Help with a design, using Java Persistence

I'm having a design issue, and I hope that someone can help.
I have a table called Item, and it essentially acts as a header table for a group of attributes for that item.
TABLE Item
.....id....................long
.....itemName.........varchar
.....StartDate........datetime
.....StopDate........datetime
If I can, I'd like to design a model that will allow for a dynamic number of attributes for any given ITEM.
I initially thought that it would be convenient to design the Attributes table like such:
TABLE Attribute
.....id....................long
.....itemID.............long (references Item.id)
.....attributeName....varchar
.....value...............?
.....StartDate.........datetime
.....StopDate.........datetime
My problem is the VALUE column. Attributes can be any given type, so this won't work if I want to enforce a data type.
I don't know where to go from here. I can create a table to include all attributes, but each attribute needs to have a date range.
Additionally, the history of the attributes must be retained; so, if I succeeded any given Attribute I would need to duplicate the
entire row (thus, all the other data that didn't change).
One thought was to create an Attribute table for each of the most common types, but that seems like a really bad idea:
TABLE AttributeLong
TABLE AttributeDateTime
TABLE AttributeVarchar
etc, etc ...
I should note that I'm using Java Persistence.

I agree with you 100%. Here is something I'm trying to get a grip on: there are a finite number of attributes per group, but the number of attribute groups can grow (maybe 20 sets max - but I just don't know yet).
I would need one table (Entity) for each set of attributes.
So, for instance, let's say I have:
Item1 is of kind KIND1 that has an attribute set of SET1
(ie, tables ITEM and SET1)
Item2 is of kind KIND2 that has an attribute set of SET2
(ie, tables ITEM and SET2)
I'd like to have my Item entity class set up like such:
myItem.getAttributeSet
instead of:
myItem.getAttributeSet1
myItem.getAttributeSet2
Since at given time I can extend my application (and add new entity classes to support a new table for SET3), I wanted to avoid changing Item. I can have getAttributeSet return an interface and then cast it, but that still requires changing Item to account for the new entities. Thus, I can't just drop in new "packages."
I want a flexible and extensible system., but maybe I'm over thinking/engineering this.

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