diff --git a/src/main.rs b/src/main.rs
index 37b3752..70128d9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,6 +14,7 @@ impl clingo::StatementHandler for StatementHandler<'_>
 				if let Err(error) = anthem::translate::verify_properties::read(rule, self.context)
 				{
 					log::error!("could not translate input program: {}", error);
+					return false;
 				}
 			},
 			_ => log::debug!("read statement (other kind)"),
@@ -33,17 +34,32 @@ impl clingo::Logger for Logger
 	}
 }
 
-fn main() -> Result<(), Box<dyn std::error::Error>>
+fn main()
 {
 	pretty_env_logger::init();
 
-	let program = std::fs::read_to_string("test.lp")?;
+	let program = match std::fs::read_to_string("test.lp")
+	{
+		Ok(value) => value,
+		Err(error) =>
+		{
+			log::error!("could not read input program: {}", error);
+			std::process::exit(1);
+		},
+	};
 	let mut context = anthem::translate::verify_properties::Context::new();
 	let mut statement_handler = StatementHandler
 	{
 		context: &mut context
 	};
-	clingo::parse_program_with_logger(&program, &mut statement_handler, &mut Logger, std::u32::MAX)?;
 
-	Ok(())
+	match clingo::parse_program_with_logger(&program, &mut statement_handler, &mut Logger, std::u32::MAX)
+	{
+		Ok(()) => (),
+		Err(error) =>
+		{
+			log::error!("could not translate input program: {}", error);
+			std::process::exit(1);
+		},
+	}
 }
diff --git a/src/translate/verify_properties.rs b/src/translate/verify_properties.rs
index 8b455b9..16c2494 100644
--- a/src/translate/verify_properties.rs
+++ b/src/translate/verify_properties.rs
@@ -9,18 +9,22 @@ use translate_head::determine_head_type;
 
 pub fn read(rule: &clingo::ast::Rule, context: &mut Context) -> Result<(), crate::Error>
 {
-	let test = translate_body(rule.body(), context)?;
+	let translated_body = translate_body(rule.body(), context)?;
 
-	println!("{:?}", test);
-
-	let test = determine_head_type(rule.head(),
+	let head_type = determine_head_type(rule.head(),
 		|name, arity| context.find_or_create_predicate_declaration(name, arity))?;
 
-	match test
+	match head_type
 	{
-		translate_head::HeadType::ChoiceWithSingleAtom(_) => println!("choice single"),
-		translate_head::HeadType::IntegrityConstraint => println!("integrity"),
-		translate_head::HeadType::Trivial => println!("trivial"),
+		translate_head::HeadType::ChoiceWithSingleAtom(test) =>
+			log::debug!("translating choice rule with single atom"),
+		translate_head::HeadType::IntegrityConstraint =>
+			log::debug!("translating integrity constraint"),
+		translate_head::HeadType::Trivial =>
+		{
+			log::debug!("skipping trivial rule");
+			return Ok(());
+		},
 		_ => (),
 	}
 
diff --git a/src/translate/verify_properties/translate_head.rs b/src/translate/verify_properties/translate_head.rs
index 4e5b799..da8996d 100644
--- a/src/translate/verify_properties/translate_head.rs
+++ b/src/translate/verify_properties/translate_head.rs
@@ -1,7 +1,7 @@
 pub struct HeadAtom<'a>
 {
-	predicate_declaration: std::rc::Rc<foliage::PredicateDeclaration>,
-	arguments: &'a [clingo::ast::Term<'a>],
+	pub predicate_declaration: std::rc::Rc<foliage::PredicateDeclaration>,
+	pub arguments: &'a [clingo::ast::Term<'a>],
 }
 
 pub enum HeadType<'a>
@@ -35,6 +35,29 @@ where
 
 	match head_literal.head_literal_type()
 	{
+		clingo::ast::HeadLiteralType::Literal(literal) =>
+		{
+			if literal.sign() != clingo::ast::Sign::None
+			{
+				return Err(crate::Error::new_unsupported_language_feature("negated head literals"));
+			}
+
+			let term = match literal.literal_type()
+			{
+				clingo::ast::LiteralType::Boolean(true) => return Ok(HeadType::Trivial),
+				clingo::ast::LiteralType::Boolean(false) => return Ok(HeadType::IntegrityConstraint),
+				clingo::ast::LiteralType::Symbolic(term) => term,
+				_ => return Err(crate::Error::new_unsupported_language_feature("elements other than terms in rule head")),
+			};
+
+			let function = match term.term_type()
+			{
+				clingo::ast::TermType::Function(function) => function,
+				_ => return Err(crate::Error::new_unsupported_language_feature("elements other than atoms in rule head")),
+			};
+
+			Ok(HeadType::SingleAtom(create_head_atom(function)?))
+		},
 		clingo::ast::HeadLiteralType::Aggregate(aggregate) =>
 		{
 			if aggregate.left_guard().is_some() || aggregate.right_guard().is_some()
@@ -65,33 +88,8 @@ where
 				_ => return Err(crate::Error::new_unsupported_language_feature("elements other than atoms in aggregates")),
 			};
 
-			return Ok(HeadType::ChoiceWithSingleAtom(create_head_atom(function)?));
+			Ok(HeadType::ChoiceWithSingleAtom(create_head_atom(function)?))
 		},
-		clingo::ast::HeadLiteralType::Literal(literal) =>
-		{
-			if literal.sign() != clingo::ast::Sign::None
-			{
-				return Err(crate::Error::new_unsupported_language_feature("negated head literals"));
-			}
-
-			let term = match literal.literal_type()
-			{
-				clingo::ast::LiteralType::Boolean(true) => return Ok(HeadType::Trivial),
-				clingo::ast::LiteralType::Boolean(false) => return Ok(HeadType::IntegrityConstraint),
-				clingo::ast::LiteralType::Symbolic(term) => term,
-				_ => return Err(crate::Error::new_unsupported_language_feature("elements other than terms in rule head")),
-			};
-
-			let function = match term.term_type()
-			{
-				clingo::ast::TermType::Function(function) => function,
-				_ => return Err(crate::Error::new_unsupported_language_feature("elements other than atoms in rule head")),
-			};
-
-			return Ok(HeadType::ChoiceWithSingleAtom(create_head_atom(function)?));
-		},
-		_ => (),
+		_ => Err(crate::Error::new_unsupported_language_feature("elements other than literals and aggregates in rule head")),
 	}
-
-	Ok(HeadType::Annotation)
 }