Log to Data, Missing Attribute Names

Hi,

After converting log values to an example set with "Log to Data" operator, following operators (such as aggregate) cannot catch the attribute names of the set. In the meta data information correct number of attributes are counted but their names are not shown and hence unusable. Is there a solution for this?

However, if I type the attribute names correctly in operators like "Generate Attributes" the process runs without error. But I cannot enter or type any name in the "aggregate" operator, only selection is allowed.