diff --git a/lib/Collection.php b/lib/Collection.php
index 3416e158..9c5e51cc 100644
--- a/lib/Collection.php
+++ b/lib/Collection.php
@@ -55,13 +55,34 @@ class Collection{
 	public function Validate(): void{
 		$error = new Exceptions\ValidationException();
 
-		$this->Name = trim($this->Name ?? '');
-		if($this->Name == ''){
+		if(isset($this->Name)){
+			$this->Name = trim($this->Name);
+
+			if($this->Name == ''){
+				$error->Add(new Exceptions\CollectionNameRequiredException());
+			}
+
+			if(strlen($this->Name) > EBOOKS_MAX_STRING_LENGTH){
+				$error->Add(new Exceptions\StringTooLongException('Collection name: '. $this->Name));
+			}
+		}
+		else{
 			$error->Add(new Exceptions\CollectionNameRequiredException());
 		}
 
-		if(strlen($this->Name) > EBOOKS_MAX_STRING_LENGTH){
-			$error->Add(new Exceptions\StringTooLongException('Collection name: '. $this->Name));
+		if(isset($this->UrlName)){
+			$this->UrlName = trim($this->UrlName);
+
+			if($this->UrlName == ''){
+				$error->Add(new Exceptions\CollectionUrlNameRequiredException());
+			}
+
+			if(strlen($this->UrlName) > EBOOKS_MAX_STRING_LENGTH){
+				$error->Add(new Exceptions\StringTooLongException('Collection UrlName: '. $this->UrlName));
+			}
+		}
+		else{
+			$error->Add(new Exceptions\CollectionUrlNameRequiredException());
 		}
 
 		if($this->Type !== null && ($this->Type != CollectionType::Series && $this->Type != CollectionType::Set)){
diff --git a/lib/Contributor.php b/lib/Contributor.php
index 2982293b..244f73d7 100644
--- a/lib/Contributor.php
+++ b/lib/Contributor.php
@@ -1,4 +1,9 @@
 <?
+
+use Safe\DateTimeImmutable;
+
+use function Safe\preg_match;
+
 class Contributor{
 	public ?int $ContributorId = null;
 	public ?int $EbookId = null;
@@ -23,7 +28,100 @@ class Contributor{
 		return $instance;
 	}
 
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
+	public function Validate(): void{
+		/** @throws void */
+		$now = new DateTimeImmutable();
+
+		$error = new Exceptions\ValidationException();
+
+		if(!isset($this->EbookId)){
+			$error->Add(new Exceptions\ContributorEbookIdRequiredException());
+		}
+
+		if(isset($this->Name)){
+			$this->Name = trim($this->Name);
+
+			if($this->Name == ''){
+				$error->Add(new Exceptions\ContributorNameRequiredException());
+			}
+		}
+		else{
+			$error->Add(new Exceptions\ContributorNameRequiredException());
+		}
+
+		if(isset($this->UrlName)){
+			$this->UrlName = trim($this->UrlName);
+
+			if($this->UrlName == ''){
+				$error->Add(new Exceptions\ContributorUrlNameRequiredException());
+			}
+		}
+		else{
+			$error->Add(new Exceptions\ContributorUrlNameRequiredException());
+		}
+
+		$this->SortName = trim($this->SortName ?? '');
+		if($this->SortName == ''){
+			$this->SortName = null;
+		}
+
+		$this->FullName = trim($this->FullName ?? '');
+		if($this->FullName == ''){
+			$this->FullName = null;
+		}
+
+		$this->WikipediaUrl = trim($this->WikipediaUrl ?? '');
+		if($this->WikipediaUrl == ''){
+			$this->WikipediaUrl = null;
+		}
+
+		if(isset($this->WikipediaUrl)){
+			if(!preg_match('|https://.*wiki.*|ius', $this->WikipediaUrl)){
+				$error->Add(new Exceptions\InvalidContributorWikipediaUrlException('Invalid Contributor WikipediaUrl: ' . $this->WikipediaUrl));
+			}
+
+			if(strlen($this->WikipediaUrl) > EBOOKS_MAX_STRING_LENGTH){
+				$error->Add(new Exceptions\StringTooLongException('Contributor WikipediaUrl'));
+			}
+		}
+
+		$this->MarcRole = trim($this->MarcRole ?? '');
+		if($this->MarcRole == ''){
+			$this->MarcRole = null;
+		}
+
+		$this->NacoafUrl = trim($this->NacoafUrl ?? '');
+		if($this->NacoafUrl == ''){
+			$this->NacoafUrl = null;
+		}
+
+		if(isset($this->NacoafUrl)){
+			if(!preg_match('|https?://id\.loc\.gov/.*|ius', $this->NacoafUrl)){
+				$error->Add(new Exceptions\InvalidContributorNacoafUrlException('Invalid Contributor NacoafUrl: ' . $this->NacoafUrl));
+			}
+
+			if(strlen($this->NacoafUrl) > EBOOKS_MAX_STRING_LENGTH){
+				$error->Add(new Exceptions\StringTooLongException('Contributor NacoafUrl'));
+			}
+		}
+
+		if(!isset($this->SortOrder)){
+			$error->Add(new Exceptions\ContributorSortOrderRequiredException());
+		}
+
+		if($error->HasExceptions){
+			throw $error;
+		}
+	}
+
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
 	public function Create(): void{
+		$this->Validate();
 		Db::Query('
 			INSERT into Contributors (EbookId, Name, UrlName, SortName, WikipediaUrl, MarcRole, FullName,
 				NacoafUrl, SortOrder)
diff --git a/lib/Ebook.php b/lib/Ebook.php
index a72e80e3..3450159b 100644
--- a/lib/Ebook.php
+++ b/lib/Ebook.php
@@ -1750,6 +1750,9 @@ class Ebook{
 		);
 	}
 
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
 	private function InsertGitCommits(): void{
 		foreach($this->GitCommits as $commit){
 			$commit->EbookId = $this->EbookId;
@@ -1765,6 +1768,9 @@ class Ebook{
 		);
 	}
 
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
 	private function InsertSources(): void{
 		foreach($this->Sources as $source){
 			$source->EbookId = $this->EbookId;
@@ -1780,6 +1786,9 @@ class Ebook{
 		);
 	}
 
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
 	private function InsertContributors(): void{
 		$allContributors = array_merge($this->Authors, $this->Illustrators, $this->Translators, $this->Contributors);
 		foreach($allContributors as $sortOrder => $contributor){
diff --git a/lib/EbookSource.php b/lib/EbookSource.php
index 4ab4dcb4..fcbc098e 100644
--- a/lib/EbookSource.php
+++ b/lib/EbookSource.php
@@ -1,4 +1,7 @@
 <?
+
+use Safe\DateTimeImmutable;
+
 class EbookSource{
 	public ?int $EbookSourceId = null;
 	public ?int $EbookId = null;
@@ -12,7 +15,40 @@ class EbookSource{
 		return $instance;
 	}
 
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
+	public function Validate(): void{
+		/** @throws void */
+		$now = new DateTimeImmutable();
+
+		$error = new Exceptions\ValidationException();
+
+		if(!isset($this->EbookId)){
+			$error->Add(new Exceptions\EbookSourceEbookIdRequiredException());
+		}
+
+		if(isset($this->Url)){
+			$this->Url = trim($this->Url);
+
+			if($this->Url == ''){
+				$error->Add(new Exceptions\EbookSourceUrlRequiredException());
+			}
+		}
+		else{
+			$error->Add(new Exceptions\EbookSourceUrlRequiredException());
+		}
+
+		if($error->HasExceptions){
+			throw $error;
+		}
+	}
+
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
 	public function Create(): void{
+		$this->Validate();
 		Db::Query('
 			INSERT into EbookSources (EbookId, Type, Url)
 			values (?,
diff --git a/lib/EbookTag.php b/lib/EbookTag.php
index 69c214ed..a38854fa 100644
--- a/lib/EbookTag.php
+++ b/lib/EbookTag.php
@@ -33,13 +33,19 @@ class EbookTag extends Tag{
 	public function Validate(): void{
 		$error = new Exceptions\ValidationException();
 
-		$this->Name = trim($this->Name ?? '');
-		if($this->Name == ''){
-			$error->Add(new Exceptions\EbookTagNameRequiredException());
-		}
+		if(isset($this->Name)){
+			$this->Name = trim($this->Name);
 
-		if(strlen($this->Name) > EBOOKS_MAX_STRING_LENGTH){
-			$error->Add(new Exceptions\StringTooLongException('Ebook tag: '. $this->Name));
+			if($this->Name == ''){
+				$error->Add(new Exceptions\EbookTagNameRequiredException());
+			}
+
+			if(strlen($this->Name) > EBOOKS_MAX_STRING_LENGTH){
+				$error->Add(new Exceptions\StringTooLongException('Ebook tag: '. $this->Name));
+			}
+		}
+		else{
+			$error->Add(new Exceptions\EbookTagNameRequiredException());
 		}
 
 		if($this->Type != TagType::Ebook){
diff --git a/lib/Exceptions/CollectionUrlNameRequiredException.php b/lib/Exceptions/CollectionUrlNameRequiredException.php
new file mode 100644
index 00000000..17f45410
--- /dev/null
+++ b/lib/Exceptions/CollectionUrlNameRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class CollectionUrlNameRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'Collection UrlName is required.';
+}
diff --git a/lib/Exceptions/ContributorEbookIdRequiredException.php b/lib/Exceptions/ContributorEbookIdRequiredException.php
new file mode 100644
index 00000000..27364943
--- /dev/null
+++ b/lib/Exceptions/ContributorEbookIdRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class ContributorEbookIdRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'Contributor EbookId required.';
+}
diff --git a/lib/Exceptions/ContributorNameRequiredException.php b/lib/Exceptions/ContributorNameRequiredException.php
new file mode 100644
index 00000000..cddeb6e1
--- /dev/null
+++ b/lib/Exceptions/ContributorNameRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class ContributorNameRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'Contributor name required.';
+}
diff --git a/lib/Exceptions/ContributorSortOrderRequiredException.php b/lib/Exceptions/ContributorSortOrderRequiredException.php
new file mode 100644
index 00000000..94dc12cc
--- /dev/null
+++ b/lib/Exceptions/ContributorSortOrderRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class ContributorSortOrderRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'Contributor SortOrder required.';
+}
diff --git a/lib/Exceptions/ContributorUrlNameRequiredException.php b/lib/Exceptions/ContributorUrlNameRequiredException.php
new file mode 100644
index 00000000..f367e336
--- /dev/null
+++ b/lib/Exceptions/ContributorUrlNameRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class ContributorUrlNameRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'Contributor UrlName required.';
+}
diff --git a/lib/Exceptions/EbookSourceEbookIdRequiredException.php b/lib/Exceptions/EbookSourceEbookIdRequiredException.php
new file mode 100644
index 00000000..acb861c0
--- /dev/null
+++ b/lib/Exceptions/EbookSourceEbookIdRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class EbookSourceEbookIdRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'EbookSource EbookId required.';
+}
diff --git a/lib/Exceptions/EbookSourceUrlRequiredException.php b/lib/Exceptions/EbookSourceUrlRequiredException.php
new file mode 100644
index 00000000..3c6966d4
--- /dev/null
+++ b/lib/Exceptions/EbookSourceUrlRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class EbookSourceUrlRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'EbookSource Url required.';
+}
diff --git a/lib/Exceptions/GitCommitCreatedDatetimeRequiredException.php b/lib/Exceptions/GitCommitCreatedDatetimeRequiredException.php
new file mode 100644
index 00000000..d17743ad
--- /dev/null
+++ b/lib/Exceptions/GitCommitCreatedDatetimeRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class GitCommitCreatedDatetimeRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'GitCommit Created datetime required.';
+}
diff --git a/lib/Exceptions/GitCommitEbookIdRequiredException.php b/lib/Exceptions/GitCommitEbookIdRequiredException.php
new file mode 100644
index 00000000..40424233
--- /dev/null
+++ b/lib/Exceptions/GitCommitEbookIdRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class GitCommitEbookIdRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'GitCommit EbookId required.';
+}
diff --git a/lib/Exceptions/GitCommitHashRequiredException.php b/lib/Exceptions/GitCommitHashRequiredException.php
new file mode 100644
index 00000000..622c381a
--- /dev/null
+++ b/lib/Exceptions/GitCommitHashRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class GitCommitHashRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'GitCommit hash required.';
+}
diff --git a/lib/Exceptions/GitCommitMessageRequiredException.php b/lib/Exceptions/GitCommitMessageRequiredException.php
new file mode 100644
index 00000000..9fceef93
--- /dev/null
+++ b/lib/Exceptions/GitCommitMessageRequiredException.php
@@ -0,0 +1,7 @@
+<?
+namespace Exceptions;
+
+class GitCommitMessageRequiredException extends AppException{
+	/** @var string $message */
+	protected $message = 'GitCommit message required.';
+}
diff --git a/lib/Exceptions/InvalidContributorNacoafUrlException.php b/lib/Exceptions/InvalidContributorNacoafUrlException.php
new file mode 100644
index 00000000..648883e7
--- /dev/null
+++ b/lib/Exceptions/InvalidContributorNacoafUrlException.php
@@ -0,0 +1,5 @@
+<?
+namespace Exceptions;
+
+class InvalidContributorNacoafUrlException extends AppException{
+}
diff --git a/lib/Exceptions/InvalidContributorWikipediaUrlException.php b/lib/Exceptions/InvalidContributorWikipediaUrlException.php
new file mode 100644
index 00000000..76c601a2
--- /dev/null
+++ b/lib/Exceptions/InvalidContributorWikipediaUrlException.php
@@ -0,0 +1,5 @@
+<?
+namespace Exceptions;
+
+class InvalidContributorWikipediaUrlException extends AppException{
+}
diff --git a/lib/Exceptions/InvalidGitCommitCreatedDatetimeException.php b/lib/Exceptions/InvalidGitCommitCreatedDatetimeException.php
new file mode 100644
index 00000000..05d210b4
--- /dev/null
+++ b/lib/Exceptions/InvalidGitCommitCreatedDatetimeException.php
@@ -0,0 +1,15 @@
+<?
+namespace Exceptions;
+
+use Safe\DateTimeImmutable;
+
+class InvalidGitCommitCreatedDatetimeException extends AppException{
+	/** @var string $message */
+	protected $message = 'Invalid GitCommit Created datetime.';
+
+	public function __construct(DateTimeImmutable $createdDatetime){
+		/** @throws void */
+		$now = new DateTimeImmutable();
+		$this->message = 'Invalid GitCommit Created datetime. ' . $createdDatetime->format('Y-m-d') . ' is not between ' . EBOOK_EARLIEST_CREATION_DATE->format('Y-m-d') . ' and ' . $now->format('Y-m-d') . '.';
+	}
+}
diff --git a/lib/GitCommit.php b/lib/GitCommit.php
index 3df150df..a2bc22d3 100644
--- a/lib/GitCommit.php
+++ b/lib/GitCommit.php
@@ -24,7 +24,60 @@ class GitCommit{
 		return $instance;
 	}
 
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
+	public function Validate(): void{
+		/** @throws void */
+		$now = new DateTimeImmutable();
+
+		$error = new Exceptions\ValidationException();
+
+		if(!isset($this->EbookId)){
+			$error->Add(new Exceptions\GitCommitEbookIdRequiredException());
+		}
+
+		if(isset($this->Created)){
+			if($this->Created > $now || $this->Created < EBOOK_EARLIEST_CREATION_DATE){
+				$error->Add(new Exceptions\InvalidGitCommitCreatedDatetimeException($this->Created));
+			}
+		}
+		else{
+			$error->Add(new Exceptions\GitCommitCreatedDatetimeRequiredException());
+		}
+
+		if(isset($this->Message)){
+			$this->Message = trim($this->Message);
+
+			if($this->Message == ''){
+				$error->Add(new Exceptions\GitCommitMessageRequiredException());
+			}
+		}
+		else{
+			$error->Add(new Exceptions\GitCommitMessageRequiredException());
+		}
+
+		if(isset($this->Hash)){
+			$this->Hash = trim($this->Hash);
+
+			if($this->Hash == ''){
+				$error->Add(new Exceptions\GitCommitHashRequiredException());
+			}
+		}
+		else{
+			$error->Add(new Exceptions\GitCommitHashRequiredException());
+		}
+
+		if($error->HasExceptions){
+			throw $error;
+		}
+	}
+
+	/**
+	 * @throws Exceptions\ValidationException
+	 */
 	public function Create(): void{
+		$this->Validate();
 		Db::Query('
 			INSERT into GitCommits (EbookId, Created, Message, Hash)
 			values (?,
diff --git a/lib/LocSubject.php b/lib/LocSubject.php
index 935dd35c..ce161e18 100644
--- a/lib/LocSubject.php
+++ b/lib/LocSubject.php
@@ -9,13 +9,19 @@ class LocSubject{
 	public function Validate(): void{
 		$error = new Exceptions\ValidationException();
 
-		$this->Name = trim($this->Name ?? '');
-		if($this->Name == ''){
-			$error->Add(new Exceptions\LocSubjectNameRequiredException());
-		}
+		if(isset($this->Name)){
+			$this->Name = trim($this->Name);
 
-		if(strlen($this->Name) > EBOOKS_MAX_STRING_LENGTH){
-			$error->Add(new Exceptions\StringTooLongException('LoC subject: '. $this->Name));
+			if($this->Name == ''){
+				$error->Add(new Exceptions\LocSubjectNameRequiredException());
+			}
+
+			if(strlen($this->Name) > EBOOKS_MAX_STRING_LENGTH){
+				$error->Add(new Exceptions\StringTooLongException('LoC subject: '. $this->Name));
+			}
+		}
+		else{
+			$error->Add(new Exceptions\LocSubjectNameRequiredException());
 		}
 
 		if($error->HasExceptions){