J2EE Interview Questions and Answers 21

What is Web server ?
Software that provides services to access the Internet, an intranet, or an extranet. A Web server hosts Web sites, provides support for HTTP and other protocols, and executes server-side programs (such as CGI scripts or servlets) that perform certain functions. In the J2EE architecture, a Web server provides services to a Web container. For example, a Web container typically relies on a Web server to provide HTTP message handling. The J2EE architecture assumes that a Web container is hosted by a Web server from the same vendor, so it does not specify the contract between these two entities. A Web server can host one or more Web containers.

What is Web server provider ?
A vendor that supplies a Web server.

What is Web service ?
An application that exists in a distributed environment, such as the Internet. A Web service accepts a request, performs its function based on the request, and returns a response. The request and the response can be part of the same operation, or they can occur separately, in which case the consumer does not need to wait for a response. Both the request and the response usually take the form of XML, a portable data-interchange format, and are delivered over a wire protocol, such as HTTP.

What is well-formed ?
An XML document that is syntactically correct. It does not have any angle brackets that are not part of tags, all tags have an ending tag or are themselves self-ending, and all tags are fully nested. Knowing that a document is well formed makes it possible to process it. However, a well-formed document may not be valid. To determine that, you need a validating parser and a DTD.

What is Xalan ?
An interpreting version of XSLT.

What is XHTML ?
An XML look-alike for HTML defined by one of several XHTML DTDs. To use XHTML for everything would of course defeat the purpose of XML, because the idea of XML is to identify information content, and not just to tell how to display it. You can reference it in a DTD, which allows you to say, for example, that the text in an element can contain <> and <> tags rather than being limited to plain text.

What is XLink ?
The part of the XLL specification that is concerned with specifying links between documents.

What is XLL ?
The XML Link Language specification, consisting of XLink and XPointer.

What is XML ?
Extensible Markup Language. A markup language that allows you to define the tags (markup) needed to identify the content, data, and text in XML documents. It differs from HTML, the markup language most often used to present information on the Internet. HTML has fixed tags that deal mainly with style or presentation. An XML document must undergo a transformation into a language with style tags under the control of a style sheet before it can be presented by a browser or other presentation mechanism. Two types of style sheets used with XML are CSS and XSL. Typically, XML is transformed into HTML for presentation. Although tags can be defined as needed in the generation of an XML document, a document type definition (DTD) can be used to define the elements allowed in a particular type of document. A document can be compared by using the rules in the DTD to determine its validity and to locate particular elements in the document. A Web services application's J2EE deployment descriptors are expressed in XML with schemas defining allowed elements. Programs for processing XML documents use SAX or DOM APIs.

What is XML registry ?
An infrastructure that enables the building, deployment, and discovery of Web services. It is a neutral third party that facilitates dynamic and loosely coupled business-to-business (B2B) interactions.

What is XML Schema ?
The W3C specification for defining the structure, content, and semantics of XML documents.

What is XPath ?
An addressing mechanism for identifying the parts of an XML document.

What is XPointer ?
The part of the XLL specification that is concerned with identifying sections of documents so that they can be referenced in links or included in other documents.

What is XSL-FO ?
A subcomponent of XSL used for describing font sizes, page layouts, and how information flows from one page to another.

What is component (JavaServer Faces technology) ?
A user interface control that outputs data to a client or allows a user to input data to a JavaServer Faces application.