(5) Cesare Pautasso

• Computer Science at Politecnico di Milano, Italy [http://www.polimi.it]
• Ph.D. at ETH Zürich [http://www.ethz.ch/index_EN] (2004)
• Post-Doc at ETH Zürich [http://www.iks.inf.ethz.ch/]
  • Software: JOpera: Process Support for more than Web services [http://www.jopera.org]
• Researcher at IBM Zurich Research Lab [http://www.zurich.ibm.com] (2007)
• Assistant Professor at the Faculty of Informatics [http://www.inf.unisi.ch/] (since September 2007)
• Representations: Web [http://www.pautasso.info]; twitter [http://twitter.com/pautasso]

(6) Erik Wilde

• Computer Science at Technical University of Berlin (TUB) [http://www.tu-berlin.de/eng/] (1988-1991)
• Ph.D. at ETH Zürich [http://www.ethz.ch/index_EN] (1992-1997)
• Post-Doc at ICSI, Berkeley [http://www.icsi.berkeley.edu/] (1997/98)
  • book on Technical Foundations of the World Wide Web [http://dret.net/netdret/publications#wil98]
• Various activities back in Switzerland (1998-2006)
  • teaching at ETH Zürich [http://www.ethz.ch/index_EN] and FHNW [http://www.fhnw.ch/]
  • working as independent consultant
  • research focus on Web architecture and XML technologies
• Professor at the School of Information [http://ischool.berkeley.edu/] (since Fall 2006)
  • technical director of the Information and Service Design (ISD) program [http://isd.ischool.berkeley.edu/]
• Representations: Web [http://dret.net/netdret/]; blog [http://dret.typepad.com/]; twitter [http://twitter.com/dret]

(8) SOA and REST

• Service-Oriented Architecture (SOA)
  • Service: How to define a service
  • Architecture: How to apply SOA in the design/implementation process
• Representational State Transfer (REST)
  • Representation: Resources (not functions) are the primary abstraction
  • State: Trying to push state to the edges (client or resource)
  • Transfer: Focus on the exchange of representations (uniform interface)

(9) What is SOA?

• What is Service-Oriented Architecture?

1. Alignment of business objectives and IT
   • can be implemented with any architecture, technology, products
   • SOA explained like this is more for business-oriented people
   • this definition is not within the realm of technical terms
2. Technical architecture (interfaces are exposing services)
   • focus on IT and the idea of services as the main abstraction
   • still little guidance on how exactly a service is identified and exposed
   • this definition is in the right space, but often highly underspecified
3. SOA as the high-level explanation for WS-* Web Services [http://en.wikipedia.org/wiki/Web_service]
   • this is how SOA as a buzzword started (SOA as architecture for Web Services)
   • most SOA products are focusing on this (overly narrow) view of Web Services
   • this definition has too many implicit decisions built-in

(10) From SOA to REST

• Starting from the second definition of SOA
  • a technical architecture for structuring/implementing a service landscape
  • many crucial aspects are undefined/underspecified and need clarification
• Services can come in a variety of flavors
  • IT services often are guided by middleware/RPC views of the world
  • Web architecture does not expose middleware/RPC views of services
  • Web services (not the WS-* kind) are exposed as resources and links
  • aligning Services and the Web means redefining services
• From SOA to REST is about SOA and Web architecture
  • SOA with the goal of designing services for the Web
  • the most important part is to get the service part right
  • RESTful SOA means properly designing/implementing Web services

(11) What are Web Services?

Definition: A Web service is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically 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.

Web Services Architecture, W3C Working Group Note, February 11, 2004 [http://www.w3.org/TR/ws-arch/#whatis]

(12) Resource Oriented Architecture (ROA)

• More concrete guidelines for Web-based implementations
• Taking services and turning them into RESTful Web services
  • Query string parameters are appropriate if they are inputs to a Resource which is an algorithm
  • Prefer pragmatic uses of putting data into URI, instead of using HTTP Headers
  • RPC-style APIs are avoided in favor of Resources and protocols
  • A representation of a resource should have many links to the other Resources in the application, so that a client can discover state transitions
  • URI templates provide the technology behind specifying families of URI to clients
• Not really an architecture, more a set of engineering principles

(13) Web Oriented Architecture (WOA)

• WOA: Putting the Web back in Web Services
• Unclear distinction from ROA (maybe no HTTP extensions?)
• Questionable conceptual landscape
  • REST is the protocol most preferred since it's a natural extension of HTTP for the purposes of sharing self-describing information and state. [http://hinchcliffe.org/archive/2006/08/05/8489.aspx]

(14) Syndication Oriented Architecture (SynOA)

• Syndication can be regarded as a pattern for information dissemination
• Atom [REST in Practice; Atom (1)] and Atom Publishing Protocol (AtomPub) [REST in Practice; Atom Publishing Protocol (AtomPub) (1)] are existing Web standards for syndication
• SynOA is a pattern for building a SOA architecture
  • services are defined around collections
  • interactions are centered around reading and updating feeds

(15) Event Oriented Architecture (EOA)

• Riding the SOA wave for event-oriented systems
• Now trademarked by eClient [http://www.eclient.com/]