Chapter 4: Generating Web Service Forms

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Introduction

The last chapter covered a lot of information about XML and InfoPath. This is important to understand when you look at InfoPath and how it uses the Web Services architecture. Web Services are defined within a set of industry standards as self-contained, self-describing , modular applications that are published, located, and invoked across a network. They are deployed as a set of software that provides a service to a client application over a network utilizing a standardized XML messaging system that provides encoded communication in and out of the Web Service.

Technically, a Web Services implementation is composed of four layers. First is the transport layer, which enables message communication between applications using standard wire protocols ”HTTP, Simple Mail Transfer Protocol (SMTP), and File Transfer Protocol (FTP). Second is the XML-based encoding schema, which defines common message formats ”SOAP and XML Remote Procedure Calls (XMLRPC). Third is the XML-based service description language (WSDL), which defines the public interfaces. Finally, there s the service discovery mechanism (UDDI), which provides the central repository and registry for the Web Service publish-and-find capabilities. This chapter focuses on each of these technology layers and how they can be extended using Visual Studio.NET 2003 and the .NET Framework. We will also discuss how once deployed, InfoPath can discover and then interface with these services to create a document-centric application. Web Services are an important data source for InfoPath-based solutions and a major part of the Services Oriented Architecture.