1. Distributed Computing with HTTP, XML, SOAP, and WSDL CHAPTER 14 MOHAMMAD BORUJERDI 1 INTERNET ENGINEERING OUTLINE : Shift in perspective from data to programs Elements of web distributed computing General Picture on web distributed computing SOAP RSS

2. Distributed Computing with HTTP, XML, SOAP, and WSDL CHAPTER 14 MOHAMMAD BORUJERDI 2 INTERNET ENGINEERING Shift in perspective from data to programs : Web brought the perspective of viewing the whole Internetas a single information space, where users accessing data could move seamlessly and transparently from machine to machine by following links. Now applications that draw upon many interconnected machines as one vast computing medium are being deployed on a large scale. Made possible by new protocols for distributed computing built upon HTTP, and designed for programs interacting with programs, rather than for people surfing with browsers.

3. Distributed Computing with HTTP, XML, SOAP, and WSDL CHAPTER 14 MOHAMMAD BORUJERDI 3 INTERNET ENGINEERING Elements (protocols) of web distributed computing : Data exchange: Something better than scraping text from Web pages intended for humans to read. You can use XML here. Program invocation: ways to do remote method invocation, that is, for programs to call programs running on other machines and to reply to such invocations. The standard here is called SOAP (Simple Object Access Protocol). Self-description: A machine-readable way for programs to describe how they are supposed to be called, e.g., with Web Services Description Language (WSDL). Discovery: A way for programs to automatically learn about other programs, e.g., with Universal Description Discovery and Integration (UDDI).

4. Distributed Computing with HTTP, XML, SOAP, and WSDL CHAPTER 14 MOHAMMAD BORUJERDI 4 INTERNET ENGINEERING General Picture on web distributed computing :

5. Distributed Computing with HTTP, XML, SOAP, and WSDL CHAPTER 14 MOHAMMAD BORUJERDI 5 INTERNET ENGINEERING SOAP :Request (plus whitespace for readability) POST /services/WhosOnline.asmx HTTP/1.1 Host: somehost Content-Type: text/xml; charset=utf-8 Content-Length: length SOAPAction: "http://jpfo.org/WhosOnline" <soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> 600

6. Distributed Computing with HTTP, XML, SOAP, and WSDL CHAPTER 14 MOHAMMAD BORUJERDI 6 INTERNET ENGINEERING SOAP :Response HTTP/1.1 200 OK Content-Type: text/xml; charset=utf-8 Content-Length: length <soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema- instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" > Eve Andersson eve@eveandersson.com Philip Greenspun philg@mit.edu Andrew Grumet aegrumet@alum.mit.edu

7. Distributed Computing with HTTP, XML, SOAP, and WSDL CHAPTER 14 MOHAMMAD BORUJERDI 7 INTERNET ENGINEERING RSS : The March of Progress has been ON from simple HTTP to "Semantic Web" and Resource Description Framework (RDF). Web development has thus become as challenging as cracking the Artificial Intelligence problem. SOAP and WSDL Apparently are closer to RDF than to HTML because it is taking many years for SOAP and WSDL to catch on as opposed to the wildfire-like spread of the human-readable Web. The dynamic world of weblogs has settled on a standard that has spread very quickly indeed and enabled the construction of quite a few computer programs that aggregate information from multiple weblogs. This standard, pushed forward primarily by Userland's Dave Winer, is known as Really Simple Syndication or RSS.