Microsoft SQL Server 2008 R2 Specifications download pdf (Page 170)

150 CHAPTER 8 Complex Event Processing with StreamInsight

If you choose to deploy CEP as a standalone server, there are some limitations that affect

the way you develop applications. First, you can use only the explicit server development

model (which is described in the next section of this chapter) when developing CEP applica-

tions for a standalone server. Second, you must connect to the CEP server by using the Web

service Uniform Resource Identier (URI) of the CEP server host process.

Application Development

You start the typical development cycle for a new CEP application by sampling the existing

data streams and developing functions to process the data. You then test the functions, re-

view the results, and determine the changes necessary to improve the functions. This process

continues in an iterative fashion until you complete development.

As part of the development of your CEP application, you create event types, adapters, and

query templates. The way you use these objects depends on the development model you

choose. When you develop using the explicit server development model, you explicitly create

and register all of these objects and can reuse these objects in multiple applications. In the

implicit server development model, you concentrate on the development of the query logic

and rely on the CEP server to act as an implicit host and to create and register the necessary

objects.

TIP You can locate and download sample applications by searching for StreamInsight at

CodePlex (http://www.codeplex.com).

Event Types

An event type denes events published by the event source or consumed by the event con-

sumer. You use event types with a typed adapter or as objects in LINQ expressions that you

use in query templates. You create an event type as a .NET Framework class or structure by

using only public elds and properties as the payload elds, like this:

public class sampleEvent

{

public string eventId { get; set; }

public double eventValue { get; set; }

}

An event type can have no more than 32 payload elds. Payload elds must be only scalar

or elementary CLR types. You can use nullable types, such as int? instead of int. The string and

byte[] types are always nullable.

You do not create an event type when your application uses untyped adapters for scenar-

ios that must support multiple event types. For example, an input adapter for tables in a SQL

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Microsoft SQL Server 2008 R2 Specifications Page 170