Re: [office-accessibility] Fw: intra-document hyperlink

[Peter Korn <Peter.Korn@Sun.COM>]

Hi Hiro,

This seems like an issue to take to our parent TC.  Would you care to 
raise the issue there?  Let's discuss this tomorrow at our (sometimes) 
weekly meeting.


Peter
>
> I will attach Ishihara-san's investigation on the intra-document link 
> issue.
>
> Malte,
> Is there any documentation for the rule of fragment identifier in 
> OpenOffice.org?
>
> ---------------------
> Hironobu Takagi, PhD.
> User Experience and Accessibility Technology
> Tokyo Research Laboratory, IBM Research
> +81-46-215-4557
> E-mail: takagih@jp.ibm.com
>
>
> ----- Forwarded by Hironobu Takagi/Japan/IBM on 2007/04/24 10:49 -----
> ---
> Tatsuya Ishihara
> IBM Tokyo Research Laboratory (Mail Code: LAB-S77)
> E-mail : tisihara@jp.ibm.com
> Tel: +81-46(215)4978     Fax: +81-46(274)4282
>
> -----
> Summary
> ------------------
>
> Current ODF documents have an interoperability issue for hyperlink 
> which refers to ODF elements within same document (intra-document links).
> This issue is caused by two reasons.
>
> 1. URI syntax of intra-document link is not defined in ODF spec.
>
> 2. In OpenOffice, a URI of intra-document link to a heading element 
> involves text content of the heading element.
>         e.g. "#5. Introduction|outline"
>        denotes "5th heading in this document, and the text contents is 
> 'Introduction' "
>   This implementation will cause interoperability issues, since this 
> type of use of fragment identifier (notation after # in URI) is not 
> popular among office editors and browsers.  
>
> Intra-document link is important for improving accessibility of 
> documents, since it allows users to jump to intended part of document 
> directly. (e.g. table of contents)
> We propose to define syntax of intra-document links ("fragment" part 
> in URI) in the ODF spec, in order to point unique ODF element without 
> ambiguity.
>
>
> Detail
> ------------------
>
> There is a interoperability problem that implementation of hyperlink 
> for headings or graphics within same document is different in office 
> applications.
>
> Blind users access documents by using screen readers. They move cursor 
> by keyboard command and reads the line where cursor is located.
> To find out what they need in the text document, they have to move 
> through the cursor
> and read the contents from the top of the documents. If intra-document 
> links are inserted, screen readers can skip the contents and jump to 
> intended part of document.
> This function is often used in "Table of Contents" function. So 
> hyperlinks within same document is necessary to improve accessibility.
>
>
> This is an example file created by OpenOffice.org v2.2.
>
>
> Hyperlink URI is shown by moving the mouse pointer over text link.
> An example of hyperlink URI for heading area is like this.
>
> "#5.Introduction|outline"
>
> It means that "5th heading in this document, and the text contents is 
> 'Introduction' ".
>
> This URI is ambiguous. If a heading with same text content is inserted 
> before the heading referred by this hyperlink,
> this hyperlink refer to the new heading.
>
> The URI should point one ODF element clearly, and ODF should define 
> this specification for
> ensuring the interoperability.
>
> In ODF 1.1 specification, URI of hyperlink is defined by "xlink:href" 
> attribute of <text:a> element.
> ODF 1.1 defines hyperlink URI as follows.
>
> -----------------------
> ODF 1.1 page 91
> Link Location
> The xlink:href attribute specifies the URL for the target location of 
> the link.
> -----------------------
>
> Current XLink specification is here.
> http://www.w3.org/TR/xlink/
>
> "xlink:href" attribute in XLink specification is defined as follows.
> This attribute should have URI value.
>
> -------------------------------
> 5.4 Locator Attribute (href)
> The value of the href attribute _must_ 
> <http://www.w3.org/TR/xlink/#dt-must> be a URI reference as defined in 
> _[IETF RFC 2396]_ <http://www.w3.org/TR/xlink/#rfc2396>, or must 
> result in a URI reference
> after the escaping procedure described below is applied. The procedure 
> is applied when passing the URI reference to a URI resolver.
> -------------------------------
>
> RFC 2396 is obsoleted by latest URI specification.
> Latest specification of URI (RFC 3986) is here.
> http://www.ietf.org/rfc/rfc3986.txt
>
> URI specification says that the subset of resource is specified by 
> "fragment".
> "fragment" and "same-document reference" is defined as follows.
> It says that fragment's format is dependent on each media type.
>
> ---------------------------
> 3.5.  Fragment
>
>  Fragment identifier semantics are independent of the URI scheme and
> thus cannot be redefined by scheme specifications. Individual media
> types may define their own restrictions on or structures within the
> fragment identifier syntax for specifying different types of subsets,
> views, or external references that are identifiable as secondary 
> resources by that media type.
>
> 4.4.  Same-Document Reference
>
>   When a URI reference refers to a URI that is, aside from its fragment
>   component (if any), identical to the base URI (Section 5.1), that
>   reference is called a "same-document" reference.  The most frequent
>   examples of same-document references are relative references that are
>   empty or include only the number sign ("#") separator followed by a
>   fragment identifier.
> ---------------------------
>
> So ODF should define syntax of hyperlink URI for same document area.
>
> ODF specification has id functions like "draw:name", or "text:name".
> We had better use these attribute for this purpose.
>
> ----------------------------
> OpenOffice 2.2 implementation
>
> <text:a xlink:href="#5.Introduction|outline">jump to title</text:a>
> ....
> <text:h>Introduction</text:h>
>
> <text:a xlink:href="#graphics1|graphics">jump to image</text:a>
> ...
> <draw:frame draw:style-name="fr1" draw:name="graphics1" 
> text:anchor-type="paragraph" svg:x="0.268cm" svg:y="0.721cm" 
> svg:width="3.394cm" svg:height="2.545cm" draw:z-index="0">
>   <draw:image 
> xlink:href="Pictures/1000000000000A6B000007D0BBB2CD79.jpg" 
> xlink:type="simple" xlink:show="embed" xlink:actuate="onLoad"/>
> </draw:frame>
> ----------------------------
>
> ----------------------------
> Proposal
>
> <text:a xlink:href="#heading1">jump to title</text:a>
> ....
> <text:h text:name="heading1">Title Contents</text:h>
>
> <text:a xlink:href="#graphics1">jump to image</text:a>
> ....
> <draw:frame draw:style-name="fr1" draw:name="graphics1" 
> text:anchor-type="paragraph" svg:x="0.268cm" svg:y="0.721cm" 
> svg:width="3.394cm" svg:height="2.545cm" draw:z-index="0">
>   <draw:image 
> xlink:href="Pictures/1000000000000A6B000007D0BBB2CD79.jpg" 
> xlink:type="simple" xlink:show="embed" xlink:actuate="onLoad"/>
> </draw:frame>
> ----------------------------