weekdaze-0.0.0.1: dtd/weekdaze.dtd

<?xml version="1.0" encoding="UTF-8"?>
<!--
	AUTHOR: Dr. Alistair Ward

	Copyright (C) 2013-2015 Dr. Alistair Ward

	This file is part of WeekDaze.

	WeekDaze is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	WeekDaze is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with WeekDaze.  If not, see <http://www.gnu.org/licenses/>.
-->
<!ELEMENT options ((configVersion)?, (executionOptions)?, (outputOptions)?, problemParameters)>	<!-- The single root of the configuration -->
	<!ELEMENT configVersion (versionElement)+>	<!-- The version of this structure -->
		<!ELEMENT versionElement EMPTY>	<!-- The ordered version-numbers, from major to minor -->
			<!ATTLIST versionElement integer CDATA #REQUIRED>	<!-- One integral part of the version-number -->
	<!ELEMENT executionOptions ((evolutionStrategies)?, (traversalOrder | inputStudentViewTimetable)?, (optimiseLessonCriteriaWeights)?, lessonCriteriaWeights, timetableCriteriaWeights)>	<!-- Configures the solution-algorithm -->
		<!ATTLIST executionOptions
			randomSeed				CDATA		#IMPLIED
			permitTemporaryStudentBodyMerger	(False | True)	#IMPLIED
			reduceStudentBodyRegister		(False | True)	#IMPLIED
			removeRedundantCourses			(False | True)	#IMPLIED
			removePointlessGroups			(False | True)	#IMPLIED
			removeUnsubscribedGroups		(False | True)	#IMPLIED
			zeroInappropriateOptions		(False | True)	#IMPLIED
		>
		<!ELEMENT evolutionStrategies (synchronisedCourseMutation, synchronisedCourseByDayMutation, excessRunlengthMutation, homogeneousStudentViewLessonMutation, incompleteCourseMutation, randomLessonMutation, singletonStudentClassMutation, splitSessionMutation, studentBodyCombinationMutation, studentViewTimetableForDayMutation, studentViewTimetableForWeekMutation, synchronousLessonMutation)>	<!-- The mutation of each candidate solution involves partially depleting & then reconstructing the current solution, using a sequence of strategies -->
			<!ATTLIST evolutionStrategies
				randomLessonMutationNTrials			CDATA	#IMPLIED
				randomLessonMutationNTimeslots			CDATA	#IMPLIED
				studentViewTimetableForDayMutationNDays		CDATA	#IMPLIED
				studentViewTimetableForWeekMutationNTrials	CDATA	#IMPLIED
				studentViewTimetableForWeekMutationNTimeslots	CDATA	#IMPLIED
				fecundityDecayRatio				CDATA	#IMPLIED
				minimumPopulationDiversityRatio			CDATA	#IMPLIED
				nInitialScouts					CDATA	#IMPLIED
			>
			<!ELEMENT synchronisedCourseByDayMutation (timetableBreederFecundity)?>
			<!ELEMENT synchronisedCourseMutation (timetableBreederFecundity)?>
			<!ELEMENT excessRunlengthMutation (timetableBreederFecundity)?>
			<!ELEMENT homogeneousStudentViewLessonMutation (timetableBreederFecundity)?>
			<!ELEMENT incompleteCourseMutation (timetableBreederFecundity)?>
			<!ELEMENT randomLessonMutation (timetableBreederFecundity)?>
			<!ELEMENT singletonStudentClassMutation (timetableBreederFecundity)?>
			<!ELEMENT splitSessionMutation (timetableBreederFecundity)?>
			<!ELEMENT studentBodyCombinationMutation (timetableBreederFecundity)?>
			<!ELEMENT studentViewTimetableForDayMutation (timetableBreederFecundity)?>
			<!ELEMENT studentViewTimetableForWeekMutation (timetableBreederFecundity)?>
			<!ELEMENT synchronousLessonMutation (timetableBreederFecundity)?>
				<!ELEMENT timetableBreederFecundity EMPTY>	<!-- The fecundity of the breeding-program, as required after depleting the timetable, by either of two re-construction algorithms -->
					<!ATTLIST timetableBreederFecundity
						deterministicConstructorFecundity	CDATA	#IMPLIED
						randomConstructorFecundity		CDATA	#IMPLIED
					>
		<!ELEMENT traversalOrder (x, y, z)>	<!-- To construct an initial solution, the three-dimensions of the timetable are traversed in a raster-scan, sequentially booking lessons. This raster can be constructed using any of the permutations of "axis"-order & "sense" of travel along each. The default is to evaluate all, & select the best -->
			<!ELEMENT x (timetableAxisTraversal)>	<!-- The "axis" whose coordinates change slowest in the raster -->
			<!ELEMENT y (timetableAxisTraversal)>
			<!ELEMENT z (timetableAxisTraversal)>	<!-- The "axis" whose coordinates change fastest in the raster -->
				<!ELEMENT timetableAxisTraversal EMPTY>	<!-- Defining a straight traverse through the timetable -->
					<!ATTLIST timetableAxisTraversal
						sense	(False | True)			#IMPLIED
						axis	(ObserverId | Day | TimeslotId)	#REQUIRED
					>
		<!ELEMENT inputStudentViewTimetable EMPTY>
			<!ATTLIST inputStudentViewTimetable filePath CDATA #REQUIRED>
		<!ELEMENT lessonCriteriaWeights EMPTY>	<!-- The solution-algorithm initially determines the set of all possible lessons, which may be booked @ a specific time-slot, then selects the best according to a weighted mean of various criteria -->
			<!ATTLIST lessonCriteriaWeights
				areResourcesReused				CDATA	#IMPLIED
				greatestMinimumConsecutiveLessons		CDATA	#IMPLIED
				greatestRemainingCourseLessons			CDATA	#IMPLIED
				greatestSynchronisedCourseSetSize		CDATA	#IMPLIED
				isCoreKnowledgeRequirement			CDATA	#IMPLIED
				isSpecialistInTopic				CDATA	#IMPLIED
				matchCourseClassSizeToLocationCapacity		CDATA	#IMPLIED
				maximiseRelativeFacilityUtilisation		CDATA	#IMPLIED
				maximiseStudentClassSizeOverCourseClassSize	CDATA	#IMPLIED
				maximiseStudentClassSizeOverLocationCapacity	CDATA	#IMPLIED
				minimiseBookingAtAnotherCoursesSpecifiedTime	CDATA	#IMPLIED
				minimiseBookingOfLocationByOtherTeachers	CDATA	#IMPLIED
				minimiseDeviationFromTimeslotRequest		CDATA	#IMPLIED
				minimiseInterCampusMigrationsOfStudents		CDATA	#IMPLIED
				minimiseInterCampusMigrationsOfTeachers		CDATA	#IMPLIED
				minimiseStudentBodyCombinations			CDATA	#IMPLIED
				minimiseTeachersLocusOperandi			CDATA	#IMPLIED
				minimiseWasteOfScarceFacilities			CDATA	#IMPLIED
			> <!-- One can vary each weight within the closed unit-interval [0,1], which @ the lower bound permits the associated criterion to be disregarded -->
		<!ELEMENT timetableCriteriaWeights EMPTY>	<!-- Using the current timetable, the sequence of "evolutionStrategies" are used to breed a population of alternative candidate solutions, from which the best according to a weighted mean over various criteria, are selected -->
			<!ATTLIST timetableCriteriaWeights
				maximiseComplianceWithFreePeriodPreferences			CDATA	#IMPLIED
				maximiseMeanRatioOfStudentClassSizeToLocationCapacity		CDATA	#IMPLIED
				maximiseMeanStudentClassSize					CDATA	#IMPLIED
				maximiseSynchronisationOfSynchronisedCourses			CDATA	#IMPLIED
				maximiseWeightedMeanStudentBodyUtilisationRatio			CDATA	#IMPLIED
				minimiseAverageAbsoluteDeviationFromIdealTimeslotRequest	CDATA	#IMPLIED
				minimiseDispersionOfStudentFreePeriodsPerDay			CDATA	#IMPLIED
				minimiseDispersionOfTeacherFreePeriodsPerDay			CDATA	#IMPLIED
				minimiseDispersionOfTeacherWorkload				CDATA	#IMPLIED
				minimiseMeanInterCampusMigrationsOfStudents			CDATA	#IMPLIED
				minimiseMeanInterCampusMigrationsOfTeachers			CDATA	#IMPLIED
				minimiseMeanLocationChangesOfTeachers				CDATA	#IMPLIED
				minimiseMeanLocusOperandiOfTeachers				CDATA	#IMPLIED
				minimiseMeanRatioOfIncompletelyBookedCoreKnowledge		CDATA	#IMPLIED
				minimiseMeanRatioOfIncompletelyBookedOptionalKnowledge		CDATA	#IMPLIED
				minimiseMeanStudentBodyCombinationsPerLesson			CDATA	#IMPLIED
				minimiseRatioOfConsecutiveEqualLessons				CDATA	#IMPLIED
				minimiseRatioOfSeparatedEqualLessonsWithinAnyDay		CDATA	#IMPLIED
			> <!-- One can vary each weight within the closed unit-interval [0,1], which @ the lower bound permits the associated criterion to be disregarded -->
		<!ELEMENT optimiseLessonCriteriaWeights EMPTY>	<!-- Using the current timetable, the sequence of "evolutionStrategies" are used to breed a population of alternative candidate solutions, from which the best according to a weighted mean over various criteria, are selected -->
			<!ATTLIST optimiseLessonCriteriaWeights
				nTrials			CDATA		#IMPLIED
				changeMagnitude		CDATA		#IMPLIED
				reductionFactor		CDATA		#IMPLIED
				useMeanOverRasterScans	(False | True)	#IMPLIED
			>
	<!ELEMENT outputOptions (fileFormats)?>	<!-- Defines the presentation of the solution -->
		<!ATTLIST outputOptions
			nDecimalDigits			CDATA					#IMPLIED
			outputConfigFilePath		CDATA					#IMPLIED
			studentBodyMnemonicSeparator	CDATA					#IMPLIED
			verbosity			(Silent | Normal | Verbose | Deafening)	#IMPLIED
		>
		<!ELEMENT fileFormats (fileFormat)+ >
			<!ELEMENT fileFormat (xhtml | xml)?>	<!-- The format in which to render the results -->
				<!ATTLIST fileFormat filePath CDATA #REQUIRED>	<!-- The location of the required output-files -->
				<!ELEMENT xhtml (style)?>			<!-- Requests that the resulting timetable, should be rendered in xhtml -->
					<!ELEMENT style ((displayViews)?, (mergeDuplicateTimeslots)?, (displayAxisLabels)?, (weekend)?, (generateLessonColour)?)>
						<!ATTLIST style
							cssURL				CDATA		#IMPLIED
							displayRuntimeInformation	(False | True)	#IMPLIED
							displaySupplementaryInformation	(False | True)	#IMPLIED
						>
						<!ELEMENT displayViews (perspective)+>		<!-- The list of perspectives, from which to display the timetable. The three-dimensional matrix which defines a timetable, is inverted so that the axis which identifies the various student-bodies, is replaced by either one defining "locationId"s or one defining "teacherId"s. The remaining two axes, representing the "day" & the "timeslotId", are unchanged -->
							<!ELEMENT perspective EMPTY>
								<!ATTLIST perspective view (LocationView | TeacherView | StudentView) #REQUIRED>	<!-- Defines whether the timetable is indexed by "locationId", "studentBody" or "teacherId"; i.e. for whom is it intended -->
						<!ELEMENT mergeDuplicateTimeslots (timeAxes)>	<!-- Whether adjacent identical time-slots should be merged, which; reduces repetition, draws attention to duplicate lessons, & uses the limited space efficiently -->
						<!ELEMENT displayAxisLabels (timeAxes)>		<!-- Whether to label the axes of the timetable, in the output XHTML -->
							<!ELEMENT timeAxes EMPTY>	<!-- Whether some attribute is switched on for each of two time-axes of a timetable -->
								<!ATTLIST timeAxes
									byDay		(False | True)	#REQUIRED
									byTimeslotId	(False | True)	#REQUIRED
								>
						<!ELEMENT weekend (day)*>			<!-- Those "day"s considered to constitute the weekend, may be treated differently in CSS -->
						<!ELEMENT generateLessonColour EMPTY>
							<!ATTLIST generateLessonColour
								generateLessonColourFrom	(Lesson | Subject | Topic | Level | ResourceIds)	#IMPLIED
								minimumContrastRatio		CDATA							#IMPLIED
							>
				<!ELEMENT xml EMPTY>	<!-- Requests a view of the resulting timetable, encoded in XML -->
					<!ATTLIST xml view (LocationView | TeacherView | StudentView) #IMPLIED>	<!-- The specific view required -->
	<!ELEMENT problemParameters ((problemValidationSwitches)?, (timetableValidationSwitches)?, timeslotIdBounds, locationCatalogue, teacherRegister, studentBodyRegister, (groupCatalogue)?)>	<!-- Defines the problem. In contrast to the previous major sections, this is changed each time the problem-specification changes -->
		<!ELEMENT problemValidationSwitches EMPTY>
			<!ATTLIST problemValidationSwitches
				checkAvailabilityOfAnyGroupMember			(False | True)	#IMPLIED
				checkCapacityOfLocationsForMeetings			(False | True)	#IMPLIED
				checkCoursesForSynchronousSpecifiedTimes		(False | True)	#IMPLIED
				checkDuplicateMeetingLocationIds			(False | True)	#IMPLIED
				checkDuplicateOwnLocationIds				(False | True)	#IMPLIED
				checkForAlternativesToSynchronisedCourses		(False | True)	#IMPLIED
				checkForDuplicateStudentIds				(False | True)	#IMPLIED
				checkForIdleStudents					(False | True)	#IMPLIED
				checkForIdleTeachers					(False | True)	#IMPLIED
				checkForInvalidMeetingTimes				(False | True)	#IMPLIED
				checkForMultipleCoursesPerTeacherPerSynchronisationId	(False | True)	#IMPLIED
				checkForNonExistentFacilities				(False | True)	#IMPLIED
				checkForNonExistentGroupIds				(False | True)	#IMPLIED
				checkForNonExistentMeetingLocationIds			(False | True)	#IMPLIED
				checkForNonExistentOwnLocationIds			(False | True)	#IMPLIED
				checkForOverloadedStudents				(False | True)	#IMPLIED
				checkForSingletonSynchronisedCourses			(False | True)	#IMPLIED
				checkForStudentsRequiringMultipleSynchronisedSubjects	(False | True)	#IMPLIED
				checkForStudentsWithUnrealisableFreePeriodPreference	(False | True)	#IMPLIED
				checkForSynchronisedCoursesWithDifferentIdealTimeslots	(False | True)	#IMPLIED
				checkForSynchronisedCoursesWithDifferentLessonsPerWeek	(False | True)	#IMPLIED
				checkForSynchronisedCoursesWithExcessLessonsPerWeek	(False | True)	#IMPLIED
				checkForSynchronisedCoursesWithExcessSpecifiedTimes	(False | True)	#IMPLIED
				checkForSynchronisedCoursesWithExcessTimeslotRequests	(False | True)	#IMPLIED
				checkForSynchronisedCoursesWithoutSuitableLocations	(False | True)	#IMPLIED
				checkForSynchronisedCoursesWithUnavailableSpecifiedDays	(False | True)	#IMPLIED
				checkForTeachersWithUnrealisableFreePeriodPreference	(False | True)	#IMPLIED
				checkIfStudentBodiesExceedTeachers			(False | True)	#IMPLIED
				checkIfStudentBodySizeExceedsCapacityOfAllLocations	(False | True)	#IMPLIED
				checkIfStudentBodySizeExceedsLocationCapacity		(False | True)	#IMPLIED
				checkIndependenceOfStudentTimeslotsRequestsAndMeetings	(False | True)	#IMPLIED
				checkIndependenceOfTeacherTimeslotsRequestsAndMeetings	(False | True)	#IMPLIED
				checkLocationsAvailabilityToSupportCourses		(False | True)	#IMPLIED
				checkLocationsForSynchronousSpecifiedTimes		(False | True)	#IMPLIED
				checkMeetingLocationsAvailability			(False | True)	#IMPLIED
				checkMinimumConsecutiveLessons				(False | True)	#IMPLIED
				checkNullGroupId					(False | True)	#IMPLIED
				checkNullLocationCatalogue				(False | True)	#IMPLIED
				checkNullStudentBodyRegister				(False | True)	#IMPLIED
				checkNullTeacherRegister				(False | True)	#IMPLIED
				checkOwnLocationsAvailability				(False | True)	#IMPLIED
				checkRequiredLessonsPerWeek				(False | True)	#IMPLIED
				checkSimultaneousAvailabilityOfGroupMembers		(False | True)	#IMPLIED
				checkStudentsAvailabilityForMandatoryMeetings		(False | True)	#IMPLIED
				checkStudentsAvailabilityForSpecifiedTimes		(False | True)	#IMPLIED
				checkStudentsForMultipleLevelsOfSameTopic		(False | True)	#IMPLIED
				checkStudentsForSynchronousMeetings			(False | True)	#IMPLIED
				checkStudentsLowerWorkloadBound				(False | True)	#IMPLIED
				checkStudentsUpperWorkloadBound				(False | True)	#IMPLIED
				checkSubjectExistence					(False | True)	#IMPLIED
				checkSuitableLocationsForKnowledgeRequirements		(False | True)	#IMPLIED
				checkTeachersAvailabilityForMandatoryMeetings		(False | True)	#IMPLIED
				checkTeachersForSynchronousMeetings			(False | True)	#IMPLIED
				checkTeachersUpperWorkloadBound				(False | True)	#IMPLIED
				checkTeachingCapacityBySubject				(False | True)	#IMPLIED
				checkTimeslotIdBounds					(False | True)	#IMPLIED
				checkTimeslotRequests					(False | True)	#IMPLIED
			> <!-- Each of these switches governs a runtime-check on the validity of the problemParameters, & is by default switched on -->
		<!ELEMENT timetableValidationSwitches EMPTY>
			<!ATTLIST timetableValidationSwitches
				checkBookedSubjectsAreRequired	(False | True)	#IMPLIED
				checkBookedSubjectsHaveService	(False | True)	#IMPLIED
				checkExistenceOfLocationIds	(False | True)	#IMPLIED
				checkExistenceOfStudentBodies	(False | True)	#IMPLIED
				checkExistenceOfTeacherIds	(False | True)	#IMPLIED
				checkForBookingMeetingClash	(False | True)	#IMPLIED
				checkForMisplacedLessons	(False | True)	#IMPLIED
				checkForOverbookedSubjects	(False | True)	#IMPLIED
				checkForOverloadedStudentBodies	(False | True)	#IMPLIED
				checkForOverloadedTeachers	(False | True)	#IMPLIED
				checkForResourceConflicts	(False | True)	#IMPLIED
				checkMinimumConsecutiveLessons	(False | True)	#IMPLIED
				checkResourceAvailability	(False | True)	#IMPLIED
				checkSynchronisedCourses	(False | True)	#IMPLIED
				checkTimeslotsPerDay		(False | True)	#IMPLIED
			> <!-- Each of these switches governs a runtime-check on the validity of an imported Student-view Timetable, & is by default switched on -->
		<!ELEMENT timeslotIdBounds (min, max)>	<!-- The constant closed interval bounding the range of integral "timeslotId"s, @ which lessons can be booked, irrespective of the "day" -->
			<!ELEMENT min EMPTY>
				<!ATTLIST min timeslotId CDATA #REQUIRED>
			<!ELEMENT max EMPTY>
				<!ATTLIST max timeslotId CDATA #REQUIRED>
		<!ELEMENT locationCatalogue (location)+>	<!-- A map indexed by "locationId" (unique across all "campus"es), of "locationProfiles" -->
			<!ELEMENT location (locationProfile)>
				<!ATTLIST location locationId ID #REQUIRED>	<!-- The unique string (composed entirely from alphanumeric characters, & starting with a letter) identifying the location -->
				<!ELEMENT locationProfile ((facilities)?, (availability)?)>	<!-- The nature of the location -->
					<!ATTLIST locationProfile
						capacity	CDATA	#REQUIRED
						campus		CDATA	#IMPLIED
					>
					<!ELEMENT facilities (facilityName)+>	<!-- Arbitrary strings, each representing some facility which might support the tuition of a "course" -->
		<!ELEMENT teacherRegister (teacher)+>	<!-- A map indexed by "teacherId", of "teacherProfiles" -->
			<!ELEMENT teacher (teacherProfile)>
				<!ATTLIST teacher teacherId ID #REQUIRED>	<!-- The unique string (composed entirely from alphanumeric characters, & starting with a letter) identifying the teacher -->
				<!ELEMENT teacherProfile ((service)?, availability, (groupMembership)?)>
					<!ATTLIST teacherProfile
						locationId		IDREF			#IMPLIED
						maximumTeachingRatio	CDATA			#REQUIRED
						specialtyTopic		CDATA			#IMPLIED
						freePeriodPreference	(Pre | Post | Terminal)	#IMPLIED
					>
					<!ELEMENT service (course)+>	<!-- The courses this "teacher" is prepared to teach -->
						<!ELEMENT course (subject, (requiredFacilities)?, (timeslotRequest)?)>	<!-- The nature of the course -->
							<!ATTLIST course
								requiredLessonsPerWeek		CDATA	#REQUIRED
								minimumConsecutiveLessons	CDATA	#IMPLIED
								maximumClassSize		CDATA	#IMPLIED
								synchronisationId		CDATA	#IMPLIED
							>
							<!ELEMENT requiredFacilities (facilityName)+>	<!-- Strings, which must be a subset of the "facilities" offered @ a "location" -->
							<!ELEMENT timeslotRequest (ideally | specifically)>
								<!ELEMENT ideally EMPTY>
									<!ATTLIST ideally timeslotId CDATA #REQUIRED>	<!-- The preferred "timeslotId" within any "day", @ which to book this "course" -->
								<!ELEMENT specifically (time)+>	<!-- The precise "time"s in any week, @ which some of the lessons of this "course" should be booked -->
		<!ELEMENT studentBodyRegister (studentBodyToProfileAssociation)+>	<!-- A map indexed by "studentBody", of "studentProfiles" -->
			<!ELEMENT studentBodyToProfileAssociation (studentBody, studentProfile)>
				<!ELEMENT studentBody (student)+>
					<!ATTLIST studentBody mnemonic ID #REQUIRED>	<!-- The unique string (composed entirely from alphanumeric characters, & starting with a letter) identifying the student-body -->
					<!ELEMENT student EMPTY>
						<!ATTLIST student studentId ID #REQUIRED>	<!-- The unique string (composed entirely from alphanumeric characters, & starting with a letter) identifying a member of the "studentBody" -->
				<!ELEMENT studentProfile (knowledgeRequirements, availability, (groupMembership)?)>	<!-- The common requirements of the members of the "studentBody" -->
					<!ATTLIST studentProfile
						stream			CDATA			#IMPLIED
						teachingRatio		CDATA			#IMPLIED
						freePeriodPreference	(Pre | Post | Terminal)	#IMPLIED
					>
					<!ELEMENT knowledgeRequirements (core, (optional)?)>	<!-- The subjects that the member-"student"s want to learn. These values must match one of the "subject"s, defined in the "course"s, offered as a part of a teacher's "service" -->
						<!ELEMENT core (subject)+>	<!-- Those "subject"s considered required by this "studentBody" -->
						<!ELEMENT optional (subject)+>	<!-- Those "subject"s considered desirable by this "studentBody" -->
		<!ELEMENT groupCatalogue (group)*>	<!-- A map indexed by "groupId", of "groupProfiles" to which "studentBody"s & "teacher"s may belong -->
			<!ELEMENT group (groupProfile)>	<!-- The nature of the group -->
				<!ATTLIST group groupId ID #REQUIRED>	<!-- The unique string (composed entirely from alphanumeric characters, & starting with a letter) identifying the group -->
				<!ELEMENT groupProfile (meetingTimes)?>
					<!ATTLIST groupProfile
						locationId		IDREF		#IMPLIED
						mandatesAttendance	(False | True)	#IMPLIED
					>
					<!ELEMENT meetingTimes (time)+>	<!-- The times @ which the "group" regularly meets -->

<!-- The following elements each exist in multiple parts of the document -->
<!ELEMENT availability (day)+>	<!-- The "day"s on which a resource is available -->

<!ELEMENT day EMPTY>
	<!ATTLIST day value (Sunday | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday) #REQUIRED>	<!-- A day within any week; there's no concept of different months or years -->

<!ELEMENT facilityName EMPTY>
	<!ATTLIST facilityName value CDATA #REQUIRED>	<!-- An arbitrary string identifying a specific facility which might be required for the teaching of a "course" -->

<!ELEMENT groupMembership (member)+>	<!-- The "groupIds" of which a human-resource is a member -->
	<!ELEMENT member EMPTY>
		<!ATTLIST member groupId IDREF #REQUIRED>

<!ELEMENT subject EMPTY>	<!-- A subject offered by a "teacher" & potentially required by "student"s -->
	<!ATTLIST subject
		topic	CDATA	#REQUIRED
		level	CDATA	#REQUIRED
	>

<!ELEMENT time (day)>	<!-- Identifies a single time-slot in the timetable -->
	<!ATTLIST time timeslotId CDATA #REQUIRED>