Chapter 8: Database Application Development For Studying

Java servlet

A Java program that is stored on the server and contains the business and database logic for a Java-based application.

fat client

A client PC that is responsible for processing presentation logic, extensive application and business rules logic, and many DBMS functions.

three-tier architecture

A client/server configuration that includes three layers: a client layer and two server layers. Although the nature of the server layers differs, a common configuration contains an application server and a database server.

Service-oriented architecture (SOA)

A collection of services that communicate with each other in some manner, usually by passing data or coordinating a business activity.

database server

A computer that is responsible for database storage, access, and processing in a client/server environment. Some people also use this term to describe a two-tier client/server application.

Extensible Stylesheet Language Transformation (XSLT)

A language used to transform complex XML documents and also used to create HTML pages from XML documents.

client/server systems

A networked computing model that distributes processes between clients and servers, which supply the requested services. In a database system, the database generally resides on a server that processes the DBMS. The clients may process the application systems or request services from another server that holds the application programs.

Web services

A set of emerging standards that define protocols for automatic communication between software programs over the Web. Web services are XML based and usually run in the background to establish transparent communication among computers.

Universal Description, Discovery, and Integration (UDDI)

A technical specification for creating a distributed registry of Web services and businesses that are open to communicating through Web services.

Extensible Markup Language (XML)

A text-based scripting language used to describe data structures hierarchically, using HTML-like tags.

Reduced risk

Again, the ability to implement small modules of code quickly and combine them with code purchased from vendors limits the risk assumed with a large-scale development project.

XQuery

An XML transformation language that allows applications to query both relational databases and XML data.

Simple Object Access Protocol (SOAP)

An XML-based communication protocol used for sending messages between applications via the Internet.

Web Services Description Language (WSDL)

An XML-based grammar or language used to describe a Webservice and specify a public interface for that service.

Open database connectivity (ODBC)

An application programming interface that provides a common language for application programs to access and process SQL databases independent of the particular DBMS that is accessed.

thin client

An application where the client (PC) accessing the application primarily provides the user interfaces and some application processing, usually with no or limited local data storage.

Technological flexibility

It is easier to change DBMS engines, although triggers and stored procedures will need to be rewritten, with a three-tier architecture. The middle tier can even be moved to a different platform. Simplified presentation services make it easier to implement various desired interfaces such as Web browsers or kiosks.

XML Schema Definition (XSD)

Language used for defining XML databases that has been recommended by the W3C.

Web browser

Microsoft's Internet Explorer, Mozilla's Firefox, Apple's Safari, Google's Chrome, and Opera are examples.

Improved customer service

Multiple interfaces on different clients can access the same business processes.

Better match of systems to business needs

New modules can be built to support specific business needs rather than building more general, complete applications.

XPath

One of a set of XML technologies that supports XQuery development. XPath expressions are used to locate data in XML documents.

application program interface (API)

Sets of routines that an application program uses to direct the performance of procedures by the computer's operating system.

middleware

Software that allows an application to interoperate with other software without requiring the user to understand and code the low-level operations necessary to achieve interoperability.

Web server

The Web server provides the basic functionality needed to receive and respond to requests from browser clients. These requests use HTTP or HTTPS as a protocol.The most common Web server software in use is Apache, but you are also likely to encounter Microsoft's Internet Information Server (IIS) Web server. Apache can run on different operating systems, such as Windows, UNIX, or Linux. IIS is primarily intended to run on Windows servers.

Competitive advantage

The ability to react to business changes quickly by changing small modules of code rather than entire applications can be used to gain a competitive advantage.

application partitioning

The process of assigning portions of application code to client or server partitions after it is written to achieve better performance and interoperability (ability of a component to function on different platforms).

database server

This server hosts the storage logic for the application and hosts the DBMS. You have read about many of them, including Oracle, Microsoft SQL Server, Informix, Sybase, DB2, Microsoft Access, and MySQL. The DBMS may reside either on a separate machine or on the same machine as the Web server.

application server

This software provides the building blocks for creating dynamic Web sites and Web-based applications. Examples include the .NET Framework from Microsoft; Java Platform, Enterprise Edition (Java EE); and ColdFusion. Also, while technically not considered an application server platform, software that enables you to write applications in languages such as PHP, Python, and Perl also belong to this category.

Scalability

Three-tier architectures are more scalable than two-tier architectures. For example, the middle tier can be used to reduce the load on a database server by using a transaction processing (TP) monitor to reduce the number of connections to a server, and additional application servers can be added to distribute application processing. A TP monitor is a program that controls data transfer between clients and servers to provide a consistent environment for online transaction processing (OLTP).

Lower long-term costs

Use of off-the-shelf components or services in the middle tier can reduce costs, as can substitution of modules within an application rather than an entire application.