Web Services (related to Ch.5)
“The W3C defines a "Web service" as "a software system designed to support interoperable machineto-machine interaction over a network". It has an interface described in a machine-processable format
(specifically Web Services Description Language, known by the acronym WSDL). Other systems
interact with the Web service in a manner prescribed by its description using SOAP messages,
typically conveyed using HTTP with an XML serialization in conjunction with other Web-related
standards."[1]
The W3C also states, "We can identify two major classes of Web services, REST-compliant Web
services, in which the primary purpose of the service is to manipulate XML representations of Web
resources using a uniform set of "stateless" operations; and arbitrary Web services, in which the
service may expose an arbitrary set of operations."[2]” (Reference: http://en.wikipedia.org/wiki/Web_service )
http://www.loc.gov/standards/sru/march06-meeting/slides/wsdl.ppt
“A Web service is a method of communication between two electronic devices over the World Wide
Web. A Web service is a software function provided at a network address over the web or the cloud,
it is a service that is "always on" as in the concept of utility computing.” (Ref.
http://en.wikipedia.org/wiki/Web_service )
“Cloud computing is the use of computing resources (hardware and software) that are delivered as a
service over a network (typically the Internet).” (Ref. http://en.wikipedia.org/wiki/Cloud_computing )
“Software as a service (SaaS, pronounced sæs or sɑs[1]), sometimes referred to as "on-demand
software", is a software delivery model in which software and associated data are centrally hosted on
the cloud. SaaS is typically accessed by users using a thin client via a web browser.” (Ref.
http://en.wikipedia.org/wiki/Software_as_a_service ) Saas can use a variety of pricing models, e.g.:
pay-as-you-go, or subscription fees.
http://catmousavi.wordpress.com/2011/11/10/what-is-web-services-according-to-w3c-bigweb-services-vs-restful-services/ Reference for the following page:
“Each web service has a public interface, WSDL (Web Services Description Language),
and through simple mechanism called UDDI (Universal Description, Discover and
Integreation) which a directory service, you publish and register your WSDL in there and
interested parties can locate its public interface for their use via UDDI. There is a soap which
is a xml based protocol to let applications exchange inforformation via http so in a very
simple way UDDI says where webservices are and WSDL describes what they do and
SOAP(Simple Object Access Protocol) talks to them.
The following flow diagram is self explanatory of how the process and flow of each call is in
a webservice.”
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Discovery - Search UDDI site(s) for the proper Web service.
Description - A description of the selected Web service is returned to the client
application as a Web Services Description Language (WSDL) file.
Proxy creation - A local proxy to the remote service is created. The proxy converts an
object’s means of method invocation into an XML message, and vice versa
Soap Message Creation - a Soap/XML message is created and sent to the URL
specified in the WSDL file.
Listener - A Soap listener at the host site receives the call and interprets it for the Web
Service.
The Web service performs its function, and returns the result back to the client, via
the listener and the proxy.
Videos about AWS
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Amazon Web Services (outside review) http://www.youtube.com/watch?v=hkl24cYc09g
Amazon Cloud Computing approach http://www.youtube.com/watch?v=CaJCmoGIW24
(good but long)
EC2 Tutorial – Amazon’s elastic computing cloud
http://www.youtube.com/watch?v=bBajLxeKqoY
Cloud Bursting http://www.youtube.com/watch?v=pg6zeXZhgRs (good, beginning, then skip
to 25m)
New Cost Models – Amazon Web Services (AWS) (Start at 2 minutes)
http://www.youtube.com/watch?v=0vCuFpIXRxc
Cloud Computing - Content Delivery Network, Cloud Front by Amazon
http://www.youtube.com/watch?v=k-nCMrmxmgs
Mechanical Turk (Business application of AWS)
http://www.youtube.com/watch?v=2Uj_YwBbzVI&playnext=1&list=PL253659793558BD65
&feature=results_main
Notable Web Service Providers
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Amazon Web Services
Google Apps
iCloud
Microsoft Office 365
Oracle
Salesforce
Concur
Windows Azure
Zoho Office Suite
Meltwater Group