Database Connectivity and Web Technologies: Comprehensive Exam Study Guide, Exams of Information Technology

Download Database Connectivity and Web Technologies: Comprehensive Exam Study Guide and more Exams Information Technology in PDF only on Docsity!

?

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

Chapter 15

Database Connectivity and Web Technologies

Discussion Focus

Begin by making sure that the students are familiar with the basic vocabulary. The following two questions are a good place to start. (You may want to examine the contents of Appendix F, “Client/Server Systems.”) There is some irony in the Web development arena … the microcomputer was supposed to liberate the end user from the mainframe computer’s “fat server, thin client” environment. However, the Web has, in effect, brought us back to the old mainframe structure in which most processing is done on the server side, while the client is the source and recipient of data/information requests and returns.

1. Describe the following: TCP/IP, Router, HTML, HTTP, and URL.

Transmission Control Protocol/Internet Protocol (TCP/IP) is the basic network protocol that determines the rules used to create and route “packets” of data between computers in the same or different networks. Each computer connected to the Internet has a unique TCP/IP address. The TCP/IP address is divided in two parts used to identify the network and the computer (or host)

Router is a special hardware/software equipment that connects multiple and diverse networks. The router is in charge of delivering packets of data from a local network to a remote network. Routers are the traffic cops of the Internet, monitoring all traffic and moving data from one network to another.

HTML stands for Hyper Text Markup Language is the standard document-formatting language for Web pages. HTML allows documents to be presented in a Web browser in a standard manner.

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

Chapter 15

Database Connectivity and Web Technologies

2. Describe the client/server model for application processing.

Client/server is a term used to describe a computing model for the development of computerized systems. This model is based on the distribution of functions between two types of independent and autonomous processes: servers and clients. A client is any process that requests specific services from server processes. A server is a process that provides requested services for clients. Client and server processes can reside in the same computer or in different computers connected by a network.

The client/server model makes possible the division of the application processing tasks into three main components: presentation logic, processing logic, and data storage.

 The presentation logic formats and presents data in output devices, such as the screen, and manages the end-user input. The application uses presentation logic to manage the graphical user interface at the client end.  The processing logic component refers to the application code that performs data validation, error checking, and business logic processing. The processing logic component represents the business rules. For example, the processing logic “knows” that a sales transaction generates an invoice record, an inventory update, and a customer’s account receivable update. The processing logic performs several functions, including enforcement of business rules, managing information flows within the business, and mapping the real-world business transactions to the actual computer database.  The data storage component deals with the actual data storage and retrieval from permanent storage devices. For example, the data manipulation logic is used to access the data in a database and to enforce data integrity.

Although there is no methodology to dictate the precise distribution of the logic components among

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

clients and servers, the client/server architectural principles of process distribution (autonomy, resource maximization, scalability, and interoperability) and hardware and software independence facilitate the creation of distributed applications running across multiple servers. Those applications provide services that communicate with each other in order to carry out specific function, therefore the term multi-tier applications. So, where should the services be placed? With the probable exception of the presentation logic, which should go on the client side, each of the remaining service components may be placed on the server side, thus becoming a service for many clients.

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

Chapter 15

Database Connectivity and Web Technologies

2. What are ODBC, DAO, and RDO? How are they related?

Open Database Connectivity (ODBC) is Microsoft’s implementation of a superset of the SQL Access Group Call Level Interface ( CLI ) standard for database access. ODBC allows any Windows application to access relational data sources using SQL via a standard application programming interface (API). ODBC was the first widely adopted database middleware standard and enjoyed rapid adoption in Windows applications. As programming languages evolved, ODBC did not provide significant functionality beyond the ability to execute SQL to manipulate relational style data. Therefore, programmers needed a better way to access data. To answer this need, Microsoft developed two other data access interfaces:

 Data Access Objects (DAO) is an object oriented API used to access MS Access, MS FoxPro and dBase databases (using the Jet data engine) from Visual Basic programs. DAO provided an optimized interface that exposed the functionality of the Jet data engine (on which MS Access database if based on) to programmers. The DAO interface can also be used to access other relational style data sources.  Remote Data Objects (RDO) is a higher-level object oriented application interface used to access remote database servers. RDO uses the lower-level DAO and ODBC for direct access to databases. RDO was optimized to deal with server based databases, such as MS SQL Server, Oracle, DB2, and so on.

3. What is the difference between DAO and RDO?

DAO is uses the MS Jet engine to access file-based relational databases such as MS Access, MS FoxPro and Dbase. In contrast, RDO allows to access relational database servers such as SQL Server, DB2, and Oracle. RDO uses DAO and ODBC to access remote database server data.

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

Chapter 15

Database Connectivity and Web Technologies

To define a data source you must create a data source name (DSN) for the data source. To create a DSN you have to provide:

 An ODBC driver. You must identify the driver to use to connect to the data source. The ODBC driver is normally provided by the database vendor; although h Microsoft provides several drives to connect to the most common databases. For example, if you are using an Oracle DBMS you will select the Oracle ODBC drive provided by Oracle or, if desired, the Microsoft-provided ODBC Driver for Oracle.  A DSN name. This is a unique name by which the data source will be known to ODBC and therefore, to the applications. ODBC offers two types of data sources: User and System. User data sources are only available to the user. System data sources are available to all users, including operating system services.  ODBC driver parameters. Most ODBC drivers require some specific parameters in order to establish a connection to the database. For example, if you are using a MS Access database you must point to the location of the MS Access (.mdb) file and, if necessary, provide the user name and password. If you are using a DBMS server, you must provide the server name, the database name, and the user name and password used to connect to the database. Figure 15.3 shows the ODBC screens required to create a System ODBC data source for an Oracle DBMS. Note that some ODBC drivers use the native driver provided by the DBMS vendor.

6. What is OLE-DB used for, and how does it differ from ODBC?

Although ODBC, DAO, and RDO were widely used, they did not provide support for non-relational data. To answer the need for non-relational data access and to simplify data connectivity, Microsoft developed Object Linking and Embedding for Database ( OLE-DB ). Based on Microsoft’s Component Object Model (COM), OLE-DB is a database middleware that was developed to add object-oriented functionality for access to relational and non-relational data. OLE-DB was the first piece of Microsoft’s strategy to provide a unified object-oriented framework for the development of next-generation applications.

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

7. Explain the OLE-DB model based on its two types of objects.

OLE-DB is composed of a series of COM objects that provide low-level database connectivity for applications. Because OLE-DB is based on the COM object model, the objects contain data and methods (also known as the interface.) The OLE-DB model is better understood when you divide its functionality in two types of objects:

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

Figure 15.5 OLE-DB ARCHITECTURE

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

OLE-DB Consumers

DATABASE EMAIL^ SQL-Server (^) DATABASE

OLE-DB Provider for ODBC

OLE-DB Provider for SQL Server

OLE-DB Provider for Exchange

OLE-DB Provider for Oracle

Chapter 15

Database Connectivity and Web Technologies

OLE-DB Services Providers Email Processing

Indexing Processing

Cursor Processing

Query Processing

9. What is ADO.NET, and what two new features make it important for application development?

ADO.NET is the data access component of Microsoft’s .NET application development framework. Microsoft’s .NET framework is a component-based platform for the development of distributed,

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

Chapter 15

Database Connectivity and Web Technologies

A DataSet is a disconnected memory-resident representation of the database. That is, the DataSet contains tables, columns, rows, relationships, and constraints. Once the data are read from a data provider, the data are placed on a memory-resident DataSet. The DataSet is then disconnected from the data provider. The data consumer application interacts with the data in the DataSet object to make changes (inserts, updates and deletes) in the dataset. Once the processing is done, the DataSet data are synchronized with the data source and the changes are made permanent.

A DataSet is in fact a simple database with tables, rows and constraints. Even, more important, the DataSet doesn’t require keeping a permanent connection to the data source. The DataAdapter uses the SelectCommand to populate the DataSet from a data source. However, once the DataSet is populated, it is completely independent of the data source – that’s why it’s called “disconnected.”

11. What are Web server interfaces used for? Give some examples.

Web server interfaces are used to extend the functionality of the web server to provide more services. If a Web server is to successfully communicate with other external programs to provide a service, both programs must use a standard way to exchange messages and respond to requests. A Web server interface defines how a Web server communicates with external programs. Currently there are two well-defined Web server interfaces:

 Common Gateway Interface (CGI)  Application Programming Interface (API)

Web server interfaces can be used to extend the services of a web server and provide support for access to external databases, fax services, telephony services, directory services, etc.

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

12. Search the Internet for Web application servers. Choose one and prepare a short presentation for your class.

You are encouraged to use any web search engine to list multiple vendors. Examples of such vendors are: Oracle Application Server, IBM WebSphere, Sun Java, Microsoft, JBOSS, etc. We encourage the student to visit the web pages of the products and compare features of at least two products. Some of the many other Web application servers, as of this writing, include Oracle Application Server by Oracle Corp., WebLogic by BEA Systems, NetDynamics by Sun Microsystems, NetObjects’ Fusion, Microsoft’s Visual Studio.NET, and WebObjects by Apple.

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

ability is limited by the lack of processing ability and the lack of a working storage area to hold variables used by all pages in a Web site.

The browser does not have computational abilities beyond formatting output text and accepting form field inputs. Even when the browser accepts form field data, there is no way to perform immediate data entry validation. Therefore, to perform such crucial processing in the client, the Web defers to other Web programming languages such as Java, JavaScript, and VBScript.

and Web Technologies

Comprehensive Exam Study Guide

Latest Updated 2024/

Chapter 15

Database Connectivity and Web Technologies

14. What is a Web application server, and how does it work from a database perspective?

Web application server extends the functionality of a web server and provides features such as:

 An integrated development environment with session management and support for persistent application variables.  Security and authentication of users through user IDs and passwords.  Computational languages to represent and store business logic in the application server.  Automatic generation of HTML pages integrated with Java, JavaScript, VBScript, ASP, and so on.  Performance and fault-tolerant features.  Database access with transaction management capabilities.  Access to multiple services, such as file transfers (FTP), database connectivity, electronic mail, and directory services.

The web application server interfaces with the database connectivity standards to access databases using any of the supported API. So, a web page will be processed by the web application server, the application server will connect to the database using the ADO, OLE-DB or ODBC standard (or any other standard supported by the application server).

15. What are scripts, and what is their function? (Think in terms of database applications development!)

A script is a series of instructions executed in interpreter mode. The script is a plain text file that is not compiled like COBOL, C++, or Java. Scripts are normally used in web application development environments. For instance, ColdFusion scripts contain the code that is required to connect, query, and update a database from a Web front end.