diff --git a/datatype/builtin/any.go b/datatype/builtin/any.go
index c7af7e9..e12dd10 100644
--- a/datatype/builtin/any.go
+++ b/datatype/builtin/any.go
@@ -6,7 +6,7 @@ import "git.xdrm.io/go/aicra/datatype"
 type AnyDataType struct{}
 
 // Build returns the validator
-func (AnyDataType) Build(typeName string) datatype.Validator {
+func (AnyDataType) Build(typeName string, registry ...datatype.T) datatype.Validator {
 	// nothing if type not handled
 	if typeName != "any" {
 		return nil
diff --git a/datatype/builtin/bool.go b/datatype/builtin/bool.go
index 2b0240b..1d5e225 100644
--- a/datatype/builtin/bool.go
+++ b/datatype/builtin/bool.go
@@ -6,7 +6,7 @@ import "git.xdrm.io/go/aicra/datatype"
 type BoolDataType struct{}
 
 // Build returns the validator
-func (BoolDataType) Build(typeName string) datatype.Validator {
+func (BoolDataType) Build(typeName string, registry ...datatype.T) datatype.Validator {
 	// nothing if type not handled
 	if typeName != "bool" {
 		return nil
diff --git a/datatype/builtin/float.go b/datatype/builtin/float.go
index 6f64e58..d2f3204 100644
--- a/datatype/builtin/float.go
+++ b/datatype/builtin/float.go
@@ -10,7 +10,7 @@ import (
 type FloatDataType struct{}
 
 // Build returns the validator
-func (FloatDataType) Build(typeName string) datatype.Validator {
+func (FloatDataType) Build(typeName string, registry ...datatype.T) datatype.Validator {
 	// nothing if type not handled
 	if typeName != "float64" && typeName != "float" {
 		return nil
diff --git a/datatype/builtin/int.go b/datatype/builtin/int.go
index 453c4f1..7dfdbf9 100644
--- a/datatype/builtin/int.go
+++ b/datatype/builtin/int.go
@@ -11,7 +11,7 @@ import (
 type IntDataType struct{}
 
 // Build returns the validator
-func (IntDataType) Build(typeName string) datatype.Validator {
+func (IntDataType) Build(typeName string, registry ...datatype.T) datatype.Validator {
 	// nothing if type not handled
 	if typeName != "int" {
 		return nil
diff --git a/datatype/builtin/string.go b/datatype/builtin/string.go
index afee83a..1a94b82 100644
--- a/datatype/builtin/string.go
+++ b/datatype/builtin/string.go
@@ -15,7 +15,7 @@ type StringDataType struct{}
 
 // Build returns the validator.
 // availables type names are : `string`, `string(length)` and `string(minLength, maxLength)`.
-func (s StringDataType) Build(typeName string) datatype.Validator {
+func (s StringDataType) Build(typeName string, registry ...datatype.T) datatype.Validator {
 	simple := typeName == "string"
 	fixedLengthMatches := fixedLengthRegex.FindStringSubmatch(typeName)
 	variableLengthMatches := variableLengthRegex.FindStringSubmatch(typeName)
diff --git a/datatype/builtin/uint.go b/datatype/builtin/uint.go
index 3f5bd76..53f71de 100644
--- a/datatype/builtin/uint.go
+++ b/datatype/builtin/uint.go
@@ -11,7 +11,7 @@ import (
 type UintDataType struct{}
 
 // Build returns the validator
-func (UintDataType) Build(typeName string) datatype.Validator {
+func (UintDataType) Build(typeName string, registry ...datatype.T) datatype.Validator {
 	// nothing if type not handled
 	if typeName != "uint" {
 		return nil
diff --git a/datatype/types.go b/datatype/types.go
index ad4be63..fe529f1 100644
--- a/datatype/types.go
+++ b/datatype/types.go
@@ -4,9 +4,9 @@ package datatype
 // and casts the value into a compatible type
 type Validator func(value interface{}) (cast interface{}, valid bool)
 
-// T builds a T from the type definition (from the
-// configuration field "type") and returns NIL if the type
-// definition does not match this T
+// T builds a T from the type definition (from the configuration field "type") and returns NIL if the type
+// definition does not match this T ; the registry is passed for recursive datatypes (e.g. slices, structs, etc)
+// to be able to access other datatypes
 type T interface {
-	Build(typeDefinition string) Validator
+	Build(typeDefinition string, registry ...T) Validator
 }
diff --git a/internal/config/parameter.go b/internal/config/parameter.go
index af08e49..9dc43fa 100644
--- a/internal/config/parameter.go
+++ b/internal/config/parameter.go
@@ -26,7 +26,7 @@ func (param *Parameter) checkAndFormat() error {
 // assigns the first matching data type from the type definition
 func (param *Parameter) assignDataType(types []datatype.T) bool {
 	for _, dtype := range types {
-		param.Validator = dtype.Build(param.Type)
+		param.Validator = dtype.Build(param.Type, types...)
 		if param.Validator != nil {
 			return true
 		}