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> Topics
> Topics can both export and import messages. Accordingly, you can configure topic definitions (in the configuration file topics.conf) with import and export properties that specify one or more external transports:
> import

> • | import instructs tibemsd to import messages that arrive on those transports from Rendezvous, and deliver them to the EMS destination.

> export

> • | export instructs tibemsd to take messages that arrive on the EMS destination, and export them to Rendezvous via those transports.

> | The EMS server never re-exports an imported message on the same topic.

> (For general information about topics.conf syntax and semantics, see topics.conf on page 246. You can also configure topics using the administration tool command addprop topic.)
> Example
> For example, the following tibemsadmin commands configure the topic myTopics.news to import messages on the transports RV01 and RV02, and to export messages on the transport RV02.
> addprop topic myTopics.news import="RV01,RV02"
> addprop topic myTopics.news export="RV02"
> Rendezvous messages with subject myTopics.news arrive at tibemsd over the transports RV01 and RV02. EMS clients can receive those messages by subscribing to myTopics.news.
> EMS messages sent to myTopics.news are exported to Rendezvous over transport RV02. Rendezvous clients of the corresponding daemons can receive those messages by subscribing to myTopics.news.
> Import Only when Subscribers Exist
> When a topic specifies import on a connected transport, tibemsd imports messages only when the topic has registered subscribers.
> Wildcards
> Wildcards in the import and export properties obey EMS syntax and semantics (which is identical to Rendezvous syntax and semantics); see Destination Name—Syntax and Semantics.
> Certified Messages
> You can import and export TIBCO Rendezvous certified messages (tibrvcm transport) to EMS topics. Rendezvous certified transports guarantee message delivery.
> RVCM Ledger
> tibrvcm transports can store information about subjects in a ledger file. You can review the ledger file using an administration tool command; see show rvcmtransportledger on page 161).
> For more information about ledger files, see TIBCO Rendezvous documentation.
> Subject Collisions
> Subscribers to destinations that import from RVCM transports are subject to the same restrictions that direct RVCM listeners. These restrictions are described in the TIBCO Rendezvous documentation, and include subject collisions.
> When importing messages from RV, the EMS server creates RVCM listeners using a single name for each transport. This can result in subject collisions if the corresponding EMS subscribers have overlapping topics.

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