Home > Articles

This chapter is from the book

This chapter is from the book

The Node Interface

The primary purpose of the Node interface is to define the base functionality for all node types. It defines the set of attributes, methods, and constants that must be available on any node within the DOM hierarchy. This makes it possible to traverse a DOM hierarchy in a uniform fashion strictly using the Node interface without having to downcast to more specific interface types. The more specific interfaces are available when necessary to access features that only make sense for a given node type.

One of the tradeoffs of a fairly general base interface like Node is that some of its operations do not apply to all of the node types. The DOM working group made a conscious decision to not factor the Node interface to the smallest common subset. Rather, the DOM working group tried to balance the benefits of type safety with the convenience and uniformity of a single model-wide interface. This compromising of type-safety means that some errors may not be detected until runtime rather than at compile-time.

For generality, the DOM does not rely on the use of runtime type identification (RTTI) in the target programming language. Rather, the nodeType attribute is used to test a node for compatibility with a derived interface (for example, Element, Document). The Node interface also defines a group of symbolic constants that correspond to the different node types.

interface Node {
  readonly attribute unsigned short nodeType;
  const unsigned short ELEMENT_NODE                  = 1;
  const unsigned short ATTRIBUTE_NODE                = 2;
  const unsigned short TEXT_NODE                     = 3;
  const unsigned short CDATA_SECTION_NODE            = 4;
  const unsigned short ENTITY_REFERENCE_NODE         = 5;
  const unsigned short ENTITY_NODE                   = 6;
  const unsigned short PROCESSING_INSTRUCTION_NODE   = 7;
  const unsigned short COMMENT_NODE                  = 8;
  const unsigned short DOCUMENT_NODE                 = 9;
  const unsigned short DOCUMENT_TYPE_NODE            = 10;
  const unsigned short DOCUMENT_FRAGMENT_NODE        = 11;
  const unsigned short NOTATION_NODE                 = 12;
   :              :                 :
};

The nodeType attribute acts as a poor man's RTTI mehanism. For example, the Java function

boolean isElement(org.w3c.dom.Node n) {
  return n.getNodeType() == org.w3c.dom.Node.ELEMENT_NODE;
}

is functionally equivalent to

boolean isElement(org.w3c.dom.Node n) {
  return n instanceof org.w3c.dom.Element;
}

The advantage of the latter is that it is integrated into the type system of the language. The advantage of that it works consistently even in typeless languages (such as ECMAScript) where RTTI is impractical. Additionally, the former approach provides implementations with more flexibility with respect to factoring which concrete classes implement which interfaces, and for that reason one should always use the former style of test to ensure portability.

Many node types support names. These names are exposed via the Node.nodeName property, and for node types such as ProcessingInstruction or Entity, this is sufficient. However, because both element and attribute names can be affiliated with a namespace URI, the Node interface also contains attributes for retrieving namespace information.

interface node {
  readonly attribute DOMString        nodeName;
  readonly attribute DOMString        namespaceURI;
           attribute DOMString        prefix;
  readonly attribute DOMString        localName;
    :           :       :                  :
}

The Node.nodeName attribute always returns the QName based on the qualified name of the element or attribute information item. More importantly, the Node interface makes the [namespace URI] and [local name] Infoset properties available via the Node.namespaceURI and Node.localName attributes. For convenience, the actual prefix used in the QName is available via the Node.prefix attribute. Since only element and attribute names may be affiliated with a namespace, these namespace-specific attributes return null for all other node types.

There are several node types that don't have an obvious name (for example, Document, Text, or Comment nodes). The DOM specification defines fixed values that must be used for the Node.nodeName of these node types. For example, the Node.nodeName attribute for Document nodes always evaluates to "#document". For text nodes the attribute must evaluate to "#text", for comment nodes "#comment," and so on.

A node's value is accessed generically via the Node.nodeValue attribute. Certain node types can have values, whereas others cannot. For example, Element nodes only have children and their nodeValue is always null. In contrast, for Text nodes, the nodeValue attribute evaluates to the character data content of the text node. Table 2.4 lists the nodeName/nodeValue values for each of the possible node types. Figure 2.6 shows the nodeName and nodeValue values for each node in the DOM hierarchy shown earlier in this section.

Figure 2.6Figure 2.6. Node types, names, and values


Both nodeType and nodeName are read-only properties. Because of this, there is no way to change a node's name once it has been created. While this does simplify DOM implementations, there are still situations where this type of functionality is necessary (such as with an XML editor). If you need to change a node's name on the fly, you're required to create a completely new node and copy the node's value as appropriate.

Table 2.4. DOM Node Types, Names and Values

NodeType # nodeName nodeValue
Element 1 Tag name Null
Attr 2 Name of attribute value of attribute
Text 3 #text Content of the text node
CDATASection 4 #cdata-section Content of the CDATA section
EntityReference 5 Name of entity referenced Null
Entity 6 Entity name Null
ProcessingInstruction 7 Target Entire content excluding the target
Comment 8 #comment Content of the comment
Document 9 #document Null
DocumentType 10 Document type name Null
DocumentFragment 11 #document-fragment Null
Notation 12 Notation name Null

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020