=Paper=
{{Paper
|id=None
|storemode=property
|title=Social Tagging for Digital Libraries using Formal Concept Analysis
|pdfUrl=https://ceur-ws.org/Vol-672/paper13.pdf
|volume=Vol-672
|dblpUrl=https://dblp.org/rec/conf/cla/EklundW10
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==Social Tagging for Digital Libraries using Formal Concept Analysis==
https://ceur-ws.org/Vol-672/paper13.pdf
Social Tagging for Digital Libraries using Formal
Concept Analysis
Tim Wray and Peter Eklund
twray,peklund@uow.edu.au
School of Information Systems and Technology
University of Wollongong
Northfields Ave, Wollongong, NSW 2522, Australia.
Abstract. This paper describes the Art Collection Ecosystem – an ap-
plication that allows users to tag and serendipitously browse content
using Formal Concept Analysis. Within this application, tags are de-
rived from meta-data of artworks within an existing asset management
system and are classified according to theories derived from social tag-
ging behaviour. We present past and recent iterations of its design, where
it is evaluated as a contextual comparison to a popular image tagging
application, Flickr. Through the process of iterative design and user eval-
uation, we produce results are of interest to any applied research and de-
velopment that involves the exploration of digital library content using
concept lattices.
1 Introduction
Digital libraries can dramatically extend the capabilities of traditional libraries
by collecting, managing and preserving long term rich digital content [2]. Within
the art and museum sector, projects such as Te Papa’s Collections Online 1
and the Brooklyn Museum’s Open Collection API 2 reflect a current industry
trend of digitising their collections for public display and research purposes.
There have also been some early experiments that involve the capture of social
tagging data to enhance the meta-data descriptors of the collection that have
been demonstrated by projects such as the steve.museum 3 and the PowerHouse
Museum 4 collection databases. This approach was supported by evidence that
there was a dissonance between audiences and institutions in their view, dialogue
and terminology associated with art content, and that user-supplied tags could
be used to fill gaps in the documentation that surround the objects [18].
Within this paper, we present the Art Collection Ecosystem, a FCA-based
system that allows the synthesis and browsing of formal concepts based on a se-
lection of artworks from the University of Wollongong’s Art Collection and their
1
http://collections.tepapa.govt.nz/
2
http://www.brooklynmuseum.org/opencollection/api/
3
http://www.steve.museum/
4
http://www.powerhousemuseum.com/collection/database/
140 Tim Wray and Peter Eklund
associated tags. The browsing and presentation of the art collection is based of
the presentation the conceptual neighbourhood paradigm, which was presented
in earlier work [7], and is detailed in section 2.2. Users have the ability to add
their own tags to the works which in turn can drive and influence the underlying
concept lattice, therefore influencing both collection content and navigation.
The idea of experimenting with FCA and collaborative tagging is not new. For
instance, Hwang et al. describe theoretical approaches for organising and mining
knowledge from user created folksonomies using FCA [12] [11]. Interestingly they
have also described similar issues that we have encountered that relate the lack
of semantics within the tagging process as described in [10]. Similarly, Schmitz
et al. have proposed a method of using FCA as a means of mining trends and
association rules within folksonomies [17]. Our work is based on the following:
the design refinements and evaluations presented in section 4, particularly with
respect to how the conceptual neighbourhood metaphor is used to guide users
through the information space derived from tags; the application domain of this
FCA-based application; and the use of a tag classification framework that allows
for faceted navigation on the collection using conceptual scales.
The paper is structured as follows: in section 2, we provide a brief overview of
the theory behind Formal Concept Analysis and the conceptual neighbourhood
paradigm along with the tag classification framework that is used to provide
faceted browsing. We then describe the Art Collection Ecosystem in section 3
and in section 4 we then follow through with two iterations of its design and
user evaluation. We then conclude the paper by summarising our results and
describing details of future work.
2 Background
2.1 Formal Concept Analysis
Formal Concept Analysis is a data analysis technique that allows the synthesis
of formal concepts based on a collection of objects and their attributes [19]. It
follows the philosophical tradition that any concept or unit of thought could be
understood in terms of its attributes (or intension) and its objects that are char-
acterised by those attributes (its extension). For instance, for a given collection
of artworks, a formal concept (A, B) can be described where A represents the
collection of artworks or their identifiers and B represents their set of tags (such
as, { ‘screenprint’, ‘aboriginal’} ).
Formal concepts can be placed into a specialisation hierarchy, where more
specific concepts (with fewer objects and more attributes) can be viewed as a
specialisation of other less specific formal concepts. The result is an algebraic
structure known as a concept lattice shown in Fig. 1.
Conceptual scales [9] are a powerful tool that store views of the data being
analysed. Conceptual scales encompass specific attribute sets and are repre-
sented by a mathematical entity called a formal context. A context is a triple
(G, M, I) where G is a set of objects, M is a set of attributes and I is an inci-
dence relation between the objects and the attributes. Within the Art Collection
Social Tagging for Digital Libraries using Formal Concept Analysis 141
Fig. 1. A concept lattice representing a sub-context of works within the Art
Collection Ecosystem
Ecosystem, we use conceptual scales to represent specific contexts with different
themes such as ‘artworks as described by medium’ or ‘artworks as described by
location.’ Conceptual scales can be used to combine multiple views on the data
– for instance, Fig. 1 represents a sub-context created by combining the concep-
tual scales of ‘materials’ and ‘location.’ Within the Art Collection Ecosystem,
conceptual scales are based on a classification of tag usage within collaborative
tagging systems (as described in section 2.3) and users can effectively extend
conceptual scales by adding their own tags to the collection.
2.2 The Conceptual Neighbourhood Paradigm
We also apply the conceptual neighbourhood paradigm for browsing the infor-
mation space provided by the concept lattice. Within this approach, the user is
placed at a single formal concept within the lattice. Users can move from one
formal concept to another by navigating across neighbouring concepts. Fig. 2
shows a lattice neighbourhood representation of the screenshot within Fig. 3.
In our implementation of this approach, objects within a formal concept are
represented as thumbnails. Users can navigate to upper neighbours (more general
concepts) or lower neighbours (more specific concepts) – this is done via textual
labels within the UI that are, in the case of the lower neighbours, weighted
according to the extent size. Clicking on these textual labels – referred to as upper
neighbour and lower neighbour controls – allow the user to move to other formal
142 Tim Wray and Peter Eklund
Fig. 2. The conceptual neighbourhood representation of the application screen-
shot as shown in Fig. 3
.
concepts within the neighbourhood. This allows the interface to move across
the lattice in an intuitive way where it is impossible to navigate to a concept
with an empty extent. It also allows users to change their conceptual view of
the collection in minimal and incremental steps. Figs. 2 and 3 both represent a
view state that describes a formal concept with attributes { ‘print’, ‘aboriginal’
} with their upper and lower neighbours. A user within this view state could
easily generalise to all ‘print’ works or all ‘aboriginal’ works, or specialise to
aboriginal print works that also feature keywords ‘etching’, ‘screenprint’, ‘female’
or ‘yolngu.’
This form of navigation helps reduce the complexity at a given ‘decision’
point due to the natural hierarchical nature of lattice generation and navigation
in which attributes can be hidden by others due to implications or attribute
hierarchies. For instance, if all ‘screenprint’ objects are in fact a subset of all
‘print’ objects, then a user would be required to navigate to all ‘print’ objects
before they could refine their query to all ‘screenprint’ objects, and vice-versa
if they were traversing upwards through the lattice. The tagging system also
supports hierarchies – if one was to tag an object as ‘arnhem land’ (which is
a region of the northern territory) then the object will also be automatically
tagged as ‘northern territory’ as the system stores explicit sub-type / super-
type association rules between the two tags.
2.3 Classification of Tags within Collaborative Tagging Systems
Collaborative tagging systems such as Flickr have become popular in recent years
due to the ability for users to annotate works with keywords that can be used for
later retrieval. Tagging can be used either as a means of ‘connecting’ with other
users and their works or as a means of organising content [1]. We focus on the
latter purpose within this paper, where we use a common typology of tags based
on actual tagging behaviour within collaborative tagging systems. According to
Golder and Huberman [10], tags can be used to:
– Denote subject, that is, people, places or things being described or depicted
within the resource.
Social Tagging for Digital Libraries using Formal Concept Analysis 143
– Denote type, whether that resource is a photo, file or bookmark.
– Denote ownership and provenance, identifying who owns authorship, control
or rights to a resource and where it came from.
– Denote category or class, used to aggregate or unify resources with common
properties.
– Describe specific qualities and characteristics of that resource, such as colour,
texture, themes etc.
Within the Art Collection Ecosystem, we class conceptual scales based on
these five types. For instance, the conceptual scales ‘artist name’ or ‘materials
and medium’ (which contains attributes { ‘canvas’, ‘clothing’, ... } ) would be
classed under qualities and characteristics, whereas the scales of ‘origin’ and ‘lo-
cation’ would be classed under ownership and provenance. These categories can
be used to aggregate any kind of content within a collaborative tagging system.
We predict that these general categorisations are useful and even necessary for
managing large groups of scales or vocabularies of tags, particularly where users
get to add their own tags. The classification of conceptual scales also permits a
form of thematic access control: for instance, in one scenario, tags that describe
an object’s ownership and provenance are set by the museum and institution and
cannot be removed or altered, or they need to rely on a fixed and standardised
vocabulary to avoid duplication of terms (eg. ’Metropolitan Museum of Art’,
’MMA’). However, end users are free to add their own tags that describe the
qualities and characteristics of its content. This approach permits appropriate
integration of user defined tags and content while preserving read-only (but still
‘taggable’) enterprise content.
3 The Art Collection Ecosystem
The Art Collection Ecosystem5 is the latest development in a series of projects
that apply Formal Concept Analysis as a means of navigating an information
space. It follows from the incremental design and evaluation improvements of
ImageSleuth [5], ImageSleuth2 [7], AnnotationSleuth [6] and the Virtual Museum
of the Pacific [8], in that order.
Results from a previous user study of its predecessor application ImageSleuth
[7] confirm the suitability of a concept lattices for the representation and naviga-
tion of image collections, and the intuitiveness of applying the conceptual neigh-
bourhood metaphor. Although the Art Collection Ecosystem addresses some
criticisms of ImageSleuth – mainly of those that relate to interface design and
layout – it also employs a number of new features discussed in section 4. The
objective of the user evaluations is therefore twofold: to validate (or improve)
new design features of the interface but to also determine the degree of user
acceptance – the degree to which users are likely to adopt or use a system – as
a Web-based tool for browsing and exploring collection content.
5
Available at http://epoc.cs.uow.edu.au/ace – to access the site, enter ‘aceuser’ as
userame and ’uowace’ as password.
144 Tim Wray and Peter Eklund
Fig. 3. A screenshot of the Art Collection Ecosystem
According to Rogers’ theory of the attributes of innovations[15], a new in-
novation is often framed and perceived in terms of how it relates, supersede or
compare to existing innovations. Therefore in our acceptibility study it is impor-
tant to provide a benchmark or point of comparison where users can cast their
judgements about the usefulness of an application. For this reason we will use
Flickr6 as a point of comparison: it is a modern, widely adopted image man-
agement and tagging application that encourages exploration and serendipity of
its vast collections. Although we do acknowledge that the content and tasks of
the two systems are different within this study, we argue that the use of Flickr
as a benchmark provides users with a common point of reference on which to
assess the overall design features and potential usefulness of the Art Collection
Ecosystem and the concept lattice metaphor.
The study follows two iterations of a design cycle. 20 participants were used
to assess and validate the original design. Some design flaws were identified and
addressed. A further 5 participants were used to validate the revised design.
Our conclusions were drawn from a thematic analysis of the results of the user
evaluations.
4 Design and Evaluation
4.1 Initial Design
Like its predecessor [7], the Art Collection Ecosystem incorporates textual labels
to provide attribute inclusion and exclusion as one would navigate to a neigh-
bouring concept. However, it benefits from a revised design of its user interface
(which was then applied to its counterpart - The Virtual Museum of the Pacific),
both to improve functionality, feedback to actions and layout. These include:
6
http://www.flickr.com
Social Tagging for Digital Libraries using Formal Concept Analysis 145
– Animation that conveys a sense of ‘drilling down’ and ‘rolling up’ as one
navigates to more lower and upper neighbours respectively. To the user, this
is intended to convey a sense of ‘refining’ and ‘generalising’ a particular point
within an information space.
– The use of a ‘tag cloud’ to represent the entire collection - this is a popular
means of representing key terms and their prominence.
– The hybrid combination of a tag cloud and a list of lower neighbour textual
labels. Here, attribute labels are positioned and weighted according to their
extent size. This allows a user to determine the prominence of a given at-
tribute within a formal concept. In Fig. 4 for example, ‘screenprint’ is shown
to be the most prominent attribute within the current conceptual view.
– An ‘auto-complete’ suggestive search field mapped to the union of all at-
tributes within the selected scales. This was to address previous criticisms of
the ImageSleuth interface regarding its ability to perform a keyword-based
search.
Fig. 4. Lower neighbour ‘tag cloud’ control within the Art Collection Ecosystem
As shown in Fig. 4 there are checkboxes on the left-hand side that allow users
to toggle conceptual scales – these effectively allow users to specify and combine
how they would view and browse the information space of the art collection.
We class and group these scales based upon the tag classification framework
discussed in section 2.3. The individual scales themselves are derived from key
attribute descriptors of the artworks from the existing database of the University
of Wollongong’s Art Collection. As with many existing digital libraries, there
were some problems of meta-data inconsistency [13], synonymy, and polysemy
during the meta-data extracting process - a common problem also found in
collaborative tagging systems [10].
4.2 Evaluation Cohort and Design
25 students and staff from the University of Wollongong were selected to par-
ticipate in a user acceptance study. A preliminary survey was conducted to
146 Tim Wray and Peter Eklund
determine the attributes of the cohort. In an answer to the question ‘On a scale
of 1 - 10, how much interest would you show in visiting and exploring an art
collection within a web browser’, the average user response was 6, although there
was a high variance within this response. 18 of the 25 surveyed users have used
or were already familiar with Web-based tagging applications. The use of Flickr
as a point of comparison was intended to standardise the level of experience
users had with existing Web-based image exploration and tagging applications,
along with providing a baseline point of comparison as described in section 3.
Users were required to perform tasks that involved searching and exploration
in both applications. Screencams and commentary were recorded as users per-
formed these tasks. A qualitative analysis was done where recurring themes and
issues were identified. 20 users undertook an initial study, then a further 5 users
were surveyed to validate the design changes described in section 4.4. After the
evaluation sessions, all users were required to complete a brief survey that doc-
umented their overall impressions with the Art Collection Ecosystem.
4.3 Initial Evaluation Results
After the initial evaluation, users generally held a positive attitude towards the
design and functionality of the user interface for the Art Collection Ecosystem.
In comparison to the functionality afforded by Flickr, users generally praised
both the aesthetics of the user interface along with the ability to ‘hold’ a cur-
rent or particular point or concept within the information space. This finding
is consistent with the previous usability study on ImageSleuth [7]. The ability
to generalise or refine’s one view within the information space contrasted with
the search functionality offered by Flickr where users had trouble refining their
search terms – for instance, if they wanted to select a particular sub-set of im-
ages within their results, users were required to alter their text string within the
search field, often generating a result set that was disjointed from the original.
Users generally praised (and understood) the effect and usefulness of having
the ability to toggle conceptual scales in order to define a context. More specif-
ically it allowed them to specify the dimensionality of their search – such as
whether they wanted to search by material type, artist name, or physical loca-
tion. Many perceived these controls “as a way of refining your search” and made
comparisons with this and Flickr’s ‘Advanced Search’ functionality. However,
the implementation and categorisation of conceptual scales into groupings such
as ‘Subject’, ‘Type’ and ‘Ownership and Provenance’ was met with a mixed re-
sponse. There were positive remarks with respect to clear demarcations of scale
options, although there was some criticism with respect to ambiguity to the
names of the scales (for instance, there was a scale called ‘location’ and another
called ‘region’) and there were some comments on the triviality of the feature.
Further criticism was directed at the meaning behind individual tags and at-
tributes – in expressing concerns of tag polysemy, one user noted that the tag
‘united kingdom’, for example, could refer to the current location of the work,
where it was sourced from, or the birthplace of the artist. This problem is caused
by the lack of semantic information in the tagging process [14] even though the
Social Tagging for Digital Libraries using Formal Concept Analysis 147
purpose of using conceptual scales was to seperate and filter the varying types
of tag-to-resource associations.
In terms of conceptual neighbourhood navigation, 18 out of 20 users imme-
diately understood the purpose and effect of the lower neighbour control (as
shown in Fig. 4), although many users thought that the size of the tag denoted
popularity (ie. the amount of times it was clicked), rather than the neighbouring
concept’s extent size. However, only 6 out of the 20 users correctly interpreted
the purpose and the function of the upper neighbour control. In an example
shown in Fig. 5, the remaining 14 users thought that the effect of the control
was that they would simply navigate to all objects tagged ‘northern territory’
and ‘print’ rather than navigate to an upper neighbour that excluded that par-
ticular attribute. Additionally, 4 out of the 20 surveyed users also expressed the
need for a ‘Back’ button. This is due to the hierarchical but non-linear mode of
navigating the information space. These users sometimes felt ‘lost’ and expressed
a need to ‘go back’ and traverse a list of previously navigated conceptual views.
4.4 Design Changes
The initial results of the study have motivated two design changes to improve
interface learnability and functionality.
The first and most pressing of these of these changes was the revision of the
upper neighbours control. Figs. 5 and 6 show two versions of the upper neigh-
bour control displaying the same navigation links.7 As shown in these examples,
users are given the opportunity to navigate to an upper neighbour by excluding
attributes ‘print’ or ‘northern territory’ from their current conceptual view.
Fig. 5. Upper neighbour control, before design revision
Fig. 6. Upper neighbour control, after design revision
The revised control demonstrates a more natural means of doing this. In
Fig. 6, the description of a formal concept’s intension contains emboldened hy-
perlinks that highlight which attributes are removable. As a user rolls their
mouse over the link, a strikethrough effect hints the intended action of clicking
on the link.
The second design change involves the placement of a ‘Back’ button, allowing
users to traverse their conceptual navigation history, which is a list of view states.
7
Please note that the colour of the navigation labels have been altered for print clarity
148 Tim Wray and Peter Eklund
Each view state contains: a) a reference to a formal concept as described by its
intension and b) the current ‘activated’ scales that were selected by the user. This
is so that a user can consistently navigate backwards and forwards through their
view history, even if the formal context changes as a result of tagging activity.
4.5 Secondary Evaluation Results
Some of the findings and common themes of these results were consistent from
the first study – these included the positive aspects of interface aesthetics along
with the ability to ‘hold’ or retain a particular position within the information
space.
All 5 users recognised the function and purpose of the upper neighbours con-
trol almost immediately, and none alluded to the incorrect assumption described
in section 4.3. Results concerning the ‘Back’ button however, were less prominent
– only 2 of the 5 users saw a need to use it. However, both of these users said it
was necessary to have the ability to traverse backwards through the information
space.
5 Discussion of Results and Future Work
The results of the study indicate a moderate level of user acceptance of the use
of the Art Collection Ecosystem in browsing and exploring tagged content. The
initial around of 20 users provided an average score of 0.3 in response to the
question “I would prefer to use the Art Collection Ecosystem to explore objects
than I would with Flickr”, were a score of -1 denotes ‘strongly disagree’ and
a score of 1 denotes ‘strongly agree’. Users generally associated the conceptual
navigation paradigm as a means of query refinement and content exploration,
where an average score of 0.9 was given for the question “It was easier to browse
serendipitously or find related images within the Art Collection Ecosystem than
it was in Flickr.” Subjective and aesthetic commentary was also given, with
many users claiming that the user experience of conceptual navigation was more
“hands on” and “involved.” Users also noted that, compared to Flickr, it may
require some time and experimentation to understand conceptual neighbour-
hood paradigm. Furthermore, the validated design features of the Art Collection
Ecosystem have also been implemented in another software application that
shares the same framework - The Virtual Museum of the Pacific [8].
One of the major themes of the results centered on the learnability of the two
interfaces – a major facet that determines a user’s willingness to adopt or use an
application [16]. Users commented that although the Art Collection Ecosystem
presents itself as a useful means for query construction and refinement, many
would state that they would be willing to a more familiar tools that facilitate
search and retrieval, such as the use of a search box, unless they had a good
reason to invest the time required to become familiar with the user interface
through experimentation.
Social Tagging for Digital Libraries using Formal Concept Analysis 149
Even though our initial meta-data source for our case study was from a single
(non-public) repository of data, the sometimes inconsistent usage of terminology
– perhaps as a result of a shift between departments or individuals who maintain
it – can affect the quality of the browsing experience. This is a classic problem
of knowledge management [3] within many digital libraries [13]. These issues
of meta-data noise and inconsistency can strongly affect the quality of results
within a search query and can be severely detrimental to the quality of results
in an application that employs concept lattices for search and navigation [4].
We argue that conceptual scales can be used to classify tags according to usage
within collaborative tagging systems (as discussed in sections 2.1 and 2.3) – this
in turn allows users to toggle specific dimensions of their navigation context or
filter out undesirable noise. We postulate that the same approach could be used
to toggle and separate between well defined and consistent enterprise data apart
from user contributed (but sometimes noisy or inconsistent) tags and attributes.
Future work and longitudinal studies based on tagging behaviour will investigate
problems of navigating digital libraries using noisy non-mediated vocabularies.
Future work will also assess the scalability of our approach, with possible
methods of using horizontal scaling to cope with the conceptual neighbourhood
computation of increasingly large data sets and contexts. This is also necessary to
incorporate the expected exponential growth of custom objects and user-defined
tags if users were to adopt this as a content presentation and tagging applica-
tion. We are currently planning to expand the data source of the Art Collection
Ecosystem with approximately 2500 artworks, representing a collection complete
implementation of an FCA-based application.
6 Conclusion
In this paper we have presented the design and evaluation results of the Art
Collection Ecosystem. The results of our study reinforce the viability of using
the conceptual neighbourhood approach in browsing tagged image collections.
The results have also driven and validated design improvements. A useful ap-
plication of applying conceptual scaling to segment tag vocabularies based on
a framework of collaborative tagging usage was also discussed, driving forward
the development of a collaborative FCA-based digital library application.
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