%!PS-Adobe-1.0
%%Creator: devps (Pipeline Associates, Inc.)
%%CreationDate: Fri Jun 21 11:15:27 2002
%%Pages: (atend)
%%DocumentFonts: (atend)
%%EndComments

/devps 180 dict def devps begin
/res 10.000000 def
/y_offset 843 def
/X{exch}bind def
/mm {transform round X round X itransform} bind def
/r{rmoveto}bind def
/m{moveto}bind def
/l{lineto}bind def
/rl{rlineto}bind def
/st{stroke}bind def
/gs{gsave}bind def
/gr{grestore}bind def
/cp{currentpoint}bind def
/np{newpath}bind def
/ct{curveto}bind def
systemdict /setpacking known
 { /savepacking currentpacking def true setpacking } if
/m0{0 0 moveto}bind def
/xc{//res div}bind def
/yc{//res neg div //y_offset add}bind def
/lc{yc X xc X l st}bind def
/mc{yc X xc X m}bind def
/el{gs /a X def a div 1 X scale cp np a xc 2 div 0 360 arc st gr}bind def
/ar{cp 7 2 roll np xc 5 1 roll atan 3 1 roll atan X arc st}bind def
/sp{yc X xc X 6 2 roll yc X xc X 6 2 roll yc X xc X 6 2 roll ct}bind def
/V{//res neg div //y_offset add
currentpoint pop X
m}bind def
/H{//res div
0 transform X round X itransform pop
currentpoint X pop
moveto}bind def
/h{//res div 0 r}bind def
/v{//res neg div 0 X r}bind def
/S{X H show}bind def
/A{H //res div 1 index stringwidth pop sub 1 index length div 0 3 2 roll ashow}bind def
/psize 10 def
/height 0 def
/cheight { height 0 ne { height } { psize } ifelse } bind def
/slant 0 def
/FF{findfont X dup 30 div 0 mm pop setlinewidth /psize X def
    [psize 0 cheight slant sin slant cos div mul cheight 0 0]
    makefont setfont}bind def
/shade{gs
 /dy X def
 /dx X def
 np m
 0 /dy rl
 /dx 0 rl
 0 /dy neg rl
 /dx neg 0 rl
 closepath
 .9 setgray
 fill
gr}bind def
1 setlinecap

/resolution res 72 mul def


/startFig {
	/SavedState save def
	userdict maxlength dict begin
	currentpoint transform

	DocumentInitState setmiterlimit setgray setdash setlinejoin setlinecap
		setlinewidth setmatrix

	itransform moveto

	/ury exch def
	/urx exch def
	/lly exch def
	/llx exch def
	/y exch 72 mul resolution div def
	/x exch 72 mul resolution div def
	
	currentpoint /cy exch def /cx exch def

	/sx x urx llx sub div def
	/sy y ury lly sub div def

	sx sy scale

	cx sx div llx sub
	cy sy div ury sub translate
	
	/DefFigCTM matrix currentmatrix def

	/initmatrix {
		DefFigCTM setmatrix
	} def
	/defaultmatrix {
		DefFigCTM exch copy
	} def

	/initgraphics {
		DocumentInitState setmiterlimit setgray setdash 
			setlinejoin setlinecap setlinewidth setmatrix
		DefFigCTM setmatrix
	} def

	/showpage {
		initgraphics
	} def

}bind  def
/clipFig {
	currentpoint 6 2 roll
	newpath 4 copy
	4 2 roll moveto
	6 -1 roll exch lineto
	exch lineto
	exch lineto
	closepath clip
	newpath
	moveto
}bind  def
/doclip { llx lly urx ury clipFig } def
/endFig {
	end SavedState restore
}bind  def
/globalstart {
	fontnum psize slant height resolution currentpoint 
	pagesave restore gsave 
}bind  def
/globalend {
	grestore moveto
	/resolution exch def /height exch def
	/slant exch def /psize exch def /fontnum exch def
	F
	/pagesave save def
}bind  def


/fontnum 1 def 
systemdict /setpacking known { savepacking setpacking} if
end
/BP{
			100 100 div dup scale
save mark devps begin m0
/DocumentInitState [ matrix currentmatrix currentlinewidth currentlinecap
currentlinejoin currentdash currentgray currentmiterlimit ] cvx def
}bind def
/EP{
end cleartomark restore showpage}def

/Encoding-1 256 array def
0 1 255 {Encoding-1 exch /.notdef put} for
Encoding-1 8#301 StandardEncoding 8#101 26 getinterval putinterval %A-B
Encoding-1 8#341 StandardEncoding 8#141 26 getinterval putinterval %a-b
Encoding-1 8#241 StandardEncoding 8#301 16 getinterval putinterval %accents
Encoding-1 8#373 StandardEncoding 8#365 1 getinterval putinterval %dotlessi
Encoding-1
dup 8#41 /copyright put
dup 8#42 /registered put
dup 8#43 /trademark put
dup 8#44 /logicalnot put
dup 8#45 /Eth put
dup 8#46 /eth put
dup 8#47 /Thorn put
dup 8#50 /thorn put
dup 8#51 /brokenbar put
dup 8#52 /degree put
dup 8#53 /divide put
dup 8#54 /multiply put
dup 8#55 /minus put
dup 8#56 /onehalf put
dup 8#57 /onequarter put
dup 8#60 /threequarters put
dup 8#101 /Aacute put
dup 8#102 /Acircumflex put
dup 8#103 /Adieresis put
dup 8#104 /Agrave put
dup 8#105 /Aring put
dup 8#106 /Atilde put
dup 8#107 /Ccedilla put
dup 8#110 /Eacute put
dup 8#111 /Ecircumflex put
dup 8#112 /Edieresis put
dup 8#113 /Egrave put
dup 8#114 /Iacute put
dup 8#115 /Icircumflex put
dup 8#116 /Idieresis put
dup 8#117 /Igrave put
dup 8#120 /Ntilde put
dup 8#121 /Oacute put
dup 8#122 /Ocircumflex put
dup 8#123 /Odieresis put
dup 8#124 /Ograve put
dup 8#125 /Otilde put
dup 8#126 /Scaron put
dup 8#127 /Uacute put
dup 8#130 /Ucircumflex put
dup 8#131 /Udieresis put
dup 8#132 /Ugrave put
dup 8#133 /Ydieresis put
dup 8#134 /Zcaron put
dup 8#135 /aacute put
dup 8#136 /acircumflex put
dup 8#137 /adieresis put
dup 8#140 /agrave put
dup 8#141 /aring put
dup 8#142 /atilde put
dup 8#143 /ccedilla put
dup 8#144 /eacute put
dup 8#145 /ecircumflex put
dup 8#146 /edieresis put
dup 8#147 /egrave put
dup 8#150 /iacute put
dup 8#151 /icircumflex put
dup 8#152 /idieresis put
dup 8#153 /igrave put
dup 8#154 /ntilde put
dup 8#155 /oacute put
dup 8#156 /ocircumflex put
dup 8#157 /odieresis put
dup 8#160 /ograve put
dup 8#161 /otilde put
dup 8#162 /scaron put
dup 8#163 /uacute put
dup 8#164 /ucircumflex put
dup 8#165 /udieresis put
dup 8#166 /ugrave put
dup 8#167 /ydieresis put
dup 8#170 /zcaron put
pop

/Enc-dict 30 dict def
Enc-dict /tmpstr1 50 string put
Enc-dict /tmpstr2 50 string put
Enc-dict /tmpstr3 50 string dup (Encoding-) exch cvs pop put
/AEnc-def { % arguments: the original font's name, encoding nr
Enc-dict begin
tmpstr2 cvs /Enc-no exch def % Remember the number in a string
dup /OrigName exch def % remember the name
findfont dup maxlength dict /newdict exch def % get dictionary for new font
{ exch dup /FID ne
   { exch newdict 3 1 roll put }
   { pop pop } % Ignore FID
   ifelse
} forall
newdict begin
/Encoding
  tmpstr3 9 Enc-no putinterval tmpstr3 0 9 Enc-no length add getinterval
  cvn load
  def % Replace encoding
currentdict /UniqueID known
{ /UniqueID UniqueID Enc-no cvi 49999 mul add def } if % Derive New UniqueID
end % newdict
/FNlength OrigName tmpstr1 cvs length def % convert name, remember length
FNlength 1 add Enc-no length add string
dup 0 OrigName tmpstr1 cvs putinterval
dup FNlength (-) putinterval
dup FNlength 1 add Enc-no putinterval
dup 0 tmpstr1 0 FNlength getinterval putinterval % Add old name
cvn dup newdict /FontName 3 2 roll put newdict definefont
end % Enc-dict
} def
/Times-Roman 1 AEnc-def pop
/R-1{/Times-Roman-1 FF}def
/R{/Times-Roman FF}def
/B{/Times-Bold FF}def
/I{/Times-Italic FF}def
/Y{/Symbol FF}def
%%EndProlog
%%Page: 1 1
BP
/slant 0 def
/height 0 def
1230 V
12 B
1417(Detecting)S
1940(copied)S
2306(submissions)S
2954(in)S
3085(computer)S
3613(science)S
4007(workshops)S
1470 V
10 I
2754(Dick)S
2970(Grune)S
1590 V
2679(Matty)S
2939(Huntjens)S
1770 V
10 R
2544(Vakgroep)S
2966(Informatica)S
1890 V
2298(Faculteit)S
(Wiskunde)407 2676 A
3108(&)S
3211(Informatica)S
2010 V
2636(Vrije)S
2869(Universiteit)S
2130 V
2605(De)S
2748(Boelelaan)S
(1081)200 3176 A
2250 V
(1081)200 2458 A
2683(HV)S
2879(AMSTERDAM)S
2490 V
2665(November)S
(1989)200 3115 A
2870 V
10 I
2752(ABSTRACT)S
3130 V
10 R
1348(In)S
1471(most)S
1705(computer)S
2125(science)S
(workshops,)460 2462 A
2962(the)S
3125(students')S
3528(submissions)S
4058(are)S
4222(graded)S
4536(by)S
4676(more)S
3250 V
1098(than)S
1307(one)S
1488(supervisor.)S
1993(This)S
2208(allows)S
2507(a)S
2587(student)S
2912(to)S
3025(submit)S
3333(work)S
3575(that)S
3761(has)S
3930(already)S
4262(been)S
(submitted)396 4487 A
3370 V
1098(before)S
1381(by)S
1506(another)S
1833(student)S
2148(to)S
2251(another)S
2578(supervisor,)S
3047(with)S
3251(minimal)S
3611(chance)S
3916(of)S
4025(being)S
4273(detected.)S
3490 V
1098(This)S
1306(leads)S
1542(to)S
1649(an)S
1773(unfair)S
2043(situation)S
2418(in)S
2525(which)S
2800(students)S
(receive)292 3158 A
3479(points)S
3754(for)S
3902(work)S
4139(they)S
4342(have)S
4562(not)S
4720(per-)S
3610 V
1098(formed)S
1429(and)S
1614(from)S
1850(which)S
2136(they)S
2349(have)S
2579(learned)S
2916(nothing.)S
3312(This)S
3530(paper)S
3793(describes)S
4207(how)S
4419(the)S
4581(Section)S
3730 V
1098(Computer)S
1525(Science)S
1864(of)S
1973(the)S
2121(Vrije)S
2354(Universiteit)S
2855(in)S
2958(Amsterdam)S
3453(attempts)S
3819(to)S
3922(prevent)S
4249(this)S
4419(situation.)S
4090 V
10 B
720(Introduction)S
4246 V
10 R
970(Computer)S
1406(science)S
(workshops)435 1738 A
2208(with)S
(multiple)335 2422 A
2792(supervisors)S
3285(pose)S
3504(a)S
3584(difficult)S
3944(problem:)S
4342(\252How)S
4618(can)S
4793(we)S
4946(see)S
5110(that)S
4366 V
720(the)S
(submitted)396 871 A
1295(work)S
1530(is)S
1625(not)S
1780(a)S
(copy?\272)285 1852 A
(Copy)217 2164 A
2408(detection)S
2804(is)S
2898(not)S
3053(trivial,)S
3346(as)S
3457(may)S
3657(be)S
3779(seen)S
3985(from)S
4208(the)S
4358(fact)S
4537(that)S
4715(the)S
(workshop)396 4865 A
4486 V
(Introductory)503 720 A
1255(Programming)S
1840(at)S
1945(our)S
2112(faculty)S
(involved)351 2425 A
2809(1)S
2892(coordinator)S
3389(and)S
3567(8)S
3650(supervisors,)S
4166(for)S
4317(a)S
4395(total)S
4607(of)S
(181)150 4724 A
4907(students,)S
4606 V
(each)185 720 A
(submitting)429 935 A
1394(10)S
1524(programs.)S
1984(This)S
2193(paper)S
2446(describes)S
2850(a)S
2924(solution)S
3276(based)S
3534(on)S
3663(the)S
3815(automatic)S
4241(mutual)S
4549(comparison)S
5047(of)S
5160(all)S
4726 V
720(submissions.)S
4966 V
10 B
720(The)S
913(Similarity)S
1369(Tester)S
5122 V
10 R
970(The)S
1159(wish)S
1381(to)S
1492(have)S
1715(a)S
1793(program)S
2167(for)S
2318(finding)S
2641(common)S
3025(sections)S
3382(in)S
3493(two)S
3677(program)S
4051(texts)S
4274(did)S
4435(not)S
4596(first)S
4792(originate)S
5183(in)S
5242 V
720(plagiarism)S
1172(detection.)S
1618(Rather,)S
1939(its)S
2061(basis)S
2289(lay)S
2439(in)S
2544(the)S
2694(experience)S
3158(that)S
3336(a)S
3408(large)S
3637(\(semi-\)completed)S
4374(software)S
4748(project)S
5054(often)S
5362 V
720(contains)S
1081(stretches)S
1461(of)S
1572(similar)S
1879(code.)S
2146(When)S
(writing)291 2413 A
2731(large)S
2960(software)S
3335(objects)S
10 R-1
3647(-)S
10 R
3704(operating)S
4111(systems,)S
4481(compilers,)S
4930(editors)S
10 R-1
5204(-)S
5482 V
10 R
720(the)S
870(programmer)S
1395(often)S
1629(needs)S
1885(code)S
2102(similar)S
2408(to)S
2512(code)S
2728(that)S
2905(has)S
3065(already)S
3388(been)S
(written)286 3604 A
3916(elsewhere)S
4346(in)S
4450(the)S
4599(same)S
4832(project.)S
5188(A)S
5602 V
720(common)S
1103(technique)S
1526(is)S
1625(to)S
1735(use)S
1901(a)S
1978(text)S
2161(editor)S
2428(to)S
2539(make)S
2790(a)S
(copy)195 2868 A
3096(of)S
3213(the)S
3369(original)S
3715(code)S
3938(and)S
4116(adjust)S
4389(it)S
4478(to)S
4589(its)S
4717(new)S
4918(purpose.)S
5722 V
(Good)223 720 A
975(software)S
1355(engineering)S
1862(practice)S
2214(would)S
2497(probably)S
2886(dictate)S
3187(turning)S
3509(the)S
3664(code)S
3886(into)S
4074(a)S
4151(generic)S
(module)301 4479 A
4811(and)S
4987(instan-)S
5842 V
720(tiate)S
932(it)S
1026(for)S
1182(its)S
1315(different)S
1701(purposes,)S
2121(but)S
2287(few)S
(languages)402 2477 A
2917(offer)S
3152(this)S
(possibility.)443 3335 A
3841(Also,)S
4094(the)S
4255(construction)S
4791(of)S
4914(a)S
4998(proper)S
5962 V
(interface)354 720 A
1102(for)S
1248(a)S
1320(generic)S
(module)301 1644 A
1972(is)S
2066(an)S
2188(intellectually)S
2741(intensive)S
3131(affair;)S
3406(so)S
3522(the)S
3672(cut-paste-adjust)S
4337(technique)S
4755(is)S
(still)151 4849 A
(popu-)234 5027 A
6082 V
720(lar.)S
6238 V
970(Once)S
1217(the)S
1374(project)S
1688(has)S
(settled)263 1856 A
2153(down,)S
2435(the)S
2592(question)S
2966(arises)S
3230(if)S
3326(these)S
3567(copied)S
3869(pairs)S
4099(can)S
4273(be)S
(found)234 4403 A
4672(back,)S
4922(to)S
5035(see)S
5199(if)S
6358 V
720(they)S
923(can)S
1093(be)S
1218(combined)S
1644(profitably.)S
2121(Most)S
(copy)195 2357 A
2582(pairs)S
(will)157 2808 A
2994(no)S
(longer)257 3123 A
3409(be)S
3533(identical)S
3909(and)S
(will)157 4083 A
4269(have)S
(undergone)424 4488 A
4941(more)S
5177(or)S
6478 V
720(less)S
(profound)368 911 A
1319(modifications;)S
(unrecognizable)615 1941 A
2597(copies)S
2895(are)S
3060(not)S
3229(interesting)S
3695(in)S
3814(this)S
4000(context,)S
4362(however.)S
4800(These)S
5082(con-)S
6598 V
720(siderations)S
1193(prompted)S
1615(the)S
1775(first)S
1974(author)S
2267(to)S
2381(design)S
2679(and)S
2860(implement)S
3326(a)S
3407(program,)S
3809(the)S
10 I
3968(software)S
4350(similarity)S
4772(tester)S
10 R
4996(.)S
5082(This)S
6718 V
720(program)S
1088(reads)S
1328(the)S
1478(code)S
1695(to)S
1800(be)S
1922(examined,)S
2365(reduces)S
2700(the)S
2850(text)S
3028(to)S
3133(a)S
3205(string)S
3461(of)S
3572(8-bits)S
3828(\252essential)S
4247(tokens\272,)S
4606(and)S
4779(then)S
4980(repeat-)S
6838 V
720(edly)S
918(finds)S
1144(the)S
(longest)290 1292 A
1607(common)S
(non-overlapping)664 1983 A
2672(substring.)S
3115(Finally)S
3425(it)S
3506(prints)S
3760(a)S
3830(report)S
4096(of)S
4205(its)S
4325(findings.)S
6994 V
970(The)S
1153(criteria)S
1466(for)S
1611(the)S
1761(reduction)S
2168(to)S
2273(essential)S
2647(tokens)S
2936(are)S
3087(programmed)S
3628(in)S
3733(a)S
(replaceable)460 3805 A
(module)301 4292 A
4620(in)S
4725(the)S
4875(similarity)S
7114 V
720(tester.)S
1019(They)S
1256(usually)S
(involve)301 1576 A
1907(reducing)S
2289(all)S
2419(identifiers)S
2857(and)S
3031(numbers)S
3406(to)S
3513(a)S
3587(single)S
3856(token,)S
4133(<idf>,)S
4413(all)S
4543(strings)S
4840(to)S
4947(a)S
5021(single)S
7234 V
720(<string>,)S
1120(all)S
1253(characters)S
1695(to)S
1805(<char>,)S
2151(removing)S
2569(all)S
2703(comment)S
3110(and)S
3288(lay-out,)S
3631(and)S
3809(replacing)S
(each)185 4217 A
4435(keyword)S
4820(of)S
4937(the)S
5093(pro-)S
7354 V
720(gramming)S
(language)363 1180 A
1590(by)S
1737(a)S
1829(separate)S
2207(token.)S
2527(The)S
2731(other)S
2985(program)S
3373(text)S
3571(symbols)S
3951(\(commas,)S
4391(semicolons,)S
4914(etc.\))S
5137(are)S
7474 V
(accepted)353 720 A
1098(unchanged)S
1558(as)S
1667(tokens.)S
2004(A)S
2102(typical)S
(2000-character)605 2401 A
3031(file)S
(will)157 3191 A
3373(result)S
3622(in)S
3725(a)S
3795(skeleton)S
4155(of)S
(about)223 4264 A
4512(a)S
(100)150 4582 A
4757(tokens.)S
7630 V
970(It)S
1063(is)S
1161(not)S
1320(at)S
1424(all)S
1556(clear)S
1784(a)S
1860(priori)S
2115(that)S
2297(this)S
2473(approach)S
2873(has)S
3038(any)S
3214(chance)S
3525(of)S
(success.)327 3640 A
4023(It)S
4116(is)S
4214(easy)S
4424(to)S
4533(imagine)S
4888(that)S
5071(even)S
7750 V
720(slight)S
(editing)279 977 A
(will)157 1289 A
1479(change)S
1797(the)S
1953(skeleton)S
2321(of)S
2438(a)S
2516(copied)S
(piece)213 2817 A
3063(of)S
3180(code)S
3403(to)S
3514(such)S
3731(a)S
3809(degree)S
4111(that)S
4295(the)S
4451(matching)S
4858(procedure)S
8427 V
EP
%%Page: 2 2
BP
/slant 0 def
/height 0 def
480 V
10 R
2906(-)S
2965(2)S
3040(-)S
840 V
720(described)S
(above)240 1142 A
(will)157 1418 A
1611(no)S
(longer)257 1747 A
(recognize)392 2040 A
2469(it.)S
2612(It)S
2711(is)S
2815(equally)S
3148(easy)S
3364(to)S
3479(imagine)S
3840(that)S
4028(this)S
4210(procedure)S
4650(is)S
(fraught)291 4754 A
5082(with)S
960 V
720(false)S
(positives.)382 940 A
1376(Practice)S
1731(shows,)S
2036(however,)S
2437(that)S
2617(meaningful)S
3104(results)S
3396(can)S
3565(be)S
3689(obtained.)S
4114(The)S
4300(dangers)S
4641(sketched)S
(above)240 5021 A
1080 V
720(do)S
852(materialize,)S
1358(but)S
1518(can)S
1691(be)S
1819(kept)S
2025(in)S
2136(check)S
2404(by)S
2537(specifying)S
2989(a)S
3067(minimum)S
3490(length)S
3774(for)S
3925(the)S
4081(common)S
4465(substrings.)S
4955(A)S
(good)200 5061 A
1200 V
720(value)S
971(is)S
1071(24)S
1204(essential)S
1584(tokens;)S
1907(values)S
2197(below)S
2476(18)S
2609(lead)S
2810(to)S
2920(spurious)S
(similarities)448 3292 A
3772(to)S
3882(be)S
4009(reported,)S
4402(for)S
4552(example)S
4925(between)S
1320 V
720(declaration)S
1194(lists;)S
1411(values)S
1695(over)S
1901(30)S
2028(cause)S
2279(some)S
2518(meaningful)S
3003(matches)S
3360(to)S
3465(be)S
3587(missed,)S
3918(for)S
4063(example)S
4431(short)S
4659(for-statements.)S
1440 V
720(With)S
949(a)S
1022(proper)S
(definition)391 1312 A
1730(of)S
1841(\252essential)S
2260(token\272)S
2555(and)S
2727(a)S
2799(suitable)S
3139(value)S
3384(of)S
3495(the)S
3645(minimum)S
4062(common)S
4440(substring)S
4835(length,)S
5138(the)S
1560 V
720(software)S
1096(similarity)S
1510(tester)S
1757(is)S
(found)234 1852 A
2114(to)S
2220(be)S
2343(a)S
2416(useful)S
2690(tool)S
2874(for)S
3020(locating)S
3373(stretches)S
3755(of)S
3868(similar)S
4177(code;)S
4424(the)S
4576(large)S
4807(majority)S
5177(of)S
1680 V
720(the)S
868(reported)S
(similarities)448 1229 A
1702(is)S
1794(meaningful.)S
1920 V
10 B
720(Testing)S
1064(for)S
1218(Copies)S
2076 V
10 R
970(Having)S
1296(had)S
1471(these)S
(good)200 1708 A
1938(experiences)S
2444(with)S
2653(the)S
2806(similarity)S
3223(tester,)S
3498(we)S
3647(started)S
3947(playing)S
4279(with)S
4489(the)S
4643(idea)S
4842(of)S
4957(using)S
5205(it)S
2196 V
720(to)S
839(find)S
1042(copied)S
1351(work)S
1599(in)S
1718(students')S
2122(submissions.)S
2703(Here,)S
2966(however,)S
3379(the)S
(doubts)267 3543 A
3851(raised)S
(above)240 4132 A
4412(were)S
4649(felt)S
4824(even)S
5054(more)S
2316 V
(strongly;)357 720 A
1114(after)S
1337(all,)S
(each)185 1500 A
(submitted)396 1722 A
2155(program)S
2533(tries)S
2744(to)S
2859(solve)S
3108(the)S
3269(same)S
3514(programming)S
4099(assignment.)S
4639(Would)S
4950(this)S
5133(not)S
2436 V
720(create)S
992(such)S
1206(a)S
1281(large)S
1513(similarity)S
1929(between)S
2295(the)S
(submitted)396 2448 A
2874(programs)S
3284(that)S
3464(the)S
3616(similarity)S
4031(tester)S
4279(would)S
4559(see)S
4717(copies)S
5003(every-)S
2556 V
720(where?)S
1063(And)S
1262(then)S
1461(there)S
1689(is)S
1782(the)S
1931(devious)S
2269(student,)S
2610(who)S
(knows)262 2809 A
3097(quite)S
3324(well)S
3524(that)S
3701(his)S
3844(program)S
(will)157 4212 A
4396(be)S
4518(checked)S
4875(automati-)S
2676 V
720(cally)S
945(and)S
1119(how)S
1321(is)S
1417(fully)S
1636(aware)S
1907(of)S
2020(how)S
2222(the)S
2374(similarity)S
2789(tester)S
3037(works.)S
3362(Would)S
3664(not)S
3821(this)S
3995(student)S
4314(be)S
4438(able)S
4635(to)S
4742(apply)S
4993(simple)S
2796 V
720(systematic)S
1170(modifications)S
1748(to)S
1851(the)S
1999(original)S
2337(code,)S
2577(so)S
2691(that)S
2867(the)S
3015(result)S
3264(would)S
3540(no)S
(longer)257 3665 A
3947(be)S
(recognized)442 4067 A
4534(as)S
4643(a)S
(copy?)240 4713 A
2952 V
10 I
970(What)S
1207(is)S
1299(\252to)S
1458(look)S
1656(like\272?)S
3108 V
10 R
970(To)S
1114(find)S
1308(an)S
1435(answer)S
1753(to)S
1863(the)S
2018(first)S
2213(question)S
2585(we)S
2735(need)S
2957(to)S
3068(examine)S
3442(the)S
3598(notion)S
3887(of)S
4004(\252similarity\272)S
4513(more)S
4753(closely.)S
5121(We)S
3228 V
720(define)S
1005(the)S
1161(similarity)S
10 I
1580(S)S
3248 V
7 I
1630(N)S
3228 V
10 R
1685(\()S
10 I
1719(A)S
10 R
1781(,)S
10 I
1814(B)S
10 R
1884(\))S
1951(of)S
2068(two)S
2252(program)S
2626(texts)S
10 I
2849(A)S
10 R
2944(en)S
10 I
3072(B)S
10 R
(under)229 3167 A
3429(a)S
3506(minimum)S
3928(string)S
4189(length)S
10 I
4472(N)S
10 R
4571(as)S
4687(follows.)S
5071(Sup-)S
3348 V
720(pose)S
929(we)S
1072(want)S
1293(to)S
1396(construct)S
1790(a)S
(copy)195 1860 A
2080(of)S
10 I
2189(A)S
10 R
2276(by)S
2401(using)S
2643(segments)S
3042(of)S
10 I
3151(B)S
10 R
3238(only,)S
3466(restricting)S
3900(ourselves)S
4305(to)S
4408(segments)S
4807(of)S
10 I
4916(N)S
10 R
5009(essen-)S
3468 V
720(tial)S
878(tokens)S
1169(or)S
1282(more.)S
1568(The)S
1754(more)S
10 I
1990(A)S
10 R
2081(and)S
10 I
2255(B)S
10 R
2346(are)S
2499(similar,)S
2833(the)S
2985(larger)S
3250(the)S
3402(part)S
3588(of)S
10 I
3701(A)S
10 R
3792(we)S
3939(can)S
4107(construct)S
4504(this)S
4677(way.)S
10 I
4923(S)S
3488 V
7 I
4973(N)S
3468 V
10 R
5028(\()S
10 I
5062(A)S
10 R
5124(,)S
10 I
5157(B)S
10 R
5227(\))S
3588 V
720(is)S
812(then)S
1010(defined)S
1337(as)S
1446(the)S
1594(percentage)S
2056(of)S
2165(essential)S
2537(tokens)S
2824(in)S
10 I
2927(A)S
10 R
3014(that)S
3190(can)S
3355(be)S
3475(constructed)S
3964(this)S
4134(way.)S
3744 V
970(Usually,)S
10 I
1341(S)S
3764 V
7 R
1402(1)S
3744 V
10 R
1445(\()S
10 I
1479(A)S
10 R
1541(,)S
10 I
1574(B)S
10 R
1644(\))S
(will)157 1711 A
1901(be)S
2030(near)S
(100%,)259 2238 A
2531(since)S
(each)185 2772 A
2991(token)S
3248(in)S
10 I
3360(A)S
10 R
(will)157 3456 A
3647(occur)S
3905(almost)S
4207(certainly)S
4594(somewhere)S
5087(in)S
10 I
5199(B)S
3864 V
10 R
720(too.)S
926(And)S
1127(for)S
1273(sufficient)S
1682(large)S
1911(values)S
2195(of)S
10 I
2306(N)S
10 R
2373(,)S
10 I
2425(S)S
3884 V
7 I
2475(N)S
3864 V
10 R
2530(\()S
10 I
2564(A)S
10 R
2626(,)S
10 I
2659(B)S
10 R
2729(\))S
(will)157 2790 A
2974(be)S
3096(equal)S
3341(to)S
3446(0%,)S
3632(unless)S
10 I
3910(A)S
10 R
3999(is)S
4093(an)S
4215(exact)S
(copy)195 4455 A
4677(of)S
10 I
4788(B)S
10 R
4850(.)S
4927(When)S
10 I
5194(N)S
3984 V
10 R
720(increases)S
1126(from)S
1358(0)S
1444(to)S
1558(the)S
1717(length)S
2004(of)S
10 I
2124(A)S
10 R
2186(,)S
10 I
2247(S)S
10 R
(will)157 2333 A
2526(decrease)S
(monotonously)573 2910 A
3519(from)S
3751(\(almost\))S
(100%)234 4124 A
4395(to)S
4510(\(almost\))S
4883(0%.)S
5104(The)S
4104 V
720(similarity)S
1136(percentage)S
10 I
1603(S)S
10 R
(will)157 1683 A
1870(decrease)S
2247(more)S
2483(sharply)S
2808(with)S
3016(increasing)S
10 I
3459(N)S
10 R
3555(for)S
(non-related)459 3702 A
10 I
4190(A)S
10 R
4281(and)S
10 I
4455(B)S
10 R
4546(than)S
4748(for)S
4895(related)S
10 I
5199(A)S
4224 V
10 R
720(and)S
10 I
894(B)S
10 R
956(.)S
1035(Experiments)S
1573(show)S
1814(that)S
1994(for)S
10 I
2141(N)S
10 Y
2216(=)S
10 R
2271(24)S
(non-related)459 2401 A
2890(solutions)S
3282(to)S
3390(a)S
3465(programming)S
4042(assignment)S
4524(have)S
4744(an)S
10 I
4869(S)S
10 R
(roughly)312 4949 A
4344 V
720(between)S
1088(20%)S
1304(and)S
1481(50%,)S
1721(whereas)S
2083(related)S
2389(solutions)S
2782(have)S
3003(an)S
10 I
3129(S)S
10 R
3210(of)S
3325(75%)S
3540(to)S
3649(80%)S
3864(at)S
3968(least.)S
4234(This)S
4444(allows)S
4738(us)S
4858(to)S
4967(make)S
5216(a)S
4464 V
720(clear)S
942(distinction)S
1391(between)S
1752(the)S
1900(two.)S
4620 V
970(We)S
(will)157 1164 A
1375(now)S
1602(examine)S
1997(assignment)S
10 I
2503(j2)S
10 R
2635(from)S
2886(the)S
(workshop)396 3064 A
3515(of)S
3654(the)S
(Introductory)503 3832 A
4390(Programming)S
4998(course)S
4740 V
720(described)S
(above,)265 1136 A
1431(for)S
1579(which)S
1854(39)S
1983(submissions)S
2502(had)S
2676(been)S
2895(made.)S
3192(Each)S
3423(of)S
3536(these)S
3772(was)S
3958(compared)S
4384(to)S
(each)185 4491 A
4705(of)S
4818(the)S
4970(38)S
5099(oth-)S
4860 V
720(ers,)S
888(yielding)S
(1274)200 1242 A
1467(match)S
1738(percentage)S
2201(values;)S
2512(these)S
2745(match)S
3017(percentages)S
3519(were)S
3742(then)S
(grouped)329 3941 A
4296(into)S
4478(ranges)S
4767(1-10,)S
5002(11-20,)S
4980 V
(....,)125 720 A
(91-100.)309 878 A
1245(Figure)S
1541(1)S
1624(shows)S
1907(the)S
2062(bar)S
2223(diagram)S
2585(of)S
2701(the)S
2856(frequencies)S
3353(of)S
3469(the)S
3624(various)S
3952(match)S
4230(percentages.)S
4788(We)S
4960(can)S
5132(see)S
5100 V
720(that)S
901(in)S
1009(this)S
1184(assignment)S
1666(most)S
1891(of)S
2005(the)S
2158(submissions)S
2678(are)S
2832(between)S
3198(1)S
3278(and)S
3453(10%)S
3667(similar.)S
4027(The)S
4214(distribution)S
4707(then)S
4910(trails)S
5143(off)S
5220 V
720(to)S
823(41-50%,)S
1191(followed)S
1574(by)S
1699(a)S
1769(few)S
(outliers.)327 1946 A
2323(Each)S
2550(of)S
2659(the)S
(outliers)302 2807 A
3134(signals)S
3438(an)S
(unusual)312 3558 A
3895(situation.)S
5376 V
970(Figure)S
1265(2)S
1347(shows)S
1630(the)S
1785(percentages)S
2293(for)S
2443(a)S
2520(single)S
2792(submission,)S
3300(compared)S
3729(to)S
3839(all)S
3972(other)S
(submitted)396 4212 A
4641(programs.)S
5104(The)S
5496 V
720(presence)S
1104(of)S
1219(a)S
1295(match)S
1572(with)S
1782(a)S
1858(high)S
2067(percentage)S
2535(\(61-70%\))S
2952(indicates)S
3341(that)S
3522(perhaps)S
3865(a)S
(copy)195 3940 A
4165(has)S
4329(been)S
4549(detected.)S
4965(Human)S
5616 V
720(intervention)S
1231(is)S
1323(then)S
1521(required)S
1882(to)S
1985(decide)S
2273(if)S
2360(indeed)S
(copying)323 2653 A
3001(has)S
3160(taken)S
(place,)238 3403 A
3666(which)S
3937(one)S
4108(is)S
4201(the)S
4350(original)S
4689(and)S
4860(if)S
4948(perhaps)S
5736 V
720(both)S
923(derive)S
1200(from)S
1421(a)S
1491(third)S
1706(source.)S
5892 V
10 I
970(Possible)S
(countermeasures)687 1336 A
6048 V
10 R
970(Assessing)S
1402(the)S
(vulnerability)514 1555 A
2099(of)S
2213(this)S
2388(test)S
2558(to)S
2666(actions)S
2981(of)S
3095(\252clever\272)S
3462(students)S
3821(requires)S
4176(us)S
4295(to)S
4403(delve)S
4651(deeper)S
4951(into)S
5138(the)S
6168 V
720(process)S
1053(of)S
1168(handing)S
1522(in)S
1631(and)S
1807(evaluating)S
2257(the)S
2411(students')S
2805(submissions.)S
3376(We)S
(will)157 3546 A
3733(again)S
3981(take)S
4179(the)S
(workshop)396 4332 A
(Introductory)503 4758 A
6288 V
720(Programming)S
1308(as)S
1427(an)S
1557(example.)S
1983(The)S
(workshop)396 2175 A
2606(consists)S
2959(of)S
3078(eleven)S
3376(programming)S
3958(assignments)S
4484(of)S
4603(increasing)S
5053(diffi-)S
6408 V
720(culty,)S
978(called)S
10 I
1251(a)S
10 R
(through)312 1333 A
10 I
1676(k)S
10 R
1721(.)S
1802(The)S
1990(six)S
2138(assignments)S
10 I
2660(a)S
10 R
(through)312 2741 A
10 I
3092(f)S
10 R
3151(are)S
3306(trivial)S
3578(and)S
3754(serve)S
3998(as)S
4113(rote)S
4301(exercises)S
4702(only;)S
4939(the)S
5093(four)S
6528 V
720(assignments)S
10 I
1245(g)S
10 R
(through)312 1329 A
10 I
1683(j)S
10 R
1745(are)S
1903(the)S
2060(main)S
2295(course;)S
2620(and)S
2799(assignment)S
10 I
3285(k)S
10 R
3364(is)S
3465(optional.)S
3878(Finished)S
4258(programming)S
4839(results)S
5137(are)S
6648 V
720(sent)S
919(by)S
1056(electronic)S
1491(mail)S
1707(to)S
1822(the)S
1982(supervisor,)S
2463(who)S
2673(tests)S
2889(the)S
3049(proper)S
3349(functioning)S
3848(of)S
3968(the)S
4127(program.)S
4554(If)S
4658(the)S
4817(program)S
5194(is)S
6768 V
720(allright,)S
1061(it)S
1142(is)S
1234(stored)S
1505(in)S
1608(a)S
1678(database)S
2050(specific)S
2389(to)S
2492(the)S
2640(assignment.)S
3167(If)S
3260(not,)S
3438(the)S
3586(supervisor)S
4030(talks)S
4245(to)S
4348(the)S
4496(student,)S
4837(explaining)S
6888 V
720(what)S
941(is)S
(wrong.)282 1033 A
1365(The)S
1547(student)S
1862(then)S
2060(corrects)S
2405(the)S
2553(work)S
2785(and)S
2955(the)S
3103(procedure)S
3531(is)S
3623(repeated.)S
7044 V
970(The)S
1162(programs)S
1577(in)S
1690(the)S
1848(database)S
2230(are)S
2389(automatically)S
2972(compared)S
3404(to)S
(each)185 3517 A
3737(other,)S
4004(using)S
4256(a)S
4336(comparison)S
4840(process)S
5177(of)S
7164 V
720(which)S
996(the)S
1149(similarity)S
1565(tester)S
1814(is)S
1911(the)S
2064(algorithmic)S
2557(core.)S
2810(If)S
2907(the)S
3059(database)S
3435(contains)S
10 I
3799(n)S
10 R
3878(programs,)S
4312(this)S
4486(process)S
4817(results)S
5109(in)S
5216(a)S
7284 V
720(list)S
868(of)S
10 I
977(n)S
10 Y
1043(-)S
10 R
1098(1)S
1173(percentages;)S
1702(a)S
1772(sample)S
2082(list)S
2230(is)S
2322(shown)S
2609(in)S
2712(Figure)S
3000(3.)S
3125(The)S
3307(supervisor)S
3751(can)S
(access)258 3916 A
4199(these)S
4432(lists.)S
4670(Programs)S
5082(with)S
7404 V
720(a)S
792(match)S
1065(percentage)S
1529(of)S
1640(60%)S
1851(or)S
1962(higher)S
2246(are)S
2397(examined)S
2815(personally)S
3261(by)S
3387(the)S
3536(supervisor,)S
4006(to)S
4110(verify)S
(originality.)444 4377 A
4872(If)S
4966(there)S
5194(is)S
7524 V
720(a)S
(strong)251 790 A
1066(suspicion)S
1470(of)S
(copying,)348 1579 A
1952(this)S
2122(is)S
2214(reported)S
2575(to)S
2678(the)S
(workshop)396 2827 A
3249(coordinator.)S
3789(Match)S
4072(percentages)S
4574(of)S
4684(80%)S
4894(or)S
5004(higher)S
7644 V
720(are)S
869(always)S
1174(reported)S
1535(automatically)S
2108(to)S
2211(the)S
(workshop)396 2359 A
2780(coordinator)S
3269(by)S
3394(the)S
3542(comparison)S
4036(process.)S
7800 V
970(If)S
1075(everything)S
1542(is)S
1646(in)S
1761(order,)S
2036(the)S
2196(program)S
2574(code)S
2801(is)S
2905(printed)S
3227(and)S
3409(graded)S
3720(by)S
3857(the)S
4017(supervisor)S
4474(for)S
4630(style,)S
4883(structure,)S
8427 V
EP
%%Page: 3 3
BP
/slant 0 def
/height 0 def
480 V
10 R
2906(-)S
2965(3)S
3040(-)S
840 V
720(conformity)S
1192(to)S
1295(guidelines,)S
1758(etc.)S
996 V
970(Students)S
1341(are)S
1490(informed)S
1884(at)S
1982(the)S
2130(start)S
2329(of)S
2438(the)S
(workshop)396 2586 A
3007(that)S
3183(their)S
3393(submissions)S
(will)157 3909 A
4092(be)S
4213(checked)S
4569(automatically)S
5143(for)S
1116 V
720(copies.)S
1052(The)S
1234(student)S
1549(who)S
1747(desires)S
2052(to)S
2155(submit)S
2453(copied)S
2746(code)S
(without)307 2961 A
3293(being)S
(caught)268 3541 A
(faces)208 3834 A
4067(the)S
4215(following)S
4631(challenges:)S
1272 V
10 R-1
720(-)S
10 R
970(The)S
1155(essential)S
1530(tokens)S
1820(of)S
1932(the)S
(fraudulent)414 2083 A
2525(code)S
2743(must)S
2966(differ)S
3219(regularly)S
3611(from)S
3835(those)S
4075(of)S
4188(the)S
4340(original)S
4682(or)S
4795(the)S
4947(similar-)S
1392 V
970(ity)S
1103(tester)S
1349(process)S
(will)157 1678 A
(sound)239 1862 A
2128(the)S
2278(alarm.)S
2585(This)S
2791(means)S
3075(that)S
3253(changing)S
3648(names)S
3932(systematically,)S
4560(adding)S
4860(or)S
4970(remov-)S
1512 V
970(ing)S
1125(comment)S
1526(and/or)S
(layout,)276 1810 A
2113(and)S
2285(code)S
2502(motion)S
2813(are)S
2964(ineffective.)S
3473(It)S
3562(is)S
3656(important)S
4074(to)S
4179(note)S
4379(that)S
4557(the)S
4707(similarity)S
5121(test)S
1632 V
970(finds)S
1212(the)S
10 I
1376(set)S
1529(of)S
(longest)290 1648 A
1979(common)S
2361(substrings)S
10 R
2773(,)S
2839(which)S
3125(is)S
(order-insensitive,)702 3232 A
3974(unlike)S
4265(the)S
4428(UNIX)S
4721(program)S
10 I
(diff)134 5102 A
10 R
5236(,)S
1752 V
970(which)S
1241(find)S
1428(the)S
10 I
(longest)290 1576 A
1891(common)S
2257(subsequence)S
10 R
2765(,)S
2815(which)S
3086(is)S
(order-sensitive.)624 3178 A
1908 V
10 R-1
720(-)S
10 R
970(The)S
(submitted)396 1154 A
1577(code)S
1794(is)S
1888(tested)S
2150(by)S
2277(the)S
2427(supervisor)S
2873(on)S
3000(a)S
3072(testbed)S
3384(specific)S
3725(to)S
3830(the)S
3980(assignment,)S
4485(and)S
4658(has)S
4820(to)S
4926(function)S
2028 V
970(properly.)S
1393(This)S
1604(means)S
1893(that)S
2076(the)S
2231(student)S
(cannot)268 2553 A
2853(compose)S
3242(the)S
(submitted)396 3397 A
3825(code)S
4047(from)S
4274(copied)S
4573(segments)S
4978(of)S
5093(pro-)S
2148 V
970(grams)S
1249(of)S
1367(other)S
1608(students.)S
(Getting)302 2021 A
2357(such)S
2575(an)S
2704(assembly)S
3112(to)S
3224(work)S
3465(properly)S
3840(would)S
4125(probably)S
(involve)301 4516 A
4851(at)S
4958(least)S
5177(as)S
2268 V
970(much)S
1221(work)S
1456(as)S
1568(doing)S
1824(the)S
1975(exercise)S
2334(in)S
2440(the)S
2591(first)S
(place.)238 2782 A
3073(The)S
3258(test)S
3426(also)S
3615(denies)S
3899(the)S
4049(student)S
4366(the)S
(possibility)418 4516 A
4961(to)S
5066(hand)S
2388 V
970(in)S
1074(a)S
1145(totally)S
1428(unrelated)S
1829(text,)S
2031(for)S
2175(example)S
2542(a)S
2614(UNIX)S
2894(manual)S
3217(page.)S
3484(Such)S
3712(a)S
3784(text)S
3962(would)S
4240(show)S
4479(a)S
4551(match)S
4824(percentage)S
2508 V
970(close)S
1202(to)S
1305(0%)S
1464(but)S
1617(would)S
1893(not)S
2046(compile,)S
2420(let)S
2546(alone)S
2789(run)S
2948(correctly.)S
2664 V
(Occasionally,)551 970 A
1546(a)S
1616(student)S
1932(submits)S
2270(his)S
2413(program)S
(under)229 2780 A
3035(the)S
(wrong)257 3184 A
3467(assignment)S
3945(name,)S
4214(or)S
4324(a)S
4395(supervisor)S
4840(stores)S
5101(it)S
5183(in)S
2784 V
970(the)S
(wrong)257 1122 A
1408(database.)S
(Suppose)340 1834 A
2203(,)S
2257(a)S
2331(solution)S
2683(to)S
2790(assignment)S
10 I
3271(j2)S
10 R
3378(is)S
(submitted)396 3474 A
3899(as)S
4011(a)S
4084(solution)S
4435(to)S
4541(assignment)S
10 I
5021(j3)S
10 R
5099(.)S
5177(In)S
2904 V
970(that)S
1150(case)S
1353(the)S
1505(match)S
1780(percentage)S
2246(is)S
2342(close)S
2578(to)S
2685(0%,)S
2873(which)S
3148(is)S
3244(noted)S
3496(by)S
3625(the)S
3777(supervisor,)S
4251(who)S
4454(can)S
4624(then)S
4827(correct)S
5138(the)S
3024 V
970(situation.)S
1391(Extremely)S
1836(low)S
2012(match)S
2283(percentages)S
2784(are)S
2933(as)S
3042(suspicious)S
3485(as)S
3594(very)S
3798(high)S
4001(match)S
4272(percentages.)S
3180 V
10 R-1
720(-)S
10 R
970(If)S
1066(the)S
1217(code)S
1435(passes)S
1720(these)S
1955(two)S
2134(hurdles,)S
2484(it)S
(will)157 2569 A
(still)151 2755 A
2935(be)S
3059(graded)S
3362(by)S
3491(personal)S
3861(inspection)S
4303(by)S
4432(the)S
4584(supervisor.)S
5082(This)S
3300 V
970(means)S
1259(that)S
1441(is)S
1539(has)S
1704(to)S
(look)178 1813 A
(good)200 2022 A
2253(and)S
2429(the)S
2583(student)S
(cannot)268 2904 A
3203(afford)S
3481(to)S
3590(add)S
3766(dummy)S
4103(statements)S
4559(at)S
4663(irregular)S
5042(inter-)S
3420 V
970(vals)S
1170(to)S
1286(throw)S
1559(off)S
1716(the)S
1878(similarity)S
2303(tester.)S
2611(Adding)S
2951(useless)S
3275(parameters)S
3757(to)S
3874(procedures)S
4355(would)S
4645(also)S
4846(attract)S
5138(the)S
3540 V
970(supervisors)S
1453(attention.)S
3780 V
10 B
720(Experiences)S
3936 V
10 R
970(Of)S
1110(course)S
1406(we)S
(cannot)268 1558 A
1860(guarantee)S
2286(that)S
2471(there)S
2707(is)S
2808(no)S
2942(strategy)S
3295(to)S
3407(create)S
3683(a)S
3762(copied)S
4064(submission)S
4549(that)S
(will)157 4734 A
(success-)336 4925 A
4056 V
720(fully)S
937(circumvent)S
1417(the)S
(above)240 1567 A
1834(obstacles,)S
2255(but)S
2410(we)S
2555(are)S
2706(not)S
2861(aware)S
3130(of)S
3241(any)S
3412(such)S
3622(strategy.)S
4017(It)S
4105(seems)S
4377(reasonable)S
4834(to)S
(suppose)323 4938 A
4176 V
720(that)S
905(such)S
1123(a)S
1202(strategy,)S
(should)267 1580 A
1881(it)S
1971(exist,)S
2220(would)S
2505(require)S
2825(an)S
(amount)301 2954 A
3289(of)S
3407(work)S
3648(similar)S
3962(to)S
4074(that)S
4259(of)S
4377(just)S
4556(doing)S
4818(the)S
4976(assign-)S
4296 V
720(ment.)S
1010(Changing)S
1438(for-statements)S
2053(to)S
2169(while)S
2431(statements,)S
(splitting)329 2919 A
3286(larger)S
3560(procedures)S
4040(into)S
4234(smaller)S
4569(ones,)S
(choosing)362 4816 A
5216(a)S
4416 V
720(somewhat)S
1153(different)S
1526(data)S
1719(structure,)S
2122(are)S
2271(techniques)S
2726(that)S
2902(come)S
3145(to)S
3248(mind.)S
3529(But)S
3699(the)S
3847(result)S
4096(of)S
4205(such)S
4415(manipulations)S
5010(would)S
4536 V
720(hardly)S
1002(be)S
1122(a)S
(copy)195 1192 A
1412(any)S
1582(more,)S
1839(and)S
2009(breaking)S
2386(the)S
2534(system)S
2838(would)S
3114(be)S
3234(interesting)S
3684(only)S
3887(as)S
3996(a)S
4066(sport.)S
4692 V
970(It)S
1064(turns)S
1297(out)S
1457(that)S
1640(copied)S
1940(submissions)S
2462(are)S
2618(the)S
2773(exception.)S
3246(The)S
3435(similarity)S
3853(tester)S
4104(detects)S
4416(between)S
4784(one)S
4961(and)S
5138(ten)S
4812 V
720(attempts)S
1115(to)S
1247(submit)S
1574(copied)S
1896(material)S
2281(per)S
(workshop,)421 2464 A
2939(depending)S
3410(on)S
3563(size)S
3773(and)S
3971(organization)S
4527(of)S
4664(the)S
(workshop.)421 4840 A
4932 V
720(Attempts)S
1119(to)S
1227(mislead)S
1570(the)S
1723(similarity)S
2139(tester)S
2389(have)S
2610(never)S
2865(been)S
3086(observed.)S
3530(For)S
(obvious)317 3701 A
4049(reasons,)S
4407(we)S
4556(have)S
4777(no)S
4908(informa-)S
5052 V
720(tion)S
(about)223 901 A
(undiscovered,)561 1149 A
(successful)414 1735 A
2174(attempts.)S
5208 V
970(All)S
1132(cases)S
(found)234 1378 A
(above)240 1645 A
1918(the)S
2074(80%)S
2291(threshold)S
2698(turned)S
2988(out)S
3149(to)S
3260(be)S
3388(real)S
3573(copies)S
(upon)200 3863 A
4096(inspection.)S
4593(In)S
(each)185 4711 A
4930(case)S
5138(the)S
5328 V
(correspondence)632 720 A
1388(between)S
1760(the)S
1919(printed)S
2240(programs)S
2656(was)S
2849(seen)S
3064(to)S
3178(be)S
3309(very)S
(strong,)276 3524 A
3835(even)S
(stronger)330 4060 A
4425(than)S
4633(the)S
4791(80%)S
5010(would)S
5448 V
(suggest.)326 720 A
1109(For)S
1287(example,)S
1692(identifiers)S
2140(matched)S
2520(textually,)S
2936(or)S
3059(comments)S
3511(were)S
3747(identical,)S
4158(two)S
4348(features)S
4707(that)S
4897(were)S
5133(not)S
5568 V
720(included)S
1091(in)S
1194(the)S
1342(essential)S
1714(tokens)S
2001(and)S
2171(thus)S
2363(could)S
2611(not)S
2764(contribute)S
3197(to)S
3300(the)S
3448(match)S
3719(percentage.)S
5724 V
970(Originally)S
1418(we)S
1570(set)S
1716(the)S
1873(threshold)S
2281(at)S
2389(60%,)S
2633(but)S
2796(this)S
2976(turned)S
3268(out)S
3431(to)S
3544(be)S
3674(too)S
3837(low.)S
4073(First,)S
4318(short)S
4554(programs)S
4969(\(one)S
5183(to)S
5844 V
720(one-and-a-half)S
1350(pages\))S
1649(contain)S
1981(so)S
2106(much)S
2365(standard)S
2742(material)S
3109(that)S
3296(the)S
3455(reported)S
3827(match)S
4109(percentage)S
4582(is)S
4685(too)S
4849(high;)S
5091(and,)S
5964 V
(second,)304 720 A
1050(even)S
1266(if)S
1354(the)S
1503(match)S
1775(percentage)S
2238(was)S
2421(reported)S
2783(correctly,)S
3193(it)S
3275(is)S
3368(difficult)S
3719(to)S
3823(tell)S
3978(if)S
4066(a)S
4137(short)S
4364(program)S
4731(is)S
4824(a)S
(copy)195 4895 A
5116(if)S
5205(it)S
6084 V
720(differs)S
1009(for)S
1152(40%)S
1361(from)S
1582(the)S
1730(purported)S
2146(original.)S
2534(No)S
2682(such)S
(doubts)267 2891 A
3183(remain)S
3488(with)S
3692(a)S
3762(threshold)S
4161(of)S
4270(80%.)S
6240 V
970(All)S
1137(students)S
1504(confronted)S
1978(with)S
2195(suspicion)S
2612(of)S
(submitting)429 2734 A
3201(copied)S
3507(work)S
3752(confirmed)S
4204(this)S
4388(suspicion,)S
4831(sometimes)S
6360 V
720(after)S
939(some)S
1184(discussion.)S
1685(Often)S
1947(their)S
2164(defense)S
2504(was)S
2693(that)S
2876(since)S
3115(they)S
3320(had)S
3497(taken)S
3747(great)S
3981(pains)S
4225(to)S
4335(change)S
4652(the)S
4807(program,)S
5205(it)S
6480 V
720(was)S
910(no)S
(longer)257 1043 A
1334(a)S
(copy.)220 1413 A
1692(These)S
1967(changes)S
2325(were,)S
2581(however,)S
2987(usually)S
3311(restricted)S
3721(to)S
3833(systematically)S
4443(replacing)S
4852(identifiers)S
6600 V
720(and)S
893(changing)S
1289(the)S
1440(order)S
1681(of)S
1793(declarations,)S
2333(so)S
2450(basically)S
2836(the)S
2987(same)S
3222(program)S
3591(was)S
(submitted.)421 3776 A
4250(We)S
4418(have)S
4636(seen)S
(above)240 4843 A
5110(that)S
6720 V
720(the)S
868(similarity)S
1279(tester)S
1523(is)S
(insensitive)430 1615 A
2070(to)S
2173(such)S
2382(changes.)S
2781(The)S
2963(10)S
3088(to)S
3191(15%)S
3400(of)S
3509(code)S
3724(that)S
10 I
3900(was)S
10 R
4089(different)S
4462(usually)S
4777(consisted)S
5177(of)S
6840 V
(rewritten)365 720 A
1110(output)S
1391(statements.)S
1891(The)S
2073(algorithm)S
2489(itself)S
2716(was)S
2898(never)S
3147(changed.)S
6996 V
970(The)S
1164(goal)S
1374(of)S
1495(our)S
1666(computer)S
2083(science)S
(workshops)435 2417 A
2889(is)S
2993(to)S
(teach)213 3108 A
3358(the)S
3518(students)S
3884(something)S
4339(rather)S
4612(than)S
4822(to)S
4938(test)S
5116(and)S
7116 V
720(evaluate)S
1085(them.)S
1365(Therefore)S
1793(it)S
1878(is)S
1974(no)S
2103(problem)S
2467(when)S
2714(students)S
3072(seek)S
3280(help)S
3482(from)S
3706(other)S
3941(students.)S
4348(It)S
4438(is)S
4533(immaterial)S
4998(if)S
5088(they)S
7236 V
720(learn)S
951(from)S
1176(the)S
1328(classroom)S
1765(lectures,)S
2133(the)S
(books)239 2285 A
2554(used)S
2768(in)S
2876(class,)S
3127(the)S
(workshop,)421 3280 A
3731(the)S
3884(supervisor,)S
4358(or)S
4472(a)S
4547(fellow)S
4835(student;)S
5183(in)S
7356 V
720(all)S
849(cases)S
1090(they)S
1291(learn)S
1521(something)S
1967(and)S
2140(that)S
2319(is)S
2414(the)S
2565(only)S
2771(thing)S
3005(that)S
3184(matters.)S
3559(Selection)S
3962(and)S
4134(evaluation)S
4580(takes)S
(places)252 4814 A
5093(dur-)S
7476 V
720(ing)S
(written)286 884 A
1206(tests.)S
1471(This)S
(attitude)302 1686 A
2024(does)S
2244(not,)S
2433(however,)S
2841(imply)S
3111(that)S
3298(doing)S
3562(the)S
(workshop)396 3721 A
4154(is)S
4258(optional.)S
4674(There)S
4947(is)S
5051(a)S
5133(big)S
7596 V
720(difference)S
1174(between)S
1554(hearing)S
1900(from)S
(somebody)412 2139 A
2594(how)S
2810(a)S
2898(problem)S
3276(can)S
3459(be)S
3597(tackled)S
3931(and)S
4119(then)S
4335(tackle)S
4619(it)S
(yourself,)355 4718 A
5116(and)S
7716 V
720(obtaining)S
1130(the)S
1284(complete)S
1684(solution)S
2039(from)S
(somebody)412 2267 A
2711(else)S
2900(and)S
3077(handing)S
3432(it)S
3520(in)S
3630(as)S
3746(original)S
4091(work.)S
4380(The)S
4569(difference)S
5011(lies)S
5183(in)S
8427 V
EP
%%Page: 4 4
BP
/slant 0 def
/height 0 def
480 V
10 R
2906(-)S
2965(4)S
3040(-)S
840 V
720(the)S
868(learning)S
1223(value.)S
1080 V
10 B
720(Conclusion)S
1236 V
10 R
970(Our)S
1163(present)S
1490(impression,)S
(though)278 1992 A
(unproven,)404 2306 A
2746(is)S
2849(that)S
3036(the)S
3195(only)S
3409(way)S
3613(to)S
3728(circumvent)S
4218(the)S
4378(similarity)S
4801(tester)S
5057(is)S
5161(by)S
1356 V
(writing)291 720 A
1052(original)S
1406(code.)S
1687(This)S
1907(means)S
2205(that)S
(anybody)345 2397 A
2783(who)S
2997(submits)S
(somebody)412 3350 A
3803(else's)S
4074(work)S
4322(as)S
4447(his)S
4605(own,)S
4844(even)S
5075(after)S
1476 V
720(modifications)S
1298(in)S
1401(comment,)S
1825(identifiers,)S
(layout)251 2284 A
2560(and)S
2730(order)S
2968(of)S
3077(program)S
3443(units,)S
3688(is)S
(exposed)329 3780 A
4134(as)S
4243(a)S
4313(cheater.)S
8427 V
EP
%%Page: 5 5
BP
/slant 0 def
/height 0 def
480 V
10 R
2906(-)S
2965(5)S
3040(-)S
840 V
10 B
720(Figures)S
996 V
970 H
2720 
3560 
0.00 
0.00 
272.00 
356.00 
startFig 
%%BeginDocument: /home/dick/src/sim/Paper/./fig1.ps
%%!PS-Adobe-2.0 EPSF-2.0
%%Title: fig1.fig
%%Creator: fig2dev Version 3.2 Patchlevel 1
%%CreationDate: Fri Jun 21 11:08:40 2002
%%For: dick@blade014.cs.vu.nl (Dick Grune)
%%Orientation: Portrait
%%BoundingBox: 0 0 272 356
%%Pages: 0
%%BeginSetup
%%EndSetup
%%Magnification: 0.8500
%%EndComments
/$F2psDict 200 dict def
$F2psDict begin
$F2psDict /mtrx matrix put
/col-1 {0 setgray} bind def
/col0 {0.000 0.000 0.000 srgb} bind def
/col1 {0.000 0.000 1.000 srgb} bind def
/col2 {0.000 1.000 0.000 srgb} bind def
/col3 {0.000 1.000 1.000 srgb} bind def
/col4 {1.000 0.000 0.000 srgb} bind def
/col5 {1.000 0.000 1.000 srgb} bind def
/col6 {1.000 1.000 0.000 srgb} bind def
/col7 {1.000 1.000 1.000 srgb} bind def
/col8 {0.000 0.000 0.560 srgb} bind def
/col9 {0.000 0.000 0.690 srgb} bind def
/col10 {0.000 0.000 0.820 srgb} bind def
/col11 {0.530 0.810 1.000 srgb} bind def
/col12 {0.000 0.560 0.000 srgb} bind def
/col13 {0.000 0.690 0.000 srgb} bind def
/col14 {0.000 0.820 0.000 srgb} bind def
/col15 {0.000 0.560 0.560 srgb} bind def
/col16 {0.000 0.690 0.690 srgb} bind def
/col17 {0.000 0.820 0.820 srgb} bind def
/col18 {0.560 0.000 0.000 srgb} bind def
/col19 {0.690 0.000 0.000 srgb} bind def
/col20 {0.820 0.000 0.000 srgb} bind def
/col21 {0.560 0.000 0.560 srgb} bind def
/col22 {0.690 0.000 0.690 srgb} bind def
/col23 {0.820 0.000 0.820 srgb} bind def
/col24 {0.500 0.190 0.000 srgb} bind def
/col25 {0.630 0.250 0.000 srgb} bind def
/col26 {0.750 0.380 0.000 srgb} bind def
/col27 {1.000 0.500 0.500 srgb} bind def
/col28 {1.000 0.630 0.630 srgb} bind def
/col29 {1.000 0.750 0.750 srgb} bind def
/col30 {1.000 0.880 0.880 srgb} bind def
/col31 {1.000 0.840 0.000 srgb} bind def

end
save
-42.0 393.0 translate
1 -1 scale

/cp {closepath} bind def
/ef {eofill} bind def
/gr {grestore} bind def
/gs {gsave} bind def
/sa {save} bind def
/rs {restore} bind def
/l {lineto} bind def
/m {moveto} bind def
/rm {rmoveto} bind def
/n {newpath} bind def
/s {stroke} bind def
/sh {show} bind def
/slc {setlinecap} bind def
/slj {setlinejoin} bind def
/slw {setlinewidth} bind def
/srgb {setrgbcolor} bind def
/rot {rotate} bind def
/sc {scale} bind def
/sd {setdash} bind def
/ff {findfont} bind def
/sf {setfont} bind def
/scf {scalefont} bind def
/sw {stringwidth} bind def
/tr {translate} bind def
/tnt {dup dup currentrgbcolor
  4 -2 roll dup 1 exch sub 3 -1 roll mul add
  4 -2 roll dup 1 exch sub 3 -1 roll mul add
  4 -2 roll dup 1 exch sub 3 -1 roll mul add srgb}
  bind def
/shd {dup dup currentrgbcolor 4 -2 roll mul 4 -2 roll mul
  4 -2 roll mul srgb} bind def
/$F2psBegin {$F2psDict begin /$F2psEnteredState save def} def
/$F2psEnd {$F2psEnteredState restore end} def
%%EndProlog

$F2psBegin
10 setmiterlimit
n -1000 8330 m -1000 -1000 l 6862 -1000 l 6862 8330 l cp clip
 0.05354 0.05354 sc
% Polyline
7.500 slw
n 1350 6750 m 5850 6750 l gs col0 s gr 
% Polyline
n 5850 6750 m 5850 6570 l 5400 6570 l 5400 6750 l gs col0 s gr 
% Polyline
n 4950 6750 m 4950 6660 l 4500 6660 l 4500 6750 l gs col0 s gr 
% Polyline
n 4500 6750 m 4500 6660 l 4050 6660 l 4050 6750 l gs col0 s gr 
% Polyline
n 3150 6750 m 3150 5940 l 2700 5940 l 2700 6750 l gs col0 s gr 
% Polyline
n 3600 6750 m 3600 6570 l 3150 6570 l 3150 6750 l gs col0 s gr 
% Polyline
n 2700 6750 m 2700 5310 l gs col0 s gr 
% Polyline
n 2250 6750 m 2250 5310 l gs col0 s gr 
% Polyline
n 1800 6750 m 1800 5310 l gs col0 s gr 
% Polyline
n 1350 6750 m 1350 5310 l gs col0 s gr 
% Polyline
n 1350 5850 m 1260 5850 l gs col0 s gr 
% Polyline
n 2700 5130 m 2700 4230 l 2250 4230 l gs col0 s gr 
% Polyline
n 2250 5220 m 2250 3690 l gs col0 s gr 
% Polyline
n 1800 5220 m 1800 3600 l gs col0 s gr 
% Polyline
n 1350 5175 m 1350 3600 l gs col0 s gr 
% Polyline
n 1350 4500 m 1260 4500 l gs col0 s gr 
% Polyline
n 2250 3510 m 2250 2520 l 1800 2520 l gs col0 s gr 
% Polyline
n 1800 3510 m 1800 2070 l gs col0 s gr 
% Polyline
n 1350 3420 m 1350 1980 l gs col0 s gr 
% Polyline
n 1350 2700 m 1260 2700 l gs col0 s gr 
% Polyline
n 1800 1890 m 1800 990 l 1350 990 l gs col0 s gr 
% Polyline
n 1350 1800 m 1350 720 l gs col0 s gr 
% Polyline
n 1350 1350 m 1260 1350 l gs col0 s gr 
% Polyline
n 2700 5310 m 2699 5310 l 2695 5307 l 2686 5303 l 2671 5295 l 2653 5287 l
 2633 5278 l 2614 5271 l 2597 5266 l 2581 5264 l 2565 5265 l
 2554 5267 l 2541 5271 l 2529 5277 l 2516 5284 l 2503 5292 l
 2489 5301 l 2475 5310 l 2461 5319 l 2447 5328 l 2434 5336 l
 2421 5343 l 2409 5349 l 2396 5353 l 2385 5355 l 2369 5356 l
 2353 5354 l 2336 5349 l 2317 5342 l 2297 5333 l 2279 5325 l
 2264 5317 l 2255 5313 l 2251 5310 l 2250 5310 l gs col0 s gr 
% Polyline
n 2250 5400 m 2250 5399 l 2247 5396 l 2241 5388 l 2231 5375 l 2218 5358 l
 2203 5339 l 2186 5320 l 2170 5302 l 2155 5287 l 2141 5276 l
 2128 5269 l 2115 5265 l 2104 5265 l 2091 5267 l 2079 5271 l
 2066 5278 l 2053 5286 l 2039 5295 l 2025 5306 l 2011 5316 l
 1997 5326 l 1984 5335 l 1971 5343 l 1959 5349 l 1946 5353 l
 1935 5355 l 1919 5356 l 1903 5354 l 1886 5349 l 1867 5342 l
 1847 5333 l 1829 5325 l 1814 5317 l 1805 5313 l 1801 5310 l
 1800 5310 l gs col0 s gr 
% Polyline
n 1800 5400 m 1800 5399 l 1797 5396 l 1791 5388 l 1781 5375 l 1768 5358 l
 1753 5339 l 1736 5320 l 1720 5302 l 1705 5287 l 1691 5276 l
 1678 5269 l 1665 5265 l 1654 5265 l 1641 5267 l 1629 5271 l
 1616 5278 l 1603 5286 l 1589 5295 l 1575 5306 l 1561 5316 l
 1547 5326 l 1534 5335 l 1521 5343 l 1509 5349 l 1496 5353 l
 1485 5355 l 1469 5356 l 1453 5354 l 1436 5349 l 1417 5342 l
 1397 5333 l 1379 5325 l 1364 5317 l 1355 5313 l 1351 5310 l
 1350 5310 l gs col0 s gr 
% Polyline
n 1800 5220 m 1800 5219 l 1797 5216 l 1791 5208 l 1781 5195 l 1768 5178 l
 1753 5159 l 1736 5140 l 1720 5122 l 1705 5107 l 1691 5096 l
 1678 5089 l 1665 5085 l 1654 5085 l 1641 5087 l 1629 5091 l
 1616 5098 l 1603 5106 l 1589 5115 l 1575 5126 l 1561 5136 l
 1547 5146 l 1534 5155 l 1521 5163 l 1509 5169 l 1496 5173 l
 1485 5175 l 1469 5176 l 1453 5174 l 1436 5169 l 1417 5162 l
 1397 5153 l 1379 5145 l 1364 5137 l 1355 5133 l 1351 5130 l
 1350 5130 l gs col0 s gr 
% Polyline
n 2250 5220 m 2250 5219 l 2247 5216 l 2241 5208 l 2231 5195 l 2218 5178 l
 2203 5159 l 2186 5140 l 2170 5122 l 2155 5107 l 2141 5096 l
 2128 5089 l 2115 5085 l 2104 5085 l 2091 5087 l 2079 5091 l
 2066 5098 l 2053 5106 l 2039 5115 l 2025 5126 l 2011 5136 l
 1997 5146 l 1984 5155 l 1971 5163 l 1959 5169 l 1946 5173 l
 1935 5175 l 1919 5176 l 1903 5174 l 1886 5169 l 1867 5162 l
 1847 5153 l 1829 5145 l 1814 5137 l 1805 5133 l 1801 5130 l
 1800 5130 l gs col0 s gr 
% Polyline
n 2700 5116 m 2699 5116 l 2695 5113 l 2686 5109 l 2671 5101 l 2653 5093 l
 2633 5084 l 2614 5077 l 2597 5072 l 2581 5070 l 2565 5071 l
 2554 5073 l 2541 5077 l 2529 5083 l 2516 5090 l 2503 5098 l
 2489 5107 l 2475 5116 l 2461 5125 l 2447 5134 l 2434 5142 l
 2421 5149 l 2409 5155 l 2396 5159 l 2385 5161 l 2369 5162 l
 2353 5160 l 2336 5155 l 2317 5148 l 2297 5139 l 2279 5131 l
 2264 5123 l 2255 5119 l 2251 5116 l 2250 5116 l gs col0 s gr 
% Polyline
n 2250 3690 m 2250 3689 l 2247 3686 l 2241 3678 l 2231 3665 l 2218 3648 l
 2203 3629 l 2186 3610 l 2170 3592 l 2155 3577 l 2141 3566 l
 2128 3559 l 2115 3555 l 2104 3555 l 2091 3557 l 2079 3561 l
 2066 3568 l 2053 3576 l 2039 3585 l 2025 3596 l 2011 3606 l
 1997 3616 l 1984 3625 l 1971 3633 l 1959 3639 l 1946 3643 l
 1935 3645 l 1919 3646 l 1903 3644 l 1886 3639 l 1867 3632 l
 1847 3623 l 1829 3615 l 1814 3607 l 1805 3603 l 1801 3600 l
 1800 3600 l gs col0 s gr 
% Polyline
n 1800 3672 m 1800 3671 l 1797 3668 l 1791 3660 l 1781 3647 l 1768 3630 l
 1753 3611 l 1736 3592 l 1720 3574 l 1705 3559 l 1691 3548 l
 1678 3541 l 1665 3537 l 1654 3537 l 1641 3539 l 1629 3543 l
 1616 3550 l 1603 3558 l 1589 3567 l 1575 3578 l 1561 3588 l
 1547 3598 l 1534 3607 l 1521 3615 l 1509 3621 l 1496 3625 l
 1485 3627 l 1469 3628 l 1453 3626 l 1436 3621 l 1417 3614 l
 1397 3605 l 1379 3597 l 1364 3589 l 1355 3585 l 1351 3582 l
 1350 3582 l gs col0 s gr 
% Polyline
n 2250 3510 m 2250 3509 l 2247 3506 l 2241 3498 l 2231 3485 l 2218 3468 l
 2203 3449 l 2186 3430 l 2170 3412 l 2155 3397 l 2141 3386 l
 2128 3379 l 2115 3375 l 2104 3375 l 2091 3377 l 2079 3381 l
 2066 3388 l 2053 3396 l 2039 3405 l 2025 3416 l 2011 3426 l
 1997 3436 l 1984 3445 l 1971 3453 l 1959 3459 l 1946 3463 l
 1935 3465 l 1919 3466 l 1903 3464 l 1886 3459 l 1867 3452 l
 1847 3443 l 1829 3435 l 1814 3427 l 1805 3423 l 1801 3420 l
 1800 3420 l gs col0 s gr 
% Polyline
n 1800 3510 m 1800 3509 l 1797 3506 l 1791 3498 l 1781 3485 l 1768 3468 l
 1753 3449 l 1736 3430 l 1720 3412 l 1705 3397 l 1691 3386 l
 1678 3379 l 1665 3375 l 1654 3375 l 1641 3377 l 1629 3381 l
 1616 3388 l 1603 3396 l 1589 3405 l 1575 3416 l 1561 3426 l
 1547 3436 l 1534 3445 l 1521 3453 l 1509 3459 l 1496 3463 l
 1485 3465 l 1469 3466 l 1453 3464 l 1436 3459 l 1417 3452 l
 1397 3443 l 1379 3435 l 1364 3427 l 1355 3423 l 1351 3420 l
 1350 3420 l gs col0 s gr 
% Polyline
n 1800 2070 m 1800 2069 l 1797 2066 l 1791 2058 l 1781 2045 l 1768 2028 l
 1753 2009 l 1736 1990 l 1720 1972 l 1705 1957 l 1691 1946 l
 1678 1939 l 1665 1935 l 1654 1935 l 1641 1937 l 1629 1941 l
 1616 1948 l 1603 1956 l 1589 1965 l 1575 1976 l 1561 1986 l
 1547 1996 l 1534 2005 l 1521 2013 l 1509 2019 l 1496 2023 l
 1485 2025 l 1469 2026 l 1453 2024 l 1436 2019 l 1417 2012 l
 1397 2003 l 1379 1995 l 1364 1987 l 1355 1983 l 1351 1980 l
 1350 1980 l gs col0 s gr 
% Polyline
n 1800 1890 m 1800 1889 l 1797 1886 l 1791 1878 l 1781 1865 l 1768 1848 l
 1753 1829 l 1736 1810 l 1720 1792 l 1705 1777 l 1691 1766 l
 1678 1759 l 1665 1755 l 1654 1755 l 1641 1757 l 1629 1761 l
 1616 1768 l 1603 1776 l 1589 1785 l 1575 1796 l 1561 1806 l
 1547 1816 l 1534 1825 l 1521 1833 l 1509 1839 l 1496 1843 l
 1485 1845 l 1469 1846 l 1453 1844 l 1436 1839 l 1417 1832 l
 1397 1823 l 1379 1815 l 1364 1807 l 1355 1803 l 1351 1800 l
 1350 1800 l gs col0 s gr 
/Times-Roman ff 150.00 scf sf
3870 6660 m
gs 1 -1 sc (0) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
5220 6660 m
gs 1 -1 sc (0) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
5850 6930 m
gs 1 -1 sc (100) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
5400 6930 m
gs 1 -1 sc (90) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4950 6930 m
gs 1 -1 sc (80) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4500 6930 m
gs 1 -1 sc (70) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4050 6930 m
gs 1 -1 sc (60) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
3600 6930 m
gs 1 -1 sc (50) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
3150 6930 m
gs 1 -1 sc (40) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2700 6930 m
gs 1 -1 sc (30) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2250 6930 m
gs 1 -1 sc (20) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
5670 6480 m
gs 1 -1 sc (2) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4770 6570 m
gs 1 -1 sc (1) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4320 6570 m
gs 1 -1 sc (1) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
3420 6480 m
gs 1 -1 sc (2) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2970 5850 m
gs 1 -1 sc (9) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1800 6930 m
gs 1 -1 sc (10) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1215 5895 m
gs 1 -1 sc (10) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2610 4140 m
gs 1 -1 sc (113) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1215 4545 m
gs 1 -1 sc (110) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2160 2430 m
gs 1 -1 sc (542) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1215 2745 m
gs 1 -1 sc (540) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1215 1395 m
gs 1 -1 sc (600) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1710 900 m
gs 1 -1 sc (604) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
900 1440 m
gs 1 -1 sc  90.0 rot (number of occurrences) dup sw pop 2 div neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
5850 7110 m
gs 1 -1 sc (matching percentage) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1080 7290 m
gs 1 -1 sc (Number of comparisons: 1274 \(38 * 39\)) col0 sh gr
$F2psEnd
rs

%%EndDocument
endFig 
4676 V
2797(Figure)S
3108(1.)S
4796 V
1421(Bar)S
1608(diagram)S
1996(of)S
2105(the)S
2265(match)S
(percentages)510 2559 A
3094(of)S
3203(39)S
3328(submissions)S
3867(to)S
3976(assignment)S
10 I
4482(j2)S
4916 V
720 H
2670 
1870 
0.00 
0.00 
267.00 
187.00 
startFig 
%%BeginDocument: /home/dick/src/sim/Paper/./fig2.ps
%%!PS-Adobe-2.0 EPSF-2.0
%%Title: fig2.fig
%%Creator: fig2dev Version 3.2 Patchlevel 1
%%CreationDate: Fri Jun 21 11:08:40 2002
%%For: dick@blade014.cs.vu.nl (Dick Grune)
%%Orientation: Portrait
%%BoundingBox: 0 0 267 187
%%Pages: 0
%%BeginSetup
%%EndSetup
%%Magnification: 0.8500
%%EndComments
/$F2psDict 200 dict def
$F2psDict begin
$F2psDict /mtrx matrix put
/col-1 {0 setgray} bind def
/col0 {0.000 0.000 0.000 srgb} bind def
/col1 {0.000 0.000 1.000 srgb} bind def
/col2 {0.000 1.000 0.000 srgb} bind def
/col3 {0.000 1.000 1.000 srgb} bind def
/col4 {1.000 0.000 0.000 srgb} bind def
/col5 {1.000 0.000 1.000 srgb} bind def
/col6 {1.000 1.000 0.000 srgb} bind def
/col7 {1.000 1.000 1.000 srgb} bind def
/col8 {0.000 0.000 0.560 srgb} bind def
/col9 {0.000 0.000 0.690 srgb} bind def
/col10 {0.000 0.000 0.820 srgb} bind def
/col11 {0.530 0.810 1.000 srgb} bind def
/col12 {0.000 0.560 0.000 srgb} bind def
/col13 {0.000 0.690 0.000 srgb} bind def
/col14 {0.000 0.820 0.000 srgb} bind def
/col15 {0.000 0.560 0.560 srgb} bind def
/col16 {0.000 0.690 0.690 srgb} bind def
/col17 {0.000 0.820 0.820 srgb} bind def
/col18 {0.560 0.000 0.000 srgb} bind def
/col19 {0.690 0.000 0.000 srgb} bind def
/col20 {0.820 0.000 0.000 srgb} bind def
/col21 {0.560 0.000 0.560 srgb} bind def
/col22 {0.690 0.000 0.690 srgb} bind def
/col23 {0.820 0.000 0.820 srgb} bind def
/col24 {0.500 0.190 0.000 srgb} bind def
/col25 {0.630 0.250 0.000 srgb} bind def
/col26 {0.750 0.380 0.000 srgb} bind def
/col27 {1.000 0.500 0.500 srgb} bind def
/col28 {1.000 0.630 0.630 srgb} bind def
/col29 {1.000 0.750 0.750 srgb} bind def
/col30 {1.000 0.880 0.880 srgb} bind def
/col31 {1.000 0.840 0.000 srgb} bind def

end
save
-23.0 224.0 translate
1 -1 scale

/cp {closepath} bind def
/ef {eofill} bind def
/gr {grestore} bind def
/gs {gsave} bind def
/sa {save} bind def
/rs {restore} bind def
/l {lineto} bind def
/m {moveto} bind def
/rm {rmoveto} bind def
/n {newpath} bind def
/s {stroke} bind def
/sh {show} bind def
/slc {setlinecap} bind def
/slj {setlinejoin} bind def
/slw {setlinewidth} bind def
/srgb {setrgbcolor} bind def
/rot {rotate} bind def
/sc {scale} bind def
/sd {setdash} bind def
/ff {findfont} bind def
/sf {setfont} bind def
/scf {scalefont} bind def
/sw {stringwidth} bind def
/tr {translate} bind def
/tnt {dup dup currentrgbcolor
  4 -2 roll dup 1 exch sub 3 -1 roll mul add
  4 -2 roll dup 1 exch sub 3 -1 roll mul add
  4 -2 roll dup 1 exch sub 3 -1 roll mul add srgb}
  bind def
/shd {dup dup currentrgbcolor 4 -2 roll mul 4 -2 roll mul
  4 -2 roll mul srgb} bind def
/$F2psBegin {$F2psDict begin /$F2psEnteredState save def} def
/$F2psEnd {$F2psEnteredState restore end} def
%%EndProlog

$F2psBegin
10 setmiterlimit
n -1000 5180 m -1000 -1000 l 6412 -1000 l 6412 5180 l cp clip
 0.05354 0.05354 sc
% Polyline
7.500 slw
n 900 3600 m 5400 3600 l gs col0 s gr 
% Polyline
n 4050 3600 m 4050 3420 l 3600 3420 l 3600 3600 l gs col0 s gr 
% Polyline
n 1350 3600 m 1350 1080 l gs col0 s gr 
% Polyline
n 900 3600 m 900 720 l gs col0 s gr 
% Polyline
n 900 2700 m 810 2700 l gs col0 s gr 
% Polyline
n 2250 3600 m 2250 2520 l 1800 2520 l 1800 3600 l gs col0 s gr 
% Polyline
n 2700 3600 m 2700 3240 l 2250 3240 l 2250 3600 l gs col0 s gr 
% Polyline
n 1800 3600 m 1800 1080 l 1350 1080 l 900 1080 l gs col0 s gr 
% Polyline
n 900 1800 m 810 1800 l gs col0 s gr 
% Polyline
n 900 900 m 810 900 l gs col0 s gr 
/Times-Roman ff 150.00 scf sf
5400 3780 m
gs 1 -1 sc (100) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4950 3780 m
gs 1 -1 sc (90) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4500 3780 m
gs 1 -1 sc (80) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4050 3780 m
gs 1 -1 sc (70) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
3600 3780 m
gs 1 -1 sc (60) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
3150 3780 m
gs 1 -1 sc (50) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2700 3780 m
gs 1 -1 sc (40) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2250 3780 m
gs 1 -1 sc (30) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1800 3780 m
gs 1 -1 sc (20) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1350 3780 m
gs 1 -1 sc (10) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
765 2745 m
gs 1 -1 sc (5) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
3870 3330 m
gs 1 -1 sc (1) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2070 2430 m
gs 1 -1 sc (6) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2520 3150 m
gs 1 -1 sc (2) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
765 1845 m
gs 1 -1 sc (10) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
765 945 m
gs 1 -1 sc (15) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1215 990 m
gs 1 -1 sc (14) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
1665 990 m
gs 1 -1 sc (14) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
540 1395 m
gs 1 -1 sc  90.0 rot (number of occurrences) dup sw pop 2 div neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
2970 3510 m
gs 1 -1 sc (0) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
3330 3510 m
gs 1 -1 sc (0) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4320 3510 m
gs 1 -1 sc (0) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
5130 3510 m
gs 1 -1 sc (0) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
4725 3510 m
gs 1 -1 sc (0) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
5400 3960 m
gs 1 -1 sc (matching percentage) dup sw pop neg 0 rm  col0 sh gr
/Times-Roman ff 150.00 scf sf
630 4140 m
gs 1 -1 sc (Number of match percentages: 37) col0 sh gr
$F2psEnd
rs

%%EndDocument
endFig 
6906 V
10 B
2797(Figure)S
3108(2.)S
7026 V
1465(Bar)S
1652(diagram)S
2040(of)S
2149(the)S
2309(match)S
(percentages)510 2603 A
3138(of)S
3247(student)S
(xxxxxxx's)423 3592 A
4040(submission)S
7146 V
2621(for)S
2775(assignment)S
10 I
3281(j2)S
8427 V
EP
%%Page: 6 6
BP
/slant 0 def
/height 0 def
480 V
10 R
2906(-)S
2965(6)S
3040(-)S
840 V
10 B
1319(Student)S
(xxxxxxx)350 1681 A
960 V
10 R
720(69%)S
(yyyyyyy)350 1054 A
1554(Lines:)S
(195)150 1831 A
2131(Tokens:)S
(627)150 2480 A
1080 V
720(31%)S
(???????)315 1054 A
1554(Lines:)S
1881(96)S
2131(Tokens:)S
(282)150 2480 A
1200 V
720(31%)S
(???????)315 1054 A
1554(Lines:)S
1881(78)S
2131(Tokens:)S
(284)150 2480 A
1320 V
720(26%)S
(???????)315 1054 A
1554(Lines:)S
1881(66)S
2131(Tokens:)S
(243)150 2480 A
1440 V
720(25%)S
(???????)315 1054 A
1554(Lines:)S
1881(66)S
2131(Tokens:)S
(233)150 2480 A
1560 V
720(24%)S
(???????)315 1054 A
1554(Lines:)S
1881(66)S
2131(Tokens:)S
(226)150 2480 A
1680 V
720(23%)S
(???????)315 1054 A
1554(Lines:)S
1881(58)S
2131(Tokens:)S
(211)150 2480 A
1800 V
720(23%)S
(???????)315 1054 A
1554(Lines:)S
1881(52)S
2131(Tokens:)S
(214)150 2480 A
1920 V
720(21%)S
(???????)315 1054 A
1554(Lines:)S
1881(61)S
2131(Tokens:)S
(196)150 2480 A
2040 V
720(20%)S
(???????)315 1054 A
1554(Lines:)S
1881(49)S
2131(Tokens:)S
(188)150 2480 A
2160 V
720(20%)S
(???????)315 1054 A
1554(Lines:)S
1881(48)S
2131(Tokens:)S
(183)150 2480 A
2280 V
720(18%)S
(???????)315 1054 A
1554(Lines:)S
1881(53)S
2131(Tokens:)S
(171)150 2480 A
2400 V
720(18%)S
(???????)315 1054 A
1554(Lines:)S
1881(41)S
2131(Tokens:)S
(169)150 2480 A
2520 V
720(16%)S
(???????)315 1054 A
1554(Lines:)S
1881(39)S
2131(Tokens:)S
(152)150 2480 A
2640 V
720(14%)S
(???????)315 1054 A
1554(Lines:)S
1881(31)S
2131(Tokens:)S
(131)150 2480 A
2760 V
720(14%)S
(???????)315 1054 A
1554(Lines:)S
1881(37)S
2131(Tokens:)S
(127)150 2480 A
2880 V
720(13%)S
(???????)315 1054 A
1554(Lines:)S
1881(33)S
2131(Tokens:)S
(124)150 2480 A
3000 V
720(13%)S
(???????)315 1054 A
1554(Lines:)S
1881(32)S
2131(Tokens:)S
(125)150 2480 A
3120 V
720(12%)S
(???????)315 1054 A
1554(Lines:)S
1881(29)S
2131(Tokens:)S
(115)150 2480 A
3240 V
720(11%)S
(???????)315 1054 A
1554(Lines:)S
1881(22)S
2131(Tokens:)S
(103)150 2480 A
3360 V
720(11%)S
(???????)315 1054 A
1554(Lines:)S
1881(29)S
2131(Tokens:)S
(104)150 2480 A
3480 V
720(11%)S
(???????)315 1054 A
1554(Lines:)S
1881(21)S
2131(Tokens:)S
(101)150 2480 A
3600 V
720(11%)S
(???????)315 1054 A
1554(Lines:)S
1881(29)S
2131(Tokens:)S
(104)150 2480 A
3720 V
720(10%)S
(???????)315 1054 A
1554(Lines:)S
1881(25)S
2131(Tokens:)S
2530(94)S
3840 V
720(10%)S
(???????)315 1054 A
1554(Lines:)S
1881(25)S
2131(Tokens:)S
2530(94)S
3960 V
720(10%)S
(???????)315 1054 A
1554(Lines:)S
1881(25)S
2131(Tokens:)S
2530(95)S
4080 V
720(10%)S
(???????)315 1054 A
1554(Lines:)S
1881(23)S
2131(Tokens:)S
2530(91)S
4200 V
720(10%)S
(???????)315 1054 A
1554(Lines:)S
1881(25)S
2131(Tokens:)S
2530(91)S
4320 V
770(9%)S
(???????)315 1054 A
1554(Lines:)S
1881(24)S
2131(Tokens:)S
2530(88)S
4440 V
770(8%)S
(???????)315 1054 A
1554(Lines:)S
1881(11)S
2131(Tokens:)S
2530(73)S
4560 V
770(8%)S
(???????)315 1054 A
1554(Lines:)S
1881(18)S
2131(Tokens:)S
2530(79)S
4680 V
770(8%)S
(???????)315 1054 A
1554(Lines:)S
1881(23)S
2131(Tokens:)S
2530(78)S
4800 V
770(8%)S
(???????)315 1054 A
1554(Lines:)S
1881(18)S
2131(Tokens:)S
2530(77)S
4920 V
770(8%)S
(???????)315 1054 A
1554(Lines:)S
1881(25)S
2131(Tokens:)S
2530(80)S
5040 V
770(3%)S
(???????)315 1054 A
1554(Lines:)S
1931(8)S
2131(Tokens:)S
2530(32)S
5160 V
770(3%)S
(???????)315 1054 A
1554(Lines:)S
1931(7)S
2131(Tokens:)S
2530(33)S
5280 V
770(3%)S
(???????)315 1054 A
1554(Lines:)S
1881(13)S
2131(Tokens:)S
2530(28)S
5460 V
10 B
2797(Figure)S
3108(3.)S
5580 V
1467(List)S
1660(of)S
1769(match)S
(percentages)510 2063 A
2598(between)S
2977(student)S
(xxxxxxx's)423 3322 A
3770(submission)S
4270(of)S
4379(the)S
5700 V
1722(program)S
2127(for)S
2281(assignment)S
10 I
2787(j2)S
10 B
2890(and)S
3077(the)S
3237(38)S
3362(other)S
10 I
3617(j2)S
10 B
3720(submissions.)S
5820 V
1592(One)S
1796(submission)S
2296(with)S
2512(a)S
2587(match)S
(percentage)471 2881 A
3377(of)S
3486(0%)S
3661(has)S
3831(been)S
4058(left)S
4224(out.)S
5940 V
1520(The)S
1713(names)S
2012(of)S
2121(the)S
2281(students)S
2665(have)S
2891(been)S
3118(replaced)S
3513(by)S
3644(question)S
4033(marks)S
4332(for)S
6060 V
2641(privacy)S
2990(reasons.)S
8427 V
EP
%%Trailer
%%DocumentFonts: Times-Roman Times-Bold Times-Italic Symbol
%%Pages: 6

.