diff --git a/Cargo.toml b/Cargo.toml
index a091148..ceed8ae 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,10 +5,12 @@ authors = ["Patrick Lühne <patrick@luehne.de>"]
 edition = "2018"
 
 [dependencies]
-clingo = "0.6"
 log = "0.4"
 pretty_env_logger = "0.3"
 
+[dependencies.clingo]
+path = "../clingo-rs"
+
 [dependencies.foliage]
 git = "ssh://gitea@git.luehne.de/patrick/foliage-rs.git"
 branch = "refactoring"
diff --git a/src/main.rs b/src/main.rs
index 242d15a..37b3752 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -11,7 +11,10 @@ impl clingo::StatementHandler for StatementHandler<'_>
 		{
 			clingo::ast::StatementType::Rule(ref rule) =>
 			{
-				anthem::translate::verify_properties::read(rule, self.context)
+				if let Err(error) = anthem::translate::verify_properties::read(rule, self.context)
+				{
+					log::error!("could not translate input program: {}", error);
+				}
 			},
 			_ => log::debug!("read statement (other kind)"),
 		}
diff --git a/src/translate/verify_properties.rs b/src/translate/verify_properties.rs
index ce560e8..8b455b9 100644
--- a/src/translate/verify_properties.rs
+++ b/src/translate/verify_properties.rs
@@ -1,10 +1,28 @@
 mod context;
 mod translate_body;
+mod translate_head;
 
 pub use context::Context;
-use translate_body::translate_body;
 
-pub fn read(rule: &clingo::ast::Rule, context: &mut Context)
+use translate_body::translate_body;
+use translate_head::determine_head_type;
+
+pub fn read(rule: &clingo::ast::Rule, context: &mut Context) -> Result<(), crate::Error>
 {
-	println!("{:?}", translate_body(rule.body(), context));
+	let test = translate_body(rule.body(), context)?;
+
+	println!("{:?}", test);
+
+	let test = determine_head_type(rule.head(),
+		|name, arity| context.find_or_create_predicate_declaration(name, arity))?;
+
+	match test
+	{
+		translate_head::HeadType::ChoiceWithSingleAtom(_) => println!("choice single"),
+		translate_head::HeadType::IntegrityConstraint => println!("integrity"),
+		translate_head::HeadType::Trivial => println!("trivial"),
+		_ => (),
+	}
+
+	Ok(())
 }
diff --git a/src/translate/verify_properties/translate_head.rs b/src/translate/verify_properties/translate_head.rs
new file mode 100644
index 0000000..4e5b799
--- /dev/null
+++ b/src/translate/verify_properties/translate_head.rs
@@ -0,0 +1,97 @@
+pub struct HeadAtom<'a>
+{
+	predicate_declaration: std::rc::Rc<foliage::PredicateDeclaration>,
+	arguments: &'a [clingo::ast::Term<'a>],
+}
+
+pub enum HeadType<'a>
+{
+	SingleAtom(HeadAtom<'a>),
+	ChoiceWithSingleAtom(HeadAtom<'a>),
+	IntegrityConstraint,
+	Trivial,
+}
+
+pub fn determine_head_type<'a, F>(head_literal: &'a clingo::ast::HeadLiteral,
+	mut find_or_create_predicate_declaration: F)
+	-> Result<HeadType<'a>, crate::Error>
+where
+	F: FnMut(&str, usize) -> std::rc::Rc<foliage::PredicateDeclaration>
+{
+	let mut create_head_atom = |function: &'a clingo::ast::Function| -> Result<_, crate::Error>
+	{
+		let function_name = function.name()
+			.map_err(|error| crate::Error::new_decode_identifier(error))?;
+
+		let predicate_declaration
+			= find_or_create_predicate_declaration(function_name, function.arguments().len());
+
+		Ok(HeadAtom
+		{
+			predicate_declaration,
+			arguments: function.arguments(),
+		})
+	};
+
+	match head_literal.head_literal_type()
+	{
+		clingo::ast::HeadLiteralType::Aggregate(aggregate) =>
+		{
+			if aggregate.left_guard().is_some() || aggregate.right_guard().is_some()
+			{
+				return Err(crate::Error::new_unsupported_language_feature("aggregates with guards"));
+			}
+
+			let literal = match aggregate.elements().split_first()
+			{
+				Some((first, remainder)) if remainder.is_empty() => first.literal(),
+				_ => return Err(crate::Error::new_unsupported_language_feature("aggregates not containing exactly one element")),
+			};
+
+			if literal.sign() != clingo::ast::Sign::None
+			{
+				return Err(crate::Error::new_unsupported_language_feature("negated literals in aggregates"));
+			}
+
+			let term = match literal.literal_type()
+			{
+				clingo::ast::LiteralType::Symbolic(term) => term,
+				_ => return Err(crate::Error::new_unsupported_language_feature("elements other than terms in aggregates")),
+			};
+
+			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 aggregates")),
+			};
+
+			return 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)?));
+		},
+		_ => (),
+	}
+
+	Ok(HeadType::Annotation)
+}