Web Services Martin Nečaský, Ph.D. Faculty of Mathematics and Physics Charles University in Prague, Czech Republic Summer 2014

Foundations of Web Services  communication of Component A and Component B  consists of sequence of messages exchanged between A and B  synchronous or asynchronous  based on standards or proprietary Component A Component B Internet or other network Internet or other network Summer 2014

Communication Patterns Request – Response  send purchase order – confirm acceptation Component A Component B request response Summer 2014

Communication Patterns Subscribe (Publish) - Notify  e.g. subscribe to newsletter – notify about new article in the newsletter Component A Component B subscribe (publish) notify … Summer 2014

Web Service  software component which can be programmatically accessed by its clients  clients send and receive messages to and from web service  messages are processed programmatically  comprises interface and implementation  interface strictly separated from implementation  interface is exposed to the clients  implementation is hidden Summer 2014

Web Service Interface  defines set of operations provided by web service  each operation has well defined name and types of input and output messages  binds operations to standardized message transfer formats  e.g. HTTP requests and responses, SOAP over HTTP  binds messages to messaging formats  e.g. XML, JSON, RDF, AtomPub, RSS, etc.  defines service location Summer 2014

Message  (human readable) document  unstructured (simple text, HTML, PDF, etc.) e.g. web page, weblog,...  semi-structured document (XML) e.g. purchase order, public contract notification, etc.  data structure (XML, JSON, AtomPub, RSS)  e.g. personal profile from social network service, newspapers feed, etc.  set of parameters  e.g. request for the weather information on given GPS location at given time  media  image, video, etc. Summer 2014

Web Service Web Service Architecture Summer 2014 op1 op2 op3 Client A Implementation Client B

Technologies/Standards for Web Services Summer 2014 W3C (+OASIS) REST Open Data Protocol Google Data Protocol Semantic Web Services Linked Data Services Message Format Message Transfer Message Type Definition Interface Definition Other technical documents

Technologies/Standards for Web Services Enterprise Summer 2014 W3C (+OASIS) REST Open Data Protocol Google Data Protocol Semantic Web Services Linked Data Services Message Format XML Message Transfer SOAP, HTTP Message Type Definition XSD Interface Definition WSDL Other technical documents WS-*

Technologies/Standards for Web Services Web Summer 2014 W3C (+OASIS) REST Open Data Protocol Google Data Protocol Semantic Web Services Linked Data Services Message Format XML, JSON or application specific XML, AtomPub, JSON AtomPub, JSON Message Transfer HTTP Message Type Definition XSD, JSON schema CSDL Interface Definition WADL Other technical documents

Technologies/Standards for Web Services Research Summer 2014 W3C (+OASIS) REST Open Data Protocol Google Data Protocol Semantic Web Services Linked Data Services Message Format XML, RDF Message Transfer SOAP, HTTP Message Type Definition RDF Schema, OWL Interface Definition SAWSDL, WSML Other technical documents

Technologies/Standards for Web Services Web/Research Summer 2014 W3C (+OASIS) REST Open Data Protocol Google Data Protocol Semantic Web Services Linked Data Services Message Format SPARQL, RDF Message Transfer HTTP, SPARQL Graph Store Protocol, SPARQL Protocol Message Type Definition RDF Schema, OWL Interface Definition SPARQL Service Description Other technical documents SPARQL Query Results

W3C-style Web Services Web Service Interface Agent System Agent Message SOAP WSDL Summer 2014

SOAP Basics  Simple Object Access Protocol   protocol for inter-application communication  applications = peers in decentralized and distributed environment Summer 2014

SOAP Message Syntax  SOAP message is XML document  envelopes exchanged data  SOAP message is transferred over network via transfer protocol  HTTP, FTP, SMTP, …  or even TCP Summer 2014

SOAP Message Syntax <env:Envelope xmlns:env=" Summer 2014 soap_example_paypal.xml

WSDL Foundations  Web Services Description Language  language for describing web service interfaces in machine-readable notation  XML format  current version: 2.0   currently mostly supported version: 1.1  Summer 2014

WSDL Foundations Summer 2014 Implementation Interface Port 1 Location: URL_1 Transport: SOAP/HTTP Port 1 Location: URL_1 Transport: SOAP/HTTP Port 2 Location: URL_2 Transport: SOAP/JMS Port 2 Location: URL_2 Transport: SOAP/JMS Client A Client B Port 3 Location: URL_3 Transport: XML/HTTP Port 3 Location: URL_3 Transport: XML/HTTP Client C

WSDL Document Structure Summer PublicContractWS.wsdl