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Essence

File Problem Notes
CarSequencing.essence 001: Car Sequencing
TemplateDesign.essence 002: Template Design
QG5.essence 003: Quasigroup Existence
QG3.essence 003: Quasigroup Existence
QG6.essence 003: Quasigroup Existence
QG4.essence 003: Quasigroup Existence
QG7.essence 003: Quasigroup Existence
LowAutocorrelationBinarySequences.essence 005: Low Autocorrelation Binary Sequences
GolombRuler.essence 006: Golomb rulers
AllIntervalSeries.essence 007: All-Interval Series
VesselLoading.essence 008: Vessel Loading
PerfectSquarePlacement.essence 009: Perfect Square Placement
SocialGolfersProblem.essence 010: Social Golfers Problem
nonogram.essence 012: Nonogram

This is a very naive specification of the problem. It is unlikely to produce good models.
ProgressivePartyProblem.essence 013: Progressive Party Problem
SchursLemma.essence 015: Schur's Lemma
TrafficLights.essence 016: Traffic Lights
RamseyNumbers.essence 017: Ramsey Numbers
MagicSquares.essence 019: Magic Squares and Sequences
Crossfigures.essence 021: Crossfigures

The Essence model. Instance data can be found in the Essence Catalog.
BusDriverScheduling.essence 022: Bus Driver Scheduling
MagicHexagon.essence 023: Magic Hexagon
Langford.essence 024: Langford's number problem
Lam.essence 025: Lam's Problem
SportsTournamentScheduling.essence 026: Sports Tournament Scheduling
prob027-alientiles-singlepass.essence 027: Alien Tiles Problem

Natural model of problem as stated, but very expensive. Will only solve (via conjure/savilerow) very small problems, roughly such that grid+colours <= 5
prob027-alientiles-multipass.zip 027: Alien Tiles Problem

Model using equivalence to determine minimality. Based on method used by Gent, Linton and Smith
BIBD.essence 028: Balanced Incomplete Block Designs
BalancedAcademicCurriculumProblem.essence 030: Balanced Academic Curriculum Problem (BACP)
RackConfiguration.essence 031: Rack Configuration Problem
MaximumDensityStillLife.essence 032: Maximum density still life
WordDesign.essence 033: Word Design for DNA Computing on Surfaces
WarehouseLocation.essence 034: Warehouse Location Problem
FixedLengthErrorCorrectingCodes.essence 036: Fixed Length Error Correcting Codes
SteelMillSlabDesignProblem.essence 038: Steel Mill Slab Design
Rehearsal.essence 039: The Rehearsal Problem
DistributionWagnerWhitin.essence 040: A Distribution Problem with Wagner-Whitin Costs
NFractionsPuzzle.essence 041: The n-Fractions Puzzle
diagnosis-single.essence 042: diagnosis
steiner.essence 044: Steiner triple systems
CoveringArray.essence 045: The Covering Array Problem
MinimumEnergyBroadcast.essence 048: Minimum Energy Broadcast (MEB)
set_partition_full.essence 049: Number Partitioning
set_partition_simple.essence 049: Number Partitioning
TankAlloc-051.essence 051: Tank Allocation
nqueens.essence 054: N-Queens

N-Queens in Essence
EFPA.essence 055: Equidistant Frequency Permutation Arrays
sonet.essence 056: Synchronous Optical Networking (SONET) Problem
KillerSudoku.essence 057: Killer Sudoku
opd.essence 065: Optimal Financial Portfolio Design

Using a set-of-sets variable
ArmiesOfQueens.essence 110: Peaceably Co-existing Armies of Queens
TailAssignment.essence 115: Tail Assignment
Vellino.essence 116: Vellino's Problem
layout.essence 132: A Layout Problem
knapsack.essence 133: Knapsack Problem