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

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  • E etech058
    Hello, I have read the pecudo code again give you my thinking here. If you delete the step 2) (start
    Message 1 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

      >

      > 

      >

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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 2 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 3 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 4 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
            > > > >
            > > > >
            > > > >
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            > > > http://docs.yahoo.com/info/terms/
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            > > >
            > > >
            > > > To unsubscribe from this group, send an email to:
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            > > >
            > > >
            > > >
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