Introduction to Web Services
A Web service is a method of communication between two electronic devices over a network (Machine-to-Machine).
The W3C defines a Web service generally as:
“a software system designed to support interoperable machine-to-machine interaction over a network”. (Source: https://en.wikipedia.org/wiki/Web_service)
History
Web services evolved from previous technologies that served the similar purpose such as Remote Procedure Call (RPC), DCOM, CORBA and JAVA Remote Method Invocation (RMI).
Web Services were intended to solve three main problems:
1. Interoperability
2. Firewall traversal
3. Complexity
Interoperability
Earlier distributed systems suffered from interoperability issues because each software vendor implemented its own format for distributed object messaging.
For example, development of DCOM apps strictly bound to Windows Operating system. And even, development of RMI bound to Java programming language.
Firewall
Collaboration across companies was an issue because distributed systems such as CORBA and DCOM used non-standard ports.
However, Web Services use HTTP as a transport protocol and most of the firewalls allow access though port 80 (HTTP), leading to easier and dynamic collaboration.
Complexity
Web Services is a developer-friendly service system.
Most of the above-mentioned technologies such as RMI, COM, and CORBA involve a whole learning curve. New technologies and languages have to be learnt to implement these services.
Web services in OpenEdge®
In OpenEdge, a Web service is usually an AppServer® application that is accessible to a client application through a Web server.
In OpenEdge, you could:
- Create new Web services that you build as ABL (Advanced Business Language) applications and deploy on an AppServer®.
- Expose existing AppServer® applications as Web services.
- Create an interface to your Web services and deploy it on a Web server.
- Create the client-side applications that interact with your Web services.
OpenEdge includes support for Web services that are based either on SOAP (Simple Object Access Protocol), or on REST (Representation State Transfer).
Both SOAP and REST are industry standards, but there are many variations on how they are implemented.
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A special note of thanks to SKIL (www.skilglobal.com) and PUG, India (www.pugindia.org) for providing me with an opportunity to deliver a webinar on this topic.
You may find the recorded session of this webinar on the youtube.com (URL: https://www.youtube.com/watch?v=dCksoJNkg2U)
Author: Raghuraman Kadambi
Linkedin: https://www.linkedin.com/pulse/accessing-non-progress-application-via-webservice-overview-pmp/