A web service is a way for systems to communicate over a network. They can be as simple as an API (e.g. Google Maps) or as complex as a brokered system that handles transactions for multiple requesters and/or providers.
Web services bring with them some huge advantages. Data is packaged via HTTP or HTTPS and can usually bypass firewalls since port 80 and 443 are commonly allowed open. This plays a big role where intranet systems need to communicate but have a very strict set of firewall rules. An example might be an Oracle DB link needing to reach a MySQL server. Typically this is a daunting task as you have to go through the bureaucracy of getting the proper ports opened, get added to one or more access-controlled lists, receive/provide access privileges at the database level, etc. Then there is the issue of direct access to data, either by view, table or procedure; the list goes on and on.
Most of these problems can be eliminated by the use of web services. This article’s objective is to explain, at a high-level, when, why and how web services are used.
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