some renaming of variables

README.md

@@ -154,8 +154,8 @@ dancers; deleting a school also deletes its dancers, groups and shows.
 
 Shows have a name, zero to six dated dayparts (`MORNING`, `AFTERNOON`, `EVENING`),
 with unique date/type combinations. The displayed date range comes from these
-dayparts. Each show stores `preferredDayParts` (x), defaulting to two or one for
+dayparts. Each show stores `preferredDayParts`, defaulting to two or one for
-one daypart. Ordinary groups, including PRE_EDUCATION, perform in exactly x
+one daypart. Ordinary groups, including PRE_EDUCATION, perform in exactly preferredDayParts
 dayparts; preschool groups once; showcases every daypart. See
 [show-scheduling-rules.md](show-scheduling-rules.md) for the full hard constraints,
 coach exceptions, ordering and optimization rules.
@@ -178,10 +178,10 @@ status. The UI supports ordering and moving performances, and displays violation
 the same body to link an existing coach. `DELETE .../coaches/{coachId}/dancer`
 removes the identity link. The dancers screen supports maintaining these links.
 
-School JSON exports use format version **3**, including x, schedule status and
+School JSON exports use format version **3**, including preferredDayParts, schedule status and
 coach-to-dancer links. Version 2 remains importable; its schedules migrate to
-drafts with default x. Version 1 is unsupported. Legacy `appearances` fields are
+drafts with default preferredDayParts. Version 1 is unsupported. Legacy `appearances` fields are
-retained for file compatibility; S18 scheduling uses x and fixed type exceptions.
+retained for file compatibility; S18 scheduling uses preferredDayParts and fixed type exceptions.
 The REST `appearances` input is deprecated; use `preferredDayParts`.
 
 Run the HTTP integration tests with:

agiledancers-be/src/main/java/nl/agilecc/agiledancers/model/scheduling/ScheduleRules.java

@@ -14,7 +14,7 @@ public final class ScheduleRules {
     public static List<String> violations(final SchedulingInput input, final List<List<Long>> parts) {
         final List<String> errors = new ArrayList<>();
         if (input.dayParts() == 0 || input.preferredDayParts() < 1 || input.preferredDayParts() > input.dayParts()) {
-            errors.add("Configure dayparts and x between 1 and the number of dayparts.");
+            errors.add("Configure dayparts and preferredDayParts between 1 and the number of dayparts.");
         }
         if (parts == null || parts.size() != input.dayParts() || parts.stream().anyMatch(java.util.Objects::isNull)) {
             errors.add("Assignments must contain one list for every daypart.");
@@ -86,7 +86,7 @@ public final class ScheduleRules {
 
     private static void attendance(
             final SchedulingInput input, final List<List<Long>> parts, final List<String> errors) {
-        final Set<Long> exempt = new HashSet<>(input.coachIds());
+        final Set<Long> exempt = new HashSet<>(input.coachDancerIds());
         input.groups().stream()
                 .filter(GroupRequirement::showcase)
                 .forEach((final GroupRequirement g) -> exempt.addAll(g.dancerIds()));
@@ -96,7 +96,8 @@ public final class ScheduleRules {
         }
         attendance.forEach((final Long dancer, final Set<Integer> dayparts) -> {
             if (!exempt.contains(dancer) && dayparts.size() > input.preferredDayParts()) {
-                errors.add("Dancer " + dancer + " exceeds x=" + input.preferredDayParts() + " dayparts.");
+                errors.add(
+                        "Dancer " + dancer + " exceeds preferredDayParts=" + input.preferredDayParts() + " dayparts.");
             }
         });
     }

agiledancers-be/src/main/java/nl/agilecc/agiledancers/model/scheduling/SchedulingInput.java

@@ -3,16 +3,21 @@ package nl.agilecc.agiledancers.model.scheduling;
 import java.util.List;
 import java.util.Set;
 
+/**
+ * Immutable solver snapshot.
+ *
+ * @param coachDancerIds dancer registration IDs linked to coaches, used for participation exemptions
+ */
 public record SchedulingInput(
         long showId,
         long revision,
         int dayParts,
         List<GroupRequirement> groups,
         int preferredDayParts,
-        Set<Long> coachIds) {
+        Set<Long> coachDancerIds) {
     public SchedulingInput {
         groups = List.copyOf(groups);
-        coachIds = Set.copyOf(coachIds);
+        coachDancerIds = Set.copyOf(coachDancerIds);
     }
 
     public SchedulingInput(

agiledancers-be/src/main/java/nl/agilecc/agiledancers/service/SchedulingInputs.java

@@ -26,7 +26,7 @@ public final class SchedulingInputs {
     }
 
     public static SchedulingInput of(final DanceSchool school, final Show show, final long revision) {
-        final int x = preferred(show);
+        final int preferredDayParts = preferred(show);
         final LocalDate date = show.getDayParts().stream()
                 .map(DayPart::getDate)
                 .min(LocalDate::compareTo)
@@ -40,7 +40,8 @@ public final class SchedulingInputs {
                 .filter(java.util.Objects::nonNull)
                 .map(Dancer::getId)
                 .collect(Collectors.toSet());
-        return new SchedulingInput(show.getId(), revision, show.getDayParts().size(), groups, x, coaches);
+        return new SchedulingInput(
+                show.getId(), revision, show.getDayParts().size(), groups, preferredDayParts, coaches);
     }
 
     private static GroupRequirement requirement(final DanceGroup group, final Show show, final LocalDate date) {

agiledancers-be/src/main/java/nl/agilecc/agiledancers/service/SchoolManagementService.java

@@ -60,7 +60,8 @@ public class SchoolManagementService {
                     "Scheduling requires at least one school group and one daypart.");
         }
         if (SchedulingInputs.preferred(show) > show.getDayParts().size()) {
-            throw new ManagementException(ManagementExceptionKind.INVALID_INPUT, "Correct x before scheduling.");
+            throw new ManagementException(
+                    ManagementExceptionKind.INVALID_INPUT, "Correct preferredDayParts before scheduling.");
         }
         running.add(showId);
         return SchedulingInputs.of(school(schoolId), show, revisions.getOrDefault(showId, 0L));

agiledancers-be/src/main/java/nl/agilecc/agiledancers/service/ShowSchedules.java

@@ -21,25 +21,26 @@ public class ShowSchedules {
         this.schools = schools;
     }
 
-    /** Retains assignments by date/type; removing dayparts may retain an invalid x in the draft. */
+    /** Retains assignments by date/type; removing dayparts may retain an invalid preferredDayParts in the draft. */
     public Show configure(final long schoolId, final Long showId, final Show settings) {
         synchronized (schools) {
             ShowConfiguration.validateParts(settings.getDayParts());
             final Show existing = showId == null ? null : schools.show(schoolId, showId);
-            final int x = settings.getPreferredDayParts() == null
+            final int preferredDayParts = settings.getPreferredDayParts() == null
                     ? (existing == null
                             ? (settings.getDayParts().size() == 1 ? 1 : 2)
                             : SchedulingInputs.preferred(existing))
                     : settings.getPreferredDayParts();
-            validateX(x, existing, settings.getDayParts().size());
+            validatePreferredDayParts(
+                    preferredDayParts, existing, settings.getDayParts().size());
             final Show show = existing == null
                     ? schools.createShow(schoolId, settings.getName(), settings.getDayParts(), null)
                     : existing;
-            final boolean changed = x != SchedulingInputs.preferred(show)
+            final boolean changed = preferredDayParts != SchedulingInputs.preferred(show)
                     || !keys(show.getDayParts()).equals(keys(settings.getDayParts()));
             show.setDayParts(ShowConfiguration.retainAssignments(show, settings.getDayParts()));
             show.setName(settings.getName());
-            show.setPreferredDayParts(x);
+            show.setPreferredDayParts(preferredDayParts);
             if (changed) {
                 schools.touch(show);
             }
@@ -53,13 +54,16 @@ public class ShowSchedules {
                 .toList();
     }
 
-    private static void validateX(final int x, final Show existing, final int parts) {
+    private static void validatePreferredDayParts(final int preferredDayParts, final Show existing, final int parts) {
-        if (x < 1
+        if (preferredDayParts < 1
-                || x > 6
+                || preferredDayParts > 6
-                || (parts > 0 && x > parts && (existing == null || x != SchedulingInputs.preferred(existing)))) {
+                || (parts > 0
+                        && preferredDayParts > parts
+                        && (existing == null || preferredDayParts != SchedulingInputs.preferred(existing)))) {
             throw new ManagementException(
                     ManagementExceptionKind.INVALID_INPUT,
-                    "x must be between 1 and the number of dayparts. Retained x must be corrected before scheduling.");
+                    "preferredDayParts must be between 1 and the number of dayparts. Retained preferredDayParts must"
+                            + " be corrected before scheduling.");
         }
     }
 

agiledancers-be/src/main/java/nl/agilecc/agiledancers/service/model/SchoolSnapshot.java

@@ -205,8 +205,9 @@ public record SchoolSnapshot(
                         .build());
             }
             ShowConfiguration.validateParts(parts);
-            final int x = show.preferredDayParts() == null ? (parts.size() == 1 ? 1 : 2) : show.preferredDayParts();
+            final int preferredDayParts =
-            check(x >= 1 && x <= 6, "x moet tussen 1 en 6 liggen");
+                    show.preferredDayParts() == null ? (parts.size() == 1 ? 1 : 2) : show.preferredDayParts();
+            check(preferredDayParts >= 1 && preferredDayParts <= 6, "preferredDayParts moet tussen 1 en 6 liggen");
             final Show entity = Show.builder()
                     .name(show.name())
                     .dayParts(parts)
@@ -214,7 +215,7 @@ public record SchoolSnapshot(
                             show.appearances() == null
                                     ? ShowConfiguration.defaults(parts.size())
                                     : Map.copyOf(show.appearances()))
-                    .preferredDayParts(x)
+                    .preferredDayParts(preferredDayParts)
                     .finalized(false)
                     .build();
             entity.setId((long) showIds.size());

agiledancers-be/src/main/java/nl/agilecc/agiledancers/solver/SchedulingObjectives.java

@@ -24,7 +24,7 @@ public final class SchedulingObjectives {
         input.groups().stream()
                 .filter(GroupRequirement::showcase)
                 .forEach((final GroupRequirement g) -> showcases.addAll(g.dancerIds()));
-        dancers.removeAll(input.coachIds());
+        dancers.removeAll(input.coachDancerIds());
         final LinearExprBuilder penalty = LinearExpr.newBuilder();
         for (final long dancer : dancers) {
             final IntVar[] parts = dancerParts(model, input, vars, dancer);

agiledancers-be/src/test/java/nl/agilecc/agiledancers/S18LifecycleTest.java

@@ -40,11 +40,11 @@ class S18LifecycleTest {
                 .toList();
     }
 
-    private Show settings(final int n, final Integer x) {
+    private Show settings(final int n, final Integer preferredDayParts) {
         return Show.builder()
                 .name("Show")
                 .dayParts(parts(n))
-                .preferredDayParts(x)
+                .preferredDayParts(preferredDayParts)
                 .build();
     }
 

agiledancers-fe/e2e/school-management.spec.ts

@@ -242,7 +242,7 @@ test('links a coach and finalizes performances spread across multiple dates', as
     data: { assignments: groupIds.map((id) => [id]) },
   });
   await page.goto(`/schools/${school.id}/shows`);
-  await expect(page.getByText(/exceeds x=1/)).toBeVisible();
+  await expect(page.getByText(/exceeds preferredDayParts=1/)).toBeVisible();
   await tab(page, 'Dansers');
   await page.getByText('Coaches koppelen aan dansers', { exact: true }).click();
   await page.getByLabel('Danser als coach registreren').selectOption({ label: 'Dancing coach' });

agiledancers-fe/src/app/schools/school-page.html

@@ -352,7 +352,8 @@
             <div class="show-details">
               <h3>{{ show.name }}</h3>
               <p>
-                {{ show.finalized ? 'Definitief' : 'Concept' }} · x = {{ show.preferredDayParts }}
+                {{ show.finalized ? 'Definitief' : 'Concept' }} · preferredDayParts =
+                {{ show.preferredDayParts }}
               </p>
               @for (violation of show.violations; track $index) {
                 <p class="alert error">{{ violation }}</p>

agiledancers-fe/src/app/shared/entity-editor.spec.ts

@@ -80,7 +80,7 @@ describe('EntityEditor', () => {
     appearances: { REGULAR: 2, SELECTION: 2, PRE_SCHOOLER: 1, SHOW_CASE: 2, PRE_EDUCATION: 2 },
   };
 
-  it('defaults x to two and rejects duplicate dated dayparts and fractional x', () => {
+  it('defaults preferredDayParts to two and rejects duplicate dated dayparts and fractional preferredDayParts', () => {
     const component = editor({ kind: 'show' });
     component.name = 'Show';
     expect(component.validDetails()).toBe(true);
@@ -99,7 +99,27 @@ describe('EntityEditor', () => {
     expect(component.validDetails()).toBe(false);
   });
 
-  it('retains x when dayparts are removed so it can be explicitly corrected', () => {
+  it('preserves an explicitly chosen preferredDayParts when adding dayparts to a new show', async () => {
+    api.saveShow.mockReturnValue(of(show));
+    const component = editor({ kind: 'show' });
+    component.name = 'Show';
+    component.addPart();
+    component.dayParts[0].date = '2027-06-01';
+    component.addPart();
+    component.dayParts[1].date = '2027-06-02';
+    component.preferredDayParts = 1;
+    component.addPart();
+    component.dayParts[2].date = '2027-06-03';
+    expect(component.preferredDayParts).toBe(1);
+    await component.save();
+    expect(api.saveShow).toHaveBeenCalledWith(
+      7,
+      expect.objectContaining({ preferredDayParts: 1 }),
+      undefined,
+    );
+  });
+
+  it('retains preferredDayParts when dayparts are removed so it can be explicitly corrected', () => {
     const component = editor({ kind: 'show', value: show });
     component.addPart();
     component.dayParts[2].date = '2027-06-03';
@@ -144,7 +164,7 @@ describe('EntityEditor', () => {
     }
   });
 
-  it('displays one editable x field with a default of one for a one-daypart show', async () => {
+  it('displays one editable preferredDayParts field with a default of one for a one-daypart show', async () => {
     // jsdom does not implement native dialog opening.
     const descriptor = Object.getOwnPropertyDescriptor(HTMLDialogElement.prototype, 'showModal');
     Object.defineProperty(HTMLDialogElement.prototype, 'showModal', {

agiledancers-fe/src/app/shared/entity-editor.ts

@@ -185,7 +185,16 @@ export class EntityEditor implements OnInit {
   readonly today = new Date().toLocaleDateString('en-CA');
   private readonly api = inject(SchoolApi);
   dayParts: DayPart[] = [];
-  preferredDayParts = 2;
+  private preferredDayPartsValue = 2;
+  private preferredDayPartsEdited = false;
+
+  get preferredDayParts(): number {
+    return this.preferredDayPartsValue;
+  }
+  set preferredDayParts(value: number) {
+    this.preferredDayPartsValue = value;
+    this.preferredDayPartsEdited = true;
+  }
   name = '';
   date = '';
   type: GroupType = 'REGULAR';
@@ -218,7 +227,8 @@ export class EntityEditor implements OnInit {
   addPart(): void {
     if (this.dayParts.length >= 6) return;
     this.dayParts.push({ date: '', type: 'AFTERNOON', danceGroupIds: [] });
-    if (!this.target().value) this.preferredDayParts = Math.min(2, this.dayParts.length);
+    if (!this.target().value && !this.preferredDayPartsEdited)
+      this.preferredDayPartsValue = Math.min(2, this.dayParts.length);
   }
   removePart(index: number): void {
     this.dayParts.splice(index, 1);

agiledancers-fe/src/app/shared/schedule-editor.ts

@@ -16,7 +16,7 @@ import { DialogFrame } from './dialog-frame';
       (dismissed)="closed.emit()"
     >
       <p>
-        {{ !dirty() && current()?.finalized ? 'Definitief' : 'Concept' }} · x =
+        {{ !dirty() && current()?.finalized ? 'Definitief' : 'Concept' }} · preferredDayParts =
         {{ show().preferredDayParts }}
       </p>
       <p>

docs/s18-validation.md

@@ -17,7 +17,7 @@ Validated on 2026-11-03 against the confirmed S18 specification.
 Focused solver tests cover showcase bookends (including extra showcases), single
 and absent showcases, changing gaps, coach exemptions, infeasibility, the strict
 priority of showcase attendance over balance, and style/age scores. Lifecycle
-and HTTP tests cover skipped empty groups, first-show-date ages, retained x after
+and HTTP tests cover skipped empty groups, first-show-date ages, retained preferredDayParts after
 daypart removal, atomic structural validation, invalid drafts, final status
 invalidation, stale solver results, timeout preservation, coach identity links,
 and ordered JSON round trips including version-2 migration.
@@ -36,7 +36,7 @@ assessed against `CODING_STANDARDS.md` and `docs/backend-review.md`:
 - `ScheduleRules` has cyclomatic signals for independent configuration checks
   and showcase cases. Each rule family is isolated in a short method and shared
   between finalization and solver-result validation.
-- `ShowSchedules` retains branching for nullable initial settings, retained x,
+- `ShowSchedules` retains branching for nullable initial settings, retained preferredDayParts,
   and structural draft validation. It stages complete replacement lists before
   mutation and uses the existing aggregate lock. It separates schedule lifecycle
   from the already broad `SchoolManagementService` aggregate owner.

show-scheduling-rules.md

@@ -5,12 +5,12 @@ calendar dates. Counts do not restart on a new date.
 
 ## Required performances
 
-The manager chooses **x**, the desired number of distinct dayparts, per show.
+The manager chooses **preferredDayParts**, the desired number of distinct dayparts, per show.
 It defaults to two, or one for a show with only one daypart. A show can be saved
-without dayparts but cannot be scheduled. If dayparts are removed, x is retained
+without dayparts but cannot be scheduled. If dayparts are removed, preferredDayParts is retained
 and must be corrected before scheduling when it exceeds the remaining count.
 
-Every nonempty regular, selection and pre-education group performs in exactly x
+Every nonempty regular, selection and pre-education group performs in exactly preferredDayParts
 dayparts, once in each. Each preschool group performs exactly once in the whole
 show. Every showcase performs once in every daypart. Groups without dancers are
 skipped completely, including for showcase positions and balancing.
@@ -22,17 +22,17 @@ twice in the same daypart. Without showcases there is no opening/closing rule.
 
 ## People and changing clothes
 
-An ordinary dancer must perform in no more than x distinct dayparts across all
+An ordinary dancer must perform in no more than preferredDayParts distinct dayparts across all
 of their groups. The same dancer registration must be used in every group.
 
 Showcase participants necessarily perform in every daypart. For their other
-performances, exceeding x dayparts is allowed but discouraged. We count their
+performances, exceeding preferredDayParts dayparts is allowed but discouraged. We count their
-non-showcase dayparts, subtract x, and count only positive excesses. The planner's
+non-showcase dayparts, subtract preferredDayParts, and count only positive excesses. The planner's
 first preference is to minimize the sum of these excesses across dancers.
 
 A coach registration must be explicitly linked to the corresponding dancer;
 names are not used to guess identity. Coaches are available throughout the show
-and are exempt from both the x limit and the excess penalty. A coach only performs
+and are exempt from both the preferredDayParts limit and the excess penalty. A coach only performs
 with a group if included in its dancer membership. Being a group's coach alone
 never adds a performance or forces that group into extra dayparts.
 
@@ -85,5 +85,5 @@ Preferences alone never block finalization.
 Manual edits and relevant membership, dancer-age, coach-link or show-setting
 changes return final schedules to draft. Existing schedules and imported schedules
 are drafts. Import retains assignment order and recalculates violations. Export
-is available for both statuses and records status, x and coach identity links;
+is available for both statuses and records status, preferredDayParts and coach identity links;
 reimport always requires a fresh finalization.

specs/in_review/S18_new-rules-for-plotting-dance-groups-in-show.md

@@ -16,11 +16,11 @@ See [validation evidence](../../docs/s18-validation.md) and
 
 - A show consists of dayparts and can span multiple dates, typically two days.
   All counts below apply across the entire show, not separately per date.
-- Each show has one configurable integer `x`, between 1 and the number of
+- Each show has one configurable integer `preferredDayParts`, between 1 and the number of
   dayparts inclusive. Its default is 2, or 1 for a one-daypart show.
 - This replaces the existing configurable appearance counts per group type.
 - A show without dayparts can be stored but cannot be scheduled.
-- If reducing the number of dayparts makes `x` invalid, require the user to
+- If reducing the number of dayparts makes `preferredDayParts` invalid, require the user to
   correct it before scheduling again; do not silently change it.
 - Groups without dancers are excluded from scheduling and from all performance
   counts and showcase-position requirements.
@@ -28,9 +28,9 @@ See [validation evidence](../../docs/s18-validation.md) and
 ## Required group appearances
 
 - Each nonempty REGULAR, SELECTION and PRE_EDUCATION group performs in exactly
-  `x` distinct dayparts, once within each selected daypart.
+  `preferredDayParts` distinct dayparts, once within each selected daypart.
 - Each nonempty PRE_SCHOOLER group performs exactly once in the complete show,
-  regardless of `x`. At most two such groups are expected. They can be assigned
+  regardless of `preferredDayParts`. At most two such groups are expected. They can be assigned
   freely to dayparts; no additional placement restriction applies.
 - Each nonempty SHOW_CASE group performs exactly once in every daypart.
 - With at least two showcase groups, each daypart starts with one showcase and
@@ -42,12 +42,12 @@ See [validation evidence](../../docs/s18-validation.md) and
 
 ## Dancer participation and coaches
 
-- A dancer without a showcase membership performs in at most `x` distinct
+- A dancer without a showcase membership performs in at most `preferredDayParts` distinct
   dayparts across the complete show. This is a hard constraint.
 - A showcase participant necessarily performs in all dayparts. Their other
-  group performances may span more than `x` dayparts, but this is undesirable.
+  group performances may span more than `preferredDayParts` dayparts, but this is undesirable.
 - For each non-coach showcase participant, count the distinct dayparts in which
-  they perform outside showcases. Their excess is `max(0, count - x)`.
+  they perform outside showcases. Their excess is `max(0, count - preferredDayParts)`.
   Minimize the sum of these excesses as the first optimization priority.
 - A person dancing in several groups must use the same dancer registration in
   every group, including when accompanying preschoolers. Up to five group