Web service: Difference between revisions

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== Definition ==
== Definition ==


According to [http://en.wikipedia.org/wiki/Web_service Wikipedia] (retrieved 20:22, 23 April 2007 (MEST)), the W3C defines a Web service as a software system designed to support interoperable Machine to Machine interaction over a network. Web services are frequently just Web APIs that can be accessed over a network, such as the Internet, and executed on a remote system hosting the requested services.
According to [http://en.wikipedia.org/wiki/Web_service Wikipedia] (retrieved 20:35, 23 April 2007 (MEST)), the W3C defines a Web service as a software system designed to support interoperable Machine to Machine interaction over a network. Web services are frequently just Web APIs that can be accessed over a network, such as the Internet, and executed on a remote system hosting the requested services.


A Web service is any piece of software that makes itself available over the Internet and uses a standardized XML messaging system. ([http://webservices.xml.com/pub/a/ws/2002/02/12/webservicefaqs.html Top Ten FAQs for Web Services], retrieved 20:22, 23 April 2007 (MEST)
A Web service is any piece of software that makes itself available over the Internet and uses a standardized XML messaging system. ([http://webservices.xml.com/pub/a/ws/2002/02/12/webservicefaqs.html Top Ten FAQs for Web Services], retrieved 20:35, 23 April 2007 (MEST)


== Web services stack components ==
== Web services frameworks ==
 
=== Web services stack components ===


The Web service protocol stack is an evolving set of protocols used to define, discover, and implement Web services. The core protocol stack consists of four layers:
The Web service protocol stack is an evolving set of protocols used to define, discover, and implement Web services. The core protocol stack consists of four layers:
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* '''Service discovery''': E.g. Universal Discovery, Description, Integration (UDDI) - a service to publish available services
* '''Service discovery''': E.g. Universal Discovery, Description, Integration (UDDI) - a service to publish available services


; List of standards (in ascending order)
; List of standards (basic and important ones first)


* Common Internet protocols (e.g. TCP/IP, HTTP)
* Common Internet protocols (e.g. TCP/IP, HTTP)
* [[XML]], the formalism
* [[XML]], the formalism
* [http://www.w3.org/TR/SOAP/ Simple Object Access Protocol (SOAP) 1.1], W3C note. "SOAP is a lightweight protocol for exchange of information in a decentralized, distributed environment. It is an XML based protocol that consists of three parts: an envelope that defines a framework for describing what is in a message and how to process it, a set of encoding rules for expressing instances of application-defined datatypes, and a convention for representing remote procedure calls and responses". Note DKS: This is generally the lowest Service Layer (just on top of HTTP) and tells how to describe messages that are sent or received.
* [http://www.w3.org/TR/SOAP/ Simple Object Access Protocol (SOAP) 1.1], W3C note. "SOAP is a lightweight protocol for exchange of information in a decentralized, distributed environment. It is an XML based protocol that consists of three parts: an envelope that defines a framework for describing what is in a message and how to process it, a set of encoding rules for expressing instances of application-defined datatypes, and a convention for representing remote procedure calls and responses". Note DKS: This is generally the lowest Service Layer (just on top of HTTP) and tells how to describe messages that are sent or received.
* [http://www.w3.org/TR/wsdl/ Web Services Description Language (WSDL)], W3C Note. WSDL is an XML format for describing network services as a set of endpoints (methodes/calls) operating on messages containing either document-oriented or procedure-oriented information.
* [http://www.w3.org/TR/wsdl Web Services Description Language (WSDL)], W3C Note. WSDL is an XML format for describing network services as a set of endpoints (methodes/calls) operating on messages containing either document-oriented or procedure-oriented information.
* [http://www.uddi.org/ UDDI (Universal Description, Discovery and Integration) ] enables organizations to (I) discover each other by a directory of service providers and services, and (II) find out what services are available
* [http://www.uddi.org/ UDDI (Universal Description, Discovery and Integration) ] enables organizations to (I) discover each other by a directory of service providers and services, and (II) find out what services are available
* [http://www-106.ibm.com/developerworks/library/ws-ref4/index.html WSFL (Web Services Flow Language)] article from IBM. WSFL is an XML language (compatible with SOAP, UDDI & WSDL) for the description of the overall process logic of Web Services. See also [Business processes and workflow in the Web services world  and ][http://xml.coverpages.org/wsfl.html Cover Pages about his]
* [http://www-106.ibm.com/developerworks/library/ws-ref4/index.html WSFL - Web Services Flow Language] (article from IBM). WSFL is an XML language (compatible with SOAP, UDDI & WSDL) for the description of the overall process logic of Web Services. See also [http://xml.coverpages.org/wsfl.html Cover Pages] about his.
* Apache references to the [http://ws.apache.org/wsif/references.html WSIF (Web Services Invocation Framework) ]. This is a description of APIs to invoke Web Services described in WSDL. (Can, but does not need to be built on top of SOAP).
* Apache references to the [http://ws.apache.org/wsif/references.html WSIF (Web Services Invocation Framework) ]. This is a description of APIs to invoke Web Services described in WSDL. (Can, but does not need to be built on top of SOAP).
* [http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-axis-wsil/java/docs/wsinspection.html WSIL (Web Services Inspection Language)] WS-Inspection specification provides an XML format for assisting in the inspection of a site for available services and a set of rules for how inspection related information should be made available for consumption (IBM/Microsoft)
* [http://www-128.ibm.com/developerworks/library/specification/ws-wsilspec/ WSIL (Web Services Inspection Language)]. The WS-Inspection specification provides an XML format for assisting in the inspection of a site for available services and a set of rules for how inspection related information should be made available for consumption (IBM/Microsoft)
* [http://www.oasis-open.org/committees/wsrp/ WSRP (Web Services for Remote Portals)]: XML and Web services standard that will allow the plug-n-play of visual, user-facing Web services with portals or other intermediary Web applications. (Oasis led initiative)
* [http://www.oasis-open.org/committees/wsrp/ WSRP (Web Services for Remote Portals)]: XML and Web services standard that will allow the plug-n-play of visual, user-facing Web services with portals or other intermediary Web applications. (Oasis led initiative)
* [http://ebxml.org/ ebXML Messaging Service Specification ] (OASIS led) provides a secure method for exchanging electronic business transactions using the Internet. (This is a rather big project with several sub-specifications). See D. Mertz [http://www-106.ibm.com/developerworks/xml/library/x-ebxml/ "Understanding ebXML"] at developerworks/IBM.
* [http://ebxml.org/ ebXML Messaging Service Specification] (OASIS led) provides a secure method for exchanging electronic business transactions using the Internet. (This is a rather big project with several sub-specifications). See D. Mertz [http://www-106.ibm.com/developerworks/xml/library/x-ebxml/ "Understanding ebXML"] at developerworks/IBM.
* There is more .... some still in the specification pipeline
 
=== Web service frameworks ===


... There are lots of WS-standards down the pipeline ...
See: [http://en.wikipedia.org/wiki/List_of_Web_service_Frameworks List of Web service Frameworks] (Wikipedia)


== Webservices in education ==
== Web services in education ==


=== Rehak et al. model ===
=== Webservices in education, Rehak et al. model ===


{{quotation | The era of monolithic Learning Technology Systems is over. Rather than building large, closed systems, the current focus is on flexible architectures that provide interoperability of components and learning content, and that rely on open standards for information exchange and component integration. The Learning Systems Architecture Lab has developed the concept of a Learning Services Architecture and the Learning Services Stack as a framework for developing the next generation of learning technology systems. We're in the process of developing learning services using Web services and Web services technologies.}} (http://lsal.org/, retrieved 20:22, 23 April 2007 (MEST)).
{{quotation | The era of monolithic Learning Technology Systems is over. Rather than building large, closed systems, the current focus is on flexible architectures that provide interoperability of components and learning content, and that rely on open standards for information exchange and component integration. The Learning Systems Architecture Lab has developed the concept of a Learning Services Architecture and the Learning Services Stack as a framework for developing the next generation of learning technology systems. We're in the process of developing learning services using Web services and Web services technologies.}} (http://lsal.org/, retrieved 20:35, 23 April 2007 (MEST)).


The stack according to Rehal et al. has three fundamental layers:
The stack according to Rehal et al. has three fundamental layers:
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* Infrastructure: Lower level protocols (e.g. HTTP), transport (e.g. SOAP), discovery (e.g. UDDI), description (WSDL), workflow (WSFL)
* Infrastructure: Lower level protocols (e.g. HTTP), transport (e.g. SOAP), discovery (e.g. UDDI), description (WSDL), workflow (WSFL)


It may look like this:
An implemented architecture may look like this:


( HTTP -> ) SOAP -> UDDI -> WSDL | WSIF ? -> WSFL ? -> -> ebXML? | WSIL ? -> WSRP? -> Portal
( HTTP -> ) SOAP -> UDDI -> WSDL | WSIF ? -> WSFL ? -> -> ebXML? | WSIL ? -> WSRP? -> Portal
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[[User:Daniel K. Schneider|Daniel K. Schneider]] wonders how one could conceptualize integration of various social software (e.g. blogs, wikis, reference management, etc.) as webservices into a portal.
[[User:Daniel K. Schneider|Daniel K. Schneider]] wonders how one could conceptualize integration of various social software (e.g. blogs, wikis, reference management, etc.) as webservices into a portal.


== Players ==
== Organizations ==
 
There are many players in this field, just a few examples:


: There are many players in this field
; Global players


* The [http://www.w3.org/2002/ws/Activity Web Services Activity Statement and ]the [http://www.w3.org/2002/ws/ Web Services Activity] give an overview of the W3's idea on application to application communication (web services). See also: [http://www.w3.org/TR/ws-desc-reqs/ Web Services Description Requirements] and [http://www.w3.org/TR/ws-gloss/ the Web Services Glossary].
* The [http://www.w3.org/2002/ws/Activity Web Services Activity Statement and ]the [http://www.w3.org/2002/ws/ Web Services Activity] give an overview of the W3's idea on application to application communication (web services). See also: [http://www.w3.org/TR/ws-desc-reqs/ Web Services Description Requirements] and [http://www.w3.org/TR/ws-gloss/ the Web Services Glossary].
* [http://www.oasis-open.org/ Oasis] is an other organization working on xml-based e-business standards
* [http://www.oasis-open.org/ Oasis] is an other organization working on xml-based e-business standards
* [http://msdn.microsoft.com/webservices/understanding/whatsnext/default.aspx "What's Next: The Future of Web Services"] from Microsoft
 
* Most major companies show an interest, e.g. see [http://msdn2.microsoft.com/en-us/library/aa480155.aspx The Future of ASP.NET Web Services in the Context of the Windows Communication Foundation] (Microsoft)
 
* [http://www.xmethods.com/ XMethods] has a long list of publicly available web services , implementations, tutorials, etc.
* [http://www.xmethods.com/ XMethods] has a long list of publicly available web services , implementations, tutorials, etc.


; In educational technology
; In educational technology
* [http://lsal.org/ Learning Systems Architecture Lab]
* [http://lsal.org/ Learning Systems Architecture Lab]



Revision as of 20:35, 23 April 2007

Draft

Definition

According to Wikipedia (retrieved 20:35, 23 April 2007 (MEST)), the W3C defines a Web service as a software system designed to support interoperable Machine to Machine interaction over a network. Web services are frequently just Web APIs that can be accessed over a network, such as the Internet, and executed on a remote system hosting the requested services.

A Web service is any piece of software that makes itself available over the Internet and uses a standardized XML messaging system. (Top Ten FAQs for Web Services, retrieved 20:35, 23 April 2007 (MEST)

Web services frameworks

Web services stack components

The Web service protocol stack is an evolving set of protocols used to define, discover, and implement Web services. The core protocol stack consists of four layers:

  • Transport: E.g. HTTP, SMTP, FTP, and newer protocols.
  • XML messaging: E.g. Simple Object Access Protocol (SOAP) or XML-RPC. These define messages containing a service request and a response. SOAP and XML-RPC etc. are independent of any particular transport and implementation technology.
  • Service description: E.g. Web Services Description Language (WSDL) - describes what a service does in a machine readable way
  • Service discovery: E.g. Universal Discovery, Description, Integration (UDDI) - a service to publish available services
List of standards (basic and important ones first)
  • Common Internet protocols (e.g. TCP/IP, HTTP)
  • XML, the formalism
  • Simple Object Access Protocol (SOAP) 1.1, W3C note. "SOAP is a lightweight protocol for exchange of information in a decentralized, distributed environment. It is an XML based protocol that consists of three parts: an envelope that defines a framework for describing what is in a message and how to process it, a set of encoding rules for expressing instances of application-defined datatypes, and a convention for representing remote procedure calls and responses". Note DKS: This is generally the lowest Service Layer (just on top of HTTP) and tells how to describe messages that are sent or received.
  • Web Services Description Language (WSDL), W3C Note. WSDL is an XML format for describing network services as a set of endpoints (methodes/calls) operating on messages containing either document-oriented or procedure-oriented information.
  • UDDI (Universal Description, Discovery and Integration) enables organizations to (I) discover each other by a directory of service providers and services, and (II) find out what services are available
  • WSFL - Web Services Flow Language (article from IBM). WSFL is an XML language (compatible with SOAP, UDDI & WSDL) for the description of the overall process logic of Web Services. See also Cover Pages about his.
  • Apache references to the WSIF (Web Services Invocation Framework) . This is a description of APIs to invoke Web Services described in WSDL. (Can, but does not need to be built on top of SOAP).
  • WSIL (Web Services Inspection Language). The WS-Inspection specification provides an XML format for assisting in the inspection of a site for available services and a set of rules for how inspection related information should be made available for consumption (IBM/Microsoft)
  • WSRP (Web Services for Remote Portals): XML and Web services standard that will allow the plug-n-play of visual, user-facing Web services with portals or other intermediary Web applications. (Oasis led initiative)
  • ebXML Messaging Service Specification (OASIS led) provides a secure method for exchanging electronic business transactions using the Internet. (This is a rather big project with several sub-specifications). See D. Mertz "Understanding ebXML" at developerworks/IBM.
  • There is more .... some still in the specification pipeline

Web service frameworks

See: List of Web service Frameworks (Wikipedia)

Web services in education

Webservices in education, Rehak et al. model

“The era of monolithic Learning Technology Systems is over. Rather than building large, closed systems, the current focus is on flexible architectures that provide interoperability of components and learning content, and that rely on open standards for information exchange and component integration. The Learning Systems Architecture Lab has developed the concept of a Learning Services Architecture and the Learning Services Stack as a framework for developing the next generation of learning technology systems. We're in the process of developing learning services using Web services and Web services technologies.” (http://lsal.org/, retrieved 20:35, 23 April 2007 (MEST)).

The stack according to Rehal et al. has three fundamental layers:

  • User agents: Authoring, delivery, management
  • Learning services: At its heart there are knowledge and content mangement, user profile and tracking, sequencing. On top of this are various tools for interaction, presentation, lectureing, assessment, simulation, collaboration, etc.
  • Infrastructure: Lower level protocols (e.g. HTTP), transport (e.g. SOAP), discovery (e.g. UDDI), description (WSDL), workflow (WSFL)

An implemented architecture may look like this:

( HTTP -> ) SOAP -> UDDI -> WSDL | WSIF ? -> WSFL ? -> -> ebXML? | WSIL ? -> WSRP? -> Portal

A social software model ?

Daniel K. Schneider wonders how one could conceptualize integration of various social software (e.g. blogs, wikis, reference management, etc.) as webservices into a portal.

Organizations

There are many players in this field, just a few examples:

Global players
  • Oasis is an other organization working on xml-based e-business standards
  • XMethods has a long list of publicly available web services , implementations, tutorials, etc.
In educational technology

Links

Standards and recommendations
For education
Other


References