diff --git a/include/cpphibernate.h b/include/cpphibernate.h
index e899e4d..08780d6 100644
--- a/include/cpphibernate.h
+++ b/include/cpphibernate.h
@@ -2,5 +2,6 @@
 
 #include <cpphibernate/config.h>
 #include <cpphibernate/misc.h>
+#include <cpphibernate/modifier.h>
 #include <cpphibernate/schema.h>
 #include <cpphibernate/types.h>
\ No newline at end of file
diff --git a/include/cpphibernate/config.h b/include/cpphibernate/config.h
index fa4a015..59ec49a 100644
--- a/include/cpphibernate/config.h
+++ b/include/cpphibernate/config.h
@@ -46,6 +46,9 @@
 #define beg_namespace_cpphibernate_misc         cpphibernate_define_namespace_beg(beg_namespace_cpphibernate, misc)
 #define end_namespace_cpphibernate_misc         cpphibernate_define_namespace_end(end_namespace_cpphibernate)
 
+#define beg_namespace_cpphibernate_modifier     cpphibernate_define_namespace_beg(beg_namespace_cpphibernate, modifier)
+#define end_namespace_cpphibernate_modifier     cpphibernate_define_namespace_end(end_namespace_cpphibernate)
+
 beg_namespace_cpphibernate
 {
 
diff --git a/include/cpphibernate/modifier.h b/include/cpphibernate/modifier.h
new file mode 100644
index 0000000..32b12a1
--- /dev/null
+++ b/include/cpphibernate/modifier.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include <cpphibernate/modifier/limit.h>
+#include <cpphibernate/modifier/modifier.h>
+#include <cpphibernate/modifier/offset.h>
+#include <cpphibernate/modifier/where.h>
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/limit.h b/include/cpphibernate/modifier/limit.h
new file mode 100644
index 0000000..0889090
--- /dev/null
+++ b/include/cpphibernate/modifier/limit.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include <cpphibernate/misc.h>
+#include <cpphibernate/config.h>
+#include <cpphibernate/modifier/modifier.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* limit_t */
+
+        template<typename T_value>
+        struct limit_t
+            : public modifier_t
+        {
+            using value_type = T_value;
+
+            value_type value;
+
+            constexpr limit_t(T_value&& p_value)
+                : value(std::forward<T_value>(p_value))
+                { }
+        };
+
+        /* limit_builder */
+
+        template<typename X, typename = void>
+        struct limit_builder
+        {
+            template<typename... T_args>
+            static constexpr decltype(auto) apply(T_args&... args)
+                { static_assert(sizeof...(args) == -1, "Invalid parameters for hibernate::modifier::limit(...)!"); }
+        };
+
+        template<typename T_value>
+        struct limit_builder<
+            mp::list<T_value>,
+            mp::enable_if<mp::is_integral<T_value>>>
+        {
+            static constexpr decltype(auto) apply(T_value&& value)
+            {
+                using value_type = mp::integral_constant<T_value, value>;
+                return limit_t<value_type>(value_type { });
+            }
+        };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_limit_modifier
+        : public mp::is_specialization_of<T, __impl::limit_t>
+        { };
+
+    /* make */
+
+    constexpr decltype(auto) limit = misc::make_generic_predicate<__impl::limit_builder> { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/modifier.h b/include/cpphibernate/modifier/modifier.h
new file mode 100644
index 0000000..766b202
--- /dev/null
+++ b/include/cpphibernate/modifier/modifier.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <cpphibernate/config.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* modifier_t */
+
+        struct modifier_t
+            { };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_modifier
+        : public mp::is_base_of<__impl::modifier_t, T>
+        { };
+
+    template<typename... T>
+    struct all_are_modifier
+        : public mp::all_true<is_modifier<T>::value...>
+        { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/offset.h b/include/cpphibernate/modifier/offset.h
new file mode 100644
index 0000000..e1e49d1
--- /dev/null
+++ b/include/cpphibernate/modifier/offset.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include <cpphibernate/misc.h>
+#include <cpphibernate/config.h>
+#include <cpphibernate/modifier/modifier.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* offset_t */
+
+        template<typename T_value>
+        struct offset_t
+            : public modifier_t
+        {
+            using value_type = T_value;
+
+            value_type value;
+
+            constexpr offset_t(T_value&& p_value)
+                : value(std::forward<T_value>(p_value))
+                { }
+        };
+
+        /* offset_builder */
+
+        template<typename X, typename = void>
+        struct offset_builder
+        {
+            template<typename... T_args>
+            static constexpr decltype(auto) apply(T_args&... args)
+                { static_assert(sizeof...(args) == -1, "Invalid parameters for hibernate::modifier::offset(...)!"); }
+        };
+
+        template<typename T_value>
+        struct offset_builder<
+            mp::list<T_value>,
+            mp::enable_if<mp::is_integral<T_value>>>
+        {
+            static constexpr decltype(auto) apply(T_value&& value)
+            {
+                using value_type = mp::integral_constant<T_value, value>;
+                return offset_t<value_type>(value_type { });
+            }
+        };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_offset_modifier
+        : public mp::is_specialization_of<T, __impl::offset_t>
+        { };
+
+    /* make */
+
+    constexpr decltype(auto) offset = misc::make_generic_predicate<__impl::offset_builder> { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where.h b/include/cpphibernate/modifier/where.h
new file mode 100644
index 0000000..e381b88
--- /dev/null
+++ b/include/cpphibernate/modifier/where.h
@@ -0,0 +1,4 @@
+#pragma once
+
+#include <cpphibernate/modifier/where/clauses.h>
+#include <cpphibernate/modifier/where/where.h>
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where/clauses.h b/include/cpphibernate/modifier/where/clauses.h
new file mode 100644
index 0000000..db63fbb
--- /dev/null
+++ b/include/cpphibernate/modifier/where/clauses.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include <cpphibernate/modifier/where/clauses/and.h>
+#include <cpphibernate/modifier/where/clauses/clause.h>
+#include <cpphibernate/modifier/where/clauses/equal.h>
+#include <cpphibernate/modifier/where/clauses/not.h>
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where/clauses/and.h b/include/cpphibernate/modifier/where/clauses/and.h
new file mode 100644
index 0000000..9daf021
--- /dev/null
+++ b/include/cpphibernate/modifier/where/clauses/and.h
@@ -0,0 +1,60 @@
+#pragma once
+
+#include <cpphibernate/config.h>
+#include <cpphibernate/modifier/where/clauses/clause.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* where_clause_and_t */
+
+        template<typename... T_clauses>
+        struct where_clause_and_t
+            : public where_clause_t
+        {
+            using clauses_type = hana::basic_tuple<T_clauses...>;
+
+            clauses_type clauses;
+
+            constexpr where_clause_and_t(T_clauses&&... p_clauses)
+                : clauses(std::forward<T_clauses>(p_clauses)...)
+                { }
+        };
+
+        /* where_clause_and_builder */
+
+        template<typename X, typename = void>
+        struct where_clause_and_builder
+        {
+            template<typename... T_args>
+            static constexpr decltype(auto) apply(T_args&&... args)
+                { static_assert(sizeof...(args) == -1, "Invalid parameters for hibernate::modifier::and(...)!"); }
+        };
+
+        template<typename... T_clauses>
+        struct where_clause_and_builder<
+            mp::list<T_clauses...>,
+            mp::enable_if<all_are_where_clauses<mp::decay_t<T_clauses>...>>>
+        {
+            static constexpr decltype(auto) apply(T_clauses&&... clauses)
+                { return where_clause_and_t<T_clauses...>(std::forward<T_clauses>(clauses)...); }
+        };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_where_clause_and
+        : public mp::is_specialization_of<T, __impl::where_clause_and_t>
+        { };
+
+    /* make */
+
+    constexpr decltype(auto) and_ = misc::make_generic_predicate<__impl::where_clause_and_builder> { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where/clauses/clause.h b/include/cpphibernate/modifier/where/clauses/clause.h
new file mode 100644
index 0000000..f1ed328
--- /dev/null
+++ b/include/cpphibernate/modifier/where/clauses/clause.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <cpphibernate/config.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* where_clause_t */
+
+        struct where_clause_t
+            { };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_where_clause
+        : public mp::is_base_of<__impl::where_clause_t, T>
+        { };
+
+    template<typename... T>
+    struct all_are_where_clauses
+        : public mp::all_true<is_where_clause<T>::value...>
+        { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where/clauses/equal.h b/include/cpphibernate/modifier/where/clauses/equal.h
new file mode 100644
index 0000000..b994fd8
--- /dev/null
+++ b/include/cpphibernate/modifier/where/clauses/equal.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include <cpphibernate/config.h>
+#include <cpphibernate/schema/field.h>
+#include <cpphibernate/modifier/where/clauses/clause.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* where_clause_equal_t */
+
+        template<typename T_field, typename T_value>
+        struct where_clause_equal_t
+            : public where_clause_t
+        {
+            using field_type = T_field;
+            using value_type = T_value;
+
+            field_type field;
+            value_type value;
+
+            constexpr where_clause_equal_t(T_field&& p_field, T_value&& p_value)
+                : field(std::forward<T_field>(p_field))
+                , value(std::forward<T_value>(p_value))
+                { }
+        };
+
+        /* where_clause_equal_builder */
+
+        template<typename X, typename = void>
+        struct where_clause_equal_builder
+        {
+            template<typename... T_args>
+            static constexpr decltype(auto) apply(T_args&&... args)
+                { static_assert(sizeof...(args) == -1, "Invalid parameters for hibernate::modifier::equal(...)!"); }
+        };
+
+        template<typename T_field, typename T_value>
+        struct where_clause_equal_builder<
+            mp::list<T_field, T_value>,
+            mp::enable_if<schema::is_field<mp::decay_t<T_field>>>>
+        {
+            static constexpr decltype(auto) apply(T_field&& field, T_value&& value)
+                { return where_clause_equal_t<T_field, T_value>(std::forward<T_field>(field), std::forward<T_value>(value)); }
+        };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_where_clause_equal
+        : public mp::is_specialization_of<T, __impl::where_clause_equal_t>
+        { };
+
+    /* make */
+
+    constexpr decltype(auto) equal = misc::make_generic_predicate<__impl::where_clause_equal_builder> { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where/clauses/not.h b/include/cpphibernate/modifier/where/clauses/not.h
new file mode 100644
index 0000000..e8cf36e
--- /dev/null
+++ b/include/cpphibernate/modifier/where/clauses/not.h
@@ -0,0 +1,60 @@
+#pragma once
+
+#include <cpphibernate/config.h>
+#include <cpphibernate/modifier/where/clauses/clause.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* where_clause_not_t */
+
+        template<typename T_clause>
+        struct where_clause_not_t
+            : public where_clause_t
+        {
+            using clause_type = T_clause;
+
+            clause_type clause;
+
+            constexpr where_clause_not_t(T_clause&& p_clause)
+                : clause(std::forward<T_clause>(p_clause))
+                { }
+        };
+
+        /* where_clause_not_builder */
+
+        template<typename X, typename = void>
+        struct where_clause_not_builder
+        {
+            template<typename... T_args>
+            static constexpr decltype(auto) apply(T_args&&... args)
+                { static_assert(sizeof...(args) == -1, "Invalid parameters for hibernate::modifier::not(...)!"); }
+        };
+
+        template<typename T_clause>
+        struct where_clause_not_builder<
+            mp::list<T_clause>,
+            mp::enable_if<is_where_clause<mp::decay_t<T_clause>>>>
+        {
+            static constexpr decltype(auto) apply(T_clause&& clause)
+                { return where_clause_not_t<T_clause>(std::forward<T_clause>(clause)); }
+        };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_where_clause_not
+        : public mp::is_specialization_of<T, __impl::where_clause_not_t>
+        { };
+
+    /* make */
+
+    constexpr decltype(auto) not_ = misc::make_generic_predicate<__impl::where_clause_not_builder> { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where/clauses/or.h b/include/cpphibernate/modifier/where/clauses/or.h
new file mode 100644
index 0000000..edac57d
--- /dev/null
+++ b/include/cpphibernate/modifier/where/clauses/or.h
@@ -0,0 +1,60 @@
+#pragma once
+
+#include <cpphibernate/config.h>
+#include <cpphibernate/modifier/where/clauses/clause.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* where_clause_or_t */
+
+        template<typename... T_clauses>
+        struct where_clause_or_t
+            : public where_clause_t
+        {
+            using clauses_type = hana::basic_tuple<T_clauses...>;
+
+            clauses_type clauses;
+
+            constexpr where_clause_or_t(T_clauses&&... p_clauses)
+                : clauses(std::forward<T_clauses>(p_clauses)...)
+                { }
+        };
+
+        /* where_clause_or_builder */
+
+        template<typename X, typename = void>
+        struct where_clause_or_builder
+        {
+            template<typename... T_args>
+            static constexpr decltype(auto) apply(T_args&&... args)
+                { static_assert(sizeof...(args) == -1, "Invalid parameters for hibernate::modifier::or(...)!"); }
+        };
+
+        template<typename... T_clauses>
+        struct where_clause_or_builder<
+            mp::list<T_clauses...>,
+            mp::enable_if<all_are_where_clauses<mp::decay_t<T_clauses>...>>>
+        {
+            static constexpr decltype(auto) apply(T_clauses&&... clauses)
+                { return where_clause_or_t<T_clauses...>(std::forward<T_clauses>(clauses)...); }
+        };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_where_clause_or
+        : public mp::is_specialization_of<T, __impl::where_clause_or_t>
+        { };
+
+    /* make */
+
+    constexpr decltype(auto) or_ = misc::make_generic_predicate<__impl::where_clause_or_builder> { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/modifier/where/where.h b/include/cpphibernate/modifier/where/where.h
new file mode 100644
index 0000000..16c33c6
--- /dev/null
+++ b/include/cpphibernate/modifier/where/where.h
@@ -0,0 +1,60 @@
+#pragma once
+
+#include <cpphibernate/misc.h>
+#include <cpphibernate/config.h>
+#include <cpphibernate/modifier/modifier.h>
+#include <cpphibernate/modifier/where/clauses/clause.h>
+
+beg_namespace_cpphibernate_modifier
+{
+
+    namespace __impl
+    {
+
+        /* where_t */
+
+        template<typename T_clause>
+        struct where_t
+            : public modifier_t
+        {
+            using clause_type = T_clause;
+
+            clause_type clause;
+
+            constexpr where_t(T_clause&& p_clause)
+                : clause(std::forward<T_clause>(p_clause))
+                { }
+        };
+
+        /* where_builder */
+
+        template<typename X, typename = void>
+        struct where_builder
+        {
+            template<typename... T_args>
+            static constexpr decltype(auto) apply(T_args&... args)
+                { static_assert(sizeof...(args) == -1, "Invalid parameters for hibernate::modifier::where(...)!"); }
+        };
+
+        template<typename T_clause>
+        struct where_builder<mp::list<T_clause>, mp::enable_if<is_where_clause<T_clause>>>
+        {
+            static constexpr decltype(auto) apply(T_clause&& clause)
+                { return where_t<T_clause>(std::forward<T_clause>(clause)); }
+        };
+
+    }
+
+    /* meta */
+
+    template<typename T>
+    struct is_where_modifier
+        : public mp::is_specialization_of<T, __impl::where_t>
+        { };
+
+    /* make */
+
+    constexpr decltype(auto) where = misc::make_generic_predicate<__impl::where_builder> { };
+
+}
+end_namespace_cpphibernate_modifier
\ No newline at end of file
diff --git a/include/cpphibernate/schema/field.h b/include/cpphibernate/schema/field.h
index 90deaef..976af98 100644
--- a/include/cpphibernate/schema/field.h
+++ b/include/cpphibernate/schema/field.h
@@ -4,6 +4,7 @@
 #include <cpphibernate/config.h>
 #include <cpphibernate/schema/getter.h>
 #include <cpphibernate/schema/setter.h>
+#include <cpphibernate/schema/attributes.h>
 
 #include <cpputils/misc/indent.h>
 #include <cpputils/misc/type_helper.h>
diff --git a/include/cpphibernate/schema/print.h b/include/cpphibernate/schema/print.h
index 42ba7e1..322ab42 100644
--- a/include/cpphibernate/schema/print.h
+++ b/include/cpphibernate/schema/print.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <iostream>
 #include <cpphibernate/config.h>
 
 namespace std