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RE: [aima-talk] POP Planner Implementation: Choose-Operator

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  • E etech058
    Hello, Which language will you use for implementation? Best regards/chenyu ... From: yougooh2000 [mailto:hugo.ferreira@mail.telepac.pt] Sent:
    Message 1 of 7 , Dec 11, 2003
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      Hello,
      Which language will you use for implementation?

      Best regards/chenyu

      -----Original Message-----
      From: yougooh2000 [mailto:hugo.ferreira@...]
      Sent: 2003年12月12日 0:06
      To: aima-talk@yahoogroups.com
      Subject: [aima-talk] POP Planner Implementation: Choose-Operator

      Hi,

      I am attempting to implement the POP planner as is described in AIMA's
      1st version (Chap. 11.). I am having doubts regarding the call
      "choose-operator" that is described in the book. The
      pseudo-code says
      that if the step to add (S-add) is selected from operator's list (not
      the plan), then it is necessary to:
      1)Add this new step to the plans already existing steps.
      2)Add the ordering: Start < S-add < Finish

      I cannot understand what is the need for step 2). Say for example I
      start the planner with a minimal plan of {Start, Finish} and on
      selecting the first operator, I only find an S-add from the operator's
      list. I will have to add the ordering S-add < S-need, where S-need =
      Finish, according to the 5th pseudo-code line of the call. After that
      I see that I have to execute steps 1 and 2 as described above. Now I
      have a _repeated_ attempt to add ordering S-add < Finish.

      I have considered not doing step 2) which would result in a missing
      ordering Start < S-add. I figure this will eventually be added to the
      orderings when I process step S-add (i.e: attempt to satisfy its
      pre-conditions).

      Am I missing something?

      TIA.
      Hugo Ferreira.



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    • yougooh2000
      Hi, First versions will (hopefully) be in Prolog. This is for research purposes. Regards, Hugo. ... AIMA s ... (not ... operator s ... that ... the ...
      Message 2 of 7 , Dec 12, 2003
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        Hi,

        First versions will (hopefully) be in Prolog. This is for research
        purposes.

        Regards,
        Hugo.


        --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...> wrote:
        > Hello,
        > Which language will you use for implementation?
        >
        > Best regards/chenyu
        >
        > -----Original Message-----
        > From: yougooh2000 [mailto:hugo.ferreira@m...]
        > Sent: 2003Äê12ÔÂ12ÈÕ 0:06
        > To: aima-talk@yahoogroups.com
        > Subject: [aima-talk] POP Planner Implementation: Choose-Operator
        >
        > Hi,
        >
        > I am attempting to implement the POP planner as is described in
        AIMA's
        > 1st version (Chap. 11.). I am having doubts regarding the call
        > "choose-operator" that is described in the book. The
        > pseudo-code says
        > that if the step to add (S-add) is selected from operator's list
        (not
        > the plan), then it is necessary to:
        > 1)Add this new step to the plans already existing steps.
        > 2)Add the ordering: Start < S-add < Finish
        >
        > I cannot understand what is the need for step 2). Say for example I
        > start the planner with a minimal plan of {Start, Finish} and on
        > selecting the first operator, I only find an S-add from the
        operator's
        > list. I will have to add the ordering S-add < S-need, where S-need =
        > Finish, according to the 5th pseudo-code line of the call. After
        that
        > I see that I have to execute steps 1 and 2 as described above. Now I
        > have a _repeated_ attempt to add ordering S-add < Finish.
        >
        > I have considered not doing step 2) which would result in a missing
        > ordering Start < S-add. I figure this will eventually be added to
        the
        > orderings when I process step S-add (i.e: attempt to satisfy its
        > pre-conditions).
        >
        > Am I missing something?
        >
        > TIA.
        > Hugo Ferreira.
        >
        >
        >
        > To unsubscribe from this group, send an email to:
        > aima-talk-unsubscribe@yahoogroups.com
        >
        >
        >
        > Your use of Yahoo! Groups is subject to
        http://docs.yahoo.com/info/terms/
      • E etech058
        Hello, I have read the pecudo code again give you my thinking here. If you delete the step 2) (start
        Message 3 of 7 , Dec 17, 2003
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          Hello,

          I have read the pecudo code again give you my thinking here. If you delete the step 2) (start < s-add < finish), the following problem will happens, To make the discussion more clearly, I give the context (To simplify the problem, I will ignore the variables):

          Context:

          1.      actions

          a)       action1

                                  i.              name:                 start

                                ii.              precondition:      nothing

                              iii.              effect:                  nothing

          b)       action2

                                  i.              name:                 finish

                                ii.              precondition:      predicate

                              iii.              effect:                  nothing

          c)        action3

                                  i.              name:                 P1action

                                ii.              precondition       nothing

                              iii.              effect:                  predicate

          2.      initial casual link set bookkeeping

          a)       empty set

          3.      initial action order set bookkeeping

          a)       start < finish

           

          Problem and discussion:

          1.      Problem:

          a)       Is it possible for you to delete the step 2) (start < s-add < finish)?

          2.      discussion:

          a)       Not correct.

          b)       My reason:

                                  i.              Requirement of Linearization:

          1.        POP”’s full name is Parital-order Planner. It means if needs, it is sure that after linearizations of POP plan, “Total order plans” can be gained.

          2.        But if you delete the “step 2)”, the order relationship between start and “P1action” will not be written down in the “action order set bookkeeping”, it is difficult for the above linearizations operation.

          3.        In last 2nd paragraph of page 350 (AIMA version 1), light arrows in the figure show ordering constraints….., Also, all causes are constrained to come before their effects, so you can think of each bold arrow as having a light arrow underneath it.

                                ii.              Requirement of procedure “RESOLVE-THREATS” and function “POP”

          1.        In the function “POP”, procedure “CHOOSE-OPERATOR” and “RESOLVE-THREATS” are closely linked, that’s, one by one. It means after adding “casual link” and “order link” in “CHOOSE-OPERATOR”, the procedure “RESOLVE-THREATS” will check the threat has been happened or not. If happens, It will try to solve it immediately. This immediately check needs the ordering information. And the solving of threat also needs the ordering information.

          2.        If the ordering information doesn’t exist, The “Resolve-threats” doesn’t work.

           

           

          I am also interested in the POP implementation for fully understanding and research later, but I want to use lisp language.

           

           

          Kind regards/chenyu

           

          -----Original Message-----
          From: yougooh2000 [mailto:hugo.ferreira@...]
          Sent: 2003年12月12日 17:18
          To: aima-talk@yahoogroups.com
          Subject: [aima-talk] Re: POP Planner Implementation: Choose-Operator

           

          Hi,

           

          First versions will (hopefully) be in Prolog. This is for research

          purposes.

           

          Regards,

          Hugo.

           

           

          --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...> wrote:

          > Hello,

          > Which language will you use for implementation?

          >

          > Best regards/chenyu

          >

          > -----Original Message-----

          > From: yougooh2000 [mailto:hugo.ferreira@m...]

          > Sent: 2003Äê12ÔÂ12ÈÕ 0:06

          > To: aima-talk@yahoogroups.com

          > Subject: [aima-talk] POP Planner Implementation: Choose-Operator

          >

          > Hi,

          >

          > I am attempting to implement the POP planner as is described in

          AIMA's

          > 1st version (Chap. 11.). I am having doubts regarding the call

          > "choose-operator" that is described in the book. The

          > pseudo-code says

          > that if the step to add (S-add) is selected from operator's list

          (not

          > the plan), then it is necessary to:

          > 1)Add this new step to the plans already existing steps.

          > 2)Add the ordering: Start < S-add < Finish

          >

          > I cannot understand what is the need for step 2). Say for example I

          > start the planner with a minimal plan of {Start, Finish} and on

          > selecting the first operator, I only find an S-add from the

          operator's

          > list. I will have to add the ordering S-add < S-need, where S-need =

          > Finish, according to the 5th pseudo-code line of the call. After

          that

          > I see that I have to execute steps 1 and 2 as described above. Now I

          > have a _repeated_ attempt to add ordering S-add < Finish.

          >

          > I have considered not doing step 2) which would result in a missing

          > ordering Start < S-add. I figure this will eventually be added to

          the

          > orderings when I process step S-add (i.e: attempt to satisfy its

          > pre-conditions).

          >

          > Am I missing something?

          >

          > TIA.

          > Hugo Ferreira.

          >

          >

          >

          > To unsubscribe from this group, send an email to:

          > aima-talk-unsubscribe@yahoogroups.com

          >

          > 

          >

          > Your use of Yahoo! Groups is subject to

          http://docs.yahoo.com/info/terms/

           

           

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        • yougooh2000
          Hi Chenyu, Thanks for the feedback. Unfortunatelly I could not understand much of your example. I cannot read the characters 8-(. As far as linearization goes,
          Message 4 of 7 , Dec 18, 2003
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            Hi Chenyu,

            Thanks for the feedback. Unfortunatelly I could not understand much of
            your example. I cannot read the characters 8-(. As far as
            linearization goes, you are correct: to check and handle threats I
            need to have the correct orderings. My initial implementation (which
            is still not working), does insert the S-add < Finish because it
            regards Start as a standard step in the plan when selecting a
            sub-goal. As far as Start < S-add I have to check on that and see how
            it influences threat detection and resolution. Nevertheless because I
            also handle Finish as a step I do get a Start < S-add, but not in the
            same point in time.

            Regards,
            Hugo F.



            --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...> wrote:
            > Hello,
            > I have read the pecudo code again give you my thinking here. If you
            delete the step 2) (start < s-add < finish), the following problem
            will happens, To make the discussion more clearly, I give the context
            (To simplify the problem, I will ignore the variables):
            > Context:
            > 1. actions
            > a) action1
            > i. name: start
            > ii. precondition: nothing
            > iii. effect:
            nothing
            > b) action2
            > i. name: finish
            > ii. precondition: predicate
            > iii. effect:
            nothing
            > c) action3
            > i. name:
            P1action
            > ii. precondition nothing
            > iii. effect:
            predicate
            > 2. initial casual link set bookkeeping
            > a) empty set
            > 3. initial action order set bookkeeping
            > a) start < finish
            >
            > Problem and discussion:
            > 1. Problem:
            > a) Is it possible for you to delete the step 2) (start < s-add
            < finish)?
            > 2. discussion:
            > a) Not correct.
            > b) My reason:
            > i. Requirement of
            Linearization:
            > 1. €  â' '¼POP€  â' '½â' '¹s full name is Parital-order
            Planner. It means
            if needs, it is sure that after linearizations of POP plan,
            €  â' '¼Total
            order plans€  â' '½ can be gained.
            > 2. But if you delete the €  â' '¼step 2)€  â' '½, the order
            relationship between start and €  â' '¼P1action€  â' '½ will not be
            written down
            in the €  â' '¼action order set bookkeeping€  â' '½, it is difficult
            for the
            above linearizations operation.
            > 3. In last 2nd paragraph of page 350 (AIMA version 1), light
            arrows in the figure show ordering constraints€  â' ¦.., Also, all
            causes
            are constrained to come before their effects, so you can think of each
            bold arrow as having a light arrow underneath it.
            > ii. Requirement of procedure
            €  â' '¼RESOLVE-THREATS€  â' '½ and function €  â' '¼POP€  â' '½
            > 1. In the function €  â' '¼POP€  â' '½, procedure
            €  â' '¼CHOOSE-OPERATOR€  â' '½
            and €  â' '¼RESOLVE-THREATS€  â' '½ are closely linked,
            that€  â' '¹s, one by one. It
            means after adding €  â' '¼casual link€  â' '½ and €  â' '¼order
            link€  â' '½ in
            €  â' '¼CHOOSE-OPERATOR€  â' '½, the procedure €  
            â' '¼RESOLVE-THREATS€  â' '½ will check
            the threat has been happened or not. If happens, It will try to solve
            it immediately. This immediately check needs the ordering information.
            And the solving of threat also needs the ordering information.
            > 2. If the ordering information doesn€  â' '¹t exist, The
            €  â' '¼Resolve-threats€  â' '½ doesn€  â' '¹t work.
            >
            >
            > I am also interested in the POP implementation for fully
            understanding and research later, but I want to use lisp language.
            >
            >
            > Kind regards/chenyu
            >
            > -----Original Message-----
            > From: yougooh2000 [mailto:hugo.ferreira@m...]
            > Sent: 2003€  å¹´12€  æ'¼'¨12€  æ'·¥ 17:18
            > To: aima-talk@yahoogroups.com
            > Subject: [aima-talk] Re: POP Planner Implementation: Choose-Operator
            >
            > Hi,
            >
            > First versions will (hopefully) be in Prolog. This is for research
            > purposes.
            >
            > Regards,
            > Hugo.
            >
            >
            > --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...> wrote:
            > > Hello,
            > > Which language will you use for implementation?
            > >
            > > Best regards/chenyu
            > >
            > > -----Original Message-----
            > > From: yougooh2000 [mailto:hugo.ferreira@m...]
            > > Sent: 2003€  Ã'¤Ãª12€  Ã'´Ã'¢12€  Ã'¨Ã'µ 0:06
            > > To: aima-talk@yahoogroups.com
            > > Subject: [aima-talk] POP Planner Implementation: Choose-Operator
            > >
            > > Hi,
            > >
            > > I am attempting to implement the POP planner as is described in
            > AIMA's
            > > 1st version (Chap. 11.). I am having doubts regarding the call
            > > "choose-operator" that is described in the book. The
            > > pseudo-code says
            > > that if the step to add (S-add) is selected from operator's list
            > (not
            > > the plan), then it is necessary to:
            > > 1)Add this new step to the plans already existing steps.
            > > 2)Add the ordering: Start < S-add < Finish
            > >
            > > I cannot understand what is the need for step 2). Say for example
            I
            > > start the planner with a minimal plan of {Start, Finish} and on
            > > selecting the first operator, I only find an S-add from the
            > operator's
            > > list. I will have to add the ordering S-add < S-need, where
            S-need =
            > > Finish, according to the 5th pseudo-code line of the call. After
            > that
            > > I see that I have to execute steps 1 and 2 as described above.
            Now I
            > > have a _repeated_ attempt to add ordering S-add < Finish.
            > >
            > > I have considered not doing step 2) which would result in a
            missing
            > > ordering Start < S-add. I figure this will eventually be added to
            > the
            > > orderings when I process step S-add (i.e: attempt to satisfy its
            > > pre-conditions).
            > >
            > > Am I missing something?
            > >
            > > TIA.
            > > Hugo Ferreira.
            > >
            > >
            > >
            > > To unsubscribe from this group, send an email to:
            > > aima-talk-unsubscribe@yahoogroups.com
            > >
            > >
            > >
            > > Your use of Yahoo! Groups is subject to
            > http://docs.yahoo.com/info/terms/
            >
            >
            >
            > To unsubscribe from this group, send an email to:
            > aima-talk-unsubscribe@yahoogroups.com
            >
            >
            >
            > Your use of Yahoo! Groups is subject to
            http://docs.yahoo.com/info/terms/
          • chenyu468
            Hello Hugo, I have use notepad to format the reply and eliminate the special characters. I hope it is readable now. In addition, for your program s problem
            Message 5 of 7 , Dec 18, 2003
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              Hello Hugo,
              I have use "notepad" to format the reply and eliminate the special
              characters. I hope it is readable now.

              In addition, for your program's problem (don't work), maybe firstly
              test the simplest planning problem as follows (context) to find the
              error, then comparing with the pceudo-code to find the problem. I
              haven't start this implementation now.


              kind regards/chenyu




              ;;;;;;;;;;;;;;;;;
              ;;last message
              ;;;;;;;;;;;;;;;;;
              I have read the pecudo code again give you my thinking here. If you
              delete the step 2) (start < s-add < finish), the following problem
              will happens, To make the discussion more clearly, I give the context
              (To simplify the problem, I will ignore the variables):

              Context:

              1. actions
              a) action1
              i. name: start
              ii. precondition: nothing
              iii. effect: nothing
              b) action2
              i. name: finish
              ii. precondition: predicate
              iii. effect: nothing
              c) action3
              i. name: P1action
              ii. precondition nothing
              iii. effect: predicate
              2. initial casual link set bookkeeping
              a) empty set
              3. initial action order set bookkeeping
              a) start < finish

              Problem and discussion:
              1. Problem:
              a) Is it possible for you to delete the step 2)
              (start < s-add < finish)?
              2. discussion:
              a) Not correct.
              b) My reason:
              i. Requirement of Linearization:
              1. "POP"'s full name is Parital-
              order Planner. It means if needs, it is sure that after
              linearizations of POP plan, "Total order plans" can be gained.
              2. But if you delete the "step
              2)", the order relationship between start and "P1action" will not be
              written down in the "action order set bookkeeping", it is difficult
              for the above linearizations operation.
              3. In last 2nd paragraph of page
              350 (AIMA version 1), light arrows in the figure show ordering
              constraints¡­.., Also, all causes are constrained to come before
              their effects, so you can think of each bold arrow as having a light
              arrow underneath it.
              ii. Requirement of procedure "RESOLVE-
              THREATS" and function "POP"
              1. In the function "POP",
              procedure "CHOOSE-OPERATOR" and "RESOLVE-THREATS" are closely linked,
              that¡¯s, one by one. It means after adding "casual link" and "order
              link" in "CHOOSE-OPERATOR", the procedure "RESOLVE-THREATS" will
              check the threat has been happened or not. If happens, It will try to
              solve it immediately. This immediately check needs the ordering
              information. And the solving of threat also needs the ordering
              information.
              2. If the ordering information
              doesn¡¯t exist, The "Resolve-threats" doesn¡¯t work.


              I am also interested in the POP implementation for fully
              understanding and research later, but I want to use lisp language.


              Kind regards/chenyu



              --- In aima-talk@yahoogroups.com, "yougooh2000" <hugo.ferreira@m...>
              wrote:
              > Hi Chenyu,
              >
              > Thanks for the feedback. Unfortunatelly I could not understand much
              of
              > your example. I cannot read the characters 8-(. As far as
              > linearization goes, you are correct: to check and handle threats I
              > need to have the correct orderings. My initial implementation (which
              > is still not working), does insert the S-add < Finish because it
              > regards Start as a standard step in the plan when selecting a
              > sub-goal. As far as Start < S-add I have to check on that and see
              how
              > it influences threat detection and resolution. Nevertheless because
              I
              > also handle Finish as a step I do get a Start < S-add, but not in
              the
              > same point in time.
              >
              > Regards,
              > Hugo F.
              >
              >
              >
              > --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...> wrote:
              > > Hello,
              > > I have read the pecudo code again give you my thinking here. If
              you
              > delete the step 2) (start < s-add < finish), the following problem
              > will happens, To make the discussion more clearly, I give the
              context
              > (To simplify the problem, I will ignore the variables):
              > > Context:
              > > 1. actions
              > > a) action1
              > > i. name:
              start
              > > ii. precondition: nothing
              > > iii. effect:
              > nothing
              > > b) action2
              > > i. name:
              finish
              > > ii. precondition:
              predicate
              > > iii. effect:
              > nothing
              > > c) action3
              > > i. name:
              > P1action
              > > ii. precondition nothing
              > > iii. effect:
              > predicate
              > > 2. initial casual link set bookkeeping
              > > a) empty set
              > > 3. initial action order set bookkeeping
              > > a) start < finish
              > >
              > > Problem and discussion:
              > > 1. Problem:
              > > a) Is it possible for you to delete the step 2) (start < s-
              add
              > < finish)?
              > > 2. discussion:
              > > a) Not correct.
              > > b) My reason:
              > > i. Requirement of
              > Linearization:
              > > 1. €  ??¼POP€  ??½â'?¹s full name is Parital-order
              > Planner. It means
              > if needs, it is sure that after linearizations of POP plan,
              > €  ??¼Total
              > order plans€  ???can be gained.
              > > 2. But if you delete the €  ??¼step 2)€  ??? the order
              > relationship between start and €  ??¼P1action€  ???will not be
              > written down
              > in the €  ??¼action order set bookkeeping€  ??? it is difficult
              > for the
              > above linearizations operation.
              > > 3. In last 2nd paragraph of page 350 (AIMA version 1),
              light
              > arrows in the figure show ordering constraints€  ? ¦.., Also, all
              > causes
              > are constrained to come before their effects, so you can think of
              each
              > bold arrow as having a light arrow underneath it.
              > > ii. Requirement of procedure
              > €  ??¼RESOLVE-THREATS€  ???and function €  ??¼POP€  ???> >
              1. In the function €  ??¼POP€  ??? procedure
              > €  ??¼CHOOSE-OPERATOR€  ???> and €  ??¼RESOLVE-THREATS€  ???are
              closely linked,
              > that€  ??¹s, one by one. It
              > means after adding €  ??¼casual link€  ???and €  ??¼order
              > link€  ???in
              > €  ??¼CHOOSE-OPERATOR€  ??? the procedure €  
              > ??¼RESOLVE-THREATS€  ???will check
              > the threat has been happened or not. If happens, It will try to
              solve
              > it immediately. This immediately check needs the ordering
              information.
              > And the solving of threat also needs the ordering information.
              > > 2. If the ordering information doesn€  ??¹t exist, The
              > €  ??¼Resolve-threats€  ???doesn€  ??¹t work.
              > >
              > >
              > > I am also interested in the POP implementation for fully
              > understanding and research later, but I want to use lisp language.
              > >
              > >
              > > Kind regards/chenyu
              > >
              > > -----Original Message-----
              > > From: yougooh2000 [mailto:hugo.ferreira@m...]
              > > Sent: 2003€  å¹?2€  ???2€  ?·¥ 17:18
              > > To: aima-talk@yahoogroups.com
              > > Subject: [aima-talk] Re: POP Planner Implementation: Choose-
              Operator
              > >
              > > Hi,
              > >
              > > First versions will (hopefully) be in Prolog. This is for research
              > > purposes.
              > >
              > > Regards,
              > > Hugo.
              > >
              > >
              > > --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...>
              wrote:
              > > > Hello,
              > > > Which language will you use for implementation?
              > > >
              > > > Best regards/chenyu
              > > >
              > > > -----Original Message-----
              > > > From: yougooh2000 [mailto:hugo.ferreira@m...]
              > > > Sent: 2003€  ?¤Ã?2€  ?´Ã'?2€  ?¨Ã'?0:06
              > > > To: aima-talk@yahoogroups.com
              > > > Subject: [aima-talk] POP Planner Implementation: Choose-Operator
              > > >
              > > > Hi,
              > > >
              > > > I am attempting to implement the POP planner as is described in
              > > AIMA's
              > > > 1st version (Chap. 11.). I am having doubts regarding the call
              > > > "choose-operator" that is described in the book. The
              > > > pseudo-code says
              > > > that if the step to add (S-add) is selected from operator's list
              > > (not
              > > > the plan), then it is necessary to:
              > > > 1)Add this new step to the plans already existing steps.
              > > > 2)Add the ordering: Start < S-add < Finish
              > > >
              > > > I cannot understand what is the need for step 2). Say for
              example
              > I
              > > > start the planner with a minimal plan of {Start, Finish} and on
              > > > selecting the first operator, I only find an S-add from the
              > > operator's
              > > > list. I will have to add the ordering S-add < S-need, where
              > S-need =
              > > > Finish, according to the 5th pseudo-code line of the call. After
              > > that
              > > > I see that I have to execute steps 1 and 2 as described above.
              > Now I
              > > > have a _repeated_ attempt to add ordering S-add < Finish.
              > > >
              > > > I have considered not doing step 2) which would result in a
              > missing
              > > > ordering Start < S-add. I figure this will eventually be added
              to
              > > the
              > > > orderings when I process step S-add (i.e: attempt to satisfy its
              > > > pre-conditions).
              > > >
              > > > Am I missing something?
              > > >
              > > > TIA.
              > > > Hugo Ferreira.
              > > >
              > > >
              > > >
              > > > To unsubscribe from this group, send an email to:
              > > > aima-talk-unsubscribe@yahoogroups.com
              > > >
              > > >
              > > >
              > > > Your use of Yahoo! Groups is subject to
              > > http://docs.yahoo.com/info/terms/
              > >
              > >
              > >
              > > To unsubscribe from this group, send an email to:
              > > aima-talk-unsubscribe@yahoogroups.com
              > >
              > >
              > >
              > > Your use of Yahoo! Groups is subject to
              > http://docs.yahoo.com/info/terms/
            • yougooh2000
              Chenyu, Thanks for the feedback. As far as the problem is concerned, my tests until now show that I do not need to add the Start
              Message 6 of 7 , Dec 22, 2003
              • 0 Attachment
                Chenyu,

                Thanks for the feedback.

                As far as the problem is concerned, my tests until now show that I do
                not need to add the Start < S-add ordering. I need to test additional
                worlds, but my initial ideia seems to be valid. I don't know if this
                is due to the way in which I implemented the algorithm or some "bug".

                Anyway here is the explanation: because the alg. is goal recursive I
                only check for preconditions before I regress. If after an
                operation/step has been selected I do not add Start < S-add, it does
                not matter because I only check for the steps/operators that I have
                selected until now with open preconditions. Start will therefore never
                be considered, it has no pre-conds.

                What about checking for consistency? This doesn't matter either
                because I cannot promote anything before Start, nor for that matter
                demote it after Finish. In other words consistency only checks for
                steps consistency between Start and Finish (exclusive).

                What about identifying threats? Just as in the case checking for
                consistency, threats may only occur for operators/steps between Start
                and Finish. So once again, if I do add a Start < S-add, I don't need
                the info to identify threats.
                Please note that the book's algo. just checks if an operator/step
                "clobbers" anothers pre-conds. This means that after ordering, the
                check for threats will still show the threats. I only use ordering
                information so as not to repeatedly (and unecessarily) resolve
                conflicts.

                I hope this explanation is valid. In case I do detect a mistake, I
                will post additional information.

                Thanks again.
                Regards,
                Hugo.




                --- In aima-talk@yahoogroups.com, "chenyu468" <chenyu468@y...> wrote:
                > Hello Hugo,
                > I have use "notepad" to format the reply and eliminate the special
                > characters. I hope it is readable now.
                >
                > In addition, for your program's problem (don't work), maybe firstly
                > test the simplest planning problem as follows (context) to find the
                > error, then comparing with the pceudo-code to find the problem. I
                > haven't start this implementation now.
                >
                >
                > kind regards/chenyu
                >
                >
                >
                >
                > ;;;;;;;;;;;;;;;;;
                > ;;last message
                > ;;;;;;;;;;;;;;;;;
                > I have read the pecudo code again give you my thinking here. If you
                > delete the step 2) (start < s-add < finish), the following problem
                > will happens, To make the discussion more clearly, I give the
                context
                > (To simplify the problem, I will ignore the variables):
                >
                > Context:
                >
                > 1. actions
                > a) action1
                > i. name: start
                > ii. precondition: nothing
                > iii. effect: nothing
                > b) action2
                > i. name: finish
                > ii. precondition: predicate
                > iii. effect: nothing
                > c) action3
                > i. name: P1action
                > ii. precondition nothing
                > iii. effect: predicate
                > 2. initial casual link set bookkeeping
                > a) empty set
                > 3. initial action order set bookkeeping
                > a) start < finish
                >
                > Problem and discussion:
                > 1. Problem:
                > a) Is it possible for you to delete the step 2)
                > (start < s-add < finish)?
                > 2. discussion:
                > a) Not correct.
                > b) My reason:
                > i. Requirement of Linearization:
                > 1. "POP"'s full name is Parital-
                > order Planner. It means if needs, it is sure that after
                > linearizations of POP plan, "Total order plans" can be gained.
                > 2. But if you delete the "step
                > 2)", the order relationship between start and "P1action" will not
                be
                > written down in the "action order set bookkeeping", it is difficult
                > for the above linearizations operation.
                > 3. In last 2nd paragraph of page
                > 350 (AIMA version 1), light arrows in the figure show ordering
                > constraints¡­.., Also, all causes are constrained to come before
                > their effects, so you can think of each bold arrow as having a
                light
                > arrow underneath it.
                > ii. Requirement of procedure "RESOLVE-
                > THREATS" and function "POP"
                > 1. In the function "POP",
                > procedure "CHOOSE-OPERATOR" and "RESOLVE-THREATS" are closely
                linked,
                > that¡¯s, one by one. It means after adding "casual link" and
                "order
                > link" in "CHOOSE-OPERATOR", the procedure "RESOLVE-THREATS" will
                > check the threat has been happened or not. If happens, It will try
                to
                > solve it immediately. This immediately check needs the ordering
                > information. And the solving of threat also needs the ordering
                > information.
                > 2. If the ordering information
                > doesn¡¯t exist, The "Resolve-threats" doesn¡¯t work.
                >
                >
                > I am also interested in the POP implementation for fully
                > understanding and research later, but I want to use lisp language.
                >
                >
                > Kind regards/chenyu
                >
                >
                >
                > --- In aima-talk@yahoogroups.com, "yougooh2000"
                <hugo.ferreira@m...>
                > wrote:
                > > Hi Chenyu,
                > >
                > > Thanks for the feedback. Unfortunatelly I could not understand
                much
                > of
                > > your example. I cannot read the characters 8-(. As far as
                > > linearization goes, you are correct: to check and handle threats I
                > > need to have the correct orderings. My initial implementation
                (which
                > > is still not working), does insert the S-add < Finish because it
                > > regards Start as a standard step in the plan when selecting a
                > > sub-goal. As far as Start < S-add I have to check on that and see
                > how
                > > it influences threat detection and resolution. Nevertheless
                because
                > I
                > > also handle Finish as a step I do get a Start < S-add, but not in
                > the
                > > same point in time.
                > >
                > > Regards,
                > > Hugo F.
                > >
                > >
                > >
                > > --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...>
                wrote:
                > > > Hello,
                > > > I have read the pecudo code again give you my thinking here. If
                > you
                > > delete the step 2) (start < s-add < finish), the following problem
                > > will happens, To make the discussion more clearly, I give the
                > context
                > > (To simplify the problem, I will ignore the variables):
                > > > Context:
                > > > 1. actions
                > > > a) action1
                > > > i. name:
                > start
                > > > ii. precondition:
                nothing
                > > > iii. effect:
                > > nothing
                > > > b) action2
                > > > i. name:
                > finish
                > > > ii. precondition:
                > predicate
                > > > iii. effect:
                > > nothing
                > > > c) action3
                > > > i. name:
                > > P1action
                > > > ii. precondition
                nothing
                > > > iii. effect:
                > > predicate
                > > > 2. initial casual link set bookkeeping
                > > > a) empty set
                > > > 3. initial action order set bookkeeping
                > > > a) start < finish
                > > >
                > > > Problem and discussion:
                > > > 1. Problem:
                > > > a) Is it possible for you to delete the step 2) (start <
                s-
                > add
                > > < finish)?
                > > > 2. discussion:
                > > > a) Not correct.
                > > > b) My reason:
                > > > i. Requirement of
                > > Linearization:
                > > > 1. € ??¼POP€ ??½â'?¹s full name is
                Parital-order
                > > Planner. It means
                > > if needs, it is sure that after linearizations of POP plan,
                > > € ??¼Total
                > > order plans€ ???can be gained.
                > > > 2. But if you delete the € ??¼step 2)€ ???
                the order
                > > relationship between start and € ??¼P1action€
                ???will not be
                > > written down
                > > in the € ??¼action order set bookkeeping€ ??? it is
                difficult
                > > for the
                > > above linearizations operation.
                > > > 3. In last 2nd paragraph of page 350 (AIMA version 1),
                > light
                > > arrows in the figure show ordering constraints€ ? ¦..,
                Also, all
                > > causes
                > > are constrained to come before their effects, so you can think of
                > each
                > > bold arrow as having a light arrow underneath it.
                > > > ii. Requirement of procedure
                > > € ??¼RESOLVE-THREATS€ ???and function €
                ??¼POP€ ???> >
                > 1. In the function € ??¼POP€ ??? procedure
                > > € ??¼CHOOSE-OPERATOR€ ???> and €
                ??¼RESOLVE-THREATS€ ???are
                > closely linked,
                > > that€ ??¹s, one by one. It
                > > means after adding € ??¼casual link€ ???and €
                ??¼order
                > > link€ ???in
                > > € ??¼CHOOSE-OPERATOR€ ??? the procedure €
                > > ??¼RESOLVE-THREATS€ ???will check
                > > the threat has been happened or not. If happens, It will try to
                > solve
                > > it immediately. This immediately check needs the ordering
                > information.
                > > And the solving of threat also needs the ordering information.
                > > > 2. If the ordering information doesn€ ??¹t
                exist, The
                > > € ??¼Resolve-threats€ ???doesn€ ??¹t work.
                > > >
                > > >
                > > > I am also interested in the POP implementation for fully
                > > understanding and research later, but I want to use lisp language.
                > > >
                > > >
                > > > Kind regards/chenyu
                > > >
                > > > -----Original Message-----
                > > > From: yougooh2000 [mailto:hugo.ferreira@m...]
                > > > Sent: 2003€ å¹?2€ ???2€ ?·¥ 17:18
                > > > To: aima-talk@yahoogroups.com
                > > > Subject: [aima-talk] Re: POP Planner Implementation: Choose-
                > Operator
                > > >
                > > > Hi,
                > > >
                > > > First versions will (hopefully) be in Prolog. This is for
                research
                > > > purposes.
                > > >
                > > > Regards,
                > > > Hugo.
                > > >
                > > >
                > > > --- In aima-talk@yahoogroups.com, E etech058 <etech058@o...>
                > wrote:
                > > > > Hello,
                > > > > Which language will you use for implementation?
                > > > >
                > > > > Best regards/chenyu
                > > > >
                > > > > -----Original Message-----
                > > > > From: yougooh2000 [mailto:hugo.ferreira@m...]
                > > > > Sent: 2003€ ?¤Ã?2€ ?´Ã'?2€ ?¨Ã'?0:06
                > > > > To: aima-talk@yahoogroups.com
                > > > > Subject: [aima-talk] POP Planner Implementation:
                Choose-Operator
                > > > >
                > > > > Hi,
                > > > >
                > > > > I am attempting to implement the POP planner as is described
                in
                > > > AIMA's
                > > > > 1st version (Chap. 11.). I am having doubts regarding the call
                > > > > "choose-operator" that is described in the book. The
                > > > > pseudo-code says
                > > > > that if the step to add (S-add) is selected from operator's
                list
                > > > (not
                > > > > the plan), then it is necessary to:
                > > > > 1)Add this new step to the plans already existing steps.
                > > > > 2)Add the ordering: Start < S-add < Finish
                > > > >
                > > > > I cannot understand what is the need for step 2). Say for
                > example
                > > I
                > > > > start the planner with a minimal plan of {Start, Finish} and
                on
                > > > > selecting the first operator, I only find an S-add from the
                > > > operator's
                > > > > list. I will have to add the ordering S-add < S-need, where
                > > S-need =
                > > > > Finish, according to the 5th pseudo-code line of the call.
                After
                > > > that
                > > > > I see that I have to execute steps 1 and 2 as described above.
                > > Now I
                > > > > have a _repeated_ attempt to add ordering S-add < Finish.
                > > > >
                > > > > I have considered not doing step 2) which would result in a
                > > missing
                > > > > ordering Start < S-add. I figure this will eventually be
                added
                > to
                > > > the
                > > > > orderings when I process step S-add (i.e: attempt to satisfy
                its
                > > > > pre-conditions).
                > > > >
                > > > > Am I missing something?
                > > > >
                > > > > TIA.
                > > > > Hugo Ferreira.
                > > > >
                > > > >
                > > > >
                > > > > To unsubscribe from this group, send an email to:
                > > > > aima-talk-unsubscribe@yahoogroups.com
                > > > >
                > > > >
                > > > >
                > > > > Your use of Yahoo! Groups is subject to
                > > > http://docs.yahoo.com/info/terms/
                > > >
                > > >
                > > >
                > > > To unsubscribe from this group, send an email to:
                > > > aima-talk-unsubscribe@yahoogroups.com
                > > >
                > > >
                > > >
                > > > Your use of Yahoo! Groups is subject to
                > > http://docs.yahoo.com/info/terms/
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