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SOAP:Simple Object Access Protocol XML-RPC

SOAP:Simple Object Access Protocol XML-RPC. Ganapathy Raman GRA-Netsolve Group ICL. SOAP: Introduction. XML - last week talk MathML, SMIL, VML Distributed Computing is here to stay Computation thro Communication Resource Heterogenity Common Language for Data exchange

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SOAP:Simple Object Access Protocol XML-RPC

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  1. SOAP:Simple Object Access ProtocolXML-RPC Ganapathy Raman GRA-Netsolve Group ICL

  2. SOAP: Introduction • XML - last week talk • MathML, SMIL, VML • Distributed Computing is here to stay • Computation thro Communication • Resource Heterogenity • Common Language for Data exchange • Leverages XML to solve the above problem

  3. SOAP:Is this Hype? • Lack of standard - Hurts Interoperability • In-memory representation • On-the-wire representation • DCOM - DCE/NDR • CORBA - IIOP/CDR • JAVA - RMI/JRMP • Netsolve - XDR • Tied to a single middleware (Monopoly?)

  4. SOAP:Is this Hype? • Security Issues • Firewalls allow only specific ports • HTTP,FTP • Most middleware dynamically assign ports • This is a real problem for internet applications

  5. Possible solutions • Use Ascii • fprintf/fscanf instead of fwrite/fread • flat stream of data • not rich enough to represent structure • producer and consumer forced to ‘know’ each other • Use CGI • http + ascii

  6. XML to the rescue • XML is not about content • XML is about structure of content • XML + DTD provides a standard way for anyone to understand data using the same set of tools • Producer and consumer can be ‘strangers’

  7. SOAP in a Nutshell 1. XML for encoding data • LANGUAGE OF COMMUNICATION 2. HTTP as transport • MEDIUM OF COMMUNICATION • Do not let Microsoft Hype fool you!! • “Simplicity over Complexity” • Surely a step in the right direction • Deserves a detailed look

  8. An example • www.weather.com • float CurrentTemp(zip_code) • The process Application Application Request Middleware Middleware Reply SOAP SOAP Error HTTP HTTP icl.cs.utk.edu www.weather.com

  9. REQUEST Example POST /Temperature HTTP/1.1 Host: www.weather.com Content-Type: text/xml Content-Length: <whatever> SOAPMethodName: <some-URI>#CurrentTemp <SOAP:Envelope xmlns:SOAP="urn:schemas-xmlsoap-org:soap.v1"> <SOAP:Body> <m:CurrentTemp xmlns:m="some-URI"> <zip_code>37919</zip_code> <m:CurrentTemp> </SOAP:BODY> <SOAP:Envelope> URI- Uniform Resource Identifier some-URI -> www.netsolve.com or www.globus.com Http Header Soap Extensions Xml Payload

  10. Http Header RESPONSE Example HTTP/1.1 200 OK Content-Type: text/xml Content-Length: <whatever> <SOAP:Envelope xmlns:SOAP="urn:schemas-xmlsoap-org:soap.v1"> <SOAP:Header> <t:Transaction xmlns:t="some-URI"> 5 </t:Transaction> </SOAP:Header> <SOAP:Body> <m:CurrentTempResponse xmlns:m="some-URI"> <return>42</return> </m:CurrentTempResponse> </SOAP:Body> </SOAP:Envelope> Xml Payload

  11. SOAP: What it’s NOT • Object Activation • who invokes CurrentTemp function? • Bi-directional Communications • Distributed Garbage Collection • Language Bindings unspecified • good for interoperability • Perl,C,java • Source of xml-rpc payload is immaterial

  12. SOAP: Analysis • Size of Messages • Latency is key, not Bandwidth • High factors of Compression • Ascii + repetitive Tags Client 100 bytes Server No compression 1000 bytes Client 100 bytes Server Compression 200 bytes

  13. SOAP:Analysis In-memory • Strings - no conversion needed • Floating Point - sprintf,sscanf • “e-commerce” applications --- GOOD • text + integers • “grid” applications --- BAD • numeric intensive • There is always a tradeoff involved xml-rpc In-memory encode decode

  14. SOAP: What the Grid needs • A standard that can find a balance between performance and inter-operability • XDR,NDR,CDR - possible candidates • Ability to represent structure is key • Maybe an extension to xml-rpc • Will enable grid infrastructures to inter-operate

  15. SOAP: Analysis • Stateless Nature - Independent transactions • Most distributed applications are stateful • Programming model is different • State info with every transaction • Size of state info need • “A cookie may not satisfy hunger”!! • Good for scalability

  16. SOAP: Analysis • Programming complexity • Standards are in flux • Maturity of tools • Need open-source xml parsers • xml.apache.org • xerces : parsers in xml,perl,c++ • A minor obstacle at best

  17. SOAP: Birds-eye-view JAVA OTHER DCOM CORBA Islands of in-compatibility interconnected by SOAP bridges Philosophy of “Do one thing and do it well” Focus on Interoperability

  18. SOAP: What can it teach us? • Use XML for data exchange • can define our own xml-rpc if needed • the idea of encoding is what is important • can use TCP as transport • HTTP tunneling • Would be a short-sight on our part to ignore because of Microsoft tag

  19. SOAP: Summary • Its not something path-breaking • “Right mix of technology at the right time” • Structure more important than content • XML - ASCII of the future • Holds lot of promise • Step in the right direction

  20. SOAP: Resources • www.cs.utk.edu/~raman/soap/soap.html • links to whitepapers, spec, articles etc • link to this presentation • Questions??? • Thank you

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