Topic strings

Topics

Topic string

Three characters have special meaning in version 7 publish/subscribe. They are allowed anywhere in a topic string, but use them with caution. The use of the special characters is explained in Topic-based wildcard scheme.

A forward slash ( /)

The topic level separator. Use the '/' character to structure the topic into a topic tree.

Avoid empty topic levels, '//', if you can. These correspond to nodes in the topic hierarchy with no topic string. A leading or trailing '/' in a topic string corresponds to a leading or trailing empty node and should be avoided too.

The hash sign ( #)

Used in combination with '/' to construct a multilevel wildcard in subscriptions. Take care using '#' adjacent to '/' in topic strings used to name published topics. Examples of topic strings shows a sensible use of '#'.

The strings '.../#/...', '#/...' and '.../#' have a special meaning in subscription topic strings. The strings match all topics at one or more levels in the topic hierarchy. Thus if you created a topic with one of those sequences, you could not subscribe to it, without also subscribing to all topics at multiple levels in the topic hierarchy.

The plus sign ( +)

Used in combination with '/' to construct a single-level wildcard in subscriptions. Take care using '+' adjacent to '/' in topic strings used to name published topics.

The strings '.../+/...', '+/...' and '.../+' have a special meaning in subscription topic strings. The strings match all topics at one level in the topic hierarchy. Thus if you created a topic with one of those sequences, you could not subscribe to it, without also subscribing to all topics at one level in the topic hierarchy.