Hi Edward,

As I said, it's just a workaround, so, yes, in order to override the filed values of an item state in the snapshot, the Data Adapter may send an ItemEvent with empty strings for the expired fields to the Lightstreamer Kernel, but the server will broadcast an ItemUpdate to all subscribed clients.
The idea behind is that a snapshot represent the state of an Item as it is represented on all subscribed clients at a certain time. So, if a new client subscribes to an Item and receives the snapshot, its state is the same as all the other already subscribed clients.
If I correctly understand, your requirement is to have instead the expired values removed only from the snapshot, so for clients which will subscribe from now on, but not on the already subscribed ones.
Since the requirements for expiration policies may vary and depends on the problem domain, this is something that should be implemented by your application.
If your data are managed in MERGE mode (am I correct?), you can for instance use a specific string to represent blank values for expired fields, so that a client may consider the value as actually blank, if it has been received as a snapshot, or ignore it, and keep the previous received value, if it has been received in a normal item update, while actual blank fields will be treated consistently on all clients.


hth
Marco