections Call showpic(<picture-name>) displays a picture from the picture database. Example call showpic (‘cars’) sound (<number>, <number>) generates a sound through the computer’s loud speaker lasting the given duration, and with the given frequency. Example call sound (10, 100) System(command_string) is used to call other applications from ESTA Example call system(‘myprog.exe’)

40. Title To represent the whole knowledge base a title can be used. The title can either be a plain text or a picture. Example You can specify a picture as a title *cars* or you can specify plain text as a title Car Knowledge Base

41. Reasoning With Uncertainty Certainty Factor • cf_and(P1, P2) -> P3 P3 is the lowest of the P1 and P2 • cf_or(P1, P2) -> P3 P3 is the biggest of the P1 and P2 • cf_not(P1) -> P3 P3 is (1-P1) • cf_add(P1, P2) -> P3 P1+P2*(1-P1) both P1, P2 > 0 (P1+P2)/(1- min(abs(P1), abs(P2)) one of P1 or P2 <0 -cf_add(-P1, -P2) both P1, P2 < 0

42. Reasoning With Uncertainty section weather ‘example section’ advice ‘The statement “it is very cold weather’’ is true with a certainty factor of’ cold_weather_cf parameter cold_weather_cf ‘certainty factor for cold weather’ type number range –1.0 1.0 rules cf_add(cold_because_of_snow, cold_because_of_ice). parameter cold_because_of_ice type number range –1.0 1.0 rules 0.8 if ice_on_the_river, -1.0.

43. Reasoning With Uncertainty parameter cold_because_of_snow type number range –1.0 1.0 rules 0.7 if it_is_snowing, -1.0. parameter it_is_snowing ‘It is snowing’ type boolean question ‘Is it snowing?’ parameter ice_on_the_river ‘there is ice on the river’ type boolean question ‘Is part of the river frozen over?’

44. Reasoning With Probability parameter prob ‘probability’ type number rules 1 if weight_loss and appetite_loss and fever and itching, 0.67 if weight_loss and fever and itching, 0.75 if weight_loss and appetite_loss and fever, 0.6 if appetite_loss and fever and itching, 0.5 if weight_loss and fever, 0.5 if weight_loss and appetite_loss, 0.35 if weight_loss and itching, 0.5 if appetite_loss and fever, 0.1 if itching. parameter hodga ‘hodgin a’ type boolean rules true if prob > 0.6.

45. Debugging • Log of the consultation can be taken by opening a dialog box before consultation begins. • File – new- new dialog • Begin consultation • ....... • Stop consultation • Investigate the consultation log • Continue consultation

47. Pictures in ESTA • Pictures are stored in PICTURES.DBA • The ESTA system includes hotspot editor allowing the specification of selectable subfields in a picture • This feature is used in conjunction with category parameters in which the options correspond to fields in the attached picture

48. DDE Communication • DDE (Dynamic Data Exchange) is a Windows protocol that lets applications talk. • ESTA can be interfaced to all Windows applications that support DDE. • You can send data to applications, you can receive information from the application, you can even execute commands in the applications.

49. DDE Communication • A conversation with a DDE server is created by the function: dde_initiate(Application, Topic) • This function returns a channel number used to identify the conversation dde_execute(Channel, Command) • Sends the commands in Command to the server for execution.Channel is the number returned from dde_initiate.

50. DDE Communication dde_poke(Channel, Item, Data) sends data to the server. Item specifies the destination. • dde_poke(CH, “R1C1”, “hello”) inserts hello to row1, column1 dde_request(Channel, Item) is used to retrieve a data item from the server.