diff --git a/src/MDActorVariantTypesSet.php b/src/MDActorVariantTypesSet.php
index 2d2661c..24cbf61 100644
--- a/src/MDActorVariantTypesSet.php
+++ b/src/MDActorVariantTypesSet.php
@@ -13,7 +13,7 @@ declare(strict_types = 1);
  */
 final class MDActorVariantTypesSet extends MDValueSet {
 
-    const ACTOR_VARIANT_TYPES = [
+    public const ACTOR_VARIANT_TYPES = [
         '',
         'birth_name',
         'civil_name',
diff --git a/src/MDAppointmentAttendanceModeSet.php b/src/MDAppointmentAttendanceModeSet.php
index 75e0d28..3d808c1 100644
--- a/src/MDAppointmentAttendanceModeSet.php
+++ b/src/MDAppointmentAttendanceModeSet.php
@@ -12,13 +12,13 @@ declare(strict_types = 1);
  */
 final class MDAppointmentAttendanceModeSet extends MDValueSet {
 
-    const MODES = [
+    public const MODES = [
         'offline',
         'online',
         'mixed',
     ];
 
-    const MODES_TO_SCHEMA_ORG = [
+    public const MODES_TO_SCHEMA_ORG = [
         'offline' => 'https://schema.org/OfflineEventAttendanceMode',
         'online' => 'https://schema.org/OnlineEventAttendanceMode',
         'mixed' => 'https://schema.org/MixedEventAttendanceMode',
diff --git a/src/MDAppointmentContributorsSet.php b/src/MDAppointmentContributorsSet.php
index 1a57406..a58a362 100644
--- a/src/MDAppointmentContributorsSet.php
+++ b/src/MDAppointmentContributorsSet.php
@@ -12,7 +12,7 @@ declare(strict_types = 1);
  */
 final class MDAppointmentContributorsSet extends MDValueSet {
 
-    const AVAILABLE_ROLES = [
+    public const AVAILABLE_ROLES = [
         'organizer',
         'presenter',
     ];
diff --git a/src/MDAppointmentRecordingSet.php b/src/MDAppointmentRecordingSet.php
index 97cd8d6..23e3954 100644
--- a/src/MDAppointmentRecordingSet.php
+++ b/src/MDAppointmentRecordingSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDAppointmentRecordingSet extends MDValueSet {
 
-    const AVAILABLE_RECORDING_TYPES = ['video'];
-    const EXTERNAL_SOURCES = ['Archive.org' => 'https://archive.org/details/'];
+    public const AVAILABLE_RECORDING_TYPES = ['video'];
+    public const EXTERNAL_SOURCES = ['Archive.org' => 'https://archive.org/details/'];
 
 }
diff --git a/src/MDAppointmentStatusSet.php b/src/MDAppointmentStatusSet.php
index 4778cbe..88d9ee4 100644
--- a/src/MDAppointmentStatusSet.php
+++ b/src/MDAppointmentStatusSet.php
@@ -11,14 +11,14 @@ declare(strict_types = 1);
  */
 final class MDAppointmentStatusSet extends MDValueSet {
 
-    const STATUS = [
+    public const STATUS = [
         'scheduled',
         'cancelled',
         'moved_online',
         'postponed',
     ];
 
-    const STATUS_TO_SCHEMA_ORG = [
+    public const STATUS_TO_SCHEMA_ORG = [
         'scheduled' => 'https://schema.org/EventScheduled',
         'cancelled' => 'https://schema.org/EventCancelled',
         'moved_online' => 'https://schema.org/EventMovedOnline',
diff --git a/src/MDBlockedMailserverSet.php b/src/MDBlockedMailserverSet.php
index 132f593..463a93f 100644
--- a/src/MDBlockedMailserverSet.php
+++ b/src/MDBlockedMailserverSet.php
@@ -13,7 +13,7 @@ declare(strict_types = 1);
  */
 final class MDBlockedMailserverSet extends MDValueSet {
 
-    const BLOCKED_DOMAINS = [
+    public const BLOCKED_DOMAINS = [
         "@magenta.de",
         "@t-online.de",
     ];
diff --git a/src/MDCloserLocationTypesSet.php b/src/MDCloserLocationTypesSet.php
index f50ee22..4064e47 100644
--- a/src/MDCloserLocationTypesSet.php
+++ b/src/MDCloserLocationTypesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDCloserLocationTypesSet extends MDValueSet {
 
-    const CLOSER_LOCATION_TYPES = [
+    public const CLOSER_LOCATION_TYPES = [
         "0", // ''
         "1", // Place of recording
         "2", // Place of finding
diff --git a/src/MDColorsSet.php b/src/MDColorsSet.php
index 3e3d988..f8c6472 100644
--- a/src/MDColorsSet.php
+++ b/src/MDColorsSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDColorsSet extends MDValueSet {
 
-    const COLOR_NAMES = [
+    public const COLOR_NAMES = [
         "black",
         "green",
         "silver",
@@ -30,7 +30,7 @@ final class MDColorsSet extends MDValueSet {
         "aqua",
     ];
 
-    const COLOR_NAMES_AND_EMPTY = [
+    public const COLOR_NAMES_AND_EMPTY = [
         '',
         "black",
         "green",
@@ -50,7 +50,7 @@ final class MDColorsSet extends MDValueSet {
         "aqua",
     ];
 
-    const COLORS_RGB = [
+    public const COLORS_RGB = [
         "black"     => [0, 0, 0],
         "green"     => [0, 128, 0],
         "silver"    => [192, 192, 192],
diff --git a/src/MDConservationReportTypeSet.php b/src/MDConservationReportTypeSet.php
index 5ce2ae3..a00fa48 100644
--- a/src/MDConservationReportTypeSet.php
+++ b/src/MDConservationReportTypeSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDConservationReportTypeSet extends MDValueSet {
 
-    const REPORT_TYPES = [
+    public const REPORT_TYPES = [
         'damage',
         'conservation',
         'condition',
diff --git a/src/MDConservationStatusSet.php b/src/MDConservationStatusSet.php
index 6d06489..73576e2 100644
--- a/src/MDConservationStatusSet.php
+++ b/src/MDConservationStatusSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDConservationStatusSet extends MDValueSet {
 
-    const STATUS_LEVELS = [
+    public const STATUS_LEVELS = [
         1 => '',
         34 => 'markedBad',
         67 => 'markedMedium',
diff --git a/src/MDCurrenciesSet.php b/src/MDCurrenciesSet.php
index 2d3a764..6d73e92 100644
--- a/src/MDCurrenciesSet.php
+++ b/src/MDCurrenciesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDCurrenciesSet extends MDValueSet {
 
-    const CURRENCIES = [
+    public const CURRENCIES = [
         '',
         'by-BYN',
         'ch-CHF',       // Swiss Franc
diff --git a/src/MDDataHistorySubjectsSet.php b/src/MDDataHistorySubjectsSet.php
index 9ce92dc..b078628 100644
--- a/src/MDDataHistorySubjectsSet.php
+++ b/src/MDDataHistorySubjectsSet.php
@@ -12,7 +12,7 @@ declare(strict_types = 1);
  */
 final class MDDataHistorySubjectsSet extends MDValueSet {
 
-    const AVAILABLE_SUBJECTS = [
+    public const AVAILABLE_SUBJECTS = [
         'appointment',
         'collection',
         'contact',
diff --git a/src/MDDisposalMethodSet.php b/src/MDDisposalMethodSet.php
index 2dc56ac..731308a 100644
--- a/src/MDDisposalMethodSet.php
+++ b/src/MDDisposalMethodSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDDisposalMethodSet extends MDValueSet {
 
-    const METHODS = [
+    public const METHODS = [
         '',
         'sold',
         'destroyed',
diff --git a/src/MDEntryTypesSet.php b/src/MDEntryTypesSet.php
index bee3999..b72024b 100644
--- a/src/MDEntryTypesSet.php
+++ b/src/MDEntryTypesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDEntryTypesSet extends MDValueSet {
 
-    const ENTRY_TYPES = [
+    public const ENTRY_TYPES = [
         '0', //
         '1', // Schenkung
         '2', // Kauf
diff --git a/src/MDExhibitionContributorsSet.php b/src/MDExhibitionContributorsSet.php
index 8ceb4a1..fcc403e 100644
--- a/src/MDExhibitionContributorsSet.php
+++ b/src/MDExhibitionContributorsSet.php
@@ -12,7 +12,7 @@ declare(strict_types = 1);
  */
 final class MDExhibitionContributorsSet extends MDValueSet {
 
-    const AVAILABLE_ROLES = [
+    public const AVAILABLE_ROLES = [
         'concept',
         'curator',
         'design',
diff --git a/src/MDExternalHostingSet.php b/src/MDExternalHostingSet.php
index 7b54003..c636933 100644
--- a/src/MDExternalHostingSet.php
+++ b/src/MDExternalHostingSet.php
@@ -11,9 +11,9 @@ declare(strict_types = 1);
  */
 final class MDExternalHostingSet extends MDValueSet {
 
-    const DEFAULT_EXTERNAL_HOSTING = 'Archive.org';
+    public const DEFAULT_EXTERNAL_HOSTING = 'Archive.org';
 
-    const EXTERNAL_SOURCES = [
+    public const EXTERNAL_SOURCES = [
         'Archive.org',
     ];
 
diff --git a/src/MDGenderSet.php b/src/MDGenderSet.php
index a5a2604..ec449cd 100644
--- a/src/MDGenderSet.php
+++ b/src/MDGenderSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDGenderSet extends MDValueSet {
 
-    const GENDERS = [
+    public const GENDERS = [
         '',
         'female',
         'male',
diff --git a/src/MDLanguagesSet.php b/src/MDLanguagesSet.php
index ff0904a..672da39 100644
--- a/src/MDLanguagesSet.php
+++ b/src/MDLanguagesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDLanguagesSet {
 
-    const AVAILABLE_LANGUAGES_SHORT = [
+    public const AVAILABLE_LANGUAGES_SHORT = [
         'aa',
         'ab',
         'ae',
@@ -203,7 +203,7 @@ final class MDLanguagesSet {
         'zu',
     ];
 
-    const AVAILABLE_LANGUAGES = [
+    public const AVAILABLE_LANGUAGES = [
         'aa' => 'Afar-áf',
         'ab' => 'аҧсуа бызшәа',
         'ae' => 'Avestan',
@@ -395,7 +395,7 @@ final class MDLanguagesSet {
         'zu' => 'Zulu',
     ];
 
-    const LANGUAGES_ISO639_2B = [
+    public const LANGUAGES_ISO639_2B = [
         'aa' => 'aar', # 'Afar-áf',
         'ab' => 'abk', # 'аҧсуа бызшәа',
         'ae' => 'ave', # 'Avestan',
diff --git a/src/MDLicensesSet.php b/src/MDLicensesSet.php
index 45056a8..7e55557 100644
--- a/src/MDLicensesSet.php
+++ b/src/MDLicensesSet.php
@@ -11,10 +11,10 @@ declare(strict_types = 1);
  */
 final class MDLicensesSet extends MDValueSet {
 
-    const DEFAULT_LICENSE_IMGS = 'CC BY-NC-SA';
-    const DEFAULT_LICENSE_METADATA = 'CC BY-NC-SA';
+    public const DEFAULT_LICENSE_IMGS = 'CC BY-NC-SA';
+    public const DEFAULT_LICENSE_METADATA = 'CC BY-NC-SA';
 
-    const AVAILABLE_LICENSES_NAMES = [
+    public const AVAILABLE_LICENSES_NAMES = [
 
         'CC BY-NC-SA',
         'CC BY-NC-ND',
@@ -31,7 +31,7 @@ final class MDLicensesSet extends MDValueSet {
 
     ];
 
-    const AVAILABLE_LICENSES = [
+    public const AVAILABLE_LICENSES = [
 
         'CC BY-NC-SA'           => 'https://creativecommons.org/licenses/by-nc-sa/4.0/',
         'CC BY-NC-ND'           => 'https://creativecommons.org/licenses/by-nc-nd/4.0/',
diff --git a/src/MDLoanTypesSet.php b/src/MDLoanTypesSet.php
index 06361e8..2389b94 100644
--- a/src/MDLoanTypesSet.php
+++ b/src/MDLoanTypesSet.php
@@ -11,9 +11,9 @@ declare(strict_types = 1);
  */
 final class MDLoanTypesSet extends MDValueSet {
 
-    const DEFAULT_LOAN_TYPE = 'outgoing';
+    public const DEFAULT_LOAN_TYPE = 'outgoing';
 
-    const LOAN_TYPES = [
+    public const LOAN_TYPES = [
         'outgoing',
         'incoming',
     ];
diff --git a/src/MDMarkingTypesSet.php b/src/MDMarkingTypesSet.php
index d2df664..3447530 100644
--- a/src/MDMarkingTypesSet.php
+++ b/src/MDMarkingTypesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDMarkingTypesSet extends MDValueSet {
 
-    const MARKING_TYPES = [
+    public const MARKING_TYPES = [
         'signature',
         'engraving',
         'watermark',
diff --git a/src/MDNodaRepositoriesSet.php b/src/MDNodaRepositoriesSet.php
index 7b8dcea..9c80b7b 100644
--- a/src/MDNodaRepositoriesSet.php
+++ b/src/MDNodaRepositoriesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDNodaRepositoriesSet extends MDValueSet {
 
-    const REPOSITORIES_ACTOR = [
+    public const REPOSITORIES_ACTOR = [
         'allgemein',
         'bne',
         'bnf',
@@ -36,7 +36,7 @@ final class MDNodaRepositoriesSet extends MDValueSet {
         'Wikipedia',
     ];
 
-    const REPOSITORIES_PLACE = [
+    public const REPOSITORIES_PLACE = [
         'allgemein',
         'bne',
         'bnf',
@@ -56,7 +56,7 @@ final class MDNodaRepositoriesSet extends MDValueSet {
         'Wikipedia',
     ];
 
-    const REPOSITORIES_TAG = [
+    public const REPOSITORIES_TAG = [
         'aat',
         'ackerbau',
         'allgemein',
diff --git a/src/MDObjectFormSet.php b/src/MDObjectFormSet.php
index c35b600..300d992 100644
--- a/src/MDObjectFormSet.php
+++ b/src/MDObjectFormSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDObjectFormSet extends MDValueSet {
 
-    const FORMS = [
+    public const FORMS = [
         '',
         'cube',
         'cuboid',
diff --git a/src/MDObjectPositionsSet.php b/src/MDObjectPositionsSet.php
index a8c762f..e38156e 100644
--- a/src/MDObjectPositionsSet.php
+++ b/src/MDObjectPositionsSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDObjectPositionsSet extends MDValueSet {
 
-    const POSITIONS = [
+    public const POSITIONS = [
         'left', 'top_left', 'top', 'top_right', 'right', 'bottom_right', 'bottom', 'bottom_left', 'center', 'rear_side', 'edge', 'inside', 'other',
     ];
 
diff --git a/src/MDObjectPublicationBackgrounds.php b/src/MDObjectPublicationBackgrounds.php
index 228f382..ba0b9b3 100644
--- a/src/MDObjectPublicationBackgrounds.php
+++ b/src/MDObjectPublicationBackgrounds.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDObjectPublicationBackgrounds extends MDValueSet {
 
-    const PUBLICATION_BACKGROUNDS = [
+    public const PUBLICATION_BACKGROUNDS = [
         '0', // Image published
         '1', // Transcript published
         '2', // Discussed
diff --git a/src/MDObjectStatusSet.php b/src/MDObjectStatusSet.php
index c0ea447..ecd9f3c 100644
--- a/src/MDObjectStatusSet.php
+++ b/src/MDObjectStatusSet.php
@@ -11,9 +11,9 @@ declare(strict_types = 1);
  */
 final class MDObjectStatusSet extends MDValueSet {
 
-    const DEFAULT_OBJECT_STATUS = 'owned';
+    public const DEFAULT_OBJECT_STATUS = 'owned';
 
-    const OBJECT_STATUS = [
+    public const OBJECT_STATUS = [
         'owned',
         'permanent_loan',
         'third_party_property',
diff --git a/src/MDObjectSyndicationSet.php b/src/MDObjectSyndicationSet.php
index c14cedd..cc91b6c 100644
--- a/src/MDObjectSyndicationSet.php
+++ b/src/MDObjectSyndicationSet.php
@@ -12,7 +12,7 @@ declare(strict_types = 1);
  */
 final class MDObjectSyndicationSet extends MDValueSet {
 
-    const REPOSITORIES = [
+    public const REPOSITORIES = [
 
         'ddb' => [
             'url'           => 'https://www.deutsche-digitale-bibliothek.de/',
diff --git a/src/MDPhoneTypesSet.php b/src/MDPhoneTypesSet.php
index 8c3683e..2985038 100644
--- a/src/MDPhoneTypesSet.php
+++ b/src/MDPhoneTypesSet.php
@@ -17,9 +17,9 @@ declare(strict_types = 1);
  */
 final class MDPhoneTypesSet extends MDValueSet {
 
-    const DEFAULT_PHONE_TYPE = 'work';
+    public const DEFAULT_PHONE_TYPE = 'work';
 
-    const PHONE_TYPES = [
+    public const PHONE_TYPES = [
         'work',
         'home',
         'mobile',
diff --git a/src/MDPlacetypesSet.php b/src/MDPlacetypesSet.php
index 12a95b3..6855e91 100644
--- a/src/MDPlacetypesSet.php
+++ b/src/MDPlacetypesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDPlacetypesSet extends MDValueSet {
 
-    const PLACE_TYPE_IDS = [
+    public const PLACE_TYPE_IDS = [
         '0', // => Administrativ
         '1', // => Historisch
         '2', // => Region - Landschaft - Naturpark
diff --git a/src/MDPodcastContributorsSet.php b/src/MDPodcastContributorsSet.php
index f8e621a..4450f17 100644
--- a/src/MDPodcastContributorsSet.php
+++ b/src/MDPodcastContributorsSet.php
@@ -12,7 +12,7 @@ declare(strict_types = 1);
  */
 final class MDPodcastContributorsSet extends MDValueSet {
 
-    const AVAILABLE_ROLES = [
+    public const AVAILABLE_ROLES = [
         'onair',
         'organization',
         'recording',
diff --git a/src/MDProcessTypesSet.php b/src/MDProcessTypesSet.php
index bdcdad8..b4392a3 100644
--- a/src/MDProcessTypesSet.php
+++ b/src/MDProcessTypesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDProcessTypesSet extends MDValueSet {
 
-    const TYPES = [
+    public const TYPES = [
         'project',
         'grant_application',
         'exhibition',
diff --git a/src/MDRecordingTypesSet.php b/src/MDRecordingTypesSet.php
index 8a716c2..7bbb07e 100644
--- a/src/MDRecordingTypesSet.php
+++ b/src/MDRecordingTypesSet.php
@@ -11,9 +11,9 @@ declare(strict_types = 1);
  */
 final class MDRecordingTypesSet extends MDValueSet {
 
-    const DEFAULT_RECORDING_TYPE = 'audio';
+    public const DEFAULT_RECORDING_TYPE = 'audio';
 
-    const RECORDING_TYPES = [
+    public const RECORDING_TYPES = [
         'audio',
         'video',
     ];
diff --git a/src/MDRequirementsSet.php b/src/MDRequirementsSet.php
index dbe3756..46667c2 100644
--- a/src/MDRequirementsSet.php
+++ b/src/MDRequirementsSet.php
@@ -15,48 +15,48 @@ final class MDRequirementsSet {
     // the given timespan. If they are not, the account will be ignored
     // and deleted.
     // 60 * 60 * 24 * 6 = 518400. 6 days.
-    const MAX_AGE_AFTER_USER_INVITE = 518400;
+    public const MAX_AGE_AFTER_USER_INVITE = 518400;
 
     // Object images need to be at least 500 px wide
-    const MIN_OBJECT_IMAGE_WIDTH = 540;
+    public const MIN_OBJECT_IMAGE_WIDTH = 540;
 
     // Object images need to be at least 500 px wide
-    const MIN_OBJECT_IMAGE_HEIGHT = 540;
+    public const MIN_OBJECT_IMAGE_HEIGHT = 540;
 
-    const MAX_FILESIZE_PDF = 20000000;
+    public const MAX_FILESIZE_PDF = 20000000;
 
-    const TIME_EARLIEST_YEAR = -6000000000;
-    const TIME_EARLIEST_DATE = '0001-01-01';
-    const TIME_LATEST_YEAR = 2099;
-    const TIME_LATEST_DATE = '9999-12-31';
-    const TIME_DEFAULT_DATE = '0001-01-01'; // Date to ignore in indexing
+    public const TIME_EARLIEST_YEAR = -6000000000;
+    public const TIME_EARLIEST_DATE = '0001-01-01';
+    public const TIME_LATEST_YEAR = 2099;
+    public const TIME_LATEST_DATE = '9999-12-31';
+    public const TIME_DEFAULT_DATE = '0001-01-01'; // Date to ignore in indexing
 
-    const MIMETYPES_USER_PROFILE_IMG = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_USER_PROFILE_IMG = ['image/jpeg', 'image/jpg'];
 
-    const MIMETYPES_OBJECT_IMAGE = ['image/jpeg', 'image/jpg', 'image/png', 'image/webp'];
-    const MIMETYPES_OBJECT_PDF = ['application/pdf'];
-    const MIMETYPES_OBJECT_PROVENANCE_REPORT = ['application/pdf'];
-    const MIMETYPES_OBJECT_RESTORATION_REPORT = ['application/pdf', 'image/jpeg', 'image/png'];
-    const MIMETYPES_OBJECT_CONDITION_REPORT = ['application/pdf', 'image/jpeg', 'image/png'];
+    public const MIMETYPES_OBJECT_IMAGE = ['image/jpeg', 'image/jpg', 'image/png', 'image/webp'];
+    public const MIMETYPES_OBJECT_PDF = ['application/pdf'];
+    public const MIMETYPES_OBJECT_PROVENANCE_REPORT = ['application/pdf'];
+    public const MIMETYPES_OBJECT_RESTORATION_REPORT = ['application/pdf', 'image/jpeg', 'image/png'];
+    public const MIMETYPES_OBJECT_CONDITION_REPORT = ['application/pdf', 'image/jpeg', 'image/png'];
 
-    const MIMETYPES_OBJECT_DOCUMENT = ['image/jpeg', 'image/jpg', 'application/pdf'];
+    public const MIMETYPES_OBJECT_DOCUMENT = ['image/jpeg', 'image/jpg', 'application/pdf'];
 
-    const MIMETYPES_COLLECTION_IMAGE = ['image/jpeg', 'image/jpg'];
-    const MIMETYPES_INSTITUTION_IMAGE = ['image/jpeg', 'image/jpg'];
-    const MIMETYPES_EXHIBITION_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_COLLECTION_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_INSTITUTION_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_EXHIBITION_IMAGE = ['image/jpeg', 'image/jpg'];
 
-    const MIMETYPES_ARTICLE_ASSET = ['image/jpeg', 'image/jpg', 'image/png'];
+    public const MIMETYPES_ARTICLE_ASSET = ['image/jpeg', 'image/jpg', 'image/png'];
 
-    const MIMETYPES_APPOINTMENT_IMAGE = ['image/jpeg', 'image/jpg'];
-    const MIMETYPES_APPOINTMENT_DOC_ASSET = ['application/pdf', 'image/jpeg', 'image/jpg', 'image/png'];
+    public const MIMETYPES_APPOINTMENT_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_APPOINTMENT_DOC_ASSET = ['application/pdf', 'image/jpeg', 'image/jpg', 'image/png'];
 
-    const MIMETYPES_PODCAST_IMAGE = ['image/jpeg', 'image/jpg'];
-    const MIMETYPES_PODCAST_EPISODE_IMAGE = ['image/jpeg', 'image/jpg'];
-    const MIMETYPES_TOUR_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_PODCAST_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_PODCAST_EPISODE_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_TOUR_IMAGE = ['image/jpeg', 'image/jpg'];
 
-    const MIMETYPES_CATALOGUE_WORK_IMAGE = ['image/jpeg', 'image/jpg'];
-    const MIMETYPES_CATALOGUE_OBJECT_SUMMARY_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_CATALOGUE_WORK_IMAGE = ['image/jpeg', 'image/jpg'];
+    public const MIMETYPES_CATALOGUE_OBJECT_SUMMARY_IMAGE = ['image/jpeg', 'image/jpg'];
 
-    const EXTENSIONS_THREE_D_ZIP = ['obj', 'mtl', 'jpg', 'jpeg', 'png'];
+    public const EXTENSIONS_THREE_D_ZIP = ['obj', 'mtl', 'jpg', 'jpeg', 'png'];
 
 }
diff --git a/src/MDResearchStatusSet.php b/src/MDResearchStatusSet.php
index 7fa61be..4449e9f 100644
--- a/src/MDResearchStatusSet.php
+++ b/src/MDResearchStatusSet.php
@@ -14,7 +14,7 @@ declare(strict_types = 1);
  */
 final class MDResearchStatusSet extends MDValueSet {
 
-    const RESEARCH_STATUS = [
+    public const RESEARCH_STATUS = [
         'bad',
         'medium',
         'good',
diff --git a/src/MDSourceTypeSet.php b/src/MDSourceTypeSet.php
index 3fe65dc..fddf33f 100644
--- a/src/MDSourceTypeSet.php
+++ b/src/MDSourceTypeSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDSourceTypeSet extends MDValueSet {
 
-    const SOURCE_TYPES = [
+    public const SOURCE_TYPES = [
         'article',
         'inbook',
         'book',
diff --git a/src/MDSpaceAccessStatusSet.php b/src/MDSpaceAccessStatusSet.php
index af41a2f..476d28d 100644
--- a/src/MDSpaceAccessStatusSet.php
+++ b/src/MDSpaceAccessStatusSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDSpaceAccessStatusSet extends MDValueSet {
 
-    const STATUS = [
+    public const STATUS = [
         'enter',
         'leave',
     ];
diff --git a/src/MDSpaceTypesSet.php b/src/MDSpaceTypesSet.php
index 86b71bb..e67458e 100644
--- a/src/MDSpaceTypesSet.php
+++ b/src/MDSpaceTypesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDSpaceTypesSet extends MDValueSet {
 
-    const TYPES = [
+    public const TYPES = [
         'building',
         'floor',
         'depot',
diff --git a/src/MDTitleTypesSet.php b/src/MDTitleTypesSet.php
index cde610f..c23378c 100644
--- a/src/MDTitleTypesSet.php
+++ b/src/MDTitleTypesSet.php
@@ -11,7 +11,7 @@ declare(strict_types = 1);
  */
 final class MDTitleTypesSet extends MDValueSet {
 
-    const TITLE_TYPES = [
+    public const TITLE_TYPES = [
         "",
         "Science",
         "Everyday speech",
diff --git a/src/MDUnitsSet.php b/src/MDUnitsSet.php
index d7067c2..3afff69 100644
--- a/src/MDUnitsSet.php
+++ b/src/MDUnitsSet.php
@@ -11,10 +11,10 @@ declare(strict_types = 1);
  */
 final class MDUnitsSet extends MDValueSet {
 
-    const UNITS_LENGTH = ['', 'm', 'dm', 'cm', 'mm', 'ft', 'in'];
-    const UNITS_WEIGHT = ['', 't', 'kg', 'g'];
+    public const UNITS_LENGTH = ['', 'm', 'dm', 'cm', 'mm', 'ft', 'in'];
+    public const UNITS_WEIGHT = ['', 't', 'kg', 'g'];
 
-    const UNITS_LENGTH_TO_MILLIMETER = [
+    public const UNITS_LENGTH_TO_MILLIMETER = [
         'm'  => 1000,
         'ft' => 304.8,
         'dm' => 100,
@@ -23,7 +23,7 @@ final class MDUnitsSet extends MDValueSet {
         'mm' => 1,
     ];
 
-    const UNITS_WEIGHT_TO_GRAMM = [
+    public const UNITS_WEIGHT_TO_GRAMM = [
         't'  => 1000000,
         'kg'  => 1000,
         'g' => 1,
diff --git a/src/enums/MDInstitutionExternalIdRepository.php b/src/enums/MDInstitutionExternalIdRepository.php
index 3a0a4eb..8a46a9a 100644
--- a/src/enums/MDInstitutionExternalIdRepository.php
+++ b/src/enums/MDInstitutionExternalIdRepository.php
@@ -14,11 +14,11 @@ enum MDInstitutionExternalIdRepository implements MDValueEnumInterface, JsonSeri
 
     case hu_ksh; // https://en.wikipedia.org/wiki/Hungarian_Central_Statistical_Office
 
-    const VALIDATION_PATTERN_HTML = [
+    private const VALIDATION_PATTERN_HTML = [
         'hu_ksh' => '[0-9]{8}-[0-9]{4}-[0-9]{3}-[0-9]{2}',
     ];
 
-    const VALIDATION_PATTERN_PHP = [
+    private const VALIDATION_PATTERN_PHP = [
         'hu_ksh' => '/^[0-9]{8}-[0-9]{4}-[0-9]{3}-[0-9]{2}$/',
     ];