WS-Topics defines a mechanism to organize and categorize items of interest for subscription known as “topics”. These are used in conjunction with the notification mechanisms defined in WS-BaseNotification. WS-Topics defines three topic expression dialects that can be used as subscription expressions in subscribe request messages and other parts of the WS-Notification system. It further specifies an XML model for describing metadata associated with topics.

These slides give a brief introduction to the WS-Topics specification.