SQL Anywhere contains a built-in HTTP server that allows you to provide web services, as well as to access web services in other SQL Anywhere databases and standard web services available over the Internet. SOAP is the standard used for this purpose, but the built-in HTTP server in SQL Anywhere also lets you handle standard HTTP and HTTPS requests from client applications.
The term web service has been used to mean a variety of things. Commonly, it refers to software that facilitates inter-computer data transfer and interoperability. Essentially, web services make segments of business logic available over the Internet. Simple Object Access Protocol (SOAP) is a simple XML-based protocol to let applications exchange information over HTTP.
SOAP provides a method for communication between applications such as those written in Java or Visual Studio .NET using the Internet. SOAP messages define the services that a server provides. Actual data transfer generally takes place using HTTP to exchange XML documents structured so as to efficiently encode relevant information. Any application, such as a client or server, that participates in SOAP communication is called a SOAP node or SOAP endpoint. Such applications can transmit, receive, or process SOAP messages. You can create SOAP nodes with SQL Anywhere.
For more information about the SOAP standards, see www.w3.org/TR/soap.
In the context of SQL Anywhere, the term web services means that SQL Anywhere has the ability to listen for and handle standard SOAP requests. Web services in SQL Anywhere provide client applications an alternative to such traditional interfaces as JDBC and ODBC. Web services can be accessed from client applications written in a variety of languages and running on a variety of platforms. Even common scripting languages such as Perl and Python provide access to web services. You create web services in a database using the CREATE SERVICE statement.
SQL Anywhere can also function as a SOAP or HTTP client, permitting applications running within the database to access standard web services available over the Internet, or provided by other SQL Anywhere databases. This client functionality is accessed through stored functions and procedures.
In addition, the term web services also refers to applications that use the built-in web server to handle HTTP requests from clients. These applications generally function like traditional database-backed web applications, but can be more compact and are easier to write as the data and the entire application can reside within a database. In this type of application, the web service typically returns documents in HTML format. The GET, HEAD, and POST methods are supported.
The collection of web services within your database together define the available URLs. Each service provides a set of web pages. Typically, the content of these pages is generated by procedures that you write and store in your database, although they can be a single statement or, optionally, allow users to execute statements of their own. These web services become available when you start the database server with options that enable it to listen for HTTP requests.
Since the HTTP server that handles web service requests is embedded in the database, performance is good. Applications that use web services are easily deployed, since no additional components are needed, beyond the database and database server.