diff --git a/mfm_machine/src/state/context.rs b/mfm_machine/src/state/context.rs
index 27a7414..1d5aac7 100644
--- a/mfm_machine/src/state/context.rs
+++ b/mfm_machine/src/state/context.rs
@@ -6,8 +6,8 @@ use serde_json::Value;
 pub type ContextWrapper = Arc<Mutex<Box<dyn Context>>>;
 
 pub trait Context {
-    fn read_input(&self) -> Result<Value, Error>;
-    fn write_output(&mut self, value: &Value) -> Result<(), Error>;
+    fn read(&self) -> Result<Value, Error>;
+    fn write(&mut self, value: &Value) -> Result<(), Error>;
 }
 
 pub fn wrap_context<C: Context + 'static>(context: C) -> ContextWrapper {
@@ -35,11 +35,11 @@ mod test {
     }
 
     impl Context for ContextA {
-        fn read_input(&self) -> Result<Value, Error> {
+        fn read(&self) -> Result<Value, Error> {
             serde_json::to_value(self).map_err(|e| anyhow!(e))
         }
 
-        fn write_output(&mut self, value: &Value) -> Result<(), Error> {
+        fn write(&mut self, value: &Value) -> Result<(), Error> {
             let ctx: ContextA = serde_json::from_value(value.clone()).map_err(|e| anyhow!(e))?;
             self.a = ctx.a;
             self.b = ctx.b;
@@ -52,18 +52,10 @@ mod test {
         let context_a: &mut dyn Context = &mut ContextA::_new(String::from("hello"), 7);
         let context_b: &dyn Context = &ContextA::_new(String::from("hellow"), 9);
 
-        assert_ne!(
-            context_a.read_input().unwrap(),
-            context_b.read_input().unwrap()
-        );
+        assert_ne!(context_a.read().unwrap(), context_b.read().unwrap());
 
-        context_a
-            .write_output(&context_b.read_input().unwrap())
-            .unwrap();
+        context_a.write(&context_b.read().unwrap()).unwrap();
 
-        assert_eq!(
-            context_a.read_input().unwrap(),
-            context_b.read_input().unwrap()
-        );
+        assert_eq!(context_a.read().unwrap(), context_b.read().unwrap());
     }
 }
diff --git a/mfm_machine/src/state_machine/mod.rs b/mfm_machine/src/state_machine/mod.rs
index 75030e9..cea9760 100644
--- a/mfm_machine/src/state_machine/mod.rs
+++ b/mfm_machine/src/state_machine/mod.rs
@@ -75,13 +75,6 @@ impl StateMachine {
         }
 
         let state = &self.states[state_index];
-        let tracker = self.tracker.as_mut();
-        // TODO: should state.label() return an &Label or Label?
-        // TODO: remove this unwrap for proper handling
-        tracker.track(
-            Index::new(state_index, state.label(), state.tags()),
-            context.clone(),
-        );
 
         // if thats true, means that no state was executed before and this is the first one
         if last_state_result.is_none() {
@@ -99,13 +92,16 @@ impl StateMachine {
                     // we should implement an well defined rule for the whole dependency
                     // system between states, and follow this definition here as well.
                     let state_depends_on = state.depends_on();
-                    let indexes_state_deps =
-                        tracker.search_by_tag(state_depends_on.first().unwrap());
+                    let indexes_state_deps = self
+                        .tracker
+                        .search_by_tag(state_depends_on.first().unwrap());
 
                     let last_index_of_first_dep = indexes_state_deps.last().unwrap().clone();
 
-                    let last_index_state_ctx =
-                        tracker.recover(last_index_of_first_dep.clone()).unwrap();
+                    let last_index_state_ctx = self
+                        .tracker
+                        .recover(last_index_of_first_dep.clone())
+                        .unwrap();
 
                     context = last_index_state_ctx.clone();
 
@@ -134,9 +130,13 @@ impl StateMachine {
             return Ok(());
         }
 
-        let current_state = &self.states[next_state_index];
+        let state = &self.states[next_state_index];
 
-        let result = current_state.handler(context.clone());
+        let result = state.handler(context.clone());
+        self.tracker.as_mut().track(
+            Index::new(next_state_index, state.label(), state.tags()),
+            context.clone(),
+        );
 
         self.execute_rec(context, next_state_index, Option::Some(result))
     }
@@ -176,11 +176,11 @@ mod test {
     }
 
     impl Context for ContextA {
-        fn read_input(&self) -> Result<Value, Error> {
+        fn read(&self) -> Result<Value, Error> {
             serde_json::to_value(self).map_err(|e| anyhow!(e))
         }
 
-        fn write_output(&mut self, value: &Value) -> Result<(), Error> {
+        fn write(&mut self, value: &Value) -> Result<(), Error> {
             let ctx: ContextA = serde_json::from_value(value.clone()).map_err(|e| anyhow!(e))?;
             self.a = ctx.a;
             self.b = ctx.b;
@@ -209,10 +209,10 @@ mod test {
 
     impl StateHandler for Setup {
         fn handler(&self, context: ContextWrapper) -> StateResult {
-            let value = context.lock().unwrap().read_input().unwrap();
+            let value = context.lock().unwrap().read().unwrap();
             let _data: ContextA = serde_json::from_value(value).unwrap();
             let data = json!({ "a": "setting up", "b": 1 });
-            match context.lock().as_mut().unwrap().write_output(&data) {
+            match context.lock().as_mut().unwrap().write(&data) {
                 Ok(()) => Ok(()),
                 Err(e) => Err(StateError::StorageAccess(
                     StateErrorRecoverability::Recoverable,
@@ -244,10 +244,10 @@ mod test {
 
     impl StateHandler for Report {
         fn handler(&self, context: ContextWrapper) -> StateResult {
-            let value = context.lock().unwrap().read_input().unwrap();
+            let value = context.lock().unwrap().read().unwrap();
             let _data: ContextA = serde_json::from_value(value).unwrap();
             let data = json!({ "a": "some new data reported", "b": 7 });
-            match context.lock().as_mut().unwrap().write_output(&data) {
+            match context.lock().as_mut().unwrap().write(&data) {
                 Ok(()) => Ok(()),
                 Err(e) => Err(StateError::StorageAccess(
                     StateErrorRecoverability::Recoverable,
@@ -297,7 +297,7 @@ mod test {
 
         let context = wrap_context(ContextA::new(String::from("hello"), 7));
         let result = state_machine.execute(context.clone());
-        let last_ctx_message = context.lock().unwrap().read_input().unwrap();
+        let last_ctx_message = context.lock().unwrap().read().unwrap();
 
         assert_eq!(state_machine.states.len(), iss.len());
 
diff --git a/mfm_machine/src/state_machine/tracker.rs b/mfm_machine/src/state_machine/tracker.rs
index d368d08..9d3d09a 100644
--- a/mfm_machine/src/state_machine/tracker.rs
+++ b/mfm_machine/src/state_machine/tracker.rs
@@ -1,19 +1,61 @@
-use std::collections::HashMap;
+use std::{collections::HashMap, fmt::Debug};
 
 use anyhow::{anyhow, Error};
 
 use crate::state::{context::ContextWrapper, Label, Tag};
 
-pub trait Tracker {
+pub trait TrackerMetadata {
+    fn indexes(&self) -> Vec<Index>;
+    fn search_by_tag(&self, tag: &Tag) -> Vec<Index>;
+    fn history(&self) -> TrackerHistory;
+}
+
+#[derive(Clone)]
+pub struct TrackerHistory(Vec<(usize, Index, ContextWrapper)>);
+
+impl Debug for TrackerHistory {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0
+            .iter()
+            .map(|(history_id, index, _)| {
+                writeln!(
+                    f,
+                    "history_id ({}); index ({:?}); context (ptr)",
+                    history_id, index
+                )
+            })
+            .collect()
+    }
+}
+
+impl TrackerHistory {
+    pub fn new() -> Self {
+        TrackerHistory(Vec::new())
+    }
+
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    pub fn push(&mut self, index: Index, context: ContextWrapper) {
+        self.0.push((self.len(), index, context))
+    }
+}
+
+impl IntoIterator for TrackerHistory {
+    type Item = (usize, Index, ContextWrapper);
+    type IntoIter = std::vec::IntoIter<Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+//TODO: should consider add an state_metadata where the state have
+// flexibility to say what kind of execution data he wants to store
+pub trait Tracker: TrackerMetadata {
     fn track(&mut self, index: Index, context: ContextWrapper) -> Result<bool, Error>;
     fn recover(&self, index: Index) -> Result<ContextWrapper, Error>;
-    // TODO: may be this Label should be tag?
-    // it may be an `search_by_tag`, and to do that we need
-    // to carry the tags of an state inside the index
-    // maybe and StateMetadata::from(state) can be an good idea,
-    // StateMetadata should be Hashable, Cloneable and Copiable
-    //
-    fn search_by_tag(&self, tag: &Tag) -> Vec<Index>;
 }
 
 // TODO: should it be public? may export methods to access it
@@ -34,11 +76,17 @@ impl Index {
     }
 }
 
-pub struct HashMapTracker(HashMap<Index, ContextWrapper>);
+pub struct HashMapTracker {
+    tracker: HashMap<Index, ContextWrapper>,
+    history: TrackerHistory,
+}
 
 impl HashMapTracker {
     pub fn new() -> Self {
-        HashMapTracker(HashMap::new())
+        Self {
+            tracker: HashMap::new(),
+            history: TrackerHistory::new(),
+        }
     }
 }
 
@@ -49,25 +97,37 @@ impl Default for HashMapTracker {
 }
 
 impl Tracker for HashMapTracker {
+    // TODO: add validations
     fn track(&mut self, index: Index, context: ContextWrapper) -> Result<bool, Error> {
-        Ok(self.0.insert(index, context).is_none())
+        self.history.push(index.clone(), context.clone());
+        Ok(self.tracker.insert(index, context).is_none())
     }
 
     fn recover(&self, index: Index) -> Result<ContextWrapper, Error> {
-        self.0
+        self.tracker
             .get(&index)
             .cloned()
             .clone()
             .ok_or(anyhow!("index not found"))
     }
+}
 
+impl TrackerMetadata for HashMapTracker {
     fn search_by_tag(&self, tag: &Tag) -> Vec<Index> {
-        self.0
+        self.tracker
             .keys()
             .filter(|index| index.state_tags.contains(tag))
             .cloned()
             .collect()
     }
+
+    fn indexes(&self) -> Vec<Index> {
+        self.tracker.keys().cloned().collect()
+    }
+
+    fn history(&self) -> TrackerHistory {
+        self.history.clone()
+    }
 }
 
 #[cfg(test)]
@@ -96,11 +156,11 @@ mod test {
     }
 
     impl Context for ContextA {
-        fn read_input(&self) -> Result<Value, Error> {
+        fn read(&self) -> Result<Value, Error> {
             serde_json::to_value(self).map_err(|e| anyhow!(e))
         }
 
-        fn write_output(&mut self, value: &Value) -> Result<(), Error> {
+        fn write(&mut self, value: &Value) -> Result<(), Error> {
             let ctx: ContextA = serde_json::from_value(value.clone()).map_err(|e| anyhow!(e))?;
             self.a = ctx.a;
             self.b = ctx.b;
@@ -143,8 +203,8 @@ mod test {
         for i in 0..indexes.len() {
             let context_recovered = tracker.recover(indexes[i].clone()).unwrap();
 
-            let value_recovered = context_recovered.lock().unwrap().read_input().unwrap();
-            let value_expected = contexts[i].lock().unwrap().read_input().unwrap();
+            let value_recovered = context_recovered.lock().unwrap().read().unwrap();
+            let value_expected = contexts[i].lock().unwrap().read().unwrap();
 
             assert_eq!(value_expected, value_recovered);
         }
@@ -191,4 +251,44 @@ mod test {
             Label::new("value_two").unwrap()
         );
     }
+
+    #[test]
+    fn test_list() {
+        let tracker: &mut dyn Tracker = &mut HashMapTracker::new();
+
+        let contexts: Vec<ContextWrapper> = vec![
+            wrap_context(ContextA::new("value".to_string(), 1)),
+            wrap_context(ContextA::new("value".to_string(), 2)),
+            wrap_context(ContextA::new("value".to_string(), 3)),
+        ];
+        let indexes = vec![
+            Index::new(
+                1,
+                Label::new("value_one").unwrap(),
+                vec![Tag::new("tag_one").unwrap()],
+            ),
+            Index::new(
+                2,
+                Label::new("value_two").unwrap(),
+                vec![Tag::new("tag_two").unwrap()],
+            ),
+            Index::new(
+                3,
+                Label::new("value_three").unwrap(),
+                vec![Tag::new("tag_three").unwrap()],
+            ),
+        ];
+
+        for i in 0..indexes.len() {
+            tracker
+                .track(indexes[i].clone(), contexts[i].clone())
+                .unwrap();
+        }
+
+        let indexes = tracker.indexes();
+
+        assert_eq!(indexes.len(), 3);
+
+        println!("indexes: {:?}", indexes);
+    }
 }
diff --git a/mfm_machine/tests/default_impls.rs b/mfm_machine/tests/default_impls.rs
index 3cad381..153ef5e 100644
--- a/mfm_machine/tests/default_impls.rs
+++ b/mfm_machine/tests/default_impls.rs
@@ -28,11 +28,11 @@ impl ContextA {
 }
 
 impl Context for ContextA {
-    fn read_input(&self) -> Result<Value, anyhow::Error> {
+    fn read(&self) -> Result<Value, anyhow::Error> {
         serde_json::to_value(self).map_err(|e| anyhow!(e))
     }
 
-    fn write_output(&mut self, value: &Value) -> Result<(), Error> {
+    fn write(&mut self, value: &Value) -> Result<(), Error> {
         let ctx: ContextA = serde_json::from_value(value.clone()).map_err(|e| anyhow!(e))?;
         self.a = ctx.a;
         self.b = ctx.b;
@@ -66,13 +66,13 @@ impl Setup {
 
 impl StateHandler for Setup {
     fn handler(&self, context: ContextWrapper) -> StateResult {
-        let value = context.lock().unwrap().read_input().unwrap();
+        let value = context.lock().unwrap().read().unwrap();
         let _data: ContextA = serde_json::from_value(value).unwrap();
 
         let mut rng = rand::thread_rng();
         let data = json!({ "a": "setting up", "b": rng.gen_range(0..9) });
 
-        match context.lock().as_mut().unwrap().write_output(&data) {
+        match context.lock().as_mut().unwrap().write(&data) {
             Ok(()) => Ok(()),
             Err(e) => Err(StateError::StorageAccess(
                 StateErrorRecoverability::Recoverable,
@@ -108,7 +108,7 @@ impl ComputePrice {
 
 impl StateHandler for ComputePrice {
     fn handler(&self, context: ContextWrapper) -> StateResult {
-        let value = context.lock().unwrap().read_input().unwrap();
+        let value = context.lock().unwrap().read().unwrap();
         let _data: ContextA = serde_json::from_value(value).unwrap();
         if _data.b % 2 == 0 {
             return Err(StateError::ParsingInput(
@@ -118,7 +118,7 @@ impl StateHandler for ComputePrice {
         }
 
         let data = json!({ "a": "the input number is odd", "b": _data.b });
-        match context.lock().as_mut().unwrap().write_output(&data) {
+        match context.lock().as_mut().unwrap().write(&data) {
             Ok(()) => Ok(()),
             Err(e) => Err(StateError::StorageAccess(
                 StateErrorRecoverability::Unrecoverable,
@@ -154,11 +154,11 @@ impl Report {
 
 impl StateHandler for Report {
     fn handler(&self, context: ContextWrapper) -> StateResult {
-        let value = context.lock().unwrap().read_input().unwrap();
+        let value = context.lock().unwrap().read().unwrap();
         let _data: ContextA = serde_json::from_value(value).unwrap();
         let data =
             json!({ "a": format!("{}: {}", "some new data reported", _data.a), "b": _data.b });
-        match context.lock().as_mut().unwrap().write_output(&data) {
+        match context.lock().as_mut().unwrap().write(&data) {
             Ok(()) => Ok(()),
             Err(e) => Err(StateError::StorageAccess(
                 StateErrorRecoverability::Recoverable,
diff --git a/mfm_machine/tests/public_api_test.rs b/mfm_machine/tests/public_api_test.rs
index 35cc070..963e884 100644
--- a/mfm_machine/tests/public_api_test.rs
+++ b/mfm_machine/tests/public_api_test.rs
@@ -34,7 +34,7 @@ fn test_state_machine_execute() {
 
     let context = wrap_context(ContextA::new(String::from("hello"), 7));
     let result = state_machine.execute(context.clone());
-    let last_ctx_message = context.lock().unwrap().read_input().unwrap();
+    let last_ctx_message = context.lock().unwrap().read().unwrap();
 
     assert_eq!(state_machine.states.len(), iss.len());