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Overview

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Overview Some hyperlinking history XML-Linking goals and status XML Base The XPointer language The XLink language Controlling traversal behavior Some Hyperlinking ... – PowerPoint PPT presentation

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Title: Overview


1
Overview
  • Some hyperlinking history
  • XML-Linking goals and status
  • XML Base
  • The XPointer language
  • The XLink language
  • Controlling traversal behavior

2
Some Hyperlinking History

3
History repeats itself
  • In word processing
  • Early systems knew text structure
  • WYSIWYG took over but skipped structure
  • As it scaled, people started to fake structure
  • Software gradually built structure all over again
  • In hypermedia
  • Many early systems had linking structure
  • HTML ltAgt took over but skipped structure
  • As projects scale, people are faking link
    structure
  • So

4
Hypermedia in the 60s (!)
  • For example, FRESS (Brown, 1969)
  • 800,000 lines of 370 assembler -- still runs
  • Grandfather of most Word processors
  • Teaching databases typesetting
  • Some features still not on Web
  • Links were structured w/ types, keywords
  • Links were truly bidirectional
  • Links overviews
  • Supported document structures / ranges
  • Out-of-line links later (1983, Intermedia)

5
HTML and hypermedia
  • WWW is powerful because of Internet, URIs, and
    documents linking is weak
  • HTML linking strengths
  • Easy syntax lta href"http//foo.net/x.html"gt
  • Trivial to implement
  • Can go to few specific targets (ID only)
  • lta href"http//foo.net/x.htmlsec2"gt
  • lta name"sec2"gt
  • Anchors move along with editing
  • (unlike, say, byte offsets)

6
Anatomy of an HTML link
lta href"http//z.uk/x.htmch2"gtInfo.lt/agt

Locallink-end
Locator
Link
lt!DOCTYPE lthtmlgtlta name"ch2"gtlt/h1gt...lt/htm
lgt
Remotelink-end
7
HTML Linking Limitations

8
1 Limited elements
  • People cant create their own subtypes
  • What if you need several sub-types of link?
  • REL/REV attributes non-standardized
  • CLASS attributes dont make it
  • Semantics/processing second-class
  • Maybe no HTML element to start from
  • Its like C without subclasses
  • CSS cannot make elements into links

9
2 Link behavior tied to type
  • A means (usually)
  • Replaces document in same window
  • Activated by user
  • IMG means (usually)
  • Embeds target inline
  • Activated upon loading
  • Graphics only
  • Why cant I have other combinations?
  • CSS doesn't have what youd need
  • Browsers cant embed HTML/XML yet

10
3 No real type system
  • Few have tackled the link type problem
  • Trigg, Bieber, DeRose, Connolly
  • REL/REV provide a hook, at least
  • No standard/portable set of types
  • Need an orderly but extensible system
  • Most proposed type-sets are grab-bags
  • Mixing rhetorical, topological, and syntactic
    types

11
4 A privileged end
  • The link is physically at one of its ends
  • Infeasible to allow annotation
  • Thus no links from read-only documents
  • Nearly all documents, for any one person
  • So no annotations that readers of the annotated
    document can see
  • Doesnt allow link databases, so
  • Cant buy or sell link-sets
  • Cant filter or select links on demand
  • Cant share many users links

12
5 Few possible destinations
  • Can point to a whole document
  • Can point to HTML lta namegt if it existslta
    href"http//xyz.com/foo.htmlid37"gt points
    to lta name"id37"gt
  • Author controls what others can reference
  • You can only quote paras 1, 12, or 20.
  • Can't do some links at all
  • Impossible to supply handles for links that
    partly overlap
  • Impractical to supply handles even at word level

13
6 No aggregate destinations
  • No multi-ended links in HTML
  • No multiple locations for a single end
  • No dynamic document assembly
  • Some uses for multi-ended links
  • Back-of-book indexes
  • Pull up multiple commentaries at once
  • Editing after multiple document reviews
  • Parallel views of editions and translations

14
7 One way A or IMG to somewhere
  • Why cant I ask who links to me?
  • (without doing a global search)
  • (even for a limited domain)
  • Why cant I make a two-way link?
  • Why cant I make multi-ended links?
  • Go back ? 2-way link
  • Only works after youve gone the one way
  • You cant start at the other end

15
Overview
  • Some hyperlinking history
  • XML-Linking introduction
  • Goals
  • History
  • Pointing vs. Linking
  • XML Base
  • The XPointer language
  • The XLink language
  • Controlling traversal behavior

16
XML-Linking goals end user
  • Links from un-writable documents
  • Which is most of the Web, for any person
  • Perhaps the most important single feature
  • -gtBidirectional and multi-ended links
  • -gtAnnotations and annotation sharing
  • Dynamic updates, patches, highlighting
  • Precise link attachment in any media
  • Large sets/databases of managed links
  • An entirely new market for links per se
  • Anyone can publish/sell their commentary

17
The XML-Linking effort
  • Started 1/1996 in the XML WG
  • Separate Working Group 1998
  • Specs
  • XPath complete 11/1999 (joint w/ XSL WG)
  • XLink complete 6/2001
  • XML Base complete 6/2001
  • XPointer being refactored
  • first 3 documents out soon

18
Pointing vs. linking
  • In HTML, many things are combined
  • lta href"eg.org/foo"gtwowlt/agt
  • Technically
  • "eg.org/foo" is a pointer (namely a URI)
  • The abstract connection itself is the link
  • The ltagt element is a link representation
  • "wow" is the local anchor
  • Anchors are also called link-ends
  • Data at eg.org is the remote anchor
  • HTML specifies the link behavior

19
Why pick all this apart?
  • Engineering/theory
  • Design each one better
  • Ease implementation
  • More easily combine them in new ways
  • Practically
  • Multiple locations can be linked at once
  • Link-ends can be organized and labeled
  • Meta-information can be added
  • Links can live outside of linked docs

20
XML-Linking specifications
  • XPath expressions on infoset nodes
  • REC http//www.w3.org/TR/xpath
  • XPointer XPath ranges, in URIs
  • CR http//www.w3.org/TR/WD-xptr
  • Xpointer Schemes failover for fragment Ids
  • Xpointer NS scheme (declare namespaces)
  • Xpointer Element scheme
  • XLink gather locations to make links
  • REC http//www.w3.org/TR/xlink/
  • (XML Base)

21
XPointer locators
ltxmlgt ltxref target"http//z.com/foo.xmlid('p3
7')"gtSee Section 1.lt/xrefgt
A way of locating data in XML structure used to
attach link end(s) to data
A pointer identifies or locates some part of a
document -- this is only the yellow part above
22
XLink connections
Someplace
Someplace
  • Describes a relationshipof referenced
    location(s),
  • To each other
  • To descriptions
  • XLink providessome key ones

A link connects data and meta-data portions,
including their relationship -- really just the
lines
role
role
role
A link may be expressed at a unique source end,
or out in a link database
Someplace
Someplace
Someplace
23
Overview
  • Some hyperlinking history
  • XML-Linking introduction
  • XML Base
  • The XML Pointer Language (XPointer)
  • Fragment identifiers
  • XPointer schemes
  • XPointer syntax/semantics
  • The XML Link language (XLink)
  • Controlling traversal behavior

24
XPointer
  • Locates parts of XML resources
  • Even things without IDs
  • Even things that aren't whole nodes
  • XPointer adds (beyond XPath)
  • Way to refer to point and range selections
  • Way to use inside URI fragment identifiers
  • Typically, a browser might load a document and
    scroll to/highlight the part

25
Anatomy of a URI reference
URI reference

URI
http//example.com/foo.htmbing
domain
path
fragment identifier
scheme
XPointer defines this part
26
Fragment identifiers
  • Part of URIs after ""
  • Says where in document is actual target
  • Separate form for each media type
  • Identifiers for graphics ? for text
  • IETF MIME definition specifies form
  • HTML
  • To scroll to lta name"coyote"gt
  • http//example.com/hello.htmlcoyote

27
The XPointer scheme system
  • A way to have several pointing mechanisms in one
    fragment ID
  • Each scheme in a fragment is tried in sequence
  • scheme1(args) scheme2(args)
  • unimplemented schemes and pointers that fail to
    locate, are simply ignored.
  • recent changes
  • Things are more split by scheme. Full XPointer
    delayed (again)
  • Last call drafts imminent

28
The 3 XPointer/XPath schemes
  • Bare names
  • An XML "name" finds element with that ID
  • Only exception to the scheme system
  • element() scheme
  • Counts Stepwise down through elements /1/4/27/2
  • May start with an ID element(intro/4/3/2)
  • xmlns() binds namespaces for schemes
  • xpointer scheme (awaits disposition of comments)
  • Full Xpointers, xpath and more
  • For now, the only "scheme" is "xpointer"

Name Letters, digits, hyphen, underscore,
period.
29
All work on XML tree
  • Address Infoset, not markup
  • Count nodes of different types
  • Root, elements, attributes, text chunks
  • Comments, PIs, namespace dcls
  • Can also work down in character data
  • Note Most of XPointer XPath
  • Adds ranges
  • Adds way to put into fragment identifier

30
XPointer's 2 parts
  • Provide 'scheme' mechanism
  • Identify media-specific pointer types
  • Allow multiple ones to co-exist
  • Pointing methods for XML
  • Point to ranges, sets, id's, coords
  • Point descriptively

31
XPointer schemes
  • XML medias type may need pointer types
  • pngRect(0,10 100,200)
  • vrml(camera1,2,3 light4,50,500)
  • map(W0?10/ N51?30)
  • Schemes label fragment identifier types
  • scheme1(args) scheme2(args)
  • Escape any extra ( ) -- tlg('(apax')
  • element(), xmlns() is the first scheme

32
Multiple schemes in a URL?
  • When a server responds to a URI, it
  • Checks what media the client can handle
  • Picks one of those to send
  • content negotiation
  • If a visually-impaired user clicks
  • lta href"http//www.example.com/foo.gif gif(0,0
    1,1) xpointer(id(chap1))"gt
  • The server may fall back to an XML file
  • The client tries fragment identifiers
    left-to-right, and uses the first one that works

33
Full XPointers
  • The content of the 'xpointer' scheme
  • Provides way to walk around trees
  • Provides way to select nodes/ranges

34
XPath/XPointer expressions
  • XPointers produce a location set
  • Location node point range(XPath only
    produces nodes)
  • Locating is stepwise
  • A step generally look along some axis
  • Candidates are then filtered by predicates
  • Special functions locate strings, ids, etc.
  • Each step operates on a context, and
  • Step are separated by a slash
  • id(foo) / childSEC3 / childLIST4

35
Points and Ranges
Hello, world.
  • Point
  • What you get by click-selection
  • Gap before/after node or char
  • Range
  • What you get by drag-selection
  • From a start point to an end point
  • Not generally a WF XML subtree
  • May partially contain some elements
  • ltpgtHello, world.lt/pgtltpgtHi, backlt/pgt
  • Crucial for creating hypertext links
  • How often do you click/drag exactly one entire
    element?

Hello, world.
36
Absolute linking functions
  • origin()
  • Locates where traversal came from
  • So if paragraphs P1 and P2 are linked, and the
    user clicks on P1 to follow a link, P1 is
    origin
  • Can make abstract links, "next chapter"...
  • here()
  • Locates the link representation itself
  • With one-way links like HTML ltagt, here origin
  • Can make a web-ring of one-ended links

37
here() and origin()
href"xpointer(here()/ following-siblingchapter
)"

origin()/ancestor2
Assuming you clicked on the title
Assuming you clicked on the xref
href"..."
38
Summary axes and functions
  • root( ), id( )
  • parent, self, child
  • ancestor, ancestor-or-self
  • descendant, descendant-or-self
  • preceding-, following-sibling
  • preceding, following
  • attribute, namespace
  • here( ), origin( )

Absolute
Relative
Absolute
39
More about ranges
  • Nodes are great handles for linkingbut most
    selections are not whole nodes
  • Typical link creation
  • Select something do "make link"
  • A click indicates a point, not a node
  • A drag indicates a range, not a node
  • A range is not a set of nodes (!)
  • It is one object, not a huge number
  • Characters are not nodes in DOM
  • Range does not have properties of node

Defined in the DOM 2 spec
40
string-range
  • string-range(n,"string", offset,length)
  • Locates selections (think cursor)
  • Finds nth occurrence of string provided
  • Offset counts positions before characters
  • 1 is before first character -1 before last
  • Length specifies length of result
  • In the cards are dealt string-range(1,"cards"
    ,1,1) c(1,"cards",1,0) point before
    c(1,"cards") point before c(1,"cards",3,2)
    rd(1,"cards",-1,5) s are

41
range-to
  • Range-to(xptr)
  • From start of context to end of xptr
  • The xptr would typically be an ID or relative
  • id('sec2')/range-to(id('sec4'))
  • id('fn37')/range-to(following-sibling3)
  • A typical form
  • xpointer( id('sec2.1')/4
    range-to(id('sec2.1')/2))

42
Some range applications
  • A typical hypertext interface
  • User selects some text
  • (a selection is hardly ever a node)
  • "make link", "make annotation"
  • Application generates an XPointer
  • Application saves links in a link-db
  • Great for referring to "milestones" or other
    non-hierarchical units

43
XPointer new datatypes
  • Extending nodes
  • Points
  • Ranges
  • Locations
  • The supertype of the extensions.
  • Location sets
  • set of locations

44
Reducing pointer/link fragility
  • Consider what will break an XPointer
  • If you just used offsets (easy but weak) the
    slightest edit
  • If you describe paths through the tree, only
    changes on the path
  • If you use paths with element type names, only
    ancestors or pr-siblings of same type
  • If you use IDs, only a specific change to
    that ID
  • When you can describe the true intent, they can
    re-attach when possible
  • Use IDs, or relative from an ID

45
XPointer robustness
  • Absolute robustness is not possible
  • Servers go down
  • Pages are deleted or moved
  • Author can mangle documents any time
  • Author can even change all IDs any time
  • But, how you construct pointers counts
  • IDs are good until explicitly changed
  • Software can manage IDs to be persistent
  • These are not true of counters, offsets, etc.

46
Overview
  • Some hyperlinking history
  • XML-Linking goals and status
  • XPath and XPointer in general
  • The XML Pointer language (XPointer)
  • The XML Linking Language (XLink)
  • Terminology
  • Inline and out-of-line links
  • Arcs and behavior
  • Linksets and link databases

47
Remember...
  • In style
  • XPath identifies set of nodes
  • XSLT itself does transforms on them
  • Similarly in linking
  • XPointer identifies sets of locations
  • XLink connects and describes them
  • These are very separate ideas

48
XLink is a language that...
  • Lets you invent your own linking elements and
    their meanings
  • In keeping with XML approach overall
  • Lets you create link databases
  • Links become first-class objects in the model
  • Provides some basic traversal behavior
  • E.g., Open the target in a new window
  • The rest is left to a style mechanism such as XSL

49
XLink terminology
  • Linking element
  • Identifies, connects, and describes anchors
  • Locator
  • Locates some link end (anchor)s data
  • Link end or anchor
  • A data portion reachable as part of a link
  • Arc
  • Explicit connection between two link ends
  • Resource
  • Anything you can point at on the Web
  • Using an arc is called Traversal

50
What links do with link-ends
  • A link identifies where its ends are
  • Using some kind of locators
  • URIXPointer will be the locator for XML
  • URIscheme()scheme() in general
  • A link attaches metadata to each end
  • Its formal role in relation to the other ends
  • A title by which to refer to it (say, in menus)
  • Some traversal behaviors
  • Arcs to say which traversals happen
  • Link itself can also have type, other info

51
Inline links
  • Linking element itself (better, the origin() end)
    is one of the links ends

52
Out-of-line links
  • Linking element itself isn't automatically made
    into one of its own resources

Requires that there be a way to find link
databases in the first place
53
Anatomy of an XML link
Link need not beat a link-end
lthtmlgtKnuths right.lt/htmlgt
ltlink type"annotated-reference"gt ltloc
role"ref" href"xptr.xmlchild(2,div)"gt ltloc
role"src" href"knut73.texs4.2.2"gt ltloc
role"com" href"http//x.com/note.html"gt ltlinkgt
Each link-end can be described
Link may have any number of ends
lt!DOCTYPE spec...ltspecgtltdivgtlt/divgtltdivgt ltheadgt.
..lt/headgt...
Link-ends need not be XML
\ 4.2.2 A tree is a set of nodes where each
node has one parent, except for a root node,
which has none.
Link-ends need not be marked up
54
XLink and namespaces
  • Xlink should be usable with any schema
  • And have any old name
  • Xlink elements are in a namespace
  • http//www.w3.org/1999/Xlink
  • Apply this in usual namespace way
  • ltxlinklocator xmlnsxlink "http//www.w3.org/19
    99/Xlink"gt
  • Namespaces can't rename, so true name goes on
    xlinktype attribute
  • This is much like architectural forms

55
Simple and extended links
  • A simple link is a
  • Starter kit of basic linking functionality
  • Only two resources are ever involved
  • It is always inline
  • An extended link is a
  • Generalized, all-purpose linking construct
  • Any number of resources can be involved
  • It might be inline or out of line
  • It enables link databases

56
The one-ended link
This is really important
Hilite'red'
  • A link can identify and describe
  • Can say the end "is a typo" or "important" or
    "highlighted in red"
  • A one-ended link still describes an end
  • Can attach tags or attributes to R/O data
  • ltclaim href"hamletid(soliloquy)" isacrux/gt
  • The description isnt properly an end
  • If it were, youd expect to navigate there
  • If it were, it would need a role and title
  • Critical for adding "standoff" markup

57
Arcs
  • Arcs specify traversal rules
  • Multi-ended links may restrict travel among their
    endpoints
  • Restrictions generic or app-specific
  • Arcs enable the description of both
  • An arc is a pair of roles, plus metadata
  • Enables traversal between ends with the given
    roles
  • May be multiple locators per role (useful for
    document assembly, multiple-choice travel)

58
Example vehicle annotations
Warning explosive
Warningtoxic
gasoline
fuel-type
warning
warning
ARCS vehicle ? fuel-type fuel-type ? warning
Link body 1
vehicle
vehicle
vehicle
59
How to detect links
  • Could have any name and content at all
  • ltfootnotegt, ltcriticismgt,
  • xlinktype attribute marks linking elements for
    applications to find
  • lt!ELEMENT footnote EMPTYgtlt!ATTLIST footnote
    xlinktype CDATA FIXED "simple"
    xlinkhref CDATA REQUIREDgt
  • For example ...has studied the issue.ltfootnote
    href"http//www.doctools.com" /gt

Defaultvalue forattribute
60
Types of links
  • simple easy, basic linking element
  • Creates link solely by means of attributes
  • So allows only one non-local end (cf ltAgt)
  • extended
  • Creates link using attributes / subelements
  • Each sub-element represents an end
  • This allows structured or multi-lingual titles
  • Both can have
  • Machine-readable role attribute
  • Human-readable title attribute

61
Simple links
  • Like HTML's ltagt
  • Has two participating resources
  • Linking element itself (if in-line)
  • Resource pointed to by the href locator attribute
  • Uni-directional
  • From simple
  • To remote resource

62
Simple link declaration
Content may be an end
  • lt!ELEMENT simple ANYgt
  • lt!ATTLIST simplexlinktype CDATA FIXED
    "simple"xlinkhref CDATA REQUIRED xlinkr
    ole CDATA IMPLIEDxlinktitle CDATA IMPLIEDgt

Identifies this as a link
Locatesresource
Describeother end
63
Extended links
  • Can be in- (like ltagt) or out-of-line
  • Have any number of resources
  • Each resource gets its own child locator
    element(s)
  • Link ends are distinguished by roles
  • Each locator has an href attribute
  • Multi-directional
  • Can start traversal from any resource
  • Can control allowed traversals via arcs
  • Application must be informed about the link
  • E.g., user subscribes to link database XYZ

64
The extended link container
  • lt!ELEMENT extended (locatorarctitle)gt
  • lt!ATTLIST extendedxlinktype CDATA FIXED
    "extended"xlinkrole CDATA IMPLIEDxlinktitl
    e CDATA IMPLIEDgt
  • Other content/attributes may be included if
    needed

Allows for the links ends
Identifiesas a link
Can supplydefaultsfor ends
65
An extended links ends
Identifies this as a locator
  • lt!ELEMENT locator EMPTYgt
  • lt!ATTLIST locatorxlinktype CDATA FIXED
    "locator" xlinkhref CDATA REQUIRED
  • xlinkrole CDATA IMPLIEDxlinktitle CDATA
    IMPLIEDgt
  • Link end locators may also have content and/or
    application-specific attributes

Locatesresource
Describethe end
66
Declaring Arcs
Identifies this as an arc
  • lt!ELEMENT go ANYgt
  • lt!ATTLIST goxlinktype (arc) FIXED "arc"
  • xlinkfrom NMTOKEN IMPLIEDxlinkto NMTOKEN I
    MPLIEDxlinkshow (newreplaceembedunknown)
    IMPLIED xlinkactuate (onLoadonRequestunknown)
    IMPLIED xlinkarcrole NMTOKEN IMPLIEDxlinkt
    itle CDATA IMPLIEDgt

Which roles to connect
Traversal semantics
Describethe arc
67
Arcs and Traversals
  • Traversal is split into
  • Behavior
  • Author's intention for behavior of a link.
  • Input to style mechanism
  • Not a presentation command
  • Actuation
  • Defines the event that triggers a link
  • Events are very generic, intentionally

68
Two kinds of behavior policies
  • show attribute
  • new to traverse and provide new context
  • replace to display in existing context
  • embed to display in the body of the initiating
    resource
  • Some semantic details are left unspecified
    combining multiple ends, style inheritance, etc.
  • actuate attribute
  • onRequest to require external request
  • onLoad to traverse when link processed

69
Replacement behavior
  • replace plus onRequest
  • Like clicking on the HTML ltAgt element
  • replace plus onLoad
  • Like a redirect when the link is processed, the
    other resource replaces the original one in which
    the link was found

70
New behavior
  • new plus onRequest
  • Like clicking on the HTML ltAgt element, except
    that it opens up a new window
  • new plus onLoad
  • Useful for revealing commentary when the link is
    processed, a new window opens up in addition to
    the original one

71
Embedding behavior
  • embed plus onRequest
  • Useful for expanding a thumbnail or when
    auto-loading of images is off when the user
    clicks, the content appears in place
  • embed plus onLoad
  • Like the HTML ltIMGgt element or an external entity
    reference the content automatically appears in
    place when the link is processed
  • This is transclusion
  • True transclusion requires that the transcluded
    data also provide access to original context

72
Simple link syntax
  • lt!ELEMENT defref (PCDATA)gtlt!ATTLIST
    defref xlinktype CDATA "simple" xlinkhref
    CDATA REQUIRED xlinkrole CDATA
    "mynscooking"gtltpgtuse any number of ltdefref
    xlinkhref"filterdef"gt filters lt/defrefgt
    (about 1 tsp)lt/pgt

Note can add "FIXED" before default value so it
will be the only value allowed.
73
Extended links
  • lt!ELEMENT term-def (locator)gt
  • lt!ATTLIST term-def xlinktype CDATA
    "extended"gt
  • lt!ELEMENT locator EMPTYgt
  • lt!ATTLIST locator
  • xlinktype CDATA "locator"
  • xlinkhref CDATA REQUIRED
  • xlinkrole (mynsmentionmynsdef) REQUIREDgt
  • ltterm-defgtltlocator href"myterm1"
    role"mention"/gtltlocator href"myterm2"
    role"mention"/gtltlocator href"definition
    role"def"/gt
  • lt/term-defgt

74
Link databases let you
  • Attach descriptive information from afar
  • Annotate other people's stuff
  • Maintain links more easily
  • When a destination changes, you dont have to
    touch documents with links to it
  • Engage in online commerce in links
  • Express, package, and sell point-of-view
  • Collect out of line links as databases

75
External Linksets
  • Users will have persistent linkdbs
  • Subscriptions, interest groups, private,...
  • Document can specify relevant link dbs
  • Linked by special type of extended link
  • Included within regular documents too
  • LinkDBs enable link management
  • Needed to author using external links
  • Example Public annotations on.

76
Declaring an External Linkset
  • lt!ELEMENT xls (linkbase)gt
  • lt!ATTLIST xls
  • xmlnsxlink CDATA FIXED "http//www.w3.org/
    1999/xlink"
  • xlinktype (extended) "extended"
  • xlinkrole NMTOKEN "xlinkextended-linkset"
  • xlinktitle CDATA IMPLIEDgt
  • lt!ATTLIST linkbase
  • xlinktype (locator) "locator"gt

77
An external Linkset Instance
  • ltxlsgtltlinkbase xlinkhref"linkset1.xml"
    /gtltlinkbase xlinkhref"linkset2.xml"
    /gtltlinkbase xlinkhref"linkset3.xml" /gt
  • lt/xlsgt

78
Notes on implementation
  • Best thing for any standard
  • Lots of implementations
  • Attention to conformance/interoperability
  • IE does not yet have these
  • Encourage implementors
  • XPointer easy on top of XPath DOM
  • XLink easy for inline, trickier for good LDBs
  • Proxy server can merge document links
  • Client app can do likewise
  • Encourage distributed linkbase dev

79
Some Resources
  • On the Web Consortium site
  • W3C XML site www.w3.org/XML/
  • Other specs www.w3.org/TR/
  • Elsewhere on the Web
  • XML FAQ www.ucc.ie/xml/
  • XML Developers list www.lists.ic.ac.uk/hypermail
    /xml-dev/
  • TEI etext.virginia.edu/
  • Robin Covers definitive site www.oasis-open.org
    /cover/
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