Ok, thank you.
For the one who is interested, this is a query to get insight, starting from an element X with attributes, which other elements are mentioned in attribute tags at attributes of element X (so from another 'direction' than I wrote in my first post).
select t_object.ea_guid as CLASSGUID, t_object.Object_Type as CLASSTYPE, 'Attribuut' as Soort, t_object.Name as Entiteittype, Attributes.Name as Attribuut, '' as Relatie, Attributes.Application as Applicatie, Attributes.Notes as Opmerkingen from t_object
inner join
(select t_attribute.Object_ID, t_attribute.Name, AttributeTags.Application, AttributeTags.Notes from t_attribute
inner join
(select t_attributetag.ElementID, t_attributetag.NOTES, t_object.Name as Application from t_attributetag
inner join t_object
on t_object.ea_guid = t_attributetag.VALUE) as AttributeTags
on AttributeTags.ElementID = t_attribute.ID) as Attributes
on Attributes.Object_ID = t_object.Object_ID
And here is the one for attribute tags at connectors (taking the element as starting point at which the connector starts):
select t_object.ea_guid as CLASSGUID, t_object.Object_Type as CLASSTYPE, 'Relatie' as Soort, t_object.Name as Entiteittype, '' as Attribuut, Connectors.Name as Relatie, Connectors.Application as Applicatie, Connectors.Notes as Opmerkingen from t_object
inner join
(select t_connector.Start_Object_ID, t_connector.Name, ConnectorTags.Application, ConnectorTags.Notes from t_connector
inner join
(select t_connectortag.ElementID, t_connectortag.NOTES, t_object.Name as Application from t_connectortag
inner join t_object
on t_object.ea_guid = t_connectortag.VALUE) as ConnectorTags
on ConnectorTags.ElementID = t_connector.Connector_ID) as Connectors
on Connectors.Start_Object_ID = t_object.Object_ID