src/Pure/Thy/presentation.scala

               sessions.map({ case (name, description) =>
                 val descr = Symbol.trim_blank_lines(description)
                 (List(HTML.link(name + "/index.html", HTML.text(name))),
                   if (descr == "") Nil
                   else HTML.break ::: List(HTML.pre(HTML.text(descr)))) })))))),
-      base = Some(presentation_dir))
+      root = Some(presentation_dir))
   }
 
   def update_root(presentation_dir: Path): Unit = {
     Isabelle_System.make_directory(presentation_dir)
     HTML.init_fonts(presentation_dir)

               node_context(file_name, file_dir).make_html(thy_elements, xml))
 
           val file_title = "File " + Symbol.cartouche_decoded(blob.src_path.implode_short)
           HTML.write_document(file_dir, file_html.file_name,
             List(HTML.title(file_title)), List(html_context.head(file_title), html),
-            base = Some(html_context.root_dir))
+            root = Some(html_context.root_dir))
           List(HTML.link(html_link, HTML.text(file_title)))
         }
 
       val thy_title = "Theory " + theory.print_short
       HTML.write_document(session_dir, html_context.theory_html(theory).implode,
         List(HTML.title(thy_title)), List(html_context.head(thy_title), thy_html),
-        base = Some(html_context.root_dir))
+        root = Some(html_context.root_dir))
 
       List(HTML.link(html_context.theory_html(theory),
         HTML.text(theory.print_short) :::
         (if (files.isEmpty) Nil else List(HTML.itemize(files)))))
     }

     val title = "Session " + session_name
       HTML.write_document(session_dir, "index.html",
         List(HTML.title(title + Isabelle_System.isabelle_heading())),
         html_context.head(title, List(HTML.par(document_links))) ::
           html_context.contents("Theories", theories),
-        base = Some(html_context.root_dir))
+        root = Some(html_context.root_dir))
   }
 }