Web Services Tutorial

Introduction to Web Services

Web Services became a hot new technology in 2002.

Microsoft first coined the term "Web Services" in June of 2000 when it introduced Web Services as a major component of its .NET technology aimed at revolutionizing distributed computing. I see it as a new vision for using the Internet in the development, engineering and use of software.

Web services standards are emerging. Several technologies combine to make up "Web Services". The main standard is Extensible Markup Language, XML.

XML was developed by the World Wide Web Consortium (W3.org) It is a meta-language for describing data and creating additional markup languages. XML tags form individual pieces of data. An XML document is text-based and is made up of XML tags. XML is portable and has been rapidly adopted throughout the industry, thus making it the preferred choice for enabling cross-platform data communication in Web Services.

XML provided the basis for many core Web services standards:

• SOAP = Simple Object Access Protocol
  
• WSDL = Web Services Description Language
  
• UDDI = Univsersal Description, Discovery and Integration specificiation

The term "XML vocabulary" means an XML-based markup language developed for a specific purpose or a specific industry. Example: Math-ML for including math equations on Web pages.

• SOAP is an XML vocabulary standard to enable programs on separate computers to interact across any network. SOAP is a simple markup language for describing messages between applications. SOAP provides a way for developers to integrate applications and business processes across the Web or an intranet, by providing the platform and programming language independence needed to create the business integration of Web Services.
  
• WSDL is an XML vocabulary standard created just for Web Services. It allows developers to describe Web Services and their capabilities, in a standard manner. WSDL helps to expose the Web Services of various businesses for public access--a desirable exposure helping to create more business
  
• UDDI is just a framework that defines XML-based registries in which businesses can upload information about themselves and the services they offer. An XML-based registry contains names of organizations, services provided, and descriptions about the capabilities of the services provided. XML registries based on the UDDI specification provide common areas through which businesses can advertise themselves and their Web Services
  
• .NET Web Services - The .NET platform of Microsoft is one of the most complete environments for building, deploying and accessing Web Services. The .NET development environment has support for multiple programming languages and tools for reusing code. Using Visual Basic.NET is one way of implementing Web Services.
  
• Java Web Services - The Java2 platform has good support for the Web Services technologies. Java is portable. Java has support for XML and standard networking technologies. This makes Java ideal for building Internet applications, including applications based on Web services.
  
• DIME - Direct Internet Message Encapsulation. DIME is a lightweight binary message format (not a protocol) used for moving data into the SOAP message packets. On the DIME page, I linked to an article also comparing DIME and MIME message formats.

Web services are software applications (programs)that use XML to exchange data (information) with other applications on other computers by using Internet protocols. Web services operate over any network (the Internet or a private intranet) to achieve specific tasks, called methods or functions, that other applications can invoke and use. Requests can be sent and responses received between two differing applications on two separate computers belonging to separate business enterprises or small businesses. Small businesses to global enterprises will benefit enormously from Web Services. Privacy issues will need to be addressed.

Java and Web Services

Java Technology and Web Services (java.sun.com) Java Web Services Tutorials (java.sun.com) Java Web Services Tutorial (java.sun.com) Java and Web Services Primer (onjava.com)

WSDL (Web Services Descriptive Language)

WSDL/SOAP Web Services Search Engine (salcentral.com) Web Services Description Language (WSDL) (W3.ORG)

Web APIs

Google Web APIs (beta)

W3C Web Services Activity

Web Services Activity at W3C

Web Services Platforms

Web Services platforms and dev. (webservices.org)

XML Schema

Understanding XML Schema (Microsoft.com)

XML Namespaces

Understanding XML Namespaces (Microsoft.com) Namespaces in XML (W3.ORG)

XML Web Services

XML Web Services (sys-con.com) XML Web Services Basics (Microsoft.com) XML in IETF Protocols