Using Web Services

Web services are widely used to perform various functions in modern application architectures. Typically, a web service is a called program or stored procedure that is accessed over the internet, using industry-standard protocols.  XML is often times used as the means for encoding the data that is transmitted by the service consumer and provider.  HTTP is a heavily used communications protocol for the transmission of service Requests and Responses.  And, SOAP is an industry-standard protocol that defines the rules and sub-protocols that are used for the invocation and provision of services.
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Web services are widely used to perform various functions in modern application architectures. Typically, a web service is a called program or stored procedure that is accessed over the internet, using industry-standard protocols.  XML is often times used as the means for encoding the data that is transmitted by the service consumer and provider.  HTTP is a heavily used communications protocol for the transmission of service Requests and Responses.  And, SOAP is an industry-standard protocol that defines the rules and sub-protocols that are used for the invocation and provision of services.
Key Benefits
The CA IDMS Web Services feature allows you to both consume external web services and expose internal web services, within CA IDMS.  A CA IDMS-based web service is a CA IDMS application program that is accessible over the internet using the SOAP protocol.  You do not typically access a web service directly using a web browser. Rather, like other called programs, you access it by another application program.
This topic describes the following information:
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Your CA IDMS system must run on GA CA IDMS Version 19.0, GA Complete, to use the Web Services Employee demonstration. If you participated in the CA IDMS Version 19.0 incremental release program, you must apply APAR RO90312.
Terminology for Web Services
Listed below are terms that are used frequently in relation to using web services. For more information about each subject, see the World Wide Web consortium (W3C).
  • HTTP (HyperText Transfer Protocol)
    HTTP is a method of text-based communication between entities on the World Wide Web. HTTP is a request-response protocol that, after a given request message, is sent from a client to a server.  The server sends back a reply message containing a status of the previous request and, typically, some additional content in the body of the reply. The SOAP protocol uses HTTP as its underlying communications methodology. Web services typically utilizes HTTP over TCP/IP.
  • SOAP (Simple Object Access Protocol)
    CA IDMS Web Services uses version 1.1 of the SOAP protocol. SOAP is a set of rules that define the passing of XML-based information between peers in a distributed environment. A SOAP message is a one-way transmission, but many applications implement a call and response architecture similar to HTTP. The SOAP protocol uses two additional standards, HTTP and XML.
  • WSDL (Web Services Definition Language)
    WSDL is an XML-format language for defining web-based services. A WSDL document defines how a service can be addressed and invoked. WSDL also describes the operations that are available for the service, as well as, the input and output elements that are needed for those operations. Consider the WSDL document as the "contract" between the caller and the web service.
  • XML (eXtensible Markup Language)
    XML is set of rules that defines a method for encoding data in a format that is understandable by humans, but can also be interpreted easily by computer programs. A properly formed XML message contains several required and optional sections. Data elements are denoted with header and footer tags that allow the reader to understand the context of the element. XML allows you to transmit customized data from different applications running on disparate platforms.
Web Services in a CA IDMS Environment
In the CA IDMS environment, a CA IDMS application program can either consume an external web service, or provide a web service for an external web service consumer. The CA IDMS application program includes the following two types of web services functions:
  • Consumer
    A web services consumer (client program) calls an external web service provider. The CA IDMS Web Services Consumer allows CA IDMS application programs to call an external Web service.
  • Provider
    A web service provider is called by an external requester. In client/server terms, a provider is a server program. The CA IDMS Web Services Provider allows a CA IDMS application program to be called by an external web service.
Using SOAP, a consumer and provider exchange messages in a synchronous manner. The consumer sends a SOAP request message to the provider. The provider responds by sending a SOAP reply message back to the consumer. Asynchronous consumption of services can be accomplished by dispatching multiple consumer tasks using, for example, a queue-initiated task.
Although less often used, it is possible to write a one-way, request-only web service. Most web services follow a request-to-response model of communication. In a request-only communications model, the consumer service sends a message without expecting a response from the provider service.
A web service has many attributes that are needed for invocation, as follows:
  • URL: Locates the service on the Internet
  • Service Name: Identifies the service program name
  • Operation Name: Identifies the desired function within the service program
  • Element Names: Defines the input and output attributes of the service
All of the attributes for a given web service are contained in its Web Services Description Language (WSDL) file.