J2EE Interviews Question page4

1. What is data ?
   The contents of an element in an XML stream, generally used when the element does not contain any subelements. When it does, the term content is generally used. When the only text in an XML structure is contained in simple elements and when elements that have subelements have little or no data mixed in, then that structure is often thought of as XML data, as opposed to an XML document.
    
2. What is DDP ?
   Document-driven programming. The use of XML to define applications.
      
3. What is declaration ?
   The very first thing in an XML document, which declares it as XML. The minimal declaration is . The declaration is part of the document prolog.
     
4. What is declarative security ?
   Mechanisms used in an application that are expressed in a declarative syntax in a deployment descriptor.
      
5. What is delegation ?
   An act whereby one principal authorizes another principal to use its identity or privileges with some restrictions.
    
6. What is deployer ?
   A person who installs J2EE modules and applications into an operational environment.
    
7. What is deployment ?
   The process whereby software is installed into an operational environment.
     
8. What is deployment descriptor ?
   An XML file provided with each module and J2EE application that describes how they should be deployed. The deployment descriptor directs a deployment tool to deploy a module or application with specific container options and describes specific configuration requirements that a deployer must resolve.
      
9. What is destination ?
   A JMS administered object that encapsulates the identity of a JMS queue or topic. See point-to-point messaging system, publish/subscribe messaging system.
      
10. What is digest authentication ?
    An authentication mechanism in which a Web application authenticates itself to a Web server by sending the server a message digest along with its HTTP request message. The digest is computed by employing a one-way hash algorithm to a concatenation of the HTTP request message and the client's password. The digest is typically much smaller than the HTTP request and doesn't contain the password.
       
11. What is distributed application ?
    An application made up of distinct components running in separate runtime environments, usually on different platforms connected via a network. Typical distributed applications are two-tier (client-server), three-tier (client-middleware-server), and multitier (client-multiple middleware-multiple servers).
       
12. What is document ?
    In general, an XML structure in which one or more elements contains text intermixed with subelements.
      
13. What is Document Object Model ?
    An API for accessing and manipulating XML documents as tree structures. DOM provides platform-neutral, language-neutral interfaces that enables programs and scripts to dynamically access and modify content and structure in XML documents.
       
14. What is document root ?
    The top-level directory of a WAR. The document root is where JSP pages, client-side classes and archives, and static Web resources are stored.
         
15. What is DTD ?
    Document type definition. An optional part of the XML document prolog, as specified by the XML standard. The DTD specifies constraints on the valid tags and tag sequences that can be in the document. The DTD has a number of shortcomings, however, and this has led to various schema proposals. For example, the DTD entry says that the XML element called username contains parsed character data-that is, text alone, with no other structural elements under it. The DTD includes both the local subset, defined in the current file, and the external subset, which consists of the definitions contained in external DTD files that are referenced in the local subset using a parameter entity.
       
16. What is durable subscription ?
    In a JMS publish/subscribe messaging system, a subscription that continues to exist whether or not there is a current active subscriber object. If there is no active subscriber, the JMS provider retains the subscription's messages until they are received by the subscription or until they expire.