diff --git a/demo/work.cpp b/demo/work.cpp
index 857758b..46f33dd 100644
--- a/demo/work.cpp
+++ b/demo/work.cpp
@@ -10,6 +10,12 @@
 #include "work/admin/UserDirectory.hpp"
 #include "work/admin/UserSession.hpp"
 
+#include "work/jobs/Job.hpp"
+#include "work/jobs/Task.hpp""
+#include "work/jobs/Payload.hpp"
+#include "work/jobs/IdPayload.hpp"
+#include "work/jobs/IdListPayload.hpp"
+
 #include "matador/object/schema.hpp"
 
 #include "matador/sql/connection.hpp"
@@ -20,7 +26,7 @@ using namespace matador;
 using namespace work::models;
 
 int main() {
-    object::schema schema;
+    object::schema schema("Administration");
 
     auto result = schema.attach<admin::CollectionCenter>("collection_center")
         .and_then([&schema] { return schema.attach<admin::InternalUserDirectory>("internal_user_directory"); })
@@ -32,7 +38,12 @@ int main() {
         .and_then([&schema] { return schema.attach<admin::Scenario>("scenario"); })
         .and_then([&schema] { return schema.attach<admin::User>("user"); })
         .and_then([&schema] { return schema.attach<admin::UserDirectory>("user_directory"); })
-        .and_then([&schema] { return schema.attach<admin::UserSession>("user_session"); });
+        .and_then([&schema] { return schema.attach<admin::UserSession>("user_session"); })
+        .and_then([&schema] { return schema.attach<jobs::Job>("jobs"); })
+        .and_then([&schema] { return schema.attach<jobs::Payload>("id_payloads"); })
+        .and_then([&schema] { return schema.attach<jobs::IdPayload>("id_list_payloads"); })
+        .and_then([&schema] { return schema.attach<jobs::IdListPayload>("payloads"); })
+        .and_then([&schema] { return schema.attach<jobs::Task>("tasks"); });
 
     if (!result.is_ok()) {
         return 0;
@@ -51,3 +62,8 @@ int main() {
 
     return 0;
 }
+
+// registering table 'collection_center' (pk field: 'id')
+// registering relation table 'collection_center_users' (first fk field: 'collection_center_id', second fk field: 'user_id')
+// registering table 'internal_user_directory' (pk field: 'id')
+//
\ No newline at end of file
diff --git a/demo/work/admin/CollectionCenter.hpp b/demo/work/admin/CollectionCenter.hpp
index f2d6522..84d5f2a 100644
--- a/demo/work/admin/CollectionCenter.hpp
+++ b/demo/work/admin/CollectionCenter.hpp
@@ -38,7 +38,7 @@ struct CollectionCenter : core::Model {
         field::attribute( op, "name", name, 511 );
         field::attribute( op, "symbol", symbol );
         field::attribute( op, "type", type );
-        field::has_many( op, "users", users, "collection_center_id", matador::utils::fetch_type::LAZY );
+        field::has_many( op, "collection_center_users", users, "collection_center_id", matador::utils::fetch_type::LAZY );
     }
 };
 
diff --git a/demo/work/core/UserInfo.hpp b/demo/work/core/UserInfo.hpp
new file mode 100644
index 0000000..bf49bdb
--- /dev/null
+++ b/demo/work/core/UserInfo.hpp
@@ -0,0 +1,22 @@
+#ifndef USERINFO_HPP
+#define USERINFO_HPP
+
+#include "matador/utils/access.hpp"
+
+namespace work::core {
+struct UserInfo {
+    unsigned long long user_session_id;
+    std::string user_role;
+    std::string database_name;
+
+    template<typename Operator>
+    void process( Operator& op ) {
+        namespace field = matador::access;
+        field::attribute( op, "user_session_id", user_session_id );
+        field::attribute( op, "user_role", user_role, 255 );
+        field::attribute( op, "database_name", database_name, 255 );
+    }
+};
+}
+
+#endif //USERINFO_HPP
diff --git a/demo/work/jobs/IdListPayload.hpp b/demo/work/jobs/IdListPayload.hpp
new file mode 100644
index 0000000..ff75438
--- /dev/null
+++ b/demo/work/jobs/IdListPayload.hpp
@@ -0,0 +1,20 @@
+#ifndef ID_LIST_PAYLOAD_HPP
+#define ID_LIST_PAYLOAD_HPP
+
+#include "Payload.hpp"
+
+#include "matador/object/collection.hpp"
+
+namespace work::models::jobs {
+struct IdListPayload : Payload {
+    matador::object::collection<unsigned long long> ids;
+    template<typename Operator>
+    void process( Operator& op ) {
+        namespace field = matador::access;
+        field::process( op, *matador::base_class<Payload>( this ) );
+        field::has_many( op, "payload_ids", ids );
+    }
+};
+}
+
+#endif //ID_LIST_PAYLOAD_HPP
diff --git a/demo/work/jobs/IdPayload.hpp b/demo/work/jobs/IdPayload.hpp
new file mode 100644
index 0000000..2470840
--- /dev/null
+++ b/demo/work/jobs/IdPayload.hpp
@@ -0,0 +1,18 @@
+#ifndef ID_PAYLOAD_HPP
+#define ID_PAYLOAD_HPP
+
+#include "Payload.hpp"
+
+namespace work::models::jobs {
+struct IdPayload : Payload {
+    unsigned long long id;
+    template<typename Operator>
+    void process( Operator& op ) {
+        namespace field = matador::access;
+        field::process( op, *matador::base_class<Payload>( this ) );
+        field::attribute( op, "id", id );
+    }
+};
+}
+
+#endif //ID_PAYLOAD_HPP
diff --git a/demo/work/jobs/Job.hpp b/demo/work/jobs/Job.hpp
new file mode 100644
index 0000000..1e350ab
--- /dev/null
+++ b/demo/work/jobs/Job.hpp
@@ -0,0 +1,46 @@
+#ifndef JOB_HPP
+#define JOB_HPP
+
+#include "JobMode.hpp"
+#include "JobState.hpp"
+#include "Payload.hpp"
+#include "Task.hpp"
+
+#include "../core/Model.hpp"
+#include "../core/Types.hpp"
+#include "../core/UserInfo.hpp"
+
+#include "matador/object/object_ptr.hpp"
+
+#include "matador/utils/base_class.hpp"
+
+namespace work::models::jobs {
+
+struct Job : core::Model {
+    std::string name;
+    std::string description;
+    JobState state;
+    JobMode mode;
+    core::timestamp created_at;
+    matador::object::object_ptr<Payload> payload;
+    matador::object::object_ptr<Task> task;
+    core::UserInfo user_info;
+
+    template<typename Operator>
+    void process( Operator& op ) {
+        namespace field = matador::access;
+        field::process( op, *matador::base_class<Model>( this ) );
+        field::attribute( op, "name", name, 511 );
+        field::attribute( op, "description", description, 511 );
+        field::attribute( op, "state", state );
+        field::attribute( op, "mode", mode );
+        field::attribute( op, "created_at", created_at );
+        field::belongs_to( op, "payload", payload, matador::utils::default_foreign_attributes );
+        field::belongs_to( op, "task", task, matador::utils::default_foreign_attributes );
+        field::attribute( op, "user_info", user_info );
+    }
+};
+
+}
+
+#endif //JOB_HPP
diff --git a/demo/work/jobs/JobMode.hpp b/demo/work/jobs/JobMode.hpp
new file mode 100644
index 0000000..11a9e02
--- /dev/null
+++ b/demo/work/jobs/JobMode.hpp
@@ -0,0 +1,20 @@
+#ifndef JOB_MODE_HPP
+#define JOB_MODE_HPP
+
+#include "matador/utils/enum_mapper.hpp"
+
+#include <cstdint>
+
+namespace work::models::jobs {
+enum class JobMode : uint8_t {
+    Background,
+    Foreground
+};
+
+static const matador::utils::enum_mapper<JobMode> JobModeEnum({
+    {JobMode::Background,  "Background"},
+    {JobMode::Foreground,  "Foreground"}
+});
+}
+
+#endif //JOB_MODE_HPP
diff --git a/demo/work/jobs/JobState.hpp b/demo/work/jobs/JobState.hpp
new file mode 100644
index 0000000..98b0597
--- /dev/null
+++ b/demo/work/jobs/JobState.hpp
@@ -0,0 +1,28 @@
+#ifndef JOB_STATE_HPP
+#define JOB_STATE_HPP
+
+#include "matador/utils/enum_mapper.hpp"
+
+#include <cstdint>
+
+namespace work::models::jobs {
+enum class JobState : uint8_t {
+    Pending,
+    Running,
+    Succeeded,
+    Failed,
+    Cancelled
+};
+
+static const matador::utils::enum_mapper<JobState> JobStateEnum({
+    {JobState::Pending,  "Pending"},
+    {JobState::Running,  "Running"},
+    {JobState::Succeeded, "Succeeded"},
+    {JobState::Failed, "Failed"},
+    {JobState::Cancelled, "Cancelled"}
+});
+
+}
+
+
+#endif //JOB_STATE_HPP
diff --git a/demo/work/jobs/Payload.hpp b/demo/work/jobs/Payload.hpp
new file mode 100644
index 0000000..4c32b0d
--- /dev/null
+++ b/demo/work/jobs/Payload.hpp
@@ -0,0 +1,20 @@
+#ifndef PAYLOAD_HPP
+#define PAYLOAD_HPP
+
+#include "../core/Model.hpp"
+
+#include "matador/utils/base_class.hpp"
+
+namespace work::models::jobs {
+struct Payload : core::Model {
+    std::string type;
+    template<typename Operator>
+    void process( Operator& op ) {
+        namespace field = matador::access;
+        field::process( op, *matador::base_class<Model>( this ) );
+        field::attribute( op, "type", type, 255 );
+    }
+};
+}
+
+#endif //PAYLOAD_HPP
diff --git a/demo/work/jobs/Task.hpp b/demo/work/jobs/Task.hpp
new file mode 100644
index 0000000..dc3c75c
--- /dev/null
+++ b/demo/work/jobs/Task.hpp
@@ -0,0 +1,42 @@
+#ifndef TASK_HPP
+#define TASK_HPP
+
+#include "TaskState.hpp"
+
+#include "../core/Model.hpp"
+#include "../core/Types.hpp"
+
+#include "matador/object/object_ptr.hpp"
+
+#include "matador/utils/base_class.hpp"
+
+namespace work::models::jobs {
+struct Task : core::Model {
+    std::string name;
+    std::string description;
+    std::string job_name;
+    TaskState state;
+    matador::object::object_ptr<Payload> payload;
+    JobMode job_mode;
+    core::timestamp start_delay;
+    core::timestamp interval;
+    unsigned long long user_session_id;
+
+    template<typename Operator>
+    void process( Operator& op ) {
+        namespace field = matador::access;
+        field::process( op, *matador::base_class<Model>( this ) );
+        field::attribute( op, "name", name, 511 );
+        field::attribute( op, "description", description, 511 );
+        field::attribute( op, "job_name", job_name, 511 );
+        field::attribute( op, "state", state );
+        field::belongs_to( op, "payload", payload, matador::utils::default_foreign_attributes );
+        field::attribute( op, "job_mode", job_mode );
+        field::attribute( op, "start_delay", start_delay );
+        field::attribute( op, "interval", interval );
+        field::attribute( op, "user_session_id", user_session_id );
+    }
+};
+}
+
+#endif //TASK_HPP
diff --git a/demo/work/jobs/TaskState.hpp b/demo/work/jobs/TaskState.hpp
new file mode 100644
index 0000000..b221b2b
--- /dev/null
+++ b/demo/work/jobs/TaskState.hpp
@@ -0,0 +1,22 @@
+#ifndef TASK_STATE_HPP
+#define TASK_STATE_HPP
+
+#include "matador/utils/enum_mapper.hpp"
+
+#include <cstdint>
+
+namespace work::models::jobs {
+enum class TaskState : uint8_t {
+    Active,
+    Inactive
+};
+
+static const matador::utils::enum_mapper<TaskState> TaskStateEnum({
+    {TaskState::Active,  "Active"},
+    {TaskState::Inactive, "Inactive"}
+});
+
+}
+
+
+#endif //TASK_STATE_HPP
diff --git a/include/matador/object/schema.hpp b/include/matador/object/schema.hpp
index f324b22..c2827c4 100644
--- a/include/matador/object/schema.hpp
+++ b/include/matador/object/schema.hpp
@@ -1,7 +1,7 @@
 #ifndef SCHEMA_HPP
 #define SCHEMA_HPP
 
-#include "primary_key_resolver.hpp"
+#include "matador/object/primary_key_resolver.hpp"
 #include "matador/object/error_code.hpp"
 #include "matador/object/schema_node.hpp"
 #include "matador/object/schema_node_iterator.hpp"
diff --git a/include/matador/utils/thread_pool.hpp b/include/matador/utils/thread_pool.hpp
new file mode 100644
index 0000000..e69de29
diff --git a/source/core/utils/thread_pool.cpp b/source/core/utils/thread_pool.cpp
new file mode 100644
index 0000000..e69de29
diff --git a/test/core/utils/ThreadPoolTest.cpp b/test/core/utils/ThreadPoolTest.cpp
new file mode 100644
index 0000000..e69de29