I like to install a component conditionally. I prefer something that the component is installed when a definition appears in 'components.xml'. The components looks like:

@Name("xService")
@Scope(ScopeType.APPLICATION)
public class XService {

@Logger
private static Log log;

@Create
public void create() {
log.debug("create()");
}  

@Observer(value = TransactionService.EVENT_TRANSACTION_ADDED, create = false)
public void event(Transaction transaction) {
...
}

The purpose of this component is to process the observed transaction in a particular configuration. So, how to create this component only in particular cases?