 | Level: Intermediate Nicholas Chase (ibmquestions@nicholaschase.com), Freelance writer, Backstop Media
19 Sep 2006
Updated 08 Mar 2007 The power of the ultimate mashup is the intelligence you'll build into it by using semantic Web techniques, specifically the Web Ontology Language (OWL). But before you can tackle OWL, you want to be familiar with its base language, the Resource Description Framework (RDF) and RDF Schema Language (RDFs). This tutorial gives you a good background in both RDF and RDFs so you'll be ready to build ontologies for your Web services, and also able to make use of RDF's power with other projects as well.
In this tutorial
The purpose of this tutorial series is to create a mashup application so smart that users can literally add and remove services at will, and the system will know what to do with them. The series progresses as follows: -
Part 1: You learn about the concept of mashups and how they work. You then build a simple version of one and also discover serious performance problems involved in making potentially dozens of Web calls.
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Part 2: You solve some of that problem by using DB2's new pureXML capabilities to build an XML cache, which saves the results of previous requests and also enables you to retrieve specific information.
- Parts 3, 4, and 5: Ultimately, you will need to use ontologies, or vocabularies that define concepts and their relationships, so in Part 3 you start that process by learning about RDF and RDFs, two key ingredients in the Web Ontology Language (OWL), which the author discusses in Part 4. In Part 5, you take the ontologies created in Part 4 and use them to enable users to change out information sources.
- Part 6: At this point, you have a working application and the framework in place so that the system can use semantic reasoning to understand the services at its disposal. In this part, you give the user control, enabling him or her to pick and choose the data that is used for a custom mashup.
Over the course of this tutorial, you will learn how to set up a database server and prepare it to receive the data that you collect as well as how to write the queries needed to specifically handle XML data in an XML column. This tutorial uses the Java language, but the concepts are the same for any programming language or operating system.
Objectives - What RDF is and what it's used for
- The relationships between RDF, RDF Schema, OWL, and the semantic Web
- The basics of RDF
- Dealing with resources, properties, and other RDF structures
- Representing RDF in XML -- and without it
- Creating classes and instances using RDF Schema
Prerequisites
This tutorial is for developers who are interested in learning about the Resource Description Framework (RDF), as well as for those interested in learning more about the semantic Web and semantic Web services in general and the building of ontologies in particular. You will learn how to build and interpret RDF information in both its familiar XML form and its non-XML shorthand form.
This tutorial does not involve any programming, but assumes that you are familiar with the general concepts behind XML.
System requirements
You will need JavaScript enabled in your browser. Although you do need various software components to run the mashup itself -- see Part 2 for the list of requirements for the current state of the application -- this tutorial is mostly conceptual, so you will need no special software to follow along. To follow along with the code in Parts 1, 2, 4, 5, and 6 of the series, you will to have the following software installed and tested.
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IBM® DB2® 9 (formerly known as "Viper"): This relational database also includes significant XML capabilities, which you'll need for this tutorial. You can download a trial version of DB2 9: DB2 Enterprise 9 or DB2 Express-C 9, a no-charge version of DB2 Express 9 data server.
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Apache Tomcat or other servlet engine: This tutorial assumes that you will build Web applications using servlets, so you'll need a servlet engine such as Apache Tomcat. If you choose to build the application using another environment, just make sure you have the appropriate software on hand. Download apache-tomcat-5.5.17.zip and install into a directory with no spaces in the directory name.
- Java: Apache Tomcat 5.5, with which this tutorial is built, requires Java 1.5 or higher. Download the J2SE SDK.
- To make things easier, you can use an IDE such as Eclipse or IBM Rational™ Web Developer for your development. You can download Eclipse at Eclipse.org, download a trial version of Rational Web Developer, or use your favorite development environment. You won't be doing anything fancy as far as compilation and deployment are concerned.
Duration
2 hours
Formats html, pdf
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