diff --git a/core/attributedef/AttributeTagSet.php b/core/attributedef/AttributeTagSet.php
new file mode 100644
index 000000000..c58a5ad23
--- /dev/null
+++ b/core/attributedef/AttributeTagSet.php
@@ -0,0 +1,641 @@
+<?php
+
+/**
+ * Multi value list of tags
+ *
+ * @see TagSetFieldData
+ * @since 2.6.0 N°931 tag fields
+ */
+class AttributeTagSet extends AttributeSet
+{
+    const SEARCH_WIDGET_TYPE = self::SEARCH_WIDGET_TYPE_TAG_SET;
+
+    public function __construct($sCode, array $aParams)
+    {
+        parent::__construct($sCode, $aParams);
+        $this->aCSSClasses[] = 'attribute-tag-set';
+    }
+
+    public function GetEditClass()
+    {
+        return 'TagSet';
+    }
+
+    public static function ListExpectedParams()
+    {
+        return array_merge(parent::ListExpectedParams(), array('tag_code_max_len'));
+    }
+
+    /**
+     * @param \ormTagSet $oValue
+     *
+     * @param $aArgs
+     *
+     * @return string JSON to be used in the itop.tagset_widget JQuery widget
+     * @throws \CoreException
+     * @throws \OQLException
+     */
+    public function GetJsonForWidget($oValue, $aArgs = array())
+    {
+        $aJson = array();
+
+        // possible_values
+        $aTagSetObjectData = $this->GetAllowedValues($aArgs);
+        $aTagSetKeyValData = array();
+        foreach ($aTagSetObjectData as $sTagCode => $sTagLabel) {
+            $aTagSetKeyValData[] = [
+                'code' => $sTagCode,
+                'label' => $sTagLabel,
+            ];
+        }
+        $aJson['possible_values'] = $aTagSetKeyValData;
+
+        if (is_null($oValue)) {
+            $aJson['partial_values'] = array();
+            $aJson['orig_value'] = array();
+            $aJson['added'] = array();
+            $aJson['removed'] = array();
+        } else {
+            $aJson['orig_value'] = array_merge($oValue->GetValues(), $oValue->GetModified());
+            $aJson['added'] = $oValue->GetAdded();
+            $aJson['removed'] = $oValue->GetRemoved();
+
+            if ($oValue->DisplayPartial()) {
+                // For bulk updates
+                $aJson['partial_values'] = $oValue->GetModified();
+            } else {
+                // For simple updates
+                $aJson['partial_values'] = array();
+            }
+        }
+
+
+        $iMaxTags = $this->GetMaxItems();
+        $aJson['max_items_allowed'] = $iMaxTags;
+
+        return json_encode($aJson);
+    }
+
+    public function FromStringToArray($proposedValue, $sDefaultSepItem = ',')
+    {
+        $aValues = array();
+        if (!empty($proposedValue)) {
+            foreach (explode(' ', $proposedValue) as $sCode) {
+                $sValue = trim($sCode);
+                $aValues[] = $sValue;
+            }
+        }
+        return $aValues;
+    }
+
+    /**
+     * Extract all existing tags from a string and ignore bad tags
+     *
+     * @param $sValue
+     * @param bool $bNoLimit : don't apply the maximum tag limit
+     *
+     * @return \ormTagSet
+     * @throws \CoreException
+     * @throws \CoreUnexpectedValue
+     */
+    public function GetExistingTagsFromString($sValue, $bNoLimit = false)
+    {
+        $aTagCodes = $this->FromStringToArray("$sValue");
+        $sAttCode = $this->GetCode();
+        $sClass = MetaModel::GetAttributeOrigin($this->GetHostClass(), $sAttCode);
+        if ($bNoLimit) {
+            $oTagSet = new ormTagSet($sClass, $sAttCode, 0);
+        } else {
+            $oTagSet = new ormTagSet($sClass, $sAttCode, $this->GetMaxItems());
+        }
+        $aGoodTags = array();
+        foreach ($aTagCodes as $sTagCode) {
+            if ($sTagCode === '') {
+                continue;
+            }
+            if ($oTagSet->IsValidTag($sTagCode)) {
+                $aGoodTags[] = $sTagCode;
+                if (!$bNoLimit && (count($aGoodTags) === $this->GetMaxItems())) {
+                    // extra and bad tags are ignored
+                    break;
+                }
+            }
+        }
+        $oTagSet->SetValues($aGoodTags);
+
+        return $oTagSet;
+    }
+
+    public function GetTagCodeMaxLength()
+    {
+        return $this->Get('tag_code_max_len');
+    }
+
+    public function GetEditValue($value, $oHostObj = null)
+    {
+        if (empty($value)) {
+            return '';
+        }
+        if ($value instanceof ormTagSet) {
+            $aValues = $value->GetValues();
+
+            return implode(' ', $aValues);
+        }
+
+        return '';
+    }
+
+    public function GetMaxSize()
+    {
+        return max(255, ($this->GetMaxItems() * $this->GetTagCodeMaxLength()) + 1);
+    }
+
+    public function Equals($val1, $val2)
+    {
+        if (($val1 instanceof ormTagSet) && ($val2 instanceof ormTagSet)) {
+            return $val1->Equals($val2);
+        }
+
+        return ($val1 == $val2);
+    }
+
+    public function GetAllowedValues($aArgs = array(), $sContains = '')
+    {
+        $sAttCode = $this->GetCode();
+        $sClass = MetaModel::GetAttributeOrigin($this->GetHostClass(), $sAttCode);
+        $aAllowedTags = TagSetFieldData::GetAllowedValues($sClass, $sAttCode);
+        $aAllowedValues = array();
+        foreach ($aAllowedTags as $oAllowedTag) {
+            $aAllowedValues[$oAllowedTag->Get('code')] = $oAllowedTag->Get('label');
+        }
+
+        return $aAllowedValues;
+    }
+
+    /**
+     * @param array $aCols
+     * @param string $sPrefix
+     *
+     * @return mixed
+     * @throws \CoreException
+     * @throws \Exception
+     */
+    public function FromSQLToValue($aCols, $sPrefix = '')
+    {
+        $sValue = $aCols["$sPrefix"];
+
+        return $this->GetExistingTagsFromString($sValue);
+    }
+
+    /**
+     * force an allowed value (type conversion and possibly forces a value as mySQL would do upon writing!
+     *
+     * @param $proposedValue
+     * @param $oHostObj
+     *
+     * @param bool $bIgnoreErrors
+     *
+     * @return mixed
+     * @throws \CoreException
+     * @throws \CoreUnexpectedValue
+     */
+    public function MakeRealValue($proposedValue, $oHostObj, $bIgnoreErrors = false)
+    {
+        $oTagSet = new ormTagSet(MetaModel::GetAttributeOrigin($this->GetHostClass(), $this->GetCode()), $this->GetCode(), $this->GetMaxItems());
+        if (is_string($proposedValue) && !empty($proposedValue)) {
+            $sJsonFromWidget = json_decode($proposedValue, true);
+            if (is_null($sJsonFromWidget)) {
+                $proposedValue = trim("$proposedValue");
+                $aTagCodes = $this->FromStringToArray($proposedValue);
+                $oTagSet->SetValues($aTagCodes);
+            }
+        } elseif ($proposedValue instanceof ormTagSet) {
+            $oTagSet = $proposedValue;
+        }
+
+        return $oTagSet;
+    }
+
+    /**
+     * Get the value from a given string (plain text, CSV import)
+     *
+     * @param string $sProposedValue
+     * @param bool $bLocalizedValue
+     * @param string $sSepItem
+     * @param string $sSepAttribute
+     * @param string $sSepValue
+     * @param string $sAttributeQualifier
+     *
+     * @return mixed null if no match could be found
+     * @throws \Exception
+     */
+    public function MakeValueFromString($sProposedValue, $bLocalizedValue = false, $sSepItem = null, $sSepAttribute = null, $sSepValue = null, $sAttributeQualifier = null)
+    {
+        if (is_null($sSepItem) || empty($sSepItem)) {
+            $sSepItem = MetaModel::GetConfig()->Get('tag_set_item_separator');
+        }
+        if (!empty($sProposedValue)) {
+            $oTagSet = new ormTagSet(MetaModel::GetAttributeOrigin($this->GetHostClass(), $this->GetCode()),
+                $this->GetCode(), $this->GetMaxItems());
+            $aLabels = explode($sSepItem, $sProposedValue);
+            $aCodes = array();
+            foreach ($aLabels as $sTagLabel) {
+                if (!empty($sTagLabel)) {
+                    $aCodes[] = ($bLocalizedValue) ? $oTagSet->GetTagFromLabel($sTagLabel) : $sTagLabel;
+                }
+            }
+            $sProposedValue = implode(' ', $aCodes);
+        }
+
+        return $this->MakeRealValue($sProposedValue, null);
+    }
+
+    public function GetNullValue()
+    {
+        return new ormTagSet(MetaModel::GetAttributeOrigin($this->GetHostClass(), $this->GetCode()), $this->GetCode(), $this->GetMaxItems());
+    }
+
+    public function GetDefaultValue(DBObject $oHostObject = null)
+    {
+        $oTagSet = new ormTagSet(MetaModel::GetAttributeOrigin($this->GetHostClass(), $this->GetCode()), $this->GetCode(), $this->GetMaxItems());
+        $oTagSet->SetValues([]);
+        return $oTagSet;
+    }
+
+    public function IsNull($proposedValue)
+    {
+        if (is_null($proposedValue)) {
+            return true;
+        }
+
+        /** @var \ormTagSet $proposedValue */
+        return count($proposedValue->GetValues()) == 0;
+    }
+
+    /**
+     * To be overloaded for localized enums
+     *
+     * @param $sValue
+     *
+     * @return string label corresponding to the given value (in plain text)
+     * @throws \CoreWarning
+     * @throws \Exception
+     */
+    public function GetValueLabel($sValue)
+    {
+        if (empty($sValue)) {
+            return '';
+        }
+        if (is_string($sValue)) {
+            $sValue = $this->GetExistingTagsFromString($sValue);
+        }
+        if ($sValue instanceof ormTagSet) {
+            $aValues = $sValue->GetLabels();
+
+            return implode(', ', $aValues);
+        }
+        throw new CoreWarning('Expected the attribute value to be a TagSet', array(
+            'found_type' => gettype($sValue),
+            'value' => $sValue,
+            'class' => $this->GetHostClass(),
+            'attribute' => $this->GetCode()
+        ));
+    }
+
+    /**
+     * @param $value
+     *
+     * @return string
+     * @throws \CoreWarning
+     */
+    public function ScalarToSQL($value)
+    {
+        if (empty($value)) {
+            return '';
+        }
+        if ($value instanceof ormTagSet) {
+            $aValues = $value->GetValues();
+
+            return implode(' ', $aValues);
+        }
+        throw new CoreWarning('Expected the attribute value to be a TagSet', array(
+            'found_type' => gettype($value),
+            'value' => $value,
+            'class' => $this->GetHostClass(),
+            'attribute' => $this->GetCode()
+        ));
+    }
+
+    /**
+     * @param $value
+     * @param \DBObject $oHostObject
+     * @param bool $bLocalize
+     *
+     * @return string|null
+     *
+     * @throws \CoreException
+     * @throws \Exception
+     */
+    public function GetAsHTML($value, $oHostObject = null, $bLocalize = true)
+    {
+        if ($value instanceof ormTagSet) {
+            if ($bLocalize) {
+                $aValues = $value->GetTags();
+            } else {
+                $aValues = $value->GetValues();
+            }
+            if (empty($aValues)) {
+                return '';
+            }
+
+            return $this->GenerateViewHtmlForValues($aValues);
+        }
+        if (is_string($value)) {
+            try {
+                $oValue = $this->MakeRealValue($value, $oHostObject);
+
+                return $this->GetAsHTML($oValue, $oHostObject, $bLocalize);
+            } catch (Exception $e) {
+                // unknown tags are present display the code instead
+            }
+            $aTagCodes = $this->FromStringToArray($value);
+            $aValues = array();
+            $oTagSet = new ormTagSet(MetaModel::GetAttributeOrigin($this->GetHostClass(), $this->GetCode()),
+                $this->GetCode(), $this->GetMaxItems());
+            foreach ($aTagCodes as $sTagCode) {
+                try {
+                    $oTagSet->Add($sTagCode);
+                } catch (Exception $e) {
+                    $aValues[] = $sTagCode;
+                }
+            }
+            $sHTML = '';
+            if (!empty($aValues)) {
+                $sHTML .= $this->GenerateViewHtmlForValues($aValues, 'attribute-set-item-undefined');
+            }
+            $aValues = $oTagSet->GetTags();
+            if (!empty($aValues)) {
+                $sHTML .= $this->GenerateViewHtmlForValues($aValues);
+            }
+
+            return $sHTML;
+        }
+
+        return parent::GetAsHTML($value, $oHostObject, $bLocalize);
+    }
+
+    // Do not display friendly names in the history of change
+    public function DescribeChangeAsHTML($sOldValue, $sNewValue, $sLabel = null)
+    {
+        $sResult = Dict::Format('Change:AttName_Changed', $this->GetLabel()) . ", ";
+
+        $aNewValues = $this->FromStringToArray($sNewValue);
+        $aOldValues = $this->FromStringToArray($sOldValue);
+
+        $aDelta['removed'] = array_diff($aOldValues, $aNewValues);
+        $aDelta['added'] = array_diff($aNewValues, $aOldValues);
+
+        $aAllowedTags = TagSetFieldData::GetAllowedValues(MetaModel::GetAttributeOrigin($this->GetHostClass(), $this->GetCode()), $this->GetCode());
+
+        if (!empty($aDelta['removed'])) {
+            $aRemoved = array();
+            foreach ($aDelta['removed'] as $idx => $sTagCode) {
+                if (empty($sTagCode)) {
+                    continue;
+                }
+                $sTagLabel = $sTagCode;
+                foreach ($aAllowedTags as $oTag) {
+                    if ($sTagCode === $oTag->Get('code')) {
+                        $sTagLabel = $oTag->Get('label');
+                    }
+                }
+                $aRemoved[] = $sTagLabel;
+            }
+
+            $sRemoved = $this->GenerateViewHtmlForValues($aRemoved, 'history-removed');
+            if (!empty($sRemoved)) {
+                $sResult .= Dict::Format('Change:LinkSet:Removed', $sRemoved);
+            }
+        }
+
+        if (!empty($aDelta['added'])) {
+            if (!empty($sRemoved)) {
+                $sResult .= ', ';
+            }
+
+            $aAdded = array();
+            foreach ($aDelta['added'] as $idx => $sTagCode) {
+                if (empty($sTagCode)) {
+                    continue;
+                }
+                $sTagLabel = $sTagCode;
+                foreach ($aAllowedTags as $oTag) {
+                    if ($sTagCode === $oTag->Get('code')) {
+                        $sTagLabel = $oTag->Get('label');
+                    }
+                }
+                $aAdded[] = $sTagLabel;
+            }
+
+            $sAdded = $this->GenerateViewHtmlForValues($aAdded, 'history-added');
+            if (!empty($sAdded)) {
+                $sResult .= Dict::Format('Change:LinkSet:Added', $sAdded);
+            }
+        }
+
+        return $sResult;
+    }
+
+    /**
+     * HTML representation of a list of tags (read-only)
+     * accept a list of strings or a list of TagSetFieldData
+     *
+     * @param array $aValues
+     * @param string $sCssClass
+     * @param bool $bWithLink if true will generate a link, otherwise just a "a" tag without href
+     *
+     * @return string
+     * @throws \CoreException
+     * @throws \OQLException
+     */
+    public function GenerateViewHtmlForValues($aValues, $sCssClass = '', $bWithLink = true)
+    {
+        if (empty($aValues)) {
+            return '';
+        }
+        $sHtml = '<span class="' . $sCssClass . ' ' . implode(' ', $this->aCSSClasses) . '">';
+        foreach ($aValues as $oTag) {
+            if ($oTag instanceof TagSetFieldData) {
+                $sClass = MetaModel::GetAttributeOrigin($this->GetHostClass(), $this->GetCode());
+                $sAttCode = $this->GetCode();
+                $sTagCode = $oTag->Get('code');
+                $sTagLabel = $oTag->Get('label');
+                $sTagDescription = $oTag->Get('description');
+                $oFilter = DBSearch::FromOQL("SELECT $sClass WHERE $sAttCode MATCHES '$sTagCode'");
+                $oAppContext = new ApplicationContext();
+                $sContext = $oAppContext->GetForLink(true);
+                $sUIPage = cmdbAbstractObject::ComputeStandardUIPage($oFilter->GetClass());
+                $sFilter = rawurlencode($oFilter->serialize());
+
+                $sLink = '';
+                if ($bWithLink && $this->bDisplayLink) {
+                    $sUrl = utils::GetAbsoluteUrlAppRoot() . "pages/$sUIPage?operation=search&filter=" . $sFilter . $sContext;
+                    $sLink = ' href="' . $sUrl . '"';
+                }
+
+                $sLabelForHtml = utils::EscapeHtml($sTagLabel);
+                $sDescriptionForHtml = utils::EscapeHtml($sTagDescription);
+                if (empty($sTagDescription)) {
+                    $sTooltipContent = $sTagLabel;
+                    $sTooltipHtmlEnabled = 'false';
+                } else {
+                    $sTagLabelEscaped = utils::EscapeHtml($sTagLabel);
+                    $sTooltipContent = <<<HTML
+<h4>$sTagLabelEscaped</h4>
+<div>$sTagDescription</div>
+HTML;
+                    $sTooltipHtmlEnabled = 'true';
+                }
+                $sTooltipContent = utils::HtmlEntities($sTooltipContent);
+
+                $sHtml .= '<a' . $sLink . ' class="attribute-set-item attribute-set-item-' . $sTagCode . '" data-code="' . $sTagCode . '" data-label="' . $sLabelForHtml . '" data-description="' . $sDescriptionForHtml . '" data-tooltip-content="' . $sTooltipContent . '" data-tooltip-html-enabled="' . $sTooltipHtmlEnabled . '">' . $sLabelForHtml . '</a>';
+            } else {
+                $sHtml .= '<span class="attribute-set-item">' . utils::EscapeHtml($oTag) . '</span>';
+            }
+        }
+        $sHtml .= '</span>';
+
+        return $sHtml;
+    }
+
+    /**
+     * @param $value
+     * @param \DBObject $oHostObject
+     * @param bool $bLocalize
+     *
+     * @return string
+     *
+     */
+    public function GetAsXML($value, $oHostObject = null, $bLocalize = true)
+    {
+        if (is_object($value) && ($value instanceof ormTagSet)) {
+            $sRes = "<Set>\n";
+            if ($bLocalize) {
+                $aValues = $value->GetLabels();
+            } else {
+                $aValues = $value->GetValues();
+            }
+            if (!empty($aValues)) {
+                $sRes .= '<Tag>' . implode('</Tag><Tag>', $aValues) . '</Tag>';
+            }
+            $sRes .= "</Set>\n";
+        } else {
+            $sRes = '';
+        }
+
+        return $sRes;
+    }
+
+    /**
+     * List the available verbs for 'GetForTemplate'
+     */
+    public function EnumTemplateVerbs()
+    {
+        return array(
+            '' => 'Plain text representation',
+            'html' => 'HTML representation (unordered list)',
+        );
+    }
+
+    /**
+     * Get various representations of the value, for insertion into a template (e.g. in Notifications)
+     *
+     * @param mixed $value The current value of the field
+     * @param string $sVerb The verb specifying the representation of the value
+     * @param DBObject $oHostObject The object
+     * @param bool $bLocalize Whether or not to localize the value
+     *
+     * @return string
+     * @throws \Exception
+     */
+    public function GetForTemplate($value, $sVerb, $oHostObject = null, $bLocalize = true)
+    {
+        if (is_object($value) && ($value instanceof ormTagSet)) {
+            if ($bLocalize) {
+                $aValues = $value->GetLabels();
+                $sSep = ', ';
+            } else {
+                $aValues = $value->GetValues();
+                $sSep = ' ';
+            }
+
+            switch ($sVerb) {
+                case '':
+                    return implode($sSep, $aValues);
+
+                case 'html':
+                    return '<ul><li>' . implode("</li><li>", $aValues) . '</li></ul>';
+
+                default:
+                    throw new Exception("Unknown verb '$sVerb' for attribute " . $this->GetCode() . ' in class ' . get_class($oHostObject));
+            }
+        }
+        throw new CoreUnexpectedValue("Bad value '$value' for attribute " . $this->GetCode() . ' in class ' . get_class($oHostObject));
+    }
+
+    /**
+     * @inheritDoc
+     *
+     * @param \ormTagSet $value
+     *
+     * @return array
+     */
+    public function GetForJSON($value)
+    {
+        $aRet = array();
+        if (is_object($value) && ($value instanceof ormTagSet)) {
+            $aRet = $value->GetValues();
+        }
+
+        return $aRet;
+    }
+
+    /**
+     * @inheritDoc
+     *
+     * @return \ormTagSet
+     * @throws \CoreException
+     * @throws \CoreUnexpectedValue
+     * @throws \Exception
+     */
+    public function FromJSONToValue($json)
+    {
+        $oSet = new ormTagSet($this->GetHostClass(), $this->GetCode(), $this->GetMaxItems());
+        $oSet->SetValues($json);
+
+        return $oSet;
+    }
+
+    /**
+     * The part of the current attribute in the object's signature, for the supplied value
+     *
+     * @param mixed $value The value of this attribute for the object
+     *
+     * @return string The "signature" for this field/attribute
+     */
+    public function Fingerprint($value)
+    {
+        if ($value instanceof ormTagSet) {
+            $aValues = $value->GetValues();
+
+            return implode(' ', $aValues);
+        }
+
+        return parent::Fingerprint($value);
+    }
+
+    public static function GetFormFieldClass()
+    {
+        return '\\Combodo\\iTop\\Form\\Field\\TagSetField';
+    }
+}
\ No newline at end of file