--- a/src/driver.rs	Sun Mar 22 23:08:08 2020 +0100
+++ b/src/driver.rs	Sun Mar 22 23:10:06 2020 +0100
@@ -26,12 +26,26 @@
     fn next(&mut self, doc: &extract::Document) -> Vec<Uri>;
 }
 
+/// Extracted information can be presented as sequence of key/value pairs.
+pub trait Extracted {
+    fn all(&mut self) -> Box<dyn iter::Iterator<Item = (String, String)> + Send> {
+        Box::new(iter::empty())
+    }
+}
+
+/// An Extractor retrieves information from a Document.
+pub trait Extractor {
+    fn extract(&mut self, doc: &extract::Document) -> Option<Box<dyn Extracted>> {
+        None
+    }
+}
+
 /// DriverLogic holds the driven implementation. The members tell the driver what to fetch, and
 /// what and how to store it.
 pub struct DriverLogic {
     pub explore: Box<dyn Explorer>,
     pub store: Box<dyn Storage>,
-    pub extract: Box<dyn extract::Extractor>,
+    pub extract: Box<dyn Extractor>,
 }
 
 pub struct Driver {

--- a/src/extract.rs	Sun Mar 22 23:08:08 2020 +0100
+++ b/src/extract.rs	Sun Mar 22 23:10:06 2020 +0100
@@ -60,18 +60,6 @@
         .map_err(|_| HTTPError::LogicError(format!("failed to parse selector {}", sel)))
 }
 
-pub trait Extracted {
-    fn all(&mut self) -> Box<dyn iter::Iterator<Item = (String, String)> + Send> {
-        Box::new(iter::empty())
-    }
-}
-
-pub trait Extractor {
-    fn extract(&mut self, doc: &Document) -> Option<Box<dyn Extracted>> {
-        None
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::Document;

--- a/src/implem.rs	Sun Mar 22 23:08:08 2020 +0100
+++ b/src/implem.rs	Sun Mar 22 23:10:06 2020 +0100
@@ -19,8 +19,8 @@
     String::from_iter(s.chars().skip(start).take(len))
 }
 
-impl extract::Extractor for AudiophilItemPriceExtractor {
-    fn extract(&mut self, doc: &extract::Document) -> Option<Box<dyn extract::Extracted>> {
+impl driver::Extractor for AudiophilItemPriceExtractor {
+    fn extract(&mut self, doc: &extract::Document) -> Option<Box<dyn driver::Extracted>> {
         let mut data = doc.get_contents(&[".bez.neu", ".preis strong"]).unwrap();
         let prices = data.pop().unwrap();
         let descs = data.pop().unwrap();