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CSA Notes for Lecture
The NAIL System
To get a temp orary account suitable to run NAIL
Fill out an account form at the desk of MJH Ask for an account on theory for which I will sign Once on theory lo ok at
u morisita nail README which will explain how to set up your direc tory to run NAIL
Please do not abuse theory account use it only to exp eriment with NAIL
Manual will b e p osted to the newsgroup
Structure of NAIL
GLUE logical rules plus conventional ow of control pro cedures etc
NAIL conventional logic front end Trans lated via magic sets and well founded nega tion to GLUE pro cedures
IGLUE back end Adaptive data structures e g indexes
Principal credits Geo Phipps GLUE Marcia Derr IGLUE Shinichi Morishita current NAIL Kate Morris old NAIL
GLUE Assignments
Assignment statements lo ok like rules but they are executed whenever and only when they are reached during program execution
Four typ es of assignment Clear and assign insert delete up date
Clear and assign represented by
Example
pXY qXZ rZY
Note p erio d at end Semicolon is an OK sub stitute
Means p q r
Executed as written whenever control ow reaches this statement
Other Assignment Op erators
Insert represented by
Example
pXY qXZ rZY
means p p q r
Delete represented by
Example
pXY qXY
means p p q
Mo dify represented by an assignment op era tor Z for some set of variables Z See manual
Three Typ es of Subgoals
GLUE rules can have three typ es of subgoals
EDB stored physically in a sub directory called edb
IDB dened by NAIL rules included with the GLUE program
Pro cedural These subgoals have their value dened by a GLUE pro cedure GLUE pro ce dures have input and output arguments and the input arguments must b e b ound when this subgoal is reached in a left to right evaluation of the GLUE statement
Pro cedure Structure
pro c nameinput args output args lo cal declarations statements end
prog for pro c in distinguished pro cedure that executes when mo dule is invoked
Example In Fig
Lines and mo duleend
Line exp ortimp ort information
Line EDB information
Lines program main This pro ce dure has no input or output arguments
Line declaration of lo cal relation new P ath
Lines initialize ar c relation
Lines seminaive evaluation
Rule Pro cessing in GLUE
Left to right evaluation uses supplementary rela tions at each subgoal Three kinds of subgoals
EDB join with supplementary relation
IDB In the compiling phase NAIL determines the binding pattern for this subgoal and gen erates a GLUE pro cedure that implements magic sets and seminaive evaluation
GLUE pro cedure
Pro cedure call must t i e take as input arguments the b ound arguments of the sub goal and return a relation over all the argu ments including input arguments
Sp ecial relations used in pro cedure declara tion
inpro c nameinput args
to receive input and returninput args output args
to return a relation
Example See Fig a nim playing mo dule
Nim rules Start with hash marks in rows of In turn take any numb er from one of the three rows You win by taking the last mark i e stalemating your opp onent
Boards are represented by triples i j k where i j and k
EDB relation l t was created by another mo d ule and contains less than facts for integers up to It is needed for safety of the rules
Lines the entire win program
Line IDB predicate inter esting true of those triples that represent nim b oards
Lines legal moves Any of the three rows can b e decreased by one or more but not b elow
Line The usual win rule with w as the predicate
Note is the negation symb ol
Line is executed by rst invoking a com piled pro cedure for inter esting f^ f^ f^ The re sult is the entire inter esting relation
Then a compiled pro cedure for w bbb^ is called it computes the well founded mo del of w in tersected with the interesting b oards those that are legal nim p ositions
w in is computed by intersecting the two re turned relations
