KI-97: IPP Homepage

Syntax of Operator Files for IPP 3.0 to 3.3

The operator file, as it's name suggests, contains the set of operators that may be applied in the planning domain. It must be a text file of the form (name).ops and IPP will try to apply all the ops which are contained in it, i.e., you need to put different operator sets into different files.

Basic Name Conventions:

Typenames are arbitary strings of small and capital letters, the numbers 0-9, dashes and underscores, for example 111, p-11, G09-7_b1.
The universal quantifier is represented with "ALL", the existential quantifier with "EX", negation with "not" or "!".
Comments start at the beginning of a line with a "#" and end with a newline.
Variable names start with "?" and followed by an arbitrary string of small and capital letters, the numbers 0-9, dashes and brackets "[" and "]".
Predicate names are arbitary strings of small and capital letters, the numbers 0-9 and dashes.
Equality is represented using the distinguished predicate name "eq", for example "!eq(?x ?y)" means that the variables ?x and ?y must be different and "eq(c ?z)" means that the variable ?z must be equal to the constant c.
Constant names can contain small and capital letters, the numbers 0-9, dashes and brackets "[" and "]".

OP_FILE      ::=  /* empty */ |  OP OP_FILE

OP           ::=  constantname ":v"  PARDEC  ":p"  FACTLIST ":e"  EFFECTS
 
PARDEC       ::= /* empty */ | VARLIST constantname  PARDEC

VARLIST      ::= /* empty */ | variablename Varlist
 
FACTLIST     ::= /* empty */ 
                 | predicatename '(' CONSTANTLIST ')'   FACTLIST 
                 | NOT PREDNAME  '(' CONSTANTLIST ')'   FACTLIST 

NOT          ::= "not" |"!" 

CONSTANTLIST ::= constantname | constantname SPC CONSTANT_LIST

SPC          ::= " "  {  " "  |  newline | tabulator }
  
EFFECTS      ::= 'ALL' PARDEC PREDLIST IMPL ADDLIST DELLIST CONTINUE
                 | FACTLIST IMPL ADDLIST DELLIST CONTINUE
                    
ADDLIST      ::= /* empty */ | ADD
                 PREDLIST
             
DELLIST      ::= /* empty */ | DEL PREDLIST-NO-NOT
                  
PREDLIST     ::= /* empty */ 
                 | predicatename '(' ARGS ')'  PREDLIST
                 | NOT PREDNAME  '(' ARGS ')'  PREDLIST
    
PREDLIST-NO-NOT ::= /* empty */ 
                 | predicatename '(' ARGS ')'  PREDLIST-NO-NOT 
        
ARGS         ::= /* empty */ | variablename SPC ARGS 
                 | constantname SPC ARGS 

CONTINUE     ::= '.' | ';' EFFECTS

IMPL         ::=  /* empty */ | IMPL

EFFECTS are list of conditional effects with the ADD effects preceeding the DEL effects which are separated by ";" . The last effect must be followed by "." NEVER use DEL effects and atomic negation at the same time!

  
Several equivalent representations of the move operator 
from the Briefcase Domain:

move
:v ?m ?l location 
:p is-at(?m)
:e ADD is-at(?l) DEL is-at(?m);
   ALL ?o object in(?o)  => ADD at(?o ?l) DEL at(?o ?m).


move
:v ?m ?l location 
:p is-at(?m)
:e ADD is-at(?l) !is-at(?m);
   ALL ?o object in(?o) => ADD at(?o ?l) !at(?o ?m).


move
:v ?l location
:p
:e ADD is-at(?l);
   ALL ?m location !eq(?m ?l) => DEL is-at(?m);
   ALL ?o object ?m location in(?o) at(?o ?m) !eq(?m ?l) 
                              => ADD at(?o ?l) DEL at(?o ?m).

move
:v ?l location 
:p 
:e ADD is-at(?l);
   ALL ?m location !eq(?m ?l) => ADD !is-at(?m);
   ALL ?o object ?m location in(?o) at(?o ?m) !eq(?m ?l) 
                              => ADD at(?o ?l) !at(?o ?m).

NOTE:

We adopt the unique name assumption, i.e., different variables stand for different objects in the world.
The effect representation of an operator must first contain the list of facts that are unconditionally added (preceeded by one single ADD), then followed by the list of all facts that are unconditionally deleted (preceeded by one single DEL).
Everything that is deleted by the operator has to be mentioned explicitly, i.e., our operators do not automatically delete their preconditions.
There can be a possibly infinite number of different conditional effects, which can be empty.
The implication sign can be dropped in conditional effects.
Operators can have empty paramaterlists, preconditions and effects.
Variables of the same type can be defined in one list: ?b1 ?b2 ?b3 block ?t1 ?t2 table etc. .
If you have a predicate without any parameters, you still have to add the "()", as in arm-empty().
Names should not be longer than 256 characters.
Using atomic negation, we require that no DELETE LISTS occur in operators! The syntax still admits it, but it makes no sense for the planner. You can either write ADD not-p(x) DEL p(x) or ADD !p(x) or ADD not p(x), but not ADD not p(x) DEL p(x). When using atomic negation it is sufficient to state the positive or negative ADD effects only!
Equality and Disequality should never occur in effects.