Database connectivity and web technologies
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This chapter discusses database connectivity and web technologies. It covers various database connectivity interfaces like ODBC, OLE-DB and ADO.NET that allow applications to connect to databases. It also discusses web-to-database middleware, client-side extensions, web application servers and XML - which has become important for exchanging structured data over the web. The chapter aims to explain how databases can be integrated with web applications and internet.
Database connectivity and web technologies
- 1. Database Systems: Design, Implementation, and Management Eighth Edition Chapter 14 Database Connectivity and Web Technologies
- 2. Database Systems, 8th Edition 2 Objectives • In this chapter, you will learn: – Different database connectivity technologies – How Web-to-database middleware is used to integrate databases with the Internet – Web browser plug-ins and extensions – Services provided by Web application servers – What Extensible Markup Language (XML) is and why it is important for Web database development
- 3. Database Systems, 8th Edition 3 Database Connectivity • Mechanisms by which application programs connect and communicate with data sources – Also known as database middleware • Data repository: – Also known as a data source – Represents the data management application • Used to store data generated by an application program • ODBC, OLE-DB, ADO.NET: the backbone of MS Universal Data Access (UDA) architecture
- 4. Database Systems, 8th Edition 4 Native SQL Connectivity • Connection interface provided by database vendors – Unique to each vendor • Example: Oracle RDBMS – Must install and configure Oracle’s SQL*Net interface in client computer • Interfaces optimized for particular vendor’s DBMS – Maintenance is a burden for the programmer
- 6. Database Systems, 8th Edition 6 ODBC, DAO, and RDO • Open Database Connectivity (ODBC) – Microsoft’s implementation of a superset of SQL Access Group Call Level Interface (CLI) – Widely supported database connectivity interface – Any Windows application can access relational data sources – Uses SQL via standard application programming interface (API)
- 7. Database Systems, 8th Edition 7 ODBC, DAO, and RDO (continued) • Data Access Objects (DAO) – Object-oriented API • Accesses MS Access, MS FoxPro, and dBase databases from Visual Basic programs – Provided an optimized interface that exposed functionality of Jet data engine to programmers – DAO interface can also be used to access other relational style data sources
- 8. Database Systems, 8th Edition 8 ODBC, DAO, and RDO (continued) • Remote Data Objects (RDO) – Higher-level object-oriented application interface used to access remote database servers – Uses lower-level DAO and ODBC for direct access to databases – Optimized to deal with server-based databases, such as MS SQL Server, Oracle, and DB2 • Implemented as shared code dynamically linked to Windows via dynamic-link libraries
- 10. Database Systems, 8th Edition 10 ODBC, DAO, and RDO (continued) • Basic ODBC architecture has three main components: – High-level ODBC API through which application programs access ODBC functionality – Driver manager that is in charge of managing all database connections – ODBC driver that communicates directly to DBMS
- 13. Database Systems, 8th Edition 13 OLE-DB • Object Linking and Embedding for Database • Database middleware that adds object-oriented functionality for access to data • Series of COM objects provides low-level database connectivity for applications • Functionality divided into two types of objects: – Consumers – Providers
- 14. Database Systems, 8th Edition 14 OLE-DB (continued) • OLE-DB did not provide support for scripting languages • ActiveX Data Objects (ADO) provides high-level application-oriented interface to interact with OLE-DB, DAO, and RDO • ADO provides unified interface to access data from any programming language that uses the underlying OLE-DB objects
- 18. Database Systems, 8th Edition 18 ADO.NET • Data access component of Microsoft’s .NET application development framework • Two new features for development of distributed applications: – DataSet is disconnected memory-resident representation of database – DataSet is internally stored in XML format • Data in DataSet made persistent as XML documents
- 20. Database Systems, 8th Edition 20 ADO.NET (continued) • Specific objects manipulate data in data source – Connection – Command – DataReader – DataAdapter – DataSet – DataTable
- 21. Database Systems, 8th Edition 21 Java Database Connectivity (JDBC) • Java is an object-oriented programming language – Runs on top of Web browser software • Advantages of JDBC: – Company can leverage existing technology and personnel training – Allows direct access to database server or access via database middleware – Provides a way to connect to databases through an ODBC driver
- 23. Database Systems, 8th Edition 23 Internet Databases • Web database connectivity allows new innovative services that: – Permit rapid response by bringing new services and products to market quickly – Increase customer satisfaction through creation of Web-based support services – Yield fast and effective information dissemination through universal access
- 25. Database Systems, 8th Edition 25 Web-to-Database Middleware: Server-Side Extensions • Web server is the main hub through which Internet services are accessed • Dynamic Web pages are at the heart of current generation Web sites • Server-side extension: a program that interacts directly with the Web server – Also known as Web-to-database middleware • Middleware must be well integrated
- 27. Database Systems, 8th Edition 27 Web Server Interfaces • Two well-defined Web server interfaces: – Common Gateway Interface (CGI) – Application Programming Interface (API) • Disadvantage of CGI scripts: – Loading external script decreases system performance – Language and method used to create script also decrease performance • API is more efficient than CGI – API is treated as part of Web server program
- 28. Database Systems, 8th Edition 28 The Web Browser • Software that lets users navigate the Web • Located in client computer • Interprets HTML code received from Web server • Presents different page components in standard way • Web is a stateless system: Web server does not know the status of any clients
- 29. Database Systems, 8th Edition 29 Client-Side Extensions • Add functionality to Web browser • Three general types: – Plug-ins – Java and JavaScript – ActiveX and VBScript
- 31. Database Systems, 8th Edition 31 Client-Side Extensions (continued) • Plug-in: an external application automatically invoked by the browser when needed • Java and JavaScript: embedded in Web page – Downloaded with the Web page and activated by an event • ActiveX and VBScript: embedded in Web page – Downloaded with page and activated by event – Oriented to Windows applications
- 32. Database Systems, 8th Edition 32 Web Application Servers • Middleware application that expands the functionality of Web servers – Links them to a wide range of services • Some uses of Web application servers: – Connect to and query database from Web page – Create dynamic Web search pages – Enforce referential integrity • Some features of Web application servers: – Security and user authentication – Access to multiple services
- 33. Database Systems, 8th Edition 33 Extensible Markup Language (XML) • Companies use Internet to create new systems that integrate their data – Increase efficiency and reduce costs • Electronic commerce enables organizations to market to millions of users • Most e-commerce transactions take place between businesses • HTML Web pages display in the browser – Tags describe how something looks on the page
- 34. Database Systems, 8th Edition 34 Extensible Markup Language (XML) (continued) • Extensible Markup Language (XML): – Metalanguage to represent and manipulate data elements – Facilitates exchange of structured documents over the Web – Allows definition of new tags • Case sensitive • Must be well-formed and properly nested • Comments indicated with <- and -> • XML and xml prefixes reserved for XML tags only
- 36. Database Systems, 8th Edition 36 Document Type Definitions (DTD) and XML Schemas • Document Type Definition (DTD) – File with .dtd extension that describes elements – Provides composition of database’s logical model – Defines the syntax rules or valid tags for each type of XML document • Companies engaging in e-commerce transaction must develop and share DTDs • DTD referenced from inside XML document
- 40. Database Systems, 8th Edition 40 Document Type Definitions (DTD) and XML Schemas (continued) • XML schema – Advanced data definition language – Describes the structure of XML data documents • Advantage of XML schema: – More closely maps to database terminology and features • XML schema definition (XSD) file uses syntax similar to XML document
- 42. Database Systems, 8th Edition 42 XML Presentation • XML separates data structure from presentation and processing • Extensible Style Language (XSL) displays XML data – Defines the rules by which XML data are formatted and displayed – Two parts: • Extensible Style Language Transformations (XSLT) • XSL style sheets
- 46. Database Systems, 8th Edition 46 XML Applications • B2B exchanges • Legacy systems integration • Web page development • Database support • Database meta-dictionaries • XML databases • XML services
- 47. Database Systems, 8th Edition 47 Summary • Database connectivity: – Ways in which programs connect and communicate with data repositories • Database connectivity software known as database middleware • Database repository also known as data source – Represents data management application used to store data generated by the program • Microsoft interfaces are dominant players – ODBC, OLE-DB, ADO.NET
- 48. Database Systems, 8th Edition 48 Summary (continued) • Microsoft’s Universal Data Access (UDA) architecture – Collection of technologies to access any type of data source using common interface • Native database connectivity: interface provided by database vendor – ODBC is Microsoft's implementation of SQL Access Group Call Level Interface • Allows any Windows application to access relational data sources using SQL
- 49. Database Systems, 8th Edition 49 Summary (continued) • OLE-DB adds object-oriented functionality for access to data • ActiveX Data Objects provide interface with OLE-DB, DAO, and RDO • ADO.NET is data access component of Microsoft .NET framework • Java Database Connectivity (JDBC) interfaces with Java applications with data sources
- 50. Database Systems, 8th Edition 50 Summary (continued) • Database access through the Web uses middleware • On client side of Web browser, use plug-ins, Java and JavaScript, ActiveX, and VBScript • On server side, middleware expands functionality of Web servers – Links them to wide range of services • XML provides semantics to share structured documents across the Web – Produces description and representation of data