Towards Visual Support for Document Navigation Through Multidimensional Catalogues

blaredsnottyAI and Robotics

Nov 15, 2013 (3 years and 8 months ago)

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Towards Visual Support for Document
Navigation Through Multidimensional Catalogues

Thomas Klement, Matthias Hemmje, Karl Aberer

GMD - German National Research Center for Information Technology
Integrated Publication and Information Systems Institute (IPSI)
Darmstadt, Germany
[klement, hemmje, aberer]@darmstadt.gmd.de
Motivation
The catalogue metaphor is in wide-spread use for information systems which divide large document
collections into subcategories to support browsing and searching [Marchionini 95]in these
collections. In most catalogue applications the document categories are structured in a hierarchical
way. The semantic organization of the catalogue's hierarchies plays a crucial role for the navigation
efficiency and also for the effectiveness of the catalogue-oriented browsing user interface as a
document exploration tool.
The primary design goal of hierarchical catalogue categorizations is to create a comprehensive,
memorable and convenient semantic organization of information relevant to the users' tasks and
information needs. Unfortunately, as the number of categories in one-dimensional catalogue
applications increases, the difficulty to classify a document into a certain category increases as well.
Furthermore, if a document’s content is to be associated with multiple categories, a user interface
based on a single tree structure of categories, as it is implemented in many of today's internet and
file system browsers, is not suited for navigation or browsing of the multidimensional catalogue
because the positioning of a document in the navigation hierarchy does not express the full
multidimensional catalogue context of the document.
The corresponding application of a multidimensional model in the catalogue user interface as well
as in the underlying catalogue representation avoids such difficulties inherent to traditional
browsing user interface approaches. If the categories are partitioned into dimensions which are
semantically independent of each other, the documents are positioned with respect to each
dimension. The browsing task can then, e.g., be supported by means of a navigation through
multiple "dimension menus" in parallel.
To take advantage of such a flexible and efficient catalogue representations based on a
multidimensional data model a project aiming at an integrated Information Catalogue Environment
(ICE) is currently performed at GMD-IPSI. The ICE system was developed with the goal to support
the semantic organization of a catalogue application by modeling the categories upon a
multidimensional data model supported by a database management system. In the following, this
paper focuses on novel navigation support mechanisms of ICE for browsing a multidimensionally
categorized document collection by means of visualizing navigation menus in an adaptable way.
Furthermore, the navigation paradigm presented in the paper is scaleable w.r.t. different user
stereotypes from novice to expert user.
Visualizations of Multidimensional Hierarchies
Two of the great challenges of multi-dimensional information visualization are to display more
dimensions and to map data dimensions more effectively on to visualization features. Due to these
challenges there were many visualization tools built over the last years to provide generic data
mappings and the new visualizations have been integrated into different applications contexts
[Hemmje 94], [Massari 98], [Feiner 97], [Keim 94], [Krohn 96]). However, the multidimensional
data model consisting of dimension hierarchies and the corresponding visualization metaphors on
the user interface level have not been adapted to many applications areas for naive users yet.
Multidimensional visualizations are mostly used for expert user interfaces, e.g. in advanced
database applications and just a minority of them could be used for wide-spread application areas
and for naive users.
Web applications with catalogue menus and search engines with category-based navigation services
are designed to provide naive users with comprehensible information structures. For these
applications the catalogue metaphor has been very successfully because it is already known to naive
users from online services. The basic idea of the ICE system is to take advantage of the wide-spread
user experience with the catalogue metaphor and to extend this metaphor by introducing multiple
navigation hierarchies based on a multidimensional categorization. The goal is to minimize the
navigational effort and to achieve adaptability to variable knowledge levels of different user
stereotypes by means of specialized navigation menus.
As a starting point, the similarities between catalogue applications and multidimensional Online
Analytical Processing (OLAP) database applications are outlined by two examples before ICE’s
navigation menu types are described in more detail. The OLAP examples described in the following
are intended to demonstrate that users of state to the art OLAP applications have to fulfill similar
tasks as users of a multidimensional catalogue information system.

Figure 1-1: OLAP Excel Client
Store Product Time
Jan.
Feb.
May
Apr.
Mar.
Dec.
Nov.
Oct.
Sep.
Aug.
Jul.
Jun.
Store 1
Store 2
Store 3
Store 4
Tables
Desks
Lamps
Shirts
Shoes
Socks
Coffee
Wine
Chairs

Figure 1-2: MD Domain Structures
Figure 1displays an OLAP client embedded in a common spreadsheet application ([Alea]). The
spreadsheet visualizes the amount of sold products according to the variable dimensions "products"
and "time". In the "time" dimension only the year 1993 is drilled down symmetrically to its four
quarters, whereas for the product dimension the drill down operation was performed
asymmetrically. In OLAP applications, an asymmetric drill down means that submenus of a
dimension tree are exploded only partially. The reason for dropping product items in the display is
that the displayed cells of the spreadsheet would have contained empty cells. If a further distinction
for such so called "null values" in OLAP application is not important, it is obviously reasonable to
save screen space. Furthermore, asynchronous drill down operations are implemented for ranked
drill downs (e. g. to support the query "visualize the top 20 of most sold products").
Another exploration mechanism for OLAP dimensions that is capable to present any number of
dimensions with little screen-space consumption is displayed in Figure 1-2. Here the users handle
sliders for each dimension to select the desired dimension members. [Thomsen 97] introduced this
metaphor as multidimensional domain structures. The metaphor is in wide spread use, e. g., linotype
used it for font exploration. Furthermore, it is often used for multidimensional range queries.
The following chapter shows an approach that is similar to the first example, but has been adapted
to multidimensional catalogue applications.
Static and Dynamic Catalogue Navigation
The example in Figure 2-1 describes the dimensions of a multidimensional trade fair & congress
catalogue. The categories in bold boxes (in multidimensional database theory called members of a
dimension) can be reached by sequential navigation in each dimension. In the following a tuple
which consists of a certain member in each dimension is called a "multidimensional address"
(MDA). The documents in a multidimensional catalogue are positioned (or categorized) manually
or automatically within each defined dimension or according to a MDA. The MDA {admin,
registration, conference} in figure 2-2 references three documents (figure 2-2) that list "registered
participants" of all "conferences" in the "service" dimension for “administration” purpos.

service
user
admin
trade fair
participant
member
conference
SIGMOD
VLDB
content
programme
registration
organization
brochures
booking

Figure 2-1: Multidimensional Address
Document 1
Document 2
Document 3
service
trade fair
conference
SIGMOD
VLDB
content
programme
registration
brochures
booking
user dimension is hidden:
user
admin
Figure 2-2: Catalogue Navigation
The top window and the left window frame in figure 2-2 display so called "navigation menus" for
the visible dimensions of the document collection. The navigation menus allow drill down and roll
up operations while displaying the resulting dimension structures and navigation contexts. All
members of a current MDA position are visualized including their submenu entries. The third frame
visualizes the documents that are referenced by an actual MDA during the navigation process. Thus,
it displays the exploration results to the user and is therefor called "document focus" frame (or
"content frame").
The so called "user dimension" in ICE is a dimension with additional features for controlling access
permissions. It is not visualized in the example because users are not allowed to change their
permissions navigationally. Authentication in the ICE system is done implicitly by selection of a
start address or menu based user areas which do not reflect the user dimension that represents the
different user groups. However, other implementations of user stereotypes and corresponding
dimensions and permissions are possible. If the actual user group was, e.g., "participant", the focus
frame could have displayed a registration form instead of a listing of registered conference
participants.
The two figures displayed in the following outline two types of navigation menus provided by ICE.
They behave different w. r. t. menu selections of the users during the navigation process.
service
trade fair
conference
SIGMOD
VLDB
content
programme
registration
brochures
booking
deaktivated:
no admin
information
about brochures
Document 1
Document 2
Figure 2-3

Document 1
Document 2
service
trade fair
conference
SIGMOD
VLDB
content
programme
registration
brochures
booking
selection
Result:
no admin
information
about brochures
and bookings
Figure 2-4: Dynamic Navigation Menus
While the so called "static navigation menus" in Figure 2-3 provides visual feedback about the
existence of accessible documents during the navigation, the so called "dynamic navigation menus"
in figure 2-4 only display menu items that would refer to documents if one of them had been
selected. The differences between the menu types are described in more detail by two more
examples.
The actual MDA during navigation as in the previous examples is "{admin, registration,
conference}". If users decided to select the member "brochures" in a static menu the focus would
display an empty list of resulting documents, because the new MDA would not reference any
documents. Obviously, there is a need for a so called "navigation look ahead" feedback, because
exploring so called areas in the document space where no documents are available does not make
sense. In static menus the members of the navigation context that refer to empty cells are visualized
in a "navigationally deactivated" style in the resulting submenus. This approach prevents users from
dealing with changing menu structures.
To provide a more economically navigation w. r. t. screen space, the ICE system's catalogue
interface components offer dynamic navigation menus. Dynamic menus may change their structure
as a result of drill down and roll up operations in other dimensions. They visualize only submenus
for a member of the actual MDA tupel that references documents. Hence, in comparison with static
menus they visualize merely activated menus. The use of dynamic menus causes a side effect
outlined by Figure 2-4. Again, the current MDA is {admin, registration, conference}, but at this
time dynamic menus are used. The selection of VLDB has the effect that the resulting MDA is
"{admin, content, VLDB}". The figure shows that any MDA obtained by a selection from the
submenu of the menu item "registration" would reference an empty cell. So the "content" dimension
has to be rolled up to obtain a valid state for the dynamic menu "content" after the "VLDB" drill
down operation. This side effect ensures that all submenus address at least one document.
Future Work and Conclusions
The approaches towards visual navigation menus presented in this paper are extensible w.r.t. the
combination of the two menu types. OLAP applications have shown that static menus can be
handled by naive users. We assume that the interaction with multiple dynamic menu in an
application interface is suitable to not naive users, because the side effects in multiple navigation
menus will not be easily understandable. Nevertheless, multiple dynamic menus can be arranged by
priority from more experienced users. The priority would then indicate what the order of the
affected dynamic menus is for side effect roll up . Furthermore, the ICE approach is can be
extended with additional navigation strategies for automatic asynchronous drill down operations .
The variation of menu types and navigation strategies allow a scaling of the user interface for
different user stereotypes.
Finally, multidimensional catalogues offer nomerous benefits for an improved orientation within the
overall context tied up to web catalogue [Looksmart] and Altavistas [Altavista] graphical view for
refined search.
References
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