Summary

SQL-NS applications generate notifications by matching subscriptions against events or chronicled data. The logic that determines when a match occurs is usually specified by developers when they create the applications. SQL-NS also offers an alternative model in which the matching logic can be specified by end users at the time they create their subscriptions. This model of user-defined logic is covered in this chapter.

User-defined logic is specified in terms of conditions on a subscription's input. The input is usually either a single event or a single row in a chronicle table. The SQL-NS condition model defines a few simple condition constructs that can be composed in various ways to create complex conditions.

Building a SQL-NS application that supports user-defined logic involves defining special subscription classes in the ADF. The rules in these subscription classes specify the kinds of conditions that can be used to express matching logic. They also define how notification rows are generated based on matches determined by user-defined logic.

The SMIs for applications that support user-defined logic provide users with a way to specify conditions when they create subscriptions. The user interface controls for creating conditions vary from application to application. However, all SMIs use the SQL-NS Condition API, an extension to the standard Subscription Management API, to represent conditions programmatically and store them in the application's database.

This chapter provides a detailed description of the techniques used to build SQL-NS applications that support user-defined logic. It explains the ADF elements that configure the use of user-defined logic, the details of the condition model itself, as well as the Condition API. All the concepts are first presented in general terms and then shown in practical use in a functional sample application.