Web Services 101 for Interface Engines

Posted on behalf of Marianne Soucy, Manager of Client Education Services 

What is a webservice?

• A webservice is a way to, unattended, interact with a web based receiver of information.
  • It communicates from one machine to another, with the expectation that a user is not sitting at the screen supplying information (like a user would be with a regular website)
• A webservice is a collection of open protocols that are designed to allow different technologies to interact and supply and receive information, ie to exchange data.

What terms do I need to know?

• There are several common terms you should understand when discussing a web service
  • XML – a web service uses XML to tag data, in order to put all the needed data into a universal, commonly agreed upon format between the systems that are communicating. XML can tag each field of data to label it, making it a good choice to pass the data between systems.
  • SOAP – Simple Object Access Protocol – a protocol for sending and receiving messages between applications. Consider it something like wrapping a message in an envelope. It allows us to deliver the message via defined protocols.
    • Probably 80% or more of the interfaces we are seeing in Healthcare use SOAP transmission
  • JSON – JavaScript Object Notation – another open standard format that allows transmission of messages. Another form of “Envelope”.
    • Maybe 10% of what we are seeing in the field is JSON
  • WSDL – Web Service Description Language – a document that describes a web service (kind of like an HL7 spec) and tells you how to access and use its methods. This document gives you a blueprint on what the web service will need for you to interact with it.
  • FHIR – (Fast Healthcare Interoperability Resources) another emerging technology we anticipate will change the above ratios Technically, FHIR is designed for the web; the resources are based on simple XML or JSON structures, with an http-based RESTful protocol where each resource has predictable URL.

What information will I need to know to set up a Web Service in Healthcare?

• The URL of the webservice
  • The URL of the WSDL is also useful. Often, that can be found by taking the URL above and placing ?WSDL after the .asmx in the URL for example:
    • http://www.webservicex.com/globalweather.asmx = the URL you will send to
    • http://www.webservicex.com/globalweather.asmx?WSDL is often the WSDL that will give you the specifications of what the service is going to be looking for, what strings and parameters it is using, etc.
      • Not all Web Services will give you a WSDL, but it makes setting things up WAY easier!
    • Do I need a certificate
    • Do I need a username and password
    • What parameter(s) does this web service expect me to supply to them

LINK for a good explanation of this :

http://www.webreference.com/authoring/web_service/index.html

How do I check out a Webservice I want to set up?

We are going to use a simple example, showing how to get a Webservice to give us back the weather for a city and country.

• First, we are going to test the URL to see if it is present and working.
  • Open Internet Explorer and plug in the URL of the Webservice like shown:
  • http://www.webservicex.com/globalweather.asmx
  • Click GetWeather and put in Madrid and Spain (this doesn’t work for all countries, please do use Madrid)
    • In theory, this is what we want our fake web service to do. We want to give it 2 parameters, and for it to give us back an answer
    • In an interface engine, we would be giving them something, like an HL7 message, or a patient ID and a test code result, and they would be giving us back an ACK, in real life terms.
  • Next, we are going to test the WSDL to see if it is present and working.
    • Open a new tab and type : http://www.webservicex.com/globalweather.asmx?WSDL
    • This should give you back a schema, a specification explaining what it needs and wants.
    • This tells me that the MethodName I need to pass will be GetWeather, and that it will expect TWO parameters, a CityName and a Country Name.
    • Many interface engines, such as Express Connect, will make this easy in a wizard later!!

Image may be NSFW.
Clik here to view.

• For less simple examples, we need to consider the following:
  • Do we need to install a certificate?
  • Do we need a username and password?
• Let’s install a certificate:
  • This is a website that needs a certificate. I can install it this way – click the LOCK icon in the IE browser. Click View Certificates

Image may be NSFW.
Clik here to view.

• Click INSTALL CERTIFICATE

Image may be NSFW.
Clik here to view.

• Browse and put it in the PERSONAL STORE of the user – Or as directed by your vendor as to where to put it.

Image may be NSFW.
Clik here to view.

SOURCE INFO and useful links:

Some generic web services to play with :

http://www.webservicex.net/ws/default.aspx – click the name of any web service, I use the GeoIPService one to test a simple pass of one parameter.

This is what a WSDL looks like : http://www.webservicex.net/WeatherForecast.asmx?wsdl

Info on Web Services: http://www.webreference.com/authoring/web_service/index.html

Microsoft HL7 Web Services info: https://msdn.microsoft.com/en-us/library/ms954603.aspx

The main things to remember about a WSDL file are that it provides you with:

• A description of a Web service
• The methods a Web service uses and the parameters that it takes
• A way to locate Web services