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Topic naming

Consider the following restrictions when deciding on your topic paths.

Restricted characters

Topics are identified by a path. A path is made up of path segments separated by the slash character (/).

Each path segment can be made up of one or more Unicode characters but must not contain any of the restricted characters mentioned below. The slash character (/) is not permitted in any path segment.

Reserved spaces

Paths starting with the path segment Diffusion are reserved for internal use.


Although all Unicode characters except the slash character (/) are supported, we recommend avoiding common regular expression metacharacters such as '*' and '?' in path names to avoid having to quote these characters in topic selector expressions.

Publisher API restricted characters

The Publisher API is used to create Java™ publishers that are hosted in the Diffusion™ server. This API has a wider set of restrictions on characters in topic paths.

In addition to the slash character (/), which is restricted in all path segments, the following characters are not permitted in paths to topics that are created by or selected by any publishers:

Table 1. Restricted characters for paths used by publishers.
Character Reason for restriction
[]\^$.|?*+() These are all metacharacters used in regular expressions. Any path String that contains any of these characters is assumed to be a topic selector. These characters cannot be used in path segments.
Control/Reserved No characters with a hexadecimal value of less than 0x2D. This includes some punctuation characters such as comma (,).
Whitespace No characters defined as whitespace in Java (as indicated by the isWhiteSpace method of the Java Character class).