diff --git a/examples/simple/Concept_Example.thy b/examples/simple/Concept_Example.thy
new file mode 100644
index 00000000..d8c3cdb7
--- /dev/null
+++ b/examples/simple/Concept_Example.thy
@@ -0,0 +1,50 @@
+chapter\<open>Setting and modifying attributes of doc-items\<close>
+
+theory Concept_Example
+  imports "../../ontologies/Conceptual" (* we use the generic "Conceptual" ontology *)
+begin
+
+text\<open>@{theory Conceptual} provides a monitor @{typ M} enforcing a particular document structure.
+     Here, we say: From now on, this structural rules are respected wrt. all doc\_classes M is
+     enabled for.\<close>
+open_monitor*[struct::M]  
+
+section*[a::A, x = "3"] \<open> Lorem ipsum dolor sit amet, ... \<close>
+
+text*[c1::C, x = "''beta''"] \<open> ... suspendisse non arcu malesuada mollis, nibh morbi, ...  \<close>
+
+text*[d::D, a1 = "X3"] \<open> ... phasellus amet id massa nunc, pede suscipit repellendus, 
+                         ... @{docitem \<open>c1\<close>} @{thm "refl"}\<close>
+
+
+update_instance*[d::D, a1 := X2]
+
+text\<open> ... in ut tortor ... @{docitem \<open>a\<close>} ... @{A \<open>a\<close>}\<close>  
+    
+text*[c2::C, x = "''delta''"]  \<open> ... in ut tortor eleifend augue pretium consectetuer.  \<close>
+
+section*[f::F] \<open> Lectus accumsan velit ultrices, ... }\<close>
+  
+theorem some_proof : "P" sorry
+
+text\<open>This is an example where we add a theorem into a kind of "result-list" of the doc-item f.\<close>
+update_instance*[f::F,r:="[@{thm ''Concept_Example.some_proof''}]"]
+
+text\<open> ..., mauris amet, id elit aliquam aptent id,  ... @{docitem \<open>a\<close>} \<close>
+
+text\<open>Here we add and maintain a link that is actually modeled as m-to-n relation ...\<close>
+update_instance*[f::F,b:="{(@{docitem  ''a''}::A,@{docitem  ''c1''}::C), 
+                           (@{docitem  ''a''},   @{docitem  ''c2''})}"] 
+  
+close_monitor*[struct]
+
+text\<open>And the trace of the monitor is:\<close>
+ML\<open>@{trace_attribute struct}\<close>
+
+print_doc_classes
+print_doc_items
+
+
+
+end 
+  
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diff --git a/examples/simple/Concept_ExampleInvariant.thy b/examples/simple/Concept_ExampleInvariant.thy
new file mode 100644
index 00000000..850ac484
--- /dev/null
+++ b/examples/simple/Concept_ExampleInvariant.thy
@@ -0,0 +1,39 @@
+chapter\<open>Setting and modifying attributes of doc-items\<close>
+
+theory Concept_ExampleInvariant
+  imports "../../ontologies/Conceptual" (* we use the generic "Conceptual" ontology *)
+begin
+
+print_doc_classes
+print_doc_items
+
+ML\<open>fun check_A_invariant oid ctxt = 
+      let val term =  AttributeAccess.calc_attr_access ctxt "x" oid @{here}
+          val (@{typ "int"},x_value) = HOLogic.dest_number term
+      in  if x_value > 5 then error("class A invariant violation") else true end
+\<close>
+
+text\<open>Watch out: The current programming interface to document class invariants is pretty low-level:
+\<^item> No inheritance principle
+\<^item> No high-level notation in HOL
+\<^item> Typing on ML level is assumed to be correct.
+The implementor of an ontology must know what he does ...
+\<close>
+setup\<open>DOF_core.update_class_invariant "Conceptual.A" (fn oid => 
+                                                       fn ctxt => 
+                                                        (writeln ("sample echo : "^oid); true))\<close>
+
+section*[b::A, x = "5"] \<open> Lorem ipsum dolor sit amet, ... \<close>
+
+setup\<open>DOF_core.update_class_invariant "Conceptual.A" check_A_invariant\<close>
+
+(* test : should fail :
+section*[c::A, x = "6"] \<open> Lorem ipsum dolor sit amet, ... \<close>
+*)
+
+(* to test : updates *)
+
+(* to do: trace example *)
+
+end 
+  
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