phuc t~p thffp ta co th~ su d~ng them cac qui tifc heuristic b6 sung them cho qua trmh xay dvng mQt m~ng suy di€n con ma d6 thi cua no co d~ng mQt
biSu d6 phan ca'p.
. Tit phu'ong phap tlm mQt t~p hQp sinh trang mQt m~ng suy di€n dff du'Qctrlnh
bay (j tren ta co thS phat triSn mQt thu~t loan tu'ong tv <is tlm mQt t~p hQp
sinh chU'amQtt~p h<JpthuQctinh cho tru'oc. 2.5.3 B6 sung gia thie"t cho bfti toaD suy di~n
Trong m~c nfiy ta se xem xet vi~c b6 sung gia thie't cho bai loan H ~ G tren mQt m~ng suy di€n (A, D) trong tru'ong hQp bai loan kh6ng giai du'<JC.Ytu'dng chinh d day 1a tie'n hanh mQt qua trlnh xay dt;r'ngmQt biSu d6 phan cffp voi t~p
hQp <iinh chU'a G va u'u lien cho vi~c d~t cac phfin tit cua H d mU'c O. Thu~t loan
co ban du'oi day cho ta mQt each d~ tlm mQt t~p thuQc tinh H' saG cho H n H' =
0 va bai loan (H u H') ~ G 1a giai du'<Jctren m~ng suy di€n.
Thuat toaD 2.8: Cho m~ng suy di€n (A, D) va bai loan H ~ G kh6ng giai du'QC
(kh6ng co Wi giai). TIm H' saG cho H n H' =0 va bai loan (H u
H') ~ G 1a giai du'<Jc.
Bu'oc1:A'+-H; D'~{}; G+-G\A';
Bu'oc 2: while (G 7: {} and D7: {}) do
2.1: Lffy ra mQt r tu D va c~p nh~t D.
2.2: if hypothesis(r) n G 7: {} or attr(r) c A' then Bo qua r
2.3: else Them r VaGD' va b6 sung attr(r) VaG A'va trang tru'ong hQp goa1(r) E A' thl1o~i ra r' tit D' (ne'u co) thoa goal(r') =goal(r)va
lO(;limQt s6 lu~t suy ra cac x E hypothesis(r) d€ bao dam tinh phan ca'p cua bi€u d6.
2.4: G ~ G - A'
Bu'oc 3: if G * {} then Ke't thuc voi ke't lu~n:Va'n d€ b6 sung gia thie't la khong giiii quye't du'qc
Bu'oc 4: else (Trang tru'ong hqp n~y Graph(A',D') co bi€u d6 phan ca'p tu'ongling hI GraphD.A')GQiLa la muc 0 cua bi€u d6 GraphD.A'.f)~t: H' ~La-H.
Menh d~ 2.9: Thu~t loan 2.8 d€ tim stf b6 sung gia thie't cho bai suy di~n la dung va co dQ phuc t(;lp la O(IAI./DI).
Ghi chu: Ta co th€ sii' dlJng them cac qui lac heuristic trong buoc 2 cua thu~t
loan tren nh~m giiim thi€u s6 thuQc tinh (j muc 0 va/hay d€ u'u lien chQn Itfa
cac thuQc tinh du'qc u'u lien cho vit$c dung b6 sung giii thie't cua bai loan. 2.6 M~NG SUY DIEN-TINH TOAN
Trong ph~n n~y chung ta xet de'n mQt mo hinh m(;lngsuy di~n lien qua de'n .
tinh loan, duqc gQi la m(;lng suy di~n - tinh loan, ma trang nhi€u ling dlJng no cho ta mQt stf bi€u di~n d~y du va thich h<;Jphon cua tri thuc c~n thie't lien quail de'n cac va'n d€ ha~ cac bai tmin c~n giiii quye't. Cach bi€u di~n nhu v~y se th€ hit$nmQt cach ttf nhien ca'u truc cua tri iliac, va giup ta thie't ke' cac thu~t giiii loan tlJ'dQng mQt cach d~ dang voi nhung loi giiii tu'ong minh phil h<;Jpvoi cach fighTva lam cua con nguoi trong cac ling d\lllg giiii loan, d~c bit$t la cac ht$ th6ng h6 trq cho vit$c hQc t~p va giiing d(;lY.Nhung ph~n m~m nhu' the' dn co cach bi€u di~n tri thuc tlJ'nhien va thich hqp cho vit$c thie't ke' cac modun giiii loan cho Wi giiii phu hqp voi hQc sinh cling nhu cac modun giiii thich, modun ki€m ITa va luyt$n t~p giiii loan.
2.6.1 M6 hinh
- Dinh m!hia 2.10: MQt m~ng suy di€n-tinh loan g6m b6n thanh ph~n:
(1) T~p h<;fpA g6m cac thuQc tinh.
(2) T~p h<;fpD g6m cac lu~t suy di~n (hay cac quail hc$ suy di~n) lIen cae
thuQC tinh.
(3) T~p h<;fpF g6m cac c6ng thlic tinh loan hay cac thu Wc tinh loan tu'dng ling voi cac lu~t suy di€n. 511tu'dng ling n~y thS hic$nboi mQt anh x~
f:D--+F
(4) T~p h<;fpR g6m mQt sO'qui Htc hay di~u kic$n rang buQc tren cac thuQc
tinh.
M~ng suy di~n tinh loan g6m 4 t~p h<;fpA, D, F va R nhu' the' se du'<;fcky hic$uboi bQ b6n (A, D, F, R). Theo dinh nghla, ta c6 (A, D) hI mQt m~ng suy di€n va loi giiii cho bai loan H --+ G lIen m~illgsuy di€n n~y se xac dinh cac c6ng thlic hay cac thu t\lCtinh loan cac ph~n tii'thuQc G tu cac ph~n nl thuQcH.
Vi du 2.16: Kie'n thlic v~ mQt tam giac c6 thS du'<;fcbiSu di€n boi mQt m~ng suy--
di~n tinh loan (A, D, F, R) nhu'sau:
A ={A, B, C, a, b, c, R, 5, p, ...} la t~p h<;fpcac ye'u to' cua mQt tam giac g6m 3 g6c, 3 c~nh, ban kinh vong troll ngo~i tie'p, dic$ntich, illra chu vi, V.v...,
D = {r1:A, B::::>C; r2: A, C => B; r3: B, C ::::>A;
r4: A, a => R; rS: A, R => a; r6: R, a ::::>A; r7: A, b, c ::::>a; ...}
F={f1: C=It-A-B; f2: B =It-A-C; D: A =It-B-C;
f4: R=a/(2.sin(A)); f5: a=2.R.sin(A); f6: A=arcsin(a/(2.R)); f7: a= b2+C2-2.b.c.cos(A); ...}
2.6.2 Giai b~litmin tren m~ng soy di~n-tinh tmin
Tren mOtmq.ng suy di~n-tinh loan ta c6 the giai quye't cac b~liloan suy di~n tinh loan ching hq.n b~li loan giai tam giac hay bai loan giai tu giac dva tren vi<$c giai bai loan suy di~n tren mq.ng suy di~n. Hon nii'a, cac cang thuc hay thu wc tinh loan c6 the du'<JCgall cho cac trQng s6 the hi<$ndO phuc tq.p tinh loan cua chung. Tu d6 ta c6 the tlm ra du'<JCnhii'ng Wi giai cho bai loan suy di~n tinh loan vOi chi phi tinh loan tha'p nha't dva tren vi<$ctlm Wi giai t6i u'u tren mq.ng suy di~n c6 trQng s6. Ngoai fa, chung ta c6 the Hm ra du'<JCcac cang thuc tu'ong minh qua cac bu'oc giai bai loan va rut gQn cac cang thuc du'oi dq.ng ky hi<$u.Nhu'the' tren mq.ng suy di~n-tinh loan mOt tam giac ta c6 the chI ra mOt cach tv dOng cac
c6ng thuc tu'ong minh de tinh mQt s6 ye'u t6 ngy tu mOt s6 ye'u t6 khac (ne'u bai
loan c6 loi giai). Ke't h<Jpdi~u ngy voi vi<$cdo tlm nhii'ng sv lien h<$suy di~n
giii'acac ye'u t6 nao d6 ma ta quail tam se cho ta mOt phu'ong phap de tv dOng
Hmra them nhii'nglu~t suy di~n va nhii'ng cang thuc tinh loan lien quail de'n cac
ye'u t6. E)i~ungy c6 ynghla nhu' mQt ky thu~t kham pha tri thuc.
MOt sV md rOng cua mq.ng suy di~n tinh loan la cho phep xet them cac quail h<$khac voi cac quail h<$suy di~n - tinh lOan aday, ching hq.n cac quail h~ hlnh
hQc giii'a cac d6i J:u'<Jnghlnh hQc diem, doq.n, ria, g6c. Sv md rOng ngy se du'<Jc
rich h<Jp trong mOt ca'u truc truu tu'<Jngtheo phu'ong phap l~p trlnh hu'ong d6i tu'<Jngma ta gQi la mQt d6i tu'<Jngtinh loan. Khai ni~m v~ d6i tu'<Jngtinh loan se du'<Jcxay dvng trong chuang tie'p theo va n6 du'<JCxem xet trong mOt ma hlnh tri thuc du'<JcgQi la ma hlnh tri thuc cac d6i tu'<Jngtinh loan.