A Journal of Software Engineering and Applications, 2013, 6, 32-36
doi:10.4236/jsea.2013.65B007 Published Online May 2013 (http://www.scirp.org/journal/jsea)
Just-In-Time Hypermedia
Zong Chen1, Li Zhang2
1School of Computer Sciences and Engineering, Fairleigh Dickinson University, Teaneck, NJ, USA; 2New Jersey Institute of Tech-
nology, Newark, NJ, USA.
Email: zchen@fdu.edu, zhangli73@yahoo.com
Received 2013
Many analytical or computational applications create documents and display screens in response to user queries “dy-
namically” or in “real time”. Hypermedia features must be generated “just in time” – automatically and dynamically.
Conversely, the hypermedia features may have to cause target documents to be generated or re-generated. This paper
presents a just-in-time hypermedia framework to provide hypermedia support of virtual documents.
Keywords: Just-in-time; Hypermedia; Virtual Document
1. Introduction
Many analytical applications, especially legacy systems,
create documents an d display screens in response to user
queries “dynamically” or in “real time”. These docu-
ments and displays do not exist in advance, and thus hy-
permedia must be generated “just in time”—automati-
cally and dynamically.
Suppose an analyst wants to determine projected prof-
its for different sales levels in her company. She per-
forms the analysis within a sales support application, and
makes comments on each resulting profit calculation. A
few days later when preparing her final report, she knows
that she will need to include the calculation results and
comments. She wishes to return to them without having
to remember the input parameter values for each and then
manually re-performing each calculation. Therefore, she
creates a bookmark to the display screen containing each
calculation result before discarding it. Invoking each
bookmark later causes the sales support application to
re-execute its calculations automatically, and the hyper-
media interface to relocate her comments in the applica-
tion’s newly re-generated display.
A just-in-time (JIT) hypermedia system is different
from a traditional hypermedia system in that it adds hy-
permedia functionality to dynamically generated virtual
documents, while traditional hypermedia systems usually
deal with static documents. The major challenges en-
countered in JIT hypermedia research are dynamic re-
generation, re-location and re-identification.
In analytical or computational applications, documents
do not exist in advance, they are generated when users do
queries or execute some commands. When the windows
close, these documents no longer exist. If a user adds
some comments to a document, next time when he tries
to visit the comments, the virtual document that was an-
notated should be re-generated. Some Web systems re-
generate analysis screens by storing all relevant parame-
ters in the virtual document’s URL (Uniform Resource
Locator), but many Web-based and non-Web based leg-
acy systems have no such mechanism. Other Web sys-
tems do not allow URLs with detailed parameters for
security or other reasons. When the user bookmarks and
returns to its URL, the system returns the user to the
home page or the initial input page. The JIT hypermedia
system must provide automatic regeneration without
asking the user to reenter parameters. Because a virtual
document does not have a file name and a specific loca-
tion to store the file content, dynamic regeneration re-
quires a unique and persistent identifier to reference each
virtual document. Dynamic regeneration also requires a
criterion and procedure to decide whether the re-gener-
ated document is same as the previously marked docu-
When a virtual document is regenerated, the virtual
document’s structure and content could be changed. It
could also be possible that virtual elements in the docu-
ment have changed. If a user has put some anchors on the
virtual document, the position and content of the anchors
could change. It is necessary to find the location of the
predefined anchors in the virtual document, and decide
whether the content is same as the previously marked one.
This is called re-location and re-identification. Moreover,
when analytical applications generate new query results,
the JIT hypermedia system should relocate and re-iden-
tify the anchors for known elements in the old query re-
sults. Re-location requires flexible and efficient mecha-
Copyright © 2013 SciRes. JSEA
Just-In-Time Hypermedia 33
nisms to record the location and content of anchors.
Re-identification requires a criterion to revalidate the
virtual elements and some information about the virtual
elements are needed.
2. Static vs Dynamic Links
Hypermedia is a concept that encourages authors to
structure information as an associative network of nodes
and interrelating links [1]. Hypermedia researchers view
the terms hypertext and hypermedia as synonymous and
use them interchangeably. Hypermedia nominally applies
hypertext concepts to multiple media. A hypertext sys-
tem is made of nodes (concepts) and links (relationships).
A node usually represents a single concept or idea. It can
contain text, graphics, animation, audio, video, images or
programs. In most hypermedia systems, a node usually is
a document. It can be semantically typed (such as detail,
proposition, collection, summary, observation, issue)
thereby carrying semantic information [2]. Nodes are
connected to other nodes by links. Links represent rela-
tionships between two nodes. Static links are direct, per-
sistent connections from one node or anchor to another.
Dynamic links on the other hand are computed each time
an attempt is made to traverse them.
The static links suffer from a variety of problems [3].
These include:
Dangling links: when a link points to a node that is
subsequently moved or deleted, that link becomes stale;
attempts to traverse it will fail.
Inexpressiveness: some conventional systems lack
link semantics information. Even in systems that do pro-
vide link types, if the number of link types is set in ad-
vance, then the information content that can be attached
to a link is restricted to the defined set.
Expensive construction: manually constructing
links is time-consuming and expensive.
Inflexibility: manual links are created once and are
thereafter fixed; they are unable to rearrange themselves
to suit the needs of the moment.
Duplication: The semantic knowledge implicit in a
particular link or link type cannot easily be reused or
Irrelevance: When a node’s content changes or
other conditions change, the link may no longer valid.
Dynamic links are created at run-time rather than be-
ing generated earlier (pre-computed links). One approach
to dynamism in hypertext focuses on computing links
based on relationships or similarities between texts or
passages of text. In this approach, the link is not defined
as a pointer from one hypertext node to another, but
rather as a query that leads to a different node [4].
Pre-computed links can be constructed at any time,
whereas dynamic links are computed at the moment they
are required [5]. A dynamic link can take into account
the specifics of the current user interaction. The query
might be based on a co mbinatio n of the browsing histor y,
user profile, content of the current document, etc.
Compared to static links, dynamic links are more
flexible than static links. Dynamic links are dynamically
computed according to the underlying relationships be-
tween nodes or elements. Since dynamic links are
computed at the time when users request to do so, there
is no need to duplicate the links manually and it is not
time consuming. On the other hand, dynamic links also
can suffer from the dangling link problems. Dynamic
link production, however, can detect a dangling link
problem when it occurs and can guarantee that no dan-
gling links are displayed. Dynamic links can allow links
to be created from and to material that the link author
does not control by overlaying the link within the docu-
ment sent to a browser. When a node’s content changes
or other conditions change, dynamic link production has
the potential to detect th at the link is no longer valid.
Advantages of dynamic links include: a simplified in-
terface to search functionality, reduced authoring effort,
and greater opportunity for customization based on the
current user’s interaction history or specific task context.
An additional benefit is decreased cost of maintenance.
However, disadvantages include computation of each
link at run-time (instead of using stored, pre-computed
links), over-completeness and problems with false links.
Computation links at run-time can be expensive in a
large system with many users [5]. Over-completeness
occurs when the reader is presen ted with more links than
he/she can comprehend [6]. False links may occur be-
cause of polysemy, i.e., multiple words and sentences
that lead the search algorithm to incorrectly judge the
similarity of text fragments. This may lead to unsound
links [6] in the hypertex t. JIT systems support both static
and dynamic links.
An anchor in the proposed JIT system is a selection
(which could be part of the document or the whole
document) in a dynamically-generated virtual document.
A link in the JIT system is the connection between two
selections or multiple selections in one or more docu-
ments. JIT supports static and dynamic links. Static links
in JIT are manual links created by users, which is similar
to traditional systems. What JIT offers new are
re-location and re-identification processing when previ-
ously-displayed documents are redisplayed. Dynamic
links in JIT system are computed, based on the inherent
relationships between elements, metadata structure,
document structure, relationships among application spe-
cific commands and parameters, user group relationships,
etc. These relationships could be analyzed before the
hypermedia interface is designed or at the time an anchor
is selected, and JIT then dynamically determines the
links. JIT can support node types by analyzing the dy-
Copyright © 2013 SciRes. JSEA
Just-In-Time Hypermedia
Copyright © 2013 SciRes. JSEA
namically-generated virtual document types, through
classification, and through categorizing the commands
and parameters.
3. Just-In-Time Hypermedia Framework
The differences between dynamically-generated virtual
documents and static documents are shown in Table 1. It
gives the following conclusion:
(1) Dynamically-generated documents can be cre-
ated in many flexible ways.
(2) It is more difficult to reference and version
virtual documents. To reference a virtual document, a
unique document identifier is required and a resolution
scheme is needed. The “just-in-time” (JIT) hypermedia
system should be able to generate unique identifiers and
maintain them. Every time a virtual document is refer-
enced, the JIT hypermedia system should resolve this ID
to the specifications of the virtual document to regener-
(3) Maintaining hypermedia within dynamically-
generated virtual documents leads to requirements that
are different from static documents, including dynamic
regeneration, relocation and re-identification.
Table 1. Dynamically -generated vs. Static Documents.
Dynamically-Generated Virtual Document Static Document
Status Dynamic and virtual: does not exist in advance, only exists when
the user visits the virtual document. Static and real, stored persistently in some physical
location with a specific file name.
Storage Only specifications or links and other information ab out the
document are stored; requires much less room. The entire content of the document is stored.
Reference Could be referenced by a unique document ident ifier or some
specifications about the document. Referenced by file name, location or a unique
document identifier.
(1) Dynamically generated by query, search, system commands or
user actions, depending on parameters specified by user. The
document contains results from the database or computation
module; or dynamic informatio n, such as date or time.
(2) The creation date and time, file size and content could change
with each generation.
(1) Often created manually.
(2) Once create d, the date, time, file size and content
are consistent.
Regeneration Regeneration is required every time the user revisits the document.No regeneration is required.
Template Usually some kind of docum ent t emplates, com positi on algo rithm s,
scripts or skeletons facilitate the document’s composition,
organization and components during dynamic regeneration. Can follow a pre-defined format or be free-form.
Usually it is not difficult to analyze the metadata. Because the
document is the result of query, search or calculation, useful
metadata should be available. For examp le, the query results from
database have some definite metadata, the user actions (commands
+ parameters) are known, the dynamic information (date, time) has
clear meanings, and the calculation has definite metadata.
Metadata may be provided. If not, then it often will
be difficult to infer.
Unless the virtual document can be saved as a static document,
the ability to edit it is irrelevant. For the purposes of dynamic
hypermedia functionality, virtual documents are not editable
and only can be generated by the underlying application.
Usually editable. The date, time and file size in-
formation could be used to indicate whether the file
has been edited.
In order to version the document:
(1) History information about the old version should be kept and
sometimes a minimal copy of the old version is req u i red.
(2) Date and time information is not very useful to indicate
that this is another version.
(3) The file size could be used to indicate that it is a new
version to the extent that two versions are treated as the same
(further discussion later).
(4) Byte-by-byte comparison is not possible, because only a
minimal co p y of the document i s kept (this also depends
on the two versions are treated as the same, as discussed later).
Usually performed by a document versioning sys-
tem. Usually the original version of the document is
kept. Then for each version, the system does a file
comparison and keeps the file di fferences (“deltas” ).
When displayi ng the new versio n, the file differe nce
is added to the old version to recreate the new
version. Date, time and file size information is very
useful for versioning purposes.
Anchoring elements
in a document
To record the anchor information, internal document addressing is
required, possibly using the same method s as with static document s.
Every time a user revisits the document, element relocation and
re-identification are required (details will be discussed later).
As long as the do cument has not been ed ited, there is
no need to re-locate and re-identify the anchors.
However, if anchors are stored in an external base,
they technically need to be relocated, but this is
Just-In-Time Hypermedia 35
Besides this, other requirements include virtual docu-
ment support; document generation; unique identifiers
for virtual documents and elements; internal document
addressing mechanisms for elements; application specific
metadata support; hypermedia functionality; integration
with viewers and integration with information systems.
These requirements are discussed in detail as follows:
Virtual document support: Traditional hypermedia
systems deal with static documents, which have persis-
tent file names and locations. A JIT system should be
able to reference a virtual document, record its informa-
tion and enable hypermedia services for these virtual
documents. Also it should enable hypermedia services
for static documents.
Document generation: A JIT system should be able
to generate a document when a user asks for it. Docu-
ment generation may be handled by an independent un-
derlying information system. However, the JIT system
should have the ability to control the generation process,
add semantic information and display the documents on
Document regeneration: When a user traverses to a
link anchor or bookmark that was put on a virtual docu-
ment, the JIT system should regenerate the document and
then revalidate the reg enerat e d d ocume nt.
Hypermedia functionality support: Hypermedia
functionality should work for the dynamically generated
virtual documents with a similar effect as for static
Re-location and re-identification: When a user trav-
erses a link or comment that was put on a virtual element
in a virtual document, the JIT system should be able to
find the location of the anchor for this element in the
document. This is called re-location. The JIT system also
should be able to re-identify the anchored virtual ele-
ments in the virtual document.
Unique, persistent identifiers for virtual documents
and virtual elements: Reference to virtual documents and
virtual elements requires unique and persistent id entifiers
across the hypermedia system.
Internal document addressing mechanisms:
Re-location and re-identification of virtual elements re-
quire flexible and efficient internal document addressing
Application specific metadata: The metadata of the
applications should be analyzed and supported to the
extent that it is used when the JIT system regenerates and
revalidates the virtual documents and elements.
Integration with viewers: A hypermedia system
could support multiple viewers (e.g., Web browsers and
interfaces of non-Web applications). Because applica-
tion-generated documents could be displayed by different
viewers, this requires integration with viewers. Integra-
tion with viewer means the JIT system has an interface
(middleware) between each viewer, which could trans-
form the JIT data formats to data formats that different
viewers could unde r st a nd or displ a y .
Integration with information systems: To supple-
ment hypermedia functionality for the underlying inde-
pendent information systems, integration with informa-
tion systems is required. Different applications give out
different source documents in different formats. Each
requires an interface or middleware to transform its
source documents into the universal documents that the
JIT system can understand and process.
A conceptual JIT architecture is proposed in Figure 1.
A brief description of the conceptual architecture is as
Viewer Wrapper: integrated with viewers. It is com-
posed of the Selection Manager; the Document Presenta-
tion Manager and the Communication Manager. The
Selection Manager gets the selections (content, location)
from the screen. The Document Presentation Manager
handles the layout of the internal virtual documents and
translates the virtual documents to the data format that
the viewer can recognize. The Communication Manger
manages the communication between the viewer and the
hypermedia engine.
Application Wrapper: manages the communication
between the application and the hypermedia engine. It
passes the application outputs to identify any potential
elements which JHE may wish to id entify as link ancho rs.
It then translates the application specific data formats to
any internal document data format that the hypermedia
engine re quires.
Hypermedia Engine: Hypermedia Engine is com-
posed of the Hypermedia Gateway, the Regeneration
Engine, the Hypermedia Service Module and the Virtual
Document Manager. The Hypermedia Gateway deals
with the communication between viewer wrapper and the
hypermedia engine and the communication between the
application wrapper and the hypermedia engine. The
Regeneration Engine deals with virtual document gen-
eration and revalidation. The Hypermedia Service Mod-
ule supplements virtual documents with hypermedia
functionality. The Virtual Document Manager manages
unique, persistent identifiers and other related informa-
tion for virtual documents and virtual elements. It also
does re-location and re-identification for the regenerated
virtual documents and virtual elements.
4. Future Work
The differences between a just-in-time hypermedia sys-
tem and a traditional hypermedia system are analyzed. A
JIT hypermedia framework was identified based on the
Copyright © 2013 SciRes. JSEA
Just-In-Time Hypermedia
Figure 1. A conceptual JIT hypermedia architecture.
analysis. In the future, a JIT hypermedia engine is
planned to be built based on the proposed architecture.
Furthermore, a prototype of JIT system is planned to be
built to provide dynamic virtual document support.
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