HTML5

The user agent should allow the user to manually trigger elements that have an activation behavior, for instance using keyboard or voice input, or through mouse clicks. When the user triggers an element with a defined activation behavior in a manner other than clicking it, the default action of the interaction event must be to run synthetic click activation steps on the element.

When a user agent is to run synthetic click activation steps on an element, the user agent must run pre-click activation steps on the element, then fire a click event at the element. The default action of this click event must be to run post-click activation steps on the element. If the event is canceled, the user agent must run canceled activation steps on the element instead.

Given an element target, the nearest activatable element is the element returned by the following algorithm:

1. If target has a defined activation behavior, then return target and abort these steps.

2. If target has a parent element, then set target to that parent element and return to the first step.

3. Otherwise, there is no nearest activatable element.

When a pointing device is clicked, the user agent must run these steps:

1. Let e be the nearest activatable element of the element designated by the user, if any.

2. If there is an element e, run pre-click activation steps on it.

3. Dispatch the required click event.

   If there is an element e, then the default action of the click event must be to run post-click activation steps on element e.

   If there is an element e but the event is canceled, the user agent must run canceled activation steps on element e.

The above doesn't happen for arbitrary synthetic events dispatched by author script. However, the click() method can be used to make it happen programmatically.

When a user agent is to run pre-click activation steps on an element, it must run the pre-click activation steps defined for that element, if any.

When a user agent is to run post-click activation steps on an element, the user agent must fire a simple event named DOMActivate that is cancelable at that element. The default action of this event must be to run final activation steps on that element. If the event is canceled, the user agent must run canceled activation steps on the element instead.

When a user agent is to run canceled activation steps on an element, it must run the canceled activation steps defined for that element, if any.

When a user agent is to run final activation steps on an element, it must run the activation behavior defined for that element. Activation behaviors can refer to the click and DOMActivate events that were fired by the steps above leading up to this point.

<p>Hello <a href="world.html"><em>wonderful</em> world</a>!</p>

<section>
  <h1>Example of paragraphs</h1>
  This is the <em>first</em> paragraph in this example.
  <p>This is the second.</p>
  <!-- This is not a paragraph. -->
</section>

<section>
  <ins><h1>Example of paragraphs</h1>
  This is the <em>first</em> paragraph in</ins> this example<del>.
  <p>This is the second.</p></del>
  <!-- This is not a paragraph. -->
</section>

Let view be a view of the DOM that replaces all a, ins, del, and map elements in the document with their contents. Then, in view, for each run of sibling phrasing content nodes uninterrupted by other types of content, in an element that accepts content other than phrasing content as well as phrasing content, let first be the first node of the run, and let last be the last node of the run. For each such run that consists of at least one node that is neither embedded content nor inter-element whitespace, a paragraph exists in the original DOM from immediately before first to immediately after last. (Paragraphs can thus span across a, ins, del, and map elements.)

Conformance checkers may warn authors of cases where they have paragraphs that overlap each other (this can happen with object, video, audio, and canvas elements, and indirectly through elements in other namespaces that allow HTML to be further embedded therein, like svg or math).

<aside>
 Welcome!
 <a href="about.html">
  This is home of...
  <h1>The Falcons!</h1>
  The Lockheed Martin multirole jet fighter aircraft!
 </a>
 This page discusses the F-16 Fighting Falcon's innermost secrets.
</aside>

<aside>
 <p>Welcome! <a href="about.html">This is home of...</a></p>
 <h1><a href="about.html">The Falcons!</a></h1>
 <p><a href="about.html">The Lockheed Martin multirole jet
 fighter aircraft!</a> This page discusses the F-16 Fighting
 Falcon's innermost secrets.</p>
</aside>

<section>
 <h1>My Cats</h1>
 You can play with my cat simulator.
 <object data="cats.sim">
  To see the cat simulator, use one of the following links:
  <ul>
   <li><a href="cats.sim">Download simulator file</a>
   <li><a href="http://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a>
  </ul>
  Alternatively, upgrade to the Mellblom Browser.
 </object>
 I'm quite proud of it.
</section>

User agents are required to implement ARIA semantics on all HTML elements, as defined in the ARIA specifications. The implicit ARIA semantics defined below must be recognised by implementations. [ARIAIMPL]

User agents may apply different defaults than those described in this section in order to expose the semantics of HTML elements in a manner more fine-grained than possible with the above definitions.

Conformance checkers are encouraged to phrase errors such that authors are encouraged to use more appropriate elements rather than remove accessibility annotations. For example, if an a element is marked as having the button role, a conformance checker could say "Either a button element or an input element is required when using the button role" rather than "The button role cannot be used with a elements".

3.4 Interactions with XPath and XSLT

Status: Last call for comments

Implementations of XPath 1.0 that operate on HTML documents parsed or created in the manners described in this specification (e.g. as part of the document.evaluate() API) must act as if the following edit was applied to the XPath 1.0 specification.

First, remove this paragraph:

A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. This is the same way expansion is done for element type names in start and end-tags except that the default namespace declared with xmlns is not used: if the QName does not have a prefix, then the namespace URI is null (this is the same way attribute names are expanded). It is an error if the QName has a prefix for which there is no namespace declaration in the expression context.

Then, insert in its place the following:

A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. If the QName has a prefix, then there must be a namespace declaration for this prefix in the expression context, and the corresponding namespace URI is the one that is associated with this prefix. It is an error if the QName has a prefix for which there is no namespace declaration in the expression context.

If the QName has no prefix and the principal node type of the axis is element, then the default element namespace is used. Otherwise if the QName has no prefix, the namespace URI is null. The default element namespace is a member of the context for the XPath expression. The value of the default element namespace when executing an XPath expression through the DOM3 XPath API is determined in the following way:

1. If the context node is from an HTML DOM, the default element namespace is "http://www.w3.org/1999/xhtml".
2. Otherwise, the default element namespace URI is null.

This is equivalent to adding the default element namespace feature of XPath 2.0 to XPath 1.0, and using the HTML namespace as the default element namespace for HTML documents. It is motivated by the desire to have implementations be compatible with legacy HTML content while still supporting the changes that this specification introduces to HTML regarding the namespace used for HTML elements, and by the desire to use XPath 1.0 rather than XPath 2.0.

This change is a willful violation of the XPath 1.0 specification, motivated by desire to have implementations be compatible with legacy content while still supporting the changes that this specification introduces to HTML regarding which namespace is used for HTML elements. [XPATH10]

---

XSLT 1.0 processors outputting to a DOM when the output method is "html" (either explicitly or via the defaulting rule in XSLT 1.0) are affected as follows:

If the transformation program outputs an element in no namespace, the processor must, prior to constructing the corresponding DOM element node, change the namespace of the element to the HTML namespace, ASCII-lowercase the element's local name, and ASCII-lowercase the names of any non-namespaced attributes on the element.

This requirement is a willful violation of the XSLT 1.0 specification, required because this specification changes the namespaces and case-sensitivity rules of HTML in a manner that would otherwise be incompatible with DOM-based XSLT transformations. (Processors that serialize the output are unaffected.) [XSLT10]

When called with two or fewer arguments, the method must act as follows:

1. If the Document object is not flagged as an HTML document, throw an INVALID_STATE_ERR exception and abort these steps.

2. Let type be the value of the first argument, if there is one, or "text/html" otherwise.

3. Let replace be true if there is a second argument and it is an ASCII case-insensitive match for the value "replace", and false otherwise.

4. If the document has an active parser that isn't a script-created parser, and the insertion point associated with that parser's input stream is not undefined (that is, it does point to somewhere in the input stream), then the method does nothing. Abort these steps and return the Document object on which the method was invoked.

   This basically causes document.open() to be ignored when it's called in an inline script found during the parsing of data sent over the network, while still letting it have an effect when called asynchronously or on a document that is itself being spoon-fed using these APIs.

5. Release the storage mutex.

6. Prompt to unload the Document object. If the user refused to allow the document to be unloaded, then these steps must be aborted.

7. Unload the Document object, with the recycle parameter set to true.

8. If the document has an active parser, then abort that parser.

9. Unregister all event listeners registered on the Document node and its descendants.

10. Remove any tasks associated with the Document in any task source.

11. Remove all child nodes of the document, without firing any mutation events.

12. Replace the Document's singleton objects with new instances of those objects. (This includes in particular the Window, Location, History, ApplicationCache, UndoManager, Navigator, and Selection objects, the various BarProp objects, the two Storage objects, and the various HTMLCollection objects. It also includes all the Web IDL prototypes in the JavaScript binding, including the Document object's prototype.)

13. Change the document's character encoding to UTF-16.

14. Change the document's address to the entry script's document's address.

15. Create a new HTML parser and associate it with the document. This is a script-created parser (meaning that it can be closed by the document.open() and document.close() methods, and that the tokenizer will wait for an explicit call to document.close() before emitting an end-of-file token). The encoding confidence is irrelevant.

16. If the type string contains a U+003B SEMICOLON character (;), remove the first such character and all characters from it up to the end of the string.

    Strip all leading and trailing space characters from type.

    If type is not now an ASCII case-insensitive match for the string "text/html", then act as if the tokenizer had emitted a start tag token with the tag name "pre", then switch the HTML parser's tokenizer to the PLAINTEXT state.

17. Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.

    This doesn't necessarily have to affect the user agent's user interface.

18. Remove any tasks queued by the history traversal task source.

19. Remove any earlier entries that share the same Document.

20. If replace is false, then add a new entry, just before the last entry, and associate with the new entry the text that was parsed by the previous parser associated with the Document object, as well as the state of the document at the start of these steps. (This allows the user to step backwards in the session history to see the page before it was blown away by the document.open() call.)

21. Finally, set the insertion point to point at just before the end of the input stream (which at this point will be empty).

22. Return the Document on which the method was invoked.

When called with three or more arguments, the open() method on the HTMLDocument object must call the open() method on the Window object of the HTMLDocument object, with the same arguments as the original call to the open() method, and return whatever that method returned. If the HTMLDocument object has no Window object, then the method must raise an INVALID_ACCESS_ERR exception.

The close() method must run the following steps:

1. If the Document object is not flagged as an HTML document, throw an INVALID_STATE_ERR exception and abort these steps.

2. If there is no script-created parser associated with the document, then abort these steps.

3. Insert an explicit "EOF" character at the end of the parser's input stream.

4. If there is a pending parsing-blocking script, then abort these steps.

5. Run the tokenizer, processing resulting tokens as they are emitted, and stopping when the tokenizer reaches the explicit "EOF" character or spins the event loop.

The document.write(...) method must act as follows:

1. If the method was invoked on an XML document, throw an INVALID_ACCESS_ERR exception and abort these steps.

2. If the insertion point is undefined, the open() method must be called (with no arguments) on the document object. If the user refused to allow the document to be unloaded, then these steps must be aborted. Otherwise, the insertion point will point at just before the end of the (empty) input stream.

3. The string consisting of the concatenation of all the arguments to the method must be inserted into the input stream just before the insertion point.

4. If there is a pending parsing-blocking script, then the method must now return without further processing of the input stream.

5. Otherwise, the tokenizer must process the characters that were inserted, one at a time, processing resulting tokens as they are emitted, and stopping when the tokenizer reaches the insertion point or when the processing of the tokenizer is aborted by the tree construction stage (this can happen if a script end tag token is emitted by the tokenizer).

   If the document.write() method was called from script executing inline (i.e. executing because the parser parsed a set of script tags), then this is a reentrant invocation of the parser.

6. Finally, the method must return.

The document.writeln(...) method, when invoked, must act as if the document.write() method had been invoked with the same argument(s), plus an extra argument consisting of a string containing a single line feed character (U+000A).

On getting, if the node's document is an HTML document, then the attribute must return the result of running the HTML fragment serialization algorithm on the node; otherwise, the node's document is an XML document, and the attribute must return the result of running the XML fragment serialization algorithm on the node instead (this might raise an exception instead of returning a string).

On setting, the following steps must be run:

1. If the node's document is an HTML document: Invoke the HTML fragment parsing algorithm.

   If the node's document is an XML document: Invoke the XML fragment parsing algorithm.

   In either case, the algorithm must be invoked with the string being assigned into the innerHTML attribute as the input. If the node is an Element node, then, in addition, that element must be passed as the context element.

   If this raises an exception, then abort these steps.

   Otherwise, let new children be the nodes returned.

2. If the attribute is being set on a Document node, and that document has an active parser, then abort that parser.

3. Remove the child nodes of the node whose innerHTML attribute is being set, firing appropriate mutation events.

4. If the attribute is being set on a Document node, let target document be that Document node. Otherwise, the attribute is being set on an Element node; let target document be the ownerDocument of that Element.

5. Set the ownerDocument of all the nodes in new children to the target document.

6. Append all the new children nodes to the node whose innerHTML attribute is being set, preserving their order, and firing mutation events as if a DocumentFragment containing the new children had been inserted.

On getting, if the node's document is an HTML document, then the attribute must return the result of running the HTML fragment serialization algorithm on a fictional node whose only child is the node on which the attribute was invoked; otherwise, the node's document is an XML document, and the attribute must return the result of running the XML fragment serialization algorithm on that fictional node instead (this might raise an exception instead of returning a string).

On setting, the following steps must be run:

1. Let target be the element whose outerHTML attribute is being set.

2. If target has no parent node, then abort these steps. There would be no way to obtain a reference to the nodes created even if the remaining steps were run.

3. If target's parent node is a Document object, throw a NO_MODIFICATION_ALLOWED_ERR exception and abort these steps.

4. Let parent be target's parent node, unless that is a DocumentFragment node, in which case let parent be an arbitrary body element.

5. If target's document is an HTML document: Invoke the HTML fragment parsing algorithm.

   If target's document is an XML document: Invoke the XML fragment parsing algorithm.

   In either case, the algorithm must be invoked with the string being assigned into the outerHTML attribute as the input, and parent as the context element.

   If this raises an exception, then abort these steps.

   Otherwise, let new children be the nodes returned.

6. Set the ownerDocument of all the nodes in new children to target's document.

7. Remove target from its parent node, firing mutation events as appropriate, and then insert in its place all the new children nodes, preserving their order, and again firing mutation events as if a DocumentFragment containing the new children had been inserted.

The insertAdjacentHTML(position, text) method, when invoked, must run the following algorithm:

1. Let position and text be the method's first and second arguments, respectively.

2. Let target be the element on which the method was invoked.

3. Use the first matching item from this list:

   If position is an ASCII case-insensitive match for the string "beforebegin"

   If position is an ASCII case-insensitive match for the string "afterend"

   If target has no parent node, then abort these steps.

   If target's parent node is a Document object, then throw a NO_MODIFICATION_ALLOWED_ERR exception and abort these steps.

   Otherwise, let context be the parent node of target.

   If position is an ASCII case-insensitive match for the string "afterbegin"

   If position is an ASCII case-insensitive match for the string "beforeend"

   Let context be the same as target.

   Otherwise

   Throw a SYNTAX_ERR exception.

4. If target's document is an HTML document: Invoke the HTML fragment parsing algorithm.

   If target's document is an XML document: Invoke the XML fragment parsing algorithm.

   In either case, the algorithm must be invoked with text as the input, and the element selected in by the previous step as the context element.

   If this raises an exception, then abort these steps.

   Otherwise, let new children be the nodes returned.

5. Set the ownerDocument of all the nodes in new children to target's document.

6. Use the first matching item from this list:

   If position is an ASCII case-insensitive match for the string "beforebegin"

   Insert all the new children nodes immediately before target.

   If position is an ASCII case-insensitive match for the string "afterbegin"

   Insert all the new children nodes before the first child of target, if there is one. If there is no such child, append them all to target.

   If position is an ASCII case-insensitive match for the string "beforeend"

   Append all the new children nodes to target.

   If position is an ASCII case-insensitive match for the string "afterend"

   Insert all the new children nodes immediately after target.

   The new children nodes must be inserted in a manner that preserves their order and fires mutation events as if a DocumentFragment containing the new children had been inserted.