What is a "web service" in plain English?
I've been reading about "web services" here on SO, on Wikipedia, Google, etc., and I don't quite understand what they are. What is the plain English definition/description?
If I make a simple website using PHP that just, say, prints a random integer to the page... is this a "web service"? If not, why not?
Solution 1:
A simple definition: A web service is a function that can be accessed by other programs over the web (HTTP).
For example, when you create a website in PHP that outputs HTML, its target is the browser and by extension the human reading the page in the browser. A web service is not targeted at humans but rather at other programs.
So your PHP site that generates a random integer could be a web service if it outputs the integer in a format that may be consumed by another program. It might be in an XML format or another format, as long as other programs can understand the output.
The full definition is obviously more complex but you asked for plain English.
Solution 2:
Simplified, non-technical explanation: A web serivce allows a PROGRAM to talk to a web page, instead of using your browser to open a web page.
Example: I can go to maps.google.com, and type in my home address, and see a map of where I live in my browser.
But what if you were writing a computer program where you wanted to take an address and show a pretty map, just like Google maps?
Well, you could write a whole new mapping program from scratch, OR you could call a web service that Google maps provides, send it the address, and it will return a graphical map of the location, which you can display in your program.
There is a lot more to it, as some of the other posts go into, but the upshot is that it allows your application to either retrieve information FROM, or submit information TO some resource. Some other examples:
- You can use a web service to retrieve information about books at Amazon.com
- You can use a similar web service to submit an order to Amazon.com
- You could CREATE a web service to allow outside applications to find out about product information within your company
- you could create a web service to allow outside applications to submit orders to your company.
Solution 3:
Yes that is a simple web service.
Web services are really nothing more than a request/ response mechanism that allows a client to remotely access/ modify data. There are formal standards for web services (SOAP, SOA etc), but your simple page is a service too.
The main downside to printing it to a page is that your service would return HTML. Preferable data formats are JSON and XML, because most client frameworks (and server frameworks) are designed around using JSON and XML.
So if you modified your service to return:
<RANDOM>some random number</RANDOM>
rather than:
<HEAD>...</HEAD>
<BODY>some random number</BODY>
then it would be more useful to most clients
Solution 4:
In over simplified terms a web service is something that provides data as a service over the http protocol. Granted that isn't alway the case....but it is close.
Standard Web Services use The SOAP protocol which defines the communication and structure of messages, and XML is the data format.
Web services are designed to allow applications built using different technologies to communicate with each other without issues.
Examples of web services are things like Weather.com providing weather information for that you can use on your site, or UPS providing a method to request shipping quotes or tracking of packages.
Edit
Changed wording in reference to SOAP, as it is not always SOAP as I mentioned, but wanted to make it more clear. The key is providing data as a service, not a UI element.