tuned signature, clarified modules;

--- a/src/Pure/Thy/present.scala	Wed Apr 15 14:54:25 2015 +0200
+++ b/src/Pure/Thy/present.scala	Wed Apr 15 15:27:45 2015 +0200
@@ -12,6 +12,32 @@
 
 object Present
 {
+  /* session graph */
+
+  def session_graph(
+    parent_session: String,
+    parent_loaded: String => Boolean,
+    deps: List[Thy_Info.Dep]): Graph_Display.Graph =
+  {
+    val parent_session_node =
+      Graph_Display.Node("[" + parent_session + "]", "session." + parent_session)
+
+    def node(name: Document.Node.Name): Graph_Display.Node =
+      if (parent_loaded(name.theory)) parent_session_node
+      else Graph_Display.Node(name.theory, "theory." + name.theory)
+
+    (Graph_Display.empty_graph /: deps) {
+      case (g, dep) =>
+        if (parent_loaded(dep.name.theory)) g
+        else {
+          val a = node(dep.name)
+          val bs = dep.header.imports.map({ case (name, _) => node(name) })
+          ((g /: (a :: bs))(_.default_node(_, Nil)) /: bs)(_.add_edge(_, a))
+        }
+    }
+  }
+
+
   /* maintain chapter index -- NOT thread-safe */
 
   private val index_path = Path.basic("index.html")
@@ -48,4 +74,3 @@
     File.write(dir + index_path, HTML.chapter_index(chapter, sessions))
   }
 }
-

--- a/src/Pure/Thy/thy_info.scala	Wed Apr 15 14:54:25 2015 +0200
+++ b/src/Pure/Thy/thy_info.scala	Wed Apr 15 15:27:45 2015 +0200
@@ -7,6 +7,15 @@
 package isabelle
 
 
+object Thy_Info
+{
+  /* dependencies */
+
+  sealed case class Dep(
+    name: Document.Node.Name,
+    header: Document.Node.Header)
+}
+
 class Thy_Info(resources: Resources)
 {
   /* messages */
@@ -24,29 +33,18 @@
 
   /* dependencies */
 
-  sealed case class Dep(
-    name: Document.Node.Name,
-    header: Document.Node.Header)
-  {
-    def loaded_files(syntax: Prover.Syntax): List[String] =
-    {
-      val string = resources.with_thy_reader(name, reader => Symbol.decode(reader.source.toString))
-      resources.loaded_files(syntax, string)
-    }
-  }
-
   object Dependencies
   {
     val empty = new Dependencies(Nil, Nil, Multi_Map.empty, Multi_Map.empty)
   }
 
   final class Dependencies private(
-    rev_deps: List[Dep],
+    rev_deps: List[Thy_Info.Dep],
     val keywords: Thy_Header.Keywords,
     val seen_names: Multi_Map[String, Document.Node.Name],
     val seen_positions: Multi_Map[String, Position.T])
   {
-    def :: (dep: Dep): Dependencies =
+    def :: (dep: Thy_Info.Dep): Dependencies =
       new Dependencies(dep :: rev_deps, dep.header.keywords ::: keywords,
         seen_names, seen_positions)
 
@@ -58,7 +56,7 @@
         seen_positions + (name.theory -> pos))
     }
 
-    def deps: List[Dep] = rev_deps.reverse
+    def deps: List[Thy_Info.Dep] = rev_deps.reverse
 
     def errors: List[String] =
     {
@@ -84,33 +82,16 @@
 
     def loaded_files: List[Path] =
     {
-      val dep_files =
-        Par_List.map(
-          (dep: Dep) =>
-            dep.loaded_files(syntax).map(a => Path.explode(dep.name.master_dir) + Path.explode(a)),
-          rev_deps)
+      def loaded(dep: Thy_Info.Dep): List[Path] =
+      {
+        val string = resources.with_thy_reader(dep.name,
+          reader => Symbol.decode(reader.source.toString))
+        resources.loaded_files(syntax, string).
+          map(a => Path.explode(dep.name.master_dir) + Path.explode(a))
+      }
+      val dep_files = Par_List.map(loaded _, rev_deps)
       ((Nil: List[Path]) /: dep_files) { case (acc_files, files) => files ::: acc_files }
     }
-
-    def deps_graph(parent_session: String, parent_loaded: String => Boolean): Graph_Display.Graph =
-    {
-      val parent_session_node =
-        Graph_Display.Node("[" + parent_session + "]", "session." + parent_session)
-
-      def node(name: Document.Node.Name): Graph_Display.Node =
-        if (parent_loaded(name.theory)) parent_session_node
-        else Graph_Display.Node(name.theory, "theory." + name.theory)
-
-      (Graph_Display.empty_graph /: rev_deps) {
-        case (g, dep) =>
-          if (parent_loaded(dep.name.theory)) g
-          else {
-            val a = node(dep.name)
-            val bs = dep.header.imports.map({ case (name, _) => node(name) })
-            ((g /: (a :: bs))(_.default_node(_, Nil)) /: bs)(_.add_edge(_, a))
-          }
-      }
-    }
   }
 
   private def require_thys(session: String, initiators: List[Document.Node.Name],
@@ -136,11 +117,12 @@
         val header =
           try { resources.check_thy(session, name, Token.Pos.file(name.node)).cat_errors(message) }
           catch { case ERROR(msg) => cat_error(msg, message) }
-        Dep(name, header) :: require_thys(session, name :: initiators, required1, header.imports)
+        Thy_Info.Dep(name, header) ::
+          require_thys(session, name :: initiators, required1, header.imports)
       }
       catch {
         case e: Throwable =>
-          Dep(name, Document.Node.bad_header(Exn.message(e))) :: required1
+          Thy_Info.Dep(name, Document.Node.bad_header(Exn.message(e))) :: required1
       }
     }
   }

--- a/src/Pure/Tools/build.scala	Wed Apr 15 14:54:25 2015 +0200
+++ b/src/Pure/Tools/build.scala	Wed Apr 15 15:27:45 2015 +0200
@@ -512,7 +512,8 @@
 
             val sources = all_files.map(p => (p, SHA1.digest(p.file)))
 
-            val session_graph = thy_deps.deps_graph(info.parent getOrElse "", loaded_theories0)
+            val session_graph =
+              Present.session_graph(info.parent getOrElse "", loaded_theories0, thy_deps.deps)
 
             val content =
               Session_Content(loaded_theories, known_theories, keywords, syntax,