What can and can not be changed/deleted BEFORE publishing?
You can change and delete everything except the schema can not be deleted.
What can and can not be changed/deleted AFTER publishing?
You can change the name of the schema or of the attribute. You can also change the unit of an attribute.
You can not change the key of a schema or attribute. You can not also change the data type or the decimals of an attribute.
Which data type should I use for which attribute?
String for text or single characters (variable unlimited length).
Boolean for true/false values.
Long, Integer (64 bit/32 bit) for signed and unsigned integers.
Double (64 bit) floating-point number for representation of decimals.
Timestamp for UNIX timestamps in milliseconds.
Time is not used anymore (deprecated).
None is not used anymore (deprecated).
All columns are also allowed to have NULL entries.
Do I need to define attributes like Thing or Timestamp as well?
No, the Thing and Timestamp columns are metadata. Every schema automatically has all metadata columns, which are: Id, Inserted, Size, Thing, Timestamp, Type.
The messages sent include all attributes defined in the event schema but the messages are put into "invalid messages". Why?
This could have several different reasons.
Any value in the message is of the wrong data type
Any value in the message includes an unexpected symbol
There are some additional attributes that are not defined in the event schema
