Fine-Grained Transclusions of Multimedia Documents in
(Graz University of Technology, Austria
Abstract: Transclusions are a technique for virtually including
existing content into new documents by reference to the original documents
rather than by copying. In principle, transclusions are used in HTML for
the inclusion of entire text documents, images, movies and similar media.
The HTML specification only takes transclusions of entire documents into
account, though. Hence it is not possible, for instance, to include a part
of an existing image into an HTML document.
In this paper, fine-grained transclusion of multimedia documents on the
Web are proposed, which presents a logical realisation of the concept of
transclusions in HTML. The proposal makes it possible, for instance, to
include sections of existing images or small portions of entire movies
into HTML documents.
Two different approaches to implementing the functionality presented are
detailed. The first architecture is based on a transparent extension module
to conventional HTTP servers, whereas the alternative design makes use
of a CGI program. Both approaches are fully self-contained, reside on an
HTTP server and do not require browser plug-ins or any other special software
components to be installed on client computers. An amendment to the HTTP
specification is not required either. A prototype implementation demonstrates
the proposal for a number of document types.
Keywords: Hypermedia, Transclusions, Xanalogical Structure, Authoring
Systems, Publishing Systems, Web-Based Applications, Multimedia.
Categories: H.1, H.3, H.4.
In 1965 Ted Nelson presented "a file structure for the complex,
the changing and the indeterminate" at the ACM Twentieth National
Conference (see [Nelson 1965]). In this publication
he introduced the term hypertext and a technique called trans-clusions.
Transclusions are the fundamental concept that allow authors to virtually
include portions of existing documents into new articles without the need
to duplicate them. From a technical perspective, transclusions are references:
the transclusion tB in document A is a reference to a portion of the content
of a document B that is virtuall included into document A.
1.1 Origin of Transclusions
Nelson regards transclusions as complete replacement for all cut-and-paste
mechanisms employed. He claims that the widely used cut-and-paste operation
is not what people actually intend to do. It is a restriction imposed upon
authors by the nature of paper.
Writers actually do not want to duplicate an existing document, cut
out the section they want to quote, and paste it in their document. They
want to include, i.e., transclude, the original content and let
readers know what the source and context of the quotation are (e.g., [Nelson
Another rather pragmatic solution that becomes necessary because of
the nature of paper are reference lists at the end of scientific publications.
They are usually not what is desired by writers and wanted by readers.
They are an attempt to preserve the context of the quotation that is lost
by copying-and-pasting a portion of printed material.
The physical restrictions of paper were embraced by most computing systems
in an attempt to resemble office environments and the common processes
in work environments (cf., [Yocom 2004]). Therefore
most current operating systems with graphical user interfaces do not make
use of the strengths of hypertext. They utilise metaphors such as a desktop,
folders and documents, where a document has to be put in exactly one folder.
There is a clipboard, and content from a different document is included
using copy-and-paste mechanisms (see [Nelson 1996]).
1.2 Ramifications of Transclusions
Transclusion technology is not only a replacement for copy-and-paste.
With transclusions, the original context of a quotation is preserved and
a visible link to the source of the transclusion can be provided. Ted Nelson's
approach to implementing this functionality involves transpointing windows
(e.g., [Nelson 1995]).
Furthermore, document authors can receive notifications whenever their
articles are transcluded by other users. Thus they can, for instance, be
informed about other researchers in the same area. Writers using transclusions,
on the other hand, can be notified automatically about changes in source
documents of the transcluded content (see [Krottmaier
The nature of transclusions has an impact on the storage space required.
Since content is not duplicated when it is quoted, disk space can be saved.
This was a major issue in the 1960s when Nelson published his ideas and
storage space was still precious. Although nowadays disk space is available
at low cost, it can become a concern when handling large amounts of multimedia
Version control systems are another area where storage space can
pose a problem (e.g., [Tichy 1985]). When
n versions of a document exist, and every version retained in
the system contains the entire content in a file, the space for
storing the content can increase rapidly. Therefore it can be more
effective to keep only the changes made from version n-1 to
version n. When version n of a document is retrieved, content
from all previous versions is transcluded into the current
Aside from obvious improvements in authoring and publishing systems,
transclusions are able to provide a solution to copyright issues experienced
on the world wide web. Authors include content into their documents by
means of transclusions instead of copying and pasting. Whenever a reader
views a transclusion information on the permissions and rights associated
with the transcluded content is added. In addition to this, an automatic
micropayment can be made to the corresponding content owner ([Nelson
1999]). Nelson coins this paradigm transcopyright (see [Nelson
1.3 Implementation of Transclusions
Ted Nelson attempts to realise his notion of hypertext in a system
named Xanadu (e.g., [Nelson 1981]). Transclusions
are a fundamental part of this system. Their implementation, however,
relies on a document model that is radically different from most
paradigms used today. In Xanadu, documents do not contain any content
but only references to the actual content. The content is retained in
dedicated content repositories. It is indexed and referenced at the
level of single characters — the finest granularity possible.
Documents in Xanadu are lists of references to content stored in the
system, e.g., a document might consist of "characters 120 to 843
and characters 11,196 to 13,101 from the repository". In such
a system transclusions can be implemented easily: transcluding content
from document B into document A corresponds to adding the references to
the actual content in the repositories to the reference list of document
Thus, both creating and retrieving transclusions in Xanadu are
trivial list operations. Functions that handle situations in which
large portions of documents are modified or deleted can also be
implemented (e.g., [Nelson 1999]). They require
content to be persistent, i.e., documents in Xanadu cannot be
deleted. When a document transcludes a portion of content that has
been changed or removed in version n of the source document the
transclusion can be retrieved from version n-1 of the
document. In this case, the user has to be notified that a more recent
version of the source document is available. Alternatively, the system
can attempt to determine which parts of the source document have been
modified and which portions in version n correspond to the content in
version n-1. In this case, the user has to decide whether the
new content transcluded is still appropriate. It can assumed, though,
that the context of an existing document remains relatively
unchanged. Thus, both sense and connotation of an existing document
remain relatively unchanged (e.g., [Nelson
In contrast to Xanadu, most other system that allow the use of
transclusions (e.g., HTML, see section 1.4) do
not require content to be persistent. Therefore these environments are
not able to handle situations in which content becomes unavailable
accordingly. When users transclude an image into their documents and
the original image is deleted or extensively modified they are usually
not notified. This is a factor that deters many authors from
transclude remote resources.
1.4 Transclusions in HTML
The Hypertext Markup Language (HTML, [HTML
1999]) used on the world wide web is a relatively simple language
for describing hypertext pages. The focus of the early development was
on simplicity, style and graphical presentation features rather than
on functionality and modern technologies. Hence innovative ideas such
as bidirectional hyperlinks were not taken into consideration (e.g.,
[Maurer 1996; Maurer and Lennon
1996; Kappe 1995]). Potential difficulties
already known before the invention of HTML including the distinction
between URLs and URIs were not handled either (e.g., [Pam 1995]).
In various aspects, HTML makes use of transclusions. Markups such as
<iframe>, <img>, <object> or
<embed> virtually include content such as entire HTML files,
images, video clips and animations into HTML pages by means of linking.
Transclusive functionality in HTML is very limited, though. The transclusion
mechanisms available can only be applied to entire documents; fine-grained
transclusions such as a small spatial selection of an image are not implemented.
This is most likely due to concessions made in favour of ease of implementation,
in order to reduce the computing power required and to increase performance
on the web.
Therefore fine-grained transclusions of multimedia documents as a logic
extension of to the infrastructure used in HTML-based environments are
proposed. This makes it possible, for example, to include only a part of
an existing sound file into a web page. The proposed functionality is an
addition to a previous work that allows users to make textual transclusions
in HTML (see [Kolbitsch and Maurer 2005]). By combining these two projects,
it becomes possible to transclude text documents and a wide range of multimedia
documents in conventional HTML pages at the finest level of granularity
and without the need to install software on client computers.
2 Fine-Grained Transclusions of Multimedia Documents
The concept of fine-grained transclusions can be applied to numerous
content types. Therefore, this section briefly explains a variety of multimedia
document types, and their use in connection with transclusions is addressed.
The syntax used in all examples resembles the syntax for
conventional HTTP GET requests and the common HTML syntax, for
instance, of <area> markups.
2.1 Drawings, Vector Graphics
Drawings and vector graphics are used very often in the technical domain
and when abstract concepts are graphically depicted. Examples are CAD drawings
such as plans of buildings, cars and machinery in general; both two- and
three-dimensional models of objects such as molecules in chemistry; flowchart
diagrams and organisational charts. A common property of most vector graphic
formats including SVG (scalable vector graphics, [SVG
2003]) is that every vector and every other object is stored in way
that it can be addressed independently. This means that even after saving
a document, a line can still be selected as a line, and its length or position
can be modified.
The same is also true of some formats that are employed to describe
three-dimensional models or "virtual reality" scenes. The recent
X3D format, for instance, stores every object separately in the file, and
it is possible to modify every object individually (see [X3D
These characteristics can be made use of when creating transclusions.
Fine-grained transclusions of vector graphics can be based on spatial selections
or on object selections. Thus when a transclusion is created, the user
can select either certain objects or a spatial region of the drawing. The
component generating the actual transclusion (see below) has to select
the given objects from a drawing and subsequently interpret, i.e., render,
the resulting data. In case of a spatial selection, the vector graphic
has to be interpreted first (window-viewport transformation), and only
then a selection can be made.
Object-based selection is most likely only reasonable when a small number
of objects have to be dealt with. Real-world models often contain millions
of polygons, which makes selecting groups of objects impracticable. In
such a scenario, spatial region selction seems to be more appropriate.
The first example in Table 1 describes the transclusion
of a rectangular shape 170 points wide and 20 points high, starting at
10 points from the left top corner.
||relative length, time
||relative lenght, frames
Table 1: Example of selections in different multimedia document
2.2 Photos and Images
Photos and rasterised images are particularly wide spread on the
world wide web. They are usually produced by conventional photo
cameras, specialized cameras such as infrared cameras, and other
imaging devices such as ultrasound and x-ray detectors or radar
units. Diverse areas such as medical imaging, satellite imaging,
microscopy, (print) publishing make use of rasterised images. Some
technologies for the description of three-dimensional models and
virtual reality scenes such as Apple's Quicktime VR utilise rasterised
information as well (e.g., [QTVR 2005]). A
series of images are stored and displayed in a particular way so that
users have the impression that they are viewing a three-dimensional
object. (The "object" is, however, merely a recombination of
two-dimensional images from different perspectives to a new
For rasterised images it is usually not possible to select separate
objects, only pixels or regions of pixels can be addressed. A more
general technique is the usage of normalised device co-ordinates
instead of pixels (NDC; e.g., [Foley et
al. 1997]). With NDC, the left-bottom corner of the image is
described with the co-ordinate pair (0,0) and the top-right corner
corresponds to (1,1). This method makes references independent, for
example, from actual devices and implementations.
A straightforward approach for creating fine-grained transclusions of
images and photos are selections based on regions. When users want to make
a fine-grained transclusion of an image they can mark a certain (spatial)
region of the image, where regions can be rectangles, other geometric objects
and arbitrary shapes defined with polygons or Bézier curves.
The examples in Table 1 list two types of spatial
selections: the fist one is a simple rectangular selection 200 pixels wide
and 200 pixels high, starting at coordinates (10, 20). The second example
is an arbitrary polygon consisting of six co-ordinate pairs.
2.3 Video Content
Most digital video content is represented as a series of frames, where
each frame is a rasterised image. Therefore basically all methods that
can be utilised with images and photos are also applicable to video content,
e.g., spatial selections using areas of pixels or normalised device coordinates.
In addition to this, two further region selection mechanisms can be identified:
- temporal selection and
- spatio-temporal selection.
When using a temporal selection, the user specifies a certain period
of time on the time line of a video clip in order to denote that a temporal
region of a movie is to be transcluded. The combination of a spatial and
a temporal selection leads to a spatio-temporal selection. This means that
a fixed area in one frame of a video clip is selected also in a number
of consecutive frames. This method is useful, for instance, when only a
certain area and a certain section filmed by a surveillance camera are
Table 1 lists two examples for temporal and spatio-temporal selections.
The first video file is a temporal selection with a length of 4 minutes
and 59 seconds, starting at 3 minutes and 42 seconds. In the second example,
an area 320 pixels wide and 200 pixel high is cropped, and a temporal selection
with a length of 47 minutes and 12 seconds, starting at the beginning of
the video file, is made.
2.4 Sound and Music
A number of different approaches for describing sound and musical data
exist. Most technologies available to date such as AIFF (see [AIFF
1989]) are frame-based. All current audio formats include some sort
of timecode, and some of them support the use of index points.
Therefore temporal region selection is the apparent method for providing
fine-grained transclusions of sound files. Users can define a start position
and either the length of the content to be transcluded or the end position.
As illustrated in Table 1, positions and length can
be given as absolute time codes (e.g., 1m13s), as index points
(e.g., index1) or as number of frames where applicable (e.g.,
2.5 Compound Multimedia Documents
Multimedia animations are much more complex than the media types introduced
above. Although they can be seen as compound documents they can usually
not be treated as composites of basic media types.
One reason is that the most common documents formats such as
Macromedia Flash are more or less proprietary (e.g., [Macromedia 2005]). This means that even if a video
clip within a multimedia animation is represented as an individual
object in the document format, it might not be possible to access it
separately or to extract it. Thus, even relatively simple operations
such as cropping the area to be displayed might be very hard to
Despite these difficulties and in order to underline the fundamental
concept, it should be mentioned that, at least in theory, it is possible
to make fine-grained transclusions of compound multimedia documents in
HTML. Examples are:
- spatial, temporal or spatio-temporal selections of entire animations;
- selections of single objects or a group of objects within complex animations;
- spatial, temporal or spatio-temporal selections of individual objects
or a group of objects of complex animations.
An actual implementation, however, would most probably require active
support from the companies maintaining the respective document format.
3 Approaches to an Implementation
Fine-grained transclusions are not only an abstract concept in hypermedia
theory but there are several potential application areas that are particularly
well suited for the proposed functionality. Therefore two approaches to
an implementation are introduced, the design goals are detailed, and a
prototype implementation that can be accessed over the Internet is presented.
3.1 Design Goals and Requirements
The idea of fine-grained transclusions attempts to foster the reuse
of information that is already available on the world wide web. A wide
range of differing media formats should be supported, and their characteristic
features should be made use of. Therefore a number of design goals have
to be considered:
- use of any document on the Web: it should be possible to make
fine-grained transclusions of any media document accessible on the Web
— not only of files from a closed repository;
- extensibility: a system for creating and retrieving fine-grained transclusions
should be extensible, i.e., adding support for new document types should
be taken into consideration;
- flexibility: the system should make use of the features offered by
the various media types, e.g., the types of selections (spatial region,
object selection, etc.) should be adapted to the document and encoding
- use of existing standards: the definition of fine-grained transclusions
should not require the introduction of new HTML markups;
- reuse of existing infrastructure: it should be possible to reuse existing
infrastructure including browser plug-ins. Moreover a seamless integration
into existing frameworks must be provided, i.e., the use of fine-grained
transclusions of multimedia documents must not break existing plug-ins,
- no additional software: users should not have to install additional
software on their client computers to be able to make use of the proposed
- transparency: an implementation should be transparent to both web browsers
- ease of use: for authors, it should be easy to create fine-grained
transclusions of media documents.
An implementation can be based on plain HTML, without any additional
markups, and plain HTTP, without the need to alter the communication protocol
used between client and server. The basic requirement is a conventional
HTTP server that can be extended with either external extension modules
or CGI programs. Most current web servers such as the popular Apache HTTP
server incorporate both capabilities (e.g., [Apache 2005]).
3.2 System Architecture
Two different implementations are proposed: an implementation that involves
an extension module for the HTTP server, and a CGI-based approach (see
sections 3.3 and 3.4). Independent of the actual approach
used, the system follows a particular architecture that is described in
the following paragraphs.
A fine-grained transclusion is defined by a number of additional parameters
that describe which portion of the content is to be extracted. They are
appended, for instance, to the src attribute of the <img>
tag in an HTML document (see Table 1 for a number of
examples). The parameters defining the fine-grained transclusion can be
provided "manually" by the author, can be generated using dedicated
authoring tools or a simple web interface.
When a web page containing fine-grained transclusions is requested,
a component on the server (extension module or CGI program) analyses the
definition of the fine-grained transclusion and retrieves the original
document. Subsequently, the specified portion of content is extracted from
the original document using an appropriate plug-in module for the corresponding
document type, and is sent to the client (see Figues 1
and 2 and section 3.5).
Thus, the implementation follows a client-server approach, where the
complexity and logic lie within the server-side component.
The major benefit of this approach is that it is completely transparent
to HTTP clients and the current infrastructure for playing back sound and
videos already present in most web browsers can be reused. No additional
software components need to be installed on client computers. A video clip,
for instance, can still be included into a web page by means of the <object>
markup. Only the URL given in the corresponding tag is a altered: it has
to define the piece of media to be transcluded.
Another advantage is that the content does not have to be stored in
any particular database or special repository. Content can be stored as
files in directories of a conventional file system, but also in a remote
file system, in databases, etc. The architecture presented also avoids
unnecessary network usage by only transferring the data actually requested
from the server to the client.
This generic structure of the system is the foundation of the implementations
of the server-side components detailed in the following two sections.
3.3 Extension Module for HTTP Servers
The functionality of many HTTP servers including the widely-used Apache
web server can be extended by means of modules (see [Apache
2005] and [Thau 2003]). Modules can perform various
tasks from authentication to enabling access to databases and handling
various error conditions. Frequently employed modules include mod_perl,
a module that implements an interpreter for the Perl programming language,
and mod_php, an extension for using the PHP scripting language.
Figure 1: Architecture of an approach, where the functionality
of the HTTP server is extended with an external module.
This implementation of fine-grained transclusions relies on an extension
module that is invoked whenever data is requested from the server (see
Figure 1). It analyses the request, and if multimedia content is requested,
the module checks whether the entire file is requested or only a part thereof,
i.e., if a fine-grained transclusion is to be made. If so, the extension
module checks if a plug-in for the corresponding document type exists (see
section 3.5) and generates the requested portion of
content. Finally, the content selected from the entire multimedia document
is returned to the HTTP client.
If the HTTP request does not refer to a multimedia document, the request
is passed on to the HTTP server. If a plug-in for a given media type is
not present or the transclusion cannot be made, an error message is returned
to the client.
This approach is completely transparent to both HTTP clients and users.
Only the parameters defining the portion of content to be transcluded can
be "seen" by users; otherwise a fine-grained transclusion can,
for instance, not be distinguished from a conventional inline image.
The disadvantage of this approach is that an extension module has to
be installed on the HTTP server. In environments where the configuration
of the HTTP server cannot or must not be changed, this implementation is
3.4 CGI Program
Similar results can be achieved by using a CGI program. When the CGI-based
approach is utilised, every fine-grained transclusion has to be loaded
through a particular CGI program (see Figure 2). The
CGI program carries out the same operations as the HTTP server extension
module: it checks if the request is valid, finds an appropriate plug-in,
extracts the requested portion of content and sends it to the client.
The difference becomes obvious when looking at the structure of an
HTML tag referring to a fine-grained transclusion. In Listing 1 an
example is illustrated: The first markup is a traditional
<img> tag. The second markup defines a fine-grained
transclusion that is loaded through an HTTP server extension module
(cf., Table 1). It is transparent to users. The
third markup is the same fine-grained transclusion loaded through a
CGI program. Although it is transparent to web browsers — they
do not "recognise" that they do not load the original
image — it is not transparent to users because they can see that an
intermediate component is used when the image is retrieved.
Figure 2: System architecture of a CGI-based approach. The
client sends a request to a CGI script that, in turn, forwards the request
to the transclusion engine.
Since CGI programs can almost always be added, even if extension modules
cannot be installed, this approach can be advantageous when the setup of
an HTTP server cannot be modified. Moreover the CGI program can be implemented
in a way that not only local documents can be transcluded but also files
from remote URLs (see section 3.6). So even users
that do not have the CGI program installed on their servers could make
use of fine-grained transclusions.
3.5 Plug-In Architecture
Both the extension module to HTTP servers and the CGI programs are mere
frameworks that offer the functionality needed to handle the requests of
clients. The requested portion of content is generated by plug-in modules.
Figure 3: Basic structure of the plug-in architecture. The "transclusion
engine" receives a request, fetches the given source document and
processes it with an appropriate plug-in module. The extracted content
When a client retrieves a fine-grained transclusion of a certain document
the HTTP server extension module or the CGI program analyse the request.
If the requested document is a multimedia document and the request is valid,
an appropriate plug-in that can handle the given document type (e.g., a
GIF image) is searched for. If a plug-in can be found the original document
is retrieved and passed on to the corresponding plug-in along with the
parameters describing the content to be selected. The plug-in extracts
the demanded portion of content and returns it to the HTTP server extension
module or the CGI program. The basic structure of the plug-in architecture
is depicted in Figure 3; the retrieval strategy with
plug-ins is shown in Figure 4.
Although this approach may seem overly complex, it has various advantages.
Every file type can be realised as separate plug-in. Therefore it is fairly
easy to offer support fort new document types or encoding standards. The
approach is flexible in that the plug-ins can take the particularities
of certain media types into account and deal with their peculiarities.
Figure 4: Retrieval strategy for multimedia documents with
the ability to make fine-grained transclusions
The implementation of a plug-in is relatively uncomplicated for simple,
open document formats such as JPEG/JFIF and PNG images or MP3 sound files.
The prototype illustrated in section 3.6, for instance,
implements a plug-in module for JPEG, PNG and GIF images. The implementation
is somewhat more complex, though, when media types such as MPEG-1 are to
be handled: the encoding is frame-based, where frames only contain the
segments different from a particular base-frame. So when a temporal selection
of an MPEG-1 video file starts at an arbitrary frame, it might be necessary
to reconstruct the entire frame first. An implementation becomes even more
difficult when proprietary document formats such as Microsoft's WMV video
files or complex media files such as animations based on Macromedia Flash
are to be handled.
3.6 Prototype Implementation
The prototype implemented follows the CGI-based approached introduced
above. It consists of two components: a script for generating a URL that
can be used to include the fine-grained transclusion into an HTML document,
and a second CGI program that actually produces the requested portion of
Currently, users can make fine-grained transclusions of three
frequently employed document types: JPEG, GIF and PNG images. It can
be assumed that a small number of content providers will create
fine-grained transclusions, and a large number of users will retrieve
them. Therefore only a very simplistic interface for that task is
provided: When users want to create a fine-grained transclusion they
are asked to supply the URL of the original file as well as the
coordinates that describe the region to be extracted (see Figure 5).
Only rectangular selections can be made; more complex geometric or even
arbitrary shapes are not supported at the moment. In the course of time,
tools that simplify the generation of fine-grained transclusions and offer
enhanced functionality should be made available.
<img src="/images/test.jpg" ALT="my image">
< src="/images/test.jpg?shape=rect&coords=0,0,100,150" ALT="my image">
shape=rect&coords=0,0,100,150" ALT="my image">
Listing 1: A conventional image tag (top). A tag with a fine-grained
transclusion is transparent to users if an HTTP server extension module
is employed. A fine-grained transclusion through a CGI script is not transparent
to users (bottom).
Upon submitting these data to the server, the first CGI program creates
a URL and displays an example of how to use the URL to integrate the fine-grained
transclusion into HTML documents. Whenever a fine-grained transclusion
is retrieved, i.e., an image whose source URL contains certain parameters
is requested, the second CGI script is invoked. It loads the original file
from its location and extracts the requested spatial region of the image
according to the given parameters (see also Listing 1).
Finally, a file with the selected region is sent to the client.
The prototype implemented impressively demonstrates the power and ease-of-use
of the proposed technology. Along with several examples, it is available
online at [Kolbitsch 2005].
A drawback of the current implementation is that it is realised as CGI
application; hence it is not transparent to users. This means users can
recognise that images are loaded through a CGI program. An advantage of
the approach is, though, that even users that do not have the two CGI programs
installed on their HTTP servers can make use of the functionality because
the software allows the use of images with remote URLs.
A further shortcoming of the implementation is that original resources
have to be loaded onto the server that hosts the CGI scripts because image
files need to be present in order to be able to crop the desired region.
This makes retrieval of a fine-grained transclusion of an image rather
inefficient and slow. Moreover it causes increased network traffic.
Therefore, ideally the CGI program for retrieving the content resides
on the same server as the content. In this case, downloading the original
file can be reduced to a simple "file open" function call.
4 Application Areas
Fine-grained transclusions of multimedia documents in web-based
environments can have numerous applications. The prototype
implementation, for instance, is designed as part of a larger system
that offers communities tools to work actively with content from
electronic encyclopaedias and digital libraries in general (see [Kolbitsch and Maurer 2005]). In this environment
users have the ability to make text-based transclusions in order to
quote, refer to, and re-assemble existing articles. With the
implementation of this proposal they will also be able to make
transclusions of multimedia content at a high granularity.
The following sections give a brief overview of further, potential
applications in differing areas from museums to news and learning
4.1 News Providers
News channels usually retain a large number of audio and video interviews.
In many cases, they are not made available on the web site of the news
providers because the files are too large, the content is simply too long,
or for economic reasons.
Figure 5: Screenshot of the prototype implementation. The
user has to provide the URL of an image and the coordinates necessary to
select a spatial region.
With fine-grained transclusions news providers could store one large
file with the original interview in their internal database. On their web
site they insert a fine-grained transclusion of the original content. The
transclusion is, for instance, a temporal selection of an audio file that
contains the most significant key issues of the interview. The entire interview
(in full length) can, for example, be made available only to subscribers
of the news service.
Thus news providers have hardly any extra effort in creating the short
version of the interview, more or less no additional disk space is required,
and providers are able to offer a complimentary service, while having the
capability to retain full control of the content.
4.2 Galleries and Museums
Visitors in museums and galleries frequently encounter situations in
which they require professional help:
- they look at paintings and do not know what to "see";
- they look at paintings and do not know how to interpret them;
- they are not familiar with the artist's life and social surroundings;
- they do not have adequate historical background; etc.
Therefore audio guides, and more recently PDA-based multimedia guides,
are readily available in museums in order to assist visitors in their striving
Basically the same is true of people looking at paintings in online
galleries or online museums (e.g., [Getty
2004]). With fine-grained transclusions it becomes possible to
store the original painting once — as high quality
image. When certain parts of the painting are explained, a
transclusion of a spatial region is made, and the selection is
described in detail. Thus, it is sufficient to store an image once,
and when only a small section is referred to, a transclusion can be
4.3 Learning Environments
Similar to museums and galleries, web-based learning environments can
utilise fine-grained transclusions to explain details of drawings and other
media documents. In medical education, details of X-rays can be explained
thoroughly, in biology in-depth descriptions of parts of photos resulting
from electron microscopy can be given, etc.
In case of a sound file, only one minute of an entire opera can be transcluded
into an e-Learning lesson. The selection contains the key scene of the
work and is supplemented with the historical background, information on
the composer, and a reference to the score of the opera.
In addition to this, lesson authors could virtually include a part of
an external multimedia resource into a local lesson. A lesson for highschool
students that explains a chemical experiment, for instance, can transclude
a particular temporal selection of a related video available on the server
of a university.
4.4 Movie Archives and Music Stores
In large archives of movies such as the Prelinger Archive (see [Prelinger
2005]) fine-grained transclusions can be employed for producing trailers
and previews of the content on-the-fly. An entire movie, for instance,
is stored in the system. When a user requests a description of the movie,
a temporal or spatio-temporal selection of the movie is made and transcluded
into an HTML page that gives a summary of the movie, lists a number of
comments and provides a rating.
The same technology can also be employed in online music stores such
as the iTunes Music Store (e.g., [iTunes 2005]).
Previews of songs are created from the original sound file when users request
it. Although the short preview clips would usually not be stored they can
be retained within the system in order to increase performance. So when
a preview is requested for the first time, the fine-grained transclusion
is generated and cached in the system. On subsequent requests, the transclusion
is not newly generated but the preview is retrieved from the server cache
Note that the use of cached files does not limit the generality of the
concept of fine-grained transclusions. The relationship between the transclusion
and its cached version is identical; caches are merely utilised in order
to reduce loading time and improve overall system performance (see also
[Nelson 1996; Nelson 1999]).
In this paper, an approach to introducing fine-grained
trans-clusions of multimedia documents in HTML was presented, which
constitutes a consistent extension to the concept of transclusions in
HTML. With this technology, users have the ability to virtually
include only a small region of an image, only a short clip of an
entire movie, etc. into their web pages.
Two approaches to an implementation were discussed: a CGI-based implementation
and an extension module for HTTP servers. Both methods offer the same functionality
in terms of fine-grained transclusions while the levels of transparency
vary, and their integration into existing systems (HTTP servers) is different.
The suggested plug-in architecture offers an easy way to make an implementation
open to third-party developers and facilitate the support of new document
A prototype implementation proves that the concept is reasonable and
that the proposed technology can make reusing multimedia documents on the
Web more efficient. Various application areas from news to museums and
learning environments can have immediate benefits from the techniques presented
in this paper.
This paper was supported by the Styria Professorship for Revolutionary
[AIFF 1989] Apple Computer, Inc.: "Audio
Interchange File Format: 'AIFF'. A Standard for Sampled Sound Files Version
1.3" (1989), http://www.tsp.ece.mcgill.ca/MMSP/Documents/AudioFormats/AIFF/Docs/AIFF-1.3.pdf,
Accessed June 13th, 2005.
[Apache 2005] Apache HTTP Server, http://httpd.apache.org/.
[Foley et al. 1997] Foley, J. D., van Dam, A., et
al., "Computer Graphics: Principles and Practice", Second
Edition in C, Addison Wesley (1997).
[Getty 2004] The Getty Museum, http://www.getty.edu/art/.
[HTML 1999] Raggett, D., Le Hors, A., and Jacobs,
I.: "HTML 4.01 Specification", (1999) http://www.w3.org/TR/html4/,
Accessed April 28th, 2005.
[iTunes 2005] iTunes Music Store, http://www.apple.com/itunes/store/.
[Kappe 1995] Kappe, F.: "Maintaining Link
Consistency in Distributed Hyperwebs", Proceedings of the INET'95
Conference, Honololu, HI, U.S.A. (1995). See also http://www.isoc.org/HMP/PAPER/073/html/paper.html.
[Kolbitsch 2005] Fine-Grained Transclusions of Multimedia
Documents in HTML, http://www.kolbitsch.org/research/mm_transclusions/.
[Kolbitsch and Maurer 2005a] Kolbitsch, J., and
Maurer, H.: "Community Building around Encyclopaedic Knowledge"
(2005), to appear.
[Kolbitsch and Maurer 2005b] Kolbitsch, J., and
Maurer, H.: "Transclusions in HTML-Based Environments"
(2005), to appear.
[Krottmaier 2002] Krottmaier, H.: "Transcluded
Documents: Advantages of Reusing Document Fragments", Proceedings
of the 6th International ICCC/IFIP Conference on Electronic Publishing
(ELPUB2002), Karlovy Vary, Czech Republic (2002), 359-367. See also
[Macromedia 2005] Macromedia, Inc.: "Macromedia
Flash File Format (SWF) Specification License" (2005), http://www.macromedia.com/software/flash/open/licensing/fileformat/,
Accessed June 16th, 2005.
[Maurer 1996] Maurer, H.: "Hyperwave-The
Next Generation Web Solution", Addison-Wesley Longman, London
[Maurer and Lennon 1996] Maurer, H., and Lennon,
J. A.: "Flexible Link Architecture in Hypermedia Systems", Proceedings
of ED-MEDIA'96, Boston, MA, U.S.A. (1996) 384-389.
[Nelson 1965] Nelson, T. H.: "A File Structure
for the Complex, the Changing and the Indeterminate", Proceedings
of the ACM 20th National Conference, Cleveland, OH, U.S.A. (1965) 84-100.
[Nelson 1981] Nelson, T. H.: "Literary Machines",
Mindful Press (1981).
[Nelson 1995] Nelson, T. H.: "The Heart of
Connection: Hypermedia Unified by Transclusion", Communications
of the ACM, 38, 8 (1995), 31-33.
[Nelson 1996] Nelson, T. H.: "Generalized
Links, Micropayment and Transcopyright" (1996), http://www.almaden.ibm.com/almaden/npuc97/1996/tnelson.htm,
Accessed May 1st, 2003.
[Nelson 1998] Nelson, T. H.: "Transcopyright:
Pre-Permission for Virtual Republishing" (1998), http://www.aus.xanadu.com/xanadu/transcopy.html,
Accessed May 3rd, 2005.
[Nelson 1999] Nelson, T. H.: "Xanalogical Structure,
Needed Now More than Ever: Parallel Documents, Deep Links to Content, Deep
Versioning and Deep Re-Use", ACM Computing Surveys, 31, 4es
(1999). See also http://xanadu.com.au/ted/XUsurvey/xuDation.html.
[Pam 1995] Pam, A.: "Where World Wide Web Went
Wrong", Proceedings of the AUUG'95 & Asia-Pacific World Wide
Web '95 Conference & Exhibition, Sydney, Australia (1995). See
[Prelinger 2005] Prelinger Archives, http://www.archive.org/details/prelinger/.
[QTVR 2005] Apple Computer, Inc.: "QuickTime
VR" (2005), http://developer.apple.com/documentation/QuickTime/InsideQT_QTVR/insideqt_qtvr.pdf,
Accessed June 13th, 2005.
[SVG 2003] Ferraiolo, J., Fujisawa, J., and Jackson,
D. (Eds.): "Scalable Vector Graphics (SVG) 1.1 Specification"
Accessed June 12th, 2005.
[Thau 2003] Thau, R. S.: "Apache API notes"
Accessed May 21st, 2005.
[Tichy 1985] Tichy, W. F.: "RCS-A System
for Version Control", Software-Practice & Experience, 15,
7 (1985), 637-654. See also http://www.hpcc.ecs.soton.ac.uk/hpci/tools/cvs/ps/rcs.ps.
[X3D 2005] Web3D Consortium: "Information technology
- Computer graphics and image processing - Extensible 3D (X3D)", International
Standard ISO/IEC FDIS 19775:200x (2005), http://www.web3d.org/x3d/specifications/ISO-IEC-19775-IS-X3DAbstractSpecification/,
Accessed June 12th, 2005.
[Yocom 2004] Yocom, M.: "Mac OS History"
Accessed May 3rd, 2005.