Chapter 18. User-Defined Matching Logic in SQL-NS Applications

IN THIS CHAPTER

• Overview of User-Defined Matching Logic

• Building the Music Store Application with User-Defined Matching Logic

At the center of every SQL-NS application is the core logic that produces notifications by matching events with subscriptions. In all the applications presented so far, this logic is coded in match rulesT-SQL statements that join views of the events and subscriptions and then select only those rows that adhere to some matching criteria. In these match rules, the matching logic is fixed at development time. The end users of the application (its subscribers) can only specify parameters to the developer-defined matching logic; they cannot change the logic itself. Only the developer of the application decides what it means for an event to match a subscription.

SQL-NS offers an alternative model in which end users can specify their own matching logic as part of their subscriptions. This is referred to as user-defined logic. Rather than evaluating some developer-defined match rule, SQL-NS evaluates the custom matching logic in each subscription to determine the matches. In this model, each user can create a unique definition of matching.

This chapter is about building SQL-NS applications that support user-defined logic. It covers the ADF elements used to configure applications for user-defined logic and the API for building subscription management interfaces by which users can specify matching logic when creating subscriptions.