diff --git a/sources/Forms/Block/AbstractFormBlock.php b/sources/Forms/Block/AbstractFormBlock.php
new file mode 100644
index 000000000..44e777043
--- /dev/null
+++ b/sources/Forms/Block/AbstractFormBlock.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block;
+
+abstract class AbstractFormBlock
+{
+
+	private array $aOptions = [];
+
+	private array $aSubFormBlocks = [];
+
+	private array $aFormInputs = [];
+
+	private array $aFormOutputs = [];
+
+	public function __construct(array $aOptions = [])
+	{
+		$this->aOptions = $aOptions;
+	}
+
+	public function GetOptions(): array
+	{
+		return $this->aOptions;
+	}
+
+	public function AddSubFormBlock(AbstractFormBlock $oSubFormBlock): void
+	{
+		$this->aSubFormBlocks[] = $oSubFormBlock;
+	}
+
+	public function GetSubFormBlocks(): array
+	{
+		return $this->aSubFormBlocks;
+	}
+
+	public function AddInput(FormInput $oFormInput): void
+	{
+		$this->aFormInputs[$oFormInput->GetName()] = $oFormInput;
+	}
+
+	public function GetInput(string $sName): FormInput
+	{
+		return $this->aFormInputs[$sName];
+	}
+
+	public function AddOutput(FormOutput $oFormOutput): void
+	{
+		$this->aFormOutputs[$oFormOutput->GetName()] = $oFormOutput;
+	}
+
+	public function GetOutput(string $sName): FormOutput
+	{
+		return $this->aFormOutputs[$sName];
+	}
+
+
+}
\ No newline at end of file
diff --git a/sources/Forms/Block/Base/ChoiceFormBlock.php b/sources/Forms/Block/Base/ChoiceFormBlock.php
new file mode 100644
index 000000000..869fc0714
--- /dev/null
+++ b/sources/Forms/Block/Base/ChoiceFormBlock.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block\Base;
+
+use Combodo\iTop\Forms\Block\FormBlock;
+
+class ChoiceFormBlock extends FormBlock
+{
+
+	public function __construct(array $aOptions = [])
+	{
+		parent::__construct($aOptions);
+	}
+
+
+}
\ No newline at end of file
diff --git a/sources/Forms/Block/Base/StringFormBlock.php b/sources/Forms/Block/Base/StringFormBlock.php
new file mode 100644
index 000000000..a04817708
--- /dev/null
+++ b/sources/Forms/Block/Base/StringFormBlock.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block\Base;
+
+use Combodo\iTop\Forms\Block\FormBlock;
+
+class StringFormBlock extends FormBlock
+{
+
+
+}
\ No newline at end of file
diff --git a/sources/Forms/Block/DataModel/AttributeChoiceFormBlock.php b/sources/Forms/Block/DataModel/AttributeChoiceFormBlock.php
new file mode 100644
index 000000000..03bceee43
--- /dev/null
+++ b/sources/Forms/Block/DataModel/AttributeChoiceFormBlock.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block\DataModel;
+
+use Combodo\iTop\Forms\Block\FormBlock;
+use Combodo\iTop\Forms\Block\FormInput;
+
+class AttributeChoiceFormBlock extends FormBlock
+{
+
+
+	public function __construct(array $aOptions = [])
+	{
+		parent::__construct($aOptions);
+
+		$this->AddInput(new FormInput('class_name', 'string'));
+	}
+
+
+}
\ No newline at end of file
diff --git a/sources/Forms/Block/DataModel/OqlFormBlock.php b/sources/Forms/Block/DataModel/OqlFormBlock.php
new file mode 100644
index 000000000..41be01dc1
--- /dev/null
+++ b/sources/Forms/Block/DataModel/OqlFormBlock.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block\DataModel;
+
+use Combodo\iTop\Forms\Block\FormBlock;
+use Combodo\iTop\Forms\Block\FormOutput;
+
+class OqlFormBlock extends FormBlock
+{
+
+
+	public function __construct(array $aOptions = [])
+	{
+		parent::__construct($aOptions);
+
+		$this->AddOutput(new FormOutput('selected_class', 'string'));
+	}
+
+
+
+}
\ No newline at end of file
diff --git a/sources/Forms/Block/FormBlock.php b/sources/Forms/Block/FormBlock.php
new file mode 100644
index 000000000..f2bfd2f76
--- /dev/null
+++ b/sources/Forms/Block/FormBlock.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block;
+
+class FormBlock extends AbstractFormBlock
+{
+
+
+
+}
\ No newline at end of file
diff --git a/sources/Forms/Block/FormInput.php b/sources/Forms/Block/FormInput.php
new file mode 100644
index 000000000..6eeeaf535
--- /dev/null
+++ b/sources/Forms/Block/FormInput.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block;
+
+class FormInput
+{
+	private string $sName;
+
+	private string $sType;
+
+	public function __construct(string $sName, string $sType)
+	{
+		$this->sName = $sName;
+		$this->sType = $sName;
+	}
+
+	public function GetName(): string
+	{
+		return $this->sName;
+	}
+
+	public function SetName(string $sName): void
+	{
+		$this->sName = $sName;
+	}
+
+	public function GetType(): string
+	{
+		return $this->sType;
+	}
+
+	public function SetType(string $sType): void
+	{
+		$this->sType = $sType;
+	}
+}
\ No newline at end of file
diff --git a/sources/Forms/Block/FormOutput.php b/sources/Forms/Block/FormOutput.php
new file mode 100644
index 000000000..cb75ec696
--- /dev/null
+++ b/sources/Forms/Block/FormOutput.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace Combodo\iTop\Forms\Block;
+
+use Combodo\iTop\Forms\Converter\AbstractConverter;
+
+class FormOutput
+{
+	private string $sName;
+
+	private string $sType;
+
+	private AbstractConverter $oConverter;
+
+	public function __construct(string $sName, string $sType, AbstractConverter $oConverter = null)
+	{
+		$this->sName = $sName;
+		$this->sType = $sName;
+		$this->oConverter = $oConverter;
+	}
+
+	public function GetName(): string
+	{
+		return $this->sName;
+	}
+
+	public function SetName(string $sName): void
+	{
+		$this->sName = $sName;
+	}
+
+	public function GetType(): string
+	{
+		return $this->sType;
+	}
+
+	public function SetType(string $sType): void
+	{
+		$this->sType = $sType;
+	}
+
+	public function GetOutputValue(mixed $oData): mixed
+	{
+		$this->oConverter->Convert($oData);
+	}
+
+
+}
\ No newline at end of file
diff --git a/sources/Forms/Converter/AbstractConverter.php b/sources/Forms/Converter/AbstractConverter.php
new file mode 100644
index 000000000..1f28571c6
--- /dev/null
+++ b/sources/Forms/Converter/AbstractConverter.php
@@ -0,0 +1,8 @@
+<?php
+
+namespace Combodo\iTop\Forms\Converter;
+
+abstract class AbstractConverter
+{
+	abstract public function Convert(mixed $oData): mixed;
+}
\ No newline at end of file
diff --git a/sources/Forms/Converter/OqlToClassName.php b/sources/Forms/Converter/OqlToClassName.php
new file mode 100644
index 000000000..f94e26914
--- /dev/null
+++ b/sources/Forms/Converter/OqlToClassName.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace Combodo\iTop\Forms\Converter;
+
+class OqlToClassName extends AbstractConverter
+{
+
+	public function Convert(mixed $oData): ?string
+	{
+		if($oData === null)
+			return null;
+		// extract selected class
+		preg_match('/SELECT\s+(\w+)/', $oData, $aMatches);
+		return $aMatches[1] ?? null;
+	}
+}
\ No newline at end of file