java.util.Calendar is modifiable, so I think it's a bad idea to let the user set a Calendar value in IDatatypeAware: <https://code.google.com/p/majortom/source/browse/majortom-api/src/main/java/de/topicmapslab/majortom/model/core/IDatatypeAware.java#101&gt;

C.f. <http://sourceforge.net/mailarchive/message.php?msg_name=a2faf9fe0807270302t2ad13664m858f4d207f53f05b%40mail.gmail.com&gt;

If IGeoCoordinate and IGeoSurface is also modifiable (I don't know what the parse(String) method does exactly), I'd avoid these datatypes as well.

Or remove parse(String) from IGeoXXX and make it immutable.

IGeoXXX replaced by immutable Wgs84XXX

We decide to keep Calendar.

ACK. I still think, keeping Calendar is dangerous:

final Calendar cal = Calendar.getInstance();

occ.setValue(cal);

cal.set(Calendar.MONTH, 1);

==> The changed value is neither recognized by the occurrence nor by the literal index nor by any event listener

Thats true,

if we clone the calendar object at setValue() calls, we can avoid something like this.

We will fix that.

calendar objects are cloned if the objects are used as values of an occurrence or variant.

the getter-methods also return only a clone never the real object, any modifcations of the calendar objects keep unrecognized by the occurrence