Digital assistants—such as chatbots—facilitate the interaction between persons and machines and a... more Digital assistants—such as chatbots—facilitate the interaction between persons and machines and are increasingly used in web pages of enterprises and organizations. This paper presents a methodology for the creation of chatbots that offer access to museum information. The paper introduces an information model that is offered through the chatbot, which subsequently maps the museum’s modeled information to structures of DialogFlow, Google’s chatbot engine. Means for automating the chatbot generation process are also presented. The evaluation of the methodology is illustrated through the application of a real case, wherein we developed a chatbot for the Archaeological Museum of Tripolis, Greece.
The GPA is a universally recognised and utilised metric of academic performance that is considere... more The GPA is a universally recognised and utilised metric of academic performance that is considered to also measure a student’s potential for academic performance in the future. In this short communication we examine to what extent the GPA of the first grade of high school predicts performance in the later grades of high school, either generally (as classified in excellent student, strong student, weak student or very weak student) or more accurately (as indicated by the exact GPA in the next grade). We also put to the test the widely held notion that it might be best if core courses such as language and mathematics contributed more to the calculation of the GPA compared to secondary courses such as physical education or music. Our findings confirm the predictive properties of the GPA but strongly rebut the notion that a weighted GPA might achieve a better reflection of students’ potential. The study is based on the academic records of every student in Greece that progressed from fir...
Collaborative filtering has proved to be one of the most popular and successful rating prediction... more Collaborative filtering has proved to be one of the most popular and successful rating prediction techniques over the last few years. In collaborative filtering, each rating prediction, concerning a product or a service, is based on the rating values that users that are considered “close” to the user for whom the prediction is being generated have given to the same product or service. In general, “close” users for some user u correspond to users that have rated items similarly to u and these users are termed as “near neighbors”. As a result, the more reliable these near neighbors are, the more successful predictions the collaborative filtering system will compute and ultimately, the more successful recommendations the recommender system will generate. However, when the dataset’s density is relatively low, it is hard to find reliable near neighbors and hence many predictions fail, resulting in low recommender system reliability. In this work, we present a method that enhances rating ...
One of the typical goals of collaborative filtering algorithms is to produce rating predictions w... more One of the typical goals of collaborative filtering algorithms is to produce rating predictions with values very close to what real users would give to an item. Afterward, the items having the largest rating prediction values will be recommended to the users by the recommender system. Collaborative filtering algorithms can be applied to both sparse and dense datasets, and each of these dataset categories involves different kinds of risks. As far as the dense collaborative filtering datasets are concerned, where the rating prediction coverage is, most of the time, very high, we usually face large rating prediction times, issues concerning the selection of a user’s near neighbours, etc. Although collaborative filtering algorithms usually achieve better results when applied to dense datasets, there is still room for improvement, since in many cases, the rating prediction error is relatively high, which leads to unsuccessful recommendations and hence to recommender system unreliability....
Exploitation and use of disruptive technologies, such as the Internet of Things, recommender syst... more Exploitation and use of disruptive technologies, such as the Internet of Things, recommender systems, and artificial intelligence, with an ambidextrous balance, are a challenge, nowadays. Users of the technologies, and stakeholders, could be part of a new organisational model that affects business procedures and processes. Additionally, the use of inclusive participatory organisational models is essential for the effective adoption of these technologies. Such models aim to transform organisational structures, as well. Public organisations, such as the parliament, could utilise information systems’ personalisation techniques. As there are a lot of efforts to define the framework, the methodology, the techniques, the platforms, and the suitable models for digital technologies adoption in public organisations, this paper aims to provide a literature review for disruptive technology inclusive use in parliaments. The review emphasises the assessment of the applicability of the technologi...
The typical goal of a collaborative filtering algorithm is the minimisation of the deviation betw... more The typical goal of a collaborative filtering algorithm is the minimisation of the deviation between rating predictions and factual user ratings so that the recommender system offers suggestions for appropriate items, achieving a higher prediction value. The datasets on which collaborative filtering algorithms are applied vary in terms of sparsity, i.e., regarding the percentage of empty cells in the user–item rating matrices. Sparsity is an important factor affecting rating prediction accuracy, since research has proven that collaborative filtering over sparse datasets exhibits a lower accuracy. The present work aims to explore, in a broader context, the factors related to rating prediction accuracy in sparse collaborative filtering datasets, indicating that recommending the items that simply achieve higher prediction values than others, without considering other factors, in some cases, can reduce recommendation accuracy and negatively affect the recommender system’s success. An ex...
European Journal of Engineering and Technology Research, 2020
This article provides a visualization of a literature review in students’ performance prediction ... more This article provides a visualization of a literature review in students’ performance prediction using educational data mining (EDM) techniques for the period 2015-2019. The results of the review are presented concisely and simply with the use of diagrams. Various aspects of the literature are examined, such as the algorithms adopted, the type of results drawn, the educational setting of the application and the actual exploitation of the outcomes. Findings indicate that tertiary education dominates the EDM field; in contrast, the focus given to secondary and primary education is minimal.
Antoniou, A., Vassilakis, C., Wallace, M., Lepouras, G., Poulopoulos, V. (2017). Experiences from... more Antoniou, A., Vassilakis, C., Wallace, M., Lepouras, G., Poulopoulos, V. (2017). Experiences from the development of thematic routes in 3 Greek museums (in Greek). Proceedings of the Europmed 2017, 2<sup>nd</sup> Panhellenic Conference on Digitization of Cultural Heritage.
Social media usage is affecting peoples’ views through opinion sharing, a fact that has started t... more Social media usage is affecting peoples’ views through opinion sharing, a fact that has started to attract cultural institutions, as it is possible that this procedure can possibly be a part of a museum experience. As the main goal of a cultural institution is the maximization of senses stimulation, the device that is offered to the visitors’ hands everyday and every moment, becomes an important tool for the art spaces. In this notion we perform research on issues that can be of great importance for the museum’s online presence and attraction. We focus on establishing the personality of influencers related to culture, as well as the characteristics of qualitative discussions on the social media. Crosscult Project is an EU funded project, that aims to spur a change in the way European citizens appraise History, and sets that basis of our research as the experiments are conducted within its scope of. Through the experimental procedure, we collect information in order to define the cha...
HCI-VR lab in Short. The Human-Computer Interaction and Virtual Reality Lab, at the Department of... more HCI-VR lab in Short. The Human-Computer Interaction and Virtual Reality Lab, at the Department of Informatics and Telecommunications of the University of Peloponnese, aims to conduct high quality research in areas related to the analysis, design, development, and evaluation of HCI and VR systems and applications, and in parallel to support the teaching requirements of the department in the respective field. Over the last years the HCI-VR lab particularly focuses on Cultural Heritage and develops technologies primarily for spaces of cultural heritage that cover the diverse needs of heterogeneous audiences providing holistic visitor experience. The HCI-VR lab is actively participating in National and European projects on Cultural Heritage, such as FP7 Experimedia (https://hci-vr.dit.uop.gr/experimedia), H2020 CrossCult (www.crosscult.eu) and multiple projects from the National Strategic Reference Framework.
This work addresses the challenges of creating usable and personalized conversational interfaces ... more This work addresses the challenges of creating usable and personalized conversational interfaces for broad, yet applicable, domains that require user engagement and learning, such as museum chatbots. Whether the chatbots are standalone or coupled with virtual agents or real-life robots, the functional requirements for interaction that targets specific learning aspects would be expected to be more or less similar. This work reports on experimental semantics-driven conversational interface design for chatbots in museum settings, targeting visitors to converse about exhibits and learn information about their style, the artists, the era, and other aspects related to them. Depending on the semantics (presentation, learning, exploration), chatbot scenarios were designed and evaluated by participants in a formative evaluation. The evaluation show that user requirement perception manifests in expectations on the semantic level, instead of just the technical level. The results between the sc...
Digital assistants—such as chatbots—facilitate the interaction between persons and machines and a... more Digital assistants—such as chatbots—facilitate the interaction between persons and machines and are increasingly used in web pages of enterprises and organizations. This paper presents a methodology for the creation of chatbots that offer access to museum information. The paper introduces an information model that is offered through the chatbot, which subsequently maps the museum’s modeled information to structures of DialogFlow, Google’s chatbot engine. Means for automating the chatbot generation process are also presented. The evaluation of the methodology is illustrated through the application of a real case, wherein we developed a chatbot for the Archaeological Museum of Tripolis, Greece.
The GPA is a universally recognised and utilised metric of academic performance that is considere... more The GPA is a universally recognised and utilised metric of academic performance that is considered to also measure a student’s potential for academic performance in the future. In this short communication we examine to what extent the GPA of the first grade of high school predicts performance in the later grades of high school, either generally (as classified in excellent student, strong student, weak student or very weak student) or more accurately (as indicated by the exact GPA in the next grade). We also put to the test the widely held notion that it might be best if core courses such as language and mathematics contributed more to the calculation of the GPA compared to secondary courses such as physical education or music. Our findings confirm the predictive properties of the GPA but strongly rebut the notion that a weighted GPA might achieve a better reflection of students’ potential. The study is based on the academic records of every student in Greece that progressed from fir...
Collaborative filtering has proved to be one of the most popular and successful rating prediction... more Collaborative filtering has proved to be one of the most popular and successful rating prediction techniques over the last few years. In collaborative filtering, each rating prediction, concerning a product or a service, is based on the rating values that users that are considered “close” to the user for whom the prediction is being generated have given to the same product or service. In general, “close” users for some user u correspond to users that have rated items similarly to u and these users are termed as “near neighbors”. As a result, the more reliable these near neighbors are, the more successful predictions the collaborative filtering system will compute and ultimately, the more successful recommendations the recommender system will generate. However, when the dataset’s density is relatively low, it is hard to find reliable near neighbors and hence many predictions fail, resulting in low recommender system reliability. In this work, we present a method that enhances rating ...
One of the typical goals of collaborative filtering algorithms is to produce rating predictions w... more One of the typical goals of collaborative filtering algorithms is to produce rating predictions with values very close to what real users would give to an item. Afterward, the items having the largest rating prediction values will be recommended to the users by the recommender system. Collaborative filtering algorithms can be applied to both sparse and dense datasets, and each of these dataset categories involves different kinds of risks. As far as the dense collaborative filtering datasets are concerned, where the rating prediction coverage is, most of the time, very high, we usually face large rating prediction times, issues concerning the selection of a user’s near neighbours, etc. Although collaborative filtering algorithms usually achieve better results when applied to dense datasets, there is still room for improvement, since in many cases, the rating prediction error is relatively high, which leads to unsuccessful recommendations and hence to recommender system unreliability....
Exploitation and use of disruptive technologies, such as the Internet of Things, recommender syst... more Exploitation and use of disruptive technologies, such as the Internet of Things, recommender systems, and artificial intelligence, with an ambidextrous balance, are a challenge, nowadays. Users of the technologies, and stakeholders, could be part of a new organisational model that affects business procedures and processes. Additionally, the use of inclusive participatory organisational models is essential for the effective adoption of these technologies. Such models aim to transform organisational structures, as well. Public organisations, such as the parliament, could utilise information systems’ personalisation techniques. As there are a lot of efforts to define the framework, the methodology, the techniques, the platforms, and the suitable models for digital technologies adoption in public organisations, this paper aims to provide a literature review for disruptive technology inclusive use in parliaments. The review emphasises the assessment of the applicability of the technologi...
The typical goal of a collaborative filtering algorithm is the minimisation of the deviation betw... more The typical goal of a collaborative filtering algorithm is the minimisation of the deviation between rating predictions and factual user ratings so that the recommender system offers suggestions for appropriate items, achieving a higher prediction value. The datasets on which collaborative filtering algorithms are applied vary in terms of sparsity, i.e., regarding the percentage of empty cells in the user–item rating matrices. Sparsity is an important factor affecting rating prediction accuracy, since research has proven that collaborative filtering over sparse datasets exhibits a lower accuracy. The present work aims to explore, in a broader context, the factors related to rating prediction accuracy in sparse collaborative filtering datasets, indicating that recommending the items that simply achieve higher prediction values than others, without considering other factors, in some cases, can reduce recommendation accuracy and negatively affect the recommender system’s success. An ex...
European Journal of Engineering and Technology Research, 2020
This article provides a visualization of a literature review in students’ performance prediction ... more This article provides a visualization of a literature review in students’ performance prediction using educational data mining (EDM) techniques for the period 2015-2019. The results of the review are presented concisely and simply with the use of diagrams. Various aspects of the literature are examined, such as the algorithms adopted, the type of results drawn, the educational setting of the application and the actual exploitation of the outcomes. Findings indicate that tertiary education dominates the EDM field; in contrast, the focus given to secondary and primary education is minimal.
Antoniou, A., Vassilakis, C., Wallace, M., Lepouras, G., Poulopoulos, V. (2017). Experiences from... more Antoniou, A., Vassilakis, C., Wallace, M., Lepouras, G., Poulopoulos, V. (2017). Experiences from the development of thematic routes in 3 Greek museums (in Greek). Proceedings of the Europmed 2017, 2<sup>nd</sup> Panhellenic Conference on Digitization of Cultural Heritage.
Social media usage is affecting peoples’ views through opinion sharing, a fact that has started t... more Social media usage is affecting peoples’ views through opinion sharing, a fact that has started to attract cultural institutions, as it is possible that this procedure can possibly be a part of a museum experience. As the main goal of a cultural institution is the maximization of senses stimulation, the device that is offered to the visitors’ hands everyday and every moment, becomes an important tool for the art spaces. In this notion we perform research on issues that can be of great importance for the museum’s online presence and attraction. We focus on establishing the personality of influencers related to culture, as well as the characteristics of qualitative discussions on the social media. Crosscult Project is an EU funded project, that aims to spur a change in the way European citizens appraise History, and sets that basis of our research as the experiments are conducted within its scope of. Through the experimental procedure, we collect information in order to define the cha...
HCI-VR lab in Short. The Human-Computer Interaction and Virtual Reality Lab, at the Department of... more HCI-VR lab in Short. The Human-Computer Interaction and Virtual Reality Lab, at the Department of Informatics and Telecommunications of the University of Peloponnese, aims to conduct high quality research in areas related to the analysis, design, development, and evaluation of HCI and VR systems and applications, and in parallel to support the teaching requirements of the department in the respective field. Over the last years the HCI-VR lab particularly focuses on Cultural Heritage and develops technologies primarily for spaces of cultural heritage that cover the diverse needs of heterogeneous audiences providing holistic visitor experience. The HCI-VR lab is actively participating in National and European projects on Cultural Heritage, such as FP7 Experimedia (https://hci-vr.dit.uop.gr/experimedia), H2020 CrossCult (www.crosscult.eu) and multiple projects from the National Strategic Reference Framework.
This work addresses the challenges of creating usable and personalized conversational interfaces ... more This work addresses the challenges of creating usable and personalized conversational interfaces for broad, yet applicable, domains that require user engagement and learning, such as museum chatbots. Whether the chatbots are standalone or coupled with virtual agents or real-life robots, the functional requirements for interaction that targets specific learning aspects would be expected to be more or less similar. This work reports on experimental semantics-driven conversational interface design for chatbots in museum settings, targeting visitors to converse about exhibits and learn information about their style, the artists, the era, and other aspects related to them. Depending on the semantics (presentation, learning, exploration), chatbot scenarios were designed and evaluated by participants in a formative evaluation. The evaluation show that user requirement perception manifests in expectations on the semantic level, instead of just the technical level. The results between the sc...
Η πρόοδος των κινητών τεχνολογιών έχει δημιουργήσει ευκαιρίες για
πιο αποτελεσματική διάχυση πλη... more Η πρόοδος των κινητών τεχνολογιών έχει δημιουργήσει ευκαιρίες για
πιο αποτελεσματική διάχυση πληροφοριών πολιτιστικής κληρονομιάς σε
όλες τις ενδιαφερόμενες πλευρές και ιδιαίτερα στους τουρίστες που
βρίσκονται εν κινήσει. Πολλοί άνθρωποι σήμερα είναι εξοπλισμένοι
με έξυπνα κινητά ή ταμπλέτες, τα οποία διαθέτουν διατάξεις εντοπισμού
θέσης, όπως π.χ. GPS και πυξίδες, ενώ παράλληλα διαθέτουν και πρόσβαση
στο διαδίκτυο. Αυτές οι κινητές συσκευές μπορούν να χρησιμοποιηθούν
αποτελεσματικά για επίκαιρη και προσαρμοσμένη στις προσωπικές προτιμήσεις
των χρηστών παροχή πληροφοριών πολιτιστικής κληρονομιάς. Επιπρόσθετα,
οι υπολογιστικοί πόροι των κινητών αυτών συσκευών είναι πλέον επαρκείς
για να υποστηρίξουν τη χρήση τεχνικών επαυξημένης πραγματικότητας,
οι οποίες παρέχουν μία «ζωντανή» και ενδιαφέρουσα εμπειρία στους
χρήστες. Ωστόσο, το ίδιο περιεχόμενη πρέπει επίσης να διαχυθεί σε
χρήστες σταθερών υπολογιστών. Στην παρούσα εργασία, παρουσιάζουμε
τον σχεδιασμό και την ανάπτυξη μιας πλατφόρμας για παρουσίαση και
διάχυση πληροφοριών πολιτιστικής κληρονομιάς που παρέχει υποστήριξη
για κινητές συσκευές, η οποία είναι εμπλουτισμένη με δυνατότητες
επαυξημένης πραγματικότητας και ολοκλήρωσης με κοινωνικά δίκτυα.
This paper describes a technique for interceding between users and
the information that they bro... more This paper describes a technique for interceding between users and
the information that they browse. This facility, that we term 'dynamic
annotation', affords a means of editing Web page content 'on-the-fly'
between the source Web server and the requesting client. Thereby,
we have a generic way of modifying the content displayed to local
users by addition, removal or reorganising any information sourced
from the World-Wide Web, whether this derives from local or remote
pages. For some time, we have been exploring the scope for this device
and we believe that it affords many potential worthwhile applications.
Here, we describe two varieties of use. The first variety focuses
on support for individual users in two contexts (second-language
support and second language learning). The second variety of use
focuses on support for groups of users. These differing applications
have a common goal which is content enrichment of the materials placed
before the user. Dynamic annotation provides a potent and flexible
means to this end.
Manual ontology development is clearly a strenuous task. Whilst a
variety of ontological enginee... more Manual ontology development is clearly a strenuous task. Whilst a
variety of ontological engineering methodologies exist, their actual
application is far from trivial, mainly due to the widely diverse
nature of the tasks involved. In this work we study these tasks and
identify the different types of human experts that are best suited
to perform each one. As a result, we present a cooperative version
of an ontological engineering methodology, together with a graphical
tool that supports it.
A requirement for electronic government initiatives to succeed is
the ability to offer a citizen... more A requirement for electronic government initiatives to succeed is
the ability to offer a citizen-centric view of the government model.
The most widely adopted paradigm supporting this task is the life
event model, which combines basic services offered from multiple
public authorities into a single, high-level service that corresponds
to an event in a citizen's life. This composition is not always straightforward
though, because the constituent services are generally developed
in an independent fashion, using incompatible input and output formats;
moreover the task of synchronising the documents required and produced
by the services is tedious to implement and costly to maintain, since
changes to requirements and legislation necessitate continuous updates
to this scheme. In this paper, we present a blackboard architecture
that can be used to deliver life-event oriented services to the citizens.
The blackboard proposed for this architecture is an active one, undertaking
the tasks of conversions, where appropriate. The blackboard couples
a data flow approach with event-condition-action rules to enable
dynamic formulation of life-event services, decentralising their
development and maintenance.
Transactions are a significant concept in database systems, facilitating
functions both at user ... more Transactions are a significant concept in database systems, facilitating
functions both at user and system level. However transaction support
in
temporal DBMSs has not yet received enough research attention. In
this paper, we present techniques for incorporating transaction support
in a temporal DBMS, which is implemented as an additional layer to
a
commercial RDBMS. These techniques overcome certain limitations
imposed by the underlying RDBMS, and avoid excessive increment of
the log size.
The paper addresses issues related to client/server technologies and
specifically the effectiven... more The paper addresses issues related to client/server technologies and
specifically the effectiveness of server-side programming techniques.
The motive for this study was the need to create a lightweight and
dynamic navigational aid for use in a web site. Towards this goal
a number of possible solutions were considered and for two of them
an experiment was run to determine the best suited for our case.
The rest of the paper outlines our findings.
Web sites employ dynamically generated pages for content delivery
more and more often, in order ... more Web sites employ dynamically generated pages for content delivery
more and more often, in order to increase their flexibility and provide
up-to-date information. This practice, however, increases server
load dramatically, since each request results to the execution of
code, which may involve processing and/or access to information repositories.
In this paper we present a scheme for maintaining a server-side cache
of dynamically generated pages, allowing for cache consistency maintenance,
without placing heavy burdens on application programmers. We also
present insights to architecture scalability and some results obtained
from conducted experiments.
Electronic government employs electronic services to facilitate interaction
with citizens and en... more Electronic government employs electronic services to facilitate interaction
with citizens and enterprises and deliver a rich and high quality
spectrum of services. Development of electronic services can be greatly
assisted, both in terms of development cost and roll-out time, by
exploiting the reusability inherent in them. Reusability may be promoted
by identifying reusable objects in the context of electronic service
development, building and populating a repository with such components
and providing the means for developers to locate, extract and adapt
them to suit the task at hand. In this paper we analyse electronic
services to recognise reusable components and present means and techniques
that empower electronic service developers to build electronic services
through reusable components.
Although form-based transactional services are fundamental to electronic
government activities, ... more Although form-based transactional services are fundamental to electronic
government activities, their widespread does neither meet the citizen's
expectations, nor the potential offered by state-of-the-art technologies.
Besides any bureaucratic impediments, the primary reason for this
is that traditional software engineering approaches cannot satisfactorily
handle all the aspects of electronic services lifecycle. In this
paper we present experiences from developing and maintaining a set
of electronic services for the Greek Ministry of Finance, and propose
a new approach for handling electronic service projects. The proposed
approach has been successfully employed for developing extensions
to the existing services, as well as some new ones.
In the context of service-oriented computing, the introduction of
the Quality-of-Service (QoS) a... more In the context of service-oriented computing, the introduction of
the Quality-of-Service (QoS) aspect leads to the need to adapt the
execution of programs to the QoS requirements of the particular execution.
This is typically achieved by finding alternate services that are
functionally equivalent to the ones originally specified in the program
and whose QoS characteristics closely match the requirements, and
invoking the alternate services instead of the originally specified
ones; the same approach can also be employed for tackling exceptions.
The techniques proposed insofar, however, cannot be applied in a
secure context, where data are encrypted and signed for the originally
intended recipient. In this paper, we introduce a framework for facilitating
adaptation in the context of secure SOA.
Econsultations constitute an effective means to inclusive and informed
participation of citizens... more Econsultations constitute an effective means to inclusive and informed
participation of citizens and society in policy, decision and law
formulation processes, and an answer to democratic deficit issues.
Econsultation platforms need to support all stages of consultation
processes including agenda setting and topics raising, legislation
proposal publicity, notification of developments, proposal debate
and commentary, collection, analysis and synthesis of views. In this
paper we present the design of an open platform assisting policy
makers and the civil society in the set-up, enactment, management
and federation of inclusive and informed digital consultations. The
proposed platform employs semantic techniques, such as semantics,
content annotation and summarization to support the consultation
processes and provide targeted and digested information to participants,
and facilitates tailoring of Econsultation procedures by offering
basic Econsultation activities as building blocks, which can be combined
according to contextual needs. The platform also enables distinct
Econsultation processes to be federated, allowing the exchange of
information, which may be subject to different semantic annotations
and classifications, according to the rules of each Econsultation
process.
Application development on top of database systems is heavily based
on the existence of embedded... more Application development on top of database systems is heavily based
on the existence of embedded and 4GL languages. However, the issue
of designing and implementing embedded or 4GL temporal languages
has not been addressed insofar. In this paper, we present a design
approach for implementing an embedded temporal language that supports
valid time. Furthermore, we introduce implementation techniques that
can be used for implementing any embedded temporal language that
supports valid time on top of a DBMS.
As the use of distributed systems is spreading, and applications designed
for such systems becom... more As the use of distributed systems is spreading, and applications designed
for such systems become more and more demanding, optimal design of
distributed systems becomes a critical issue. Designing a distributed
system has become more complex, due to the number of alternatives
for each decision that must be made and because of the existence
of many parameters which influence the overal performance of the
distributed system. Thus, it is necessary to use software tools,
capable of accepting a description of the user's requirements and
suggesting solutions to the problem of designing a distributed system
which meets the user's requirements. In this paper, we present a
disciplined approach to the construction of such a software tool,
which combines methods from the Artificial Intelligence domain, that
are used in order to design the distributed system, along with simulation
techniques, used to estimate the system's overall performance.
Human History, is a huge mesh of interrelated facts and concepts,
spanning beyond borders, encom... more Human History, is a huge mesh of interrelated facts and concepts,
spanning beyond borders, encompassing global aspects and finally
constituting a shared, global experience. This is especially the
case regarding European history, which is highly interconnected by
nature; however, most History-related experiences that are today
offered to the greater public, from schools to museums, are siloed.
The CrossCult project aims to provide the means for o ering citizens
and cultural venue visitors a more holistic view of history, in the
light of cross-border interconnections among pieces of cultural heritage,
other citizens viewpoints and physical venues. To this end, the CrossCult
project will built a comprehensive knowledge base encompassing information
and semantic relationships across cultural information elements,
and will provide the technological means for delivering the contents
of this knowledge base to citizens and venue visitors in a highly
personalized manner, creating narratives for the interactive experiences
that maximise situational curiosity and serendipitous learning. The
CrossCult platform will also exploit the cognitive/emotional profiles
of the participants as well as temporal, spatial and miscellaneous
features of context, including holidays and anniversaries, social
media trending topics and so forth.
Banyan Networks are a major class of Multistage Interconnection Networks
(MINs). They have been ... more Banyan Networks are a major class of Multistage Interconnection Networks
(MINs). They have been widely used as efficient interconnection structures
for parallel computer systems, as well as switching nodes for high-speed
communication networks. The performance of them is mainly determined
by their communication throughput and their mean packet delay. In
this paper we use a model that is based on a universal performance
factor, which includes the importance aspect of each of the above
main performance factors (throughput and delay) in the design process
of a MIN. The model can also uniformly be applied to several representative
networks. The complexity of the model requires to be investigated
by time-consuming simulations. In this paper we study a typical (8X8)
Baseline Banyan Switch that consists of (2X2) Switching Elements
(SEs). The objective of this simulation is to determine the optimal
buffer size for the MIN stages under different conditions.
Multistage Interconnection Networks (MINs) are frequently used for
connecting processors in para... more Multistage Interconnection Networks (MINs) are frequently used for
connecting processors in parallel computing systems or constructing
high speed networks such as ATM (based on Asynchronous Transfer Mode)
and Gigabit Ethernet Switches. New applications require distributed
computing implementations, but old networks are too slow to allow
efficient use of remote resources. Moreover, multimedia are considered
as applications with high bandwidth requirements. Some of them are
also sensitive to packet loss and claim reliable data transmission.
Specific applications require bulk data transfers for database replication
or load balancing and therefore packet loss minimization is necessary
in order to increase the performance of them. The demand for high
performance multimedia services such as full motion video on demand
is becoming an increasingly important driving force in the communication
market in the Digital Age. Thus, the performance of MINs is a crucial
factor, which we have to take into account in the design of new applications.
Their performance is mainly determined by their communication throughput
and cell latency, which have to be investigated either by time-consuming
simulations or approximated by mathematical models. In this paper
we investigate the performance of MINs in order to determine optimal
values for hardware parameters under diferent operating conditions.
Electronic commerce, nowadays, is trying to extend its target audience
and elevate the quality o... more Electronic commerce, nowadays, is trying to extend its target audience
and elevate the quality of services offered to end-users. Two important
directions towards meeting these goals are the embracement of mobile
users, whose number grows following the advent of communication technologies,
and the inclusion of context-aware features in the delivered services
to improve the efficiency of the dialogues between users and systems.
The context taken into account may involve characteristics regarding
the human user, the geographical location and the time of access,
the devices employed to access the service, the network through which
the user communicates with the system, the nature of the transaction
carried out and so forth. It is clear that the development and successful
operation of mobile and context-aware e-commerce introduce new challenges.
In order to tackle such challenges, new methodologies, tools, architectures
and platforms should be made available to assist analysts, designers,
developers and operators in handling the various phases of the Mobile
and Context-Aware E-Commerce Services (MCACS) lifecycle.
Documents submitted by citizens through electronic services deployed
in the context of e-Governm... more Documents submitted by citizens through electronic services deployed
in the context of e-Government must usually undergo processing by
some organisational information system, in order to complete the
citizens? requests and for the reply to be returned to the citizen.
The integration, however, of the e-service delivery platform and
the organisational information system is often hindered for a number
of reasons, including security considerations, platform diversity
or idiosyncrasies of legacy information systems. In this paper we
present a generic method for providing seamless communication between
the two platforms, enabling the full integration of documents submitted
through electronic services into the organisational workflow, leveraging
thus the quality of services offered to the citizens and facilitating
e-service development and operation.
With the need for electronic services to be developed and deployed
more and more rapidly, it is ... more With the need for electronic services to be developed and deployed
more and more rapidly, it is imperative that concrete models of electronic
services are developed, to facilitate systematic work of electronic
service stakeholders, concrete semantics and coherent representations
across services developed within an organisation. Using the XML language
to develop such a model, offers a number of additional advantages,
such as rich semantics, facilitation of data interchange, extensibility,
high abstraction levels and possibility for mechanical processing.
In this paper we present the design aspects of an XML model for electronic
services, which has been used for building a repository of interlinked
elements representing e-services. A web-based interface for the management
of this repository and a tool for automatically compiling e-service
descriptions into executable images have been developed alongside.
The model has been evaluated by a mixture of electronic service stakeholders,
and the results of this evaluation are also presented.
E-government initiatives have been proven to deliver significant benefits,
both for suppliers of... more E-government initiatives have been proven to deliver significant benefits,
both for suppliers of electronic services (public authorities and
organizations) and for the public, to whom services are addressed.
However, the pace with which electronic services are made available
and adopted is lower than planned or expected; governments tend to
be slow in releasing new services, and citizens often prefer to conduct
business with the government through paper forms and physical presence,
rather than using online methods. This indicates that certain barriers
exist that hinder the transition to electronic services. In this
paper, we present the results of a survey among electronic service
stakeholder groups, to identify the most important barriers to electronic
service development. Documentation of barriers is considered important,
since administrations may take certain measures to overcome them.
Hints on how specific barriers may be overcome are also provided.
In the context of electronic government, e-services are a valuable
instrument for offering high ... more In the context of electronic government, e-services are a valuable
instrument for offering high quality services to enterprises and
individual citizens alike. While developing an e-service, it is usually
possible to reuse elements that have already crafted for other e-services,
such as personal detail forms or widgets for collecting social security
numbers, decreasing thus both development effort and the time for
deployment. A more generic framework for supporting reusability in
development of e-services includes the identification of reusable
objects, the creation and population of a repository containing such
components, and the empowerment of developers with tools allowing
for location, retrieval and adaptation of components for suiting
their specific tasks. In this paper, we conduct an analysis to recognise
e-service component that offer reusability opportunities and we present
facilities and methods to enable e-service developers to exploit
these opportunities while developing electronic services.
The paper presents an integrated environment which enables museum
personnel to catalogue and at ... more The paper presents an integrated environment which enables museum
personnel to catalogue and at the same time publish online museum
exhibits. The system is based on international standards and is highly
customisable to cater the needs of a variety of museum types. Moreover,
the underlying database allows storing for the same exhibit documentations
for different audiences and in multiple languages, while it is extendable
to accommodate new media types, languages, exhibits and information
categories. The administrative part of the environment permits the
restriction of certain functions to specific personnel roles, enforcing
thus a general museum security policy regarding access to and modification
of information. The environment presented is currently in use at
the Athens University History Museum.
Queries in temporal databases often employ the coalesce operator,
either to coalesce results of ... more Queries in temporal databases often employ the coalesce operator,
either to coalesce results of projections, or data which are not
coalesced upon storage. Therefore, the performance and the optimisation
schemes utilised for this operator is of major importance for the
performance of temporal DBMSs. Insofar, performance studies for various
algorithms that implement this operator have been conducted, however,
the joint optimisation of the coalesce operator with other algebraic
operators that appear in the query execution plan has only received
minimal attention. In this paper, we propose a scheme for combining
the coalesce operator with selection operators which are applied
to the valid time of the tuples produced from a coalescing operation.
The proposed scheme aims at reducing the number of tuples that a
coalescing operator must process, while at the same time allows the
optimiser to exploit temporal indices on the valid time of the data.
In this paper, the modelling, analysis and performance evaluation
of a novel architecture for in... more In this paper, the modelling, analysis and performance evaluation
of a novel architecture for internal priority finite-buffered Multistage
Interconnection Networks (MINs) is presented. We model the proposed
architecture giving the details of its operation and describing its
states and detailing conditions and effects of state transition;
we also provide a formal model for evaluating its performance. The
proposed architecture’s performance is subsequently analyzed under
the uniform traffic condition, considering various offered loads,
buffer-lengths and MIN sizes, using simulations. We compare the internal
priority scheme vs. the non priority (or single priority) scheme,
by gathering metrics for the two most important network performance
factors, namely packet throughput and the mean time a packet needs
to traverse the network. We demonstrate and quantify the improvements
on MIN performance stemming from the introduction of priorities in
terms of throughput and a combined performance indicator which depicts
the overall performance of the MIN. These performance measures can
be valuable assets for designers of parallel multiprocessor systems
and networks in order to minimize the overall deployment costs and
delivering efficient systems.
Next-generation network architectures strive to achieve high bandwidth
and ultralow latency for ... more Next-generation network architectures strive to achieve high bandwidth
and ultralow latency for the packets traversing the offered end-to-end
paths. Multistage Interconnection Networks (MINs) are often employed
for implementing NGNs, but while MINs are fairly flexible in handling
varieties of traffic loads, they tend to quickly saturate under broadcast
and multicast traffic, especially at increasing size networks. As
a response to this issue, multilayer MINs have been proposed, however
their performance prediction and evaluation has not been studied
sufficiently insofar. In this paper, we evaluate and discuss the
performance of multilayer MINs under multicast traffic, considering
also two levels of packet priorities, since support for multiple
QoS levels is an indispensible requirement for NGNs. Different offered
loads and buffer size configurations are examined in this context,
and performance results are given for the two most important network
performance factors, namely packet throughput and delay. We also
introduce and calculate a universal performance fac¬tor, which includes
the importance aspect of each of the above main performance factors.
The findings of this study can be used by NGN system designers in
order to predict the performance of each configuration and adjust
the design of their communication infrastructure to the traffic requirements
at hand.
Contemporary networks support multiple priorities, aiming to differentiate
the QoS levels offere... more Contemporary networks support multiple priorities, aiming to differentiate
the QoS levels offered to individual traffic classes. Support for
multiple priorities necessitates the introduction of a scheduling
algorithm, to select each time the next packet to transmit over the
data link. Class-based Weighted Fair Queuing (CBWFQ) scheduling and
its variations, is widely used as a scheduling technique, since it
is easy to implement and prevents the low-priority queues from starvation,
i.e. receiving no service during periods of high-priority traffic.
CBWFQ effectively thus offers low-priority queues the opportunity
to transmit packets even though the high-priority queues are not
empty. In this paper, we present the modeling and performance evaluation
of a single-buffered, four-priority multistage interconnection network
(MIN) operating under the CBWFQ scheduling policy. Performance evaluation
is conducted through simulation, and the performance metrics obtained
can be used by MIN designers to set the appropriate queue weights
according to the expected traffic and the desired QoS levels for
each priority class, delivering efficient thus systems.
In this paper, we model, analyze and evaluate the performance of a
2-class priority architecture... more In this paper, we model, analyze and evaluate the performance of a
2-class priority architecture for finite-buffered Multistage Interconnection
Networks (MINs). The MIN operation modelling is based on a state
diagram, which includes the possible MIN states, transitions and
conditions under which each transition occurs. Equations expressing
state and transition probabilities are subsequently given, providing
a formal model for evaluating the MIN's performance. The proposed
architecture's performance is subsequently analyzed using simulations;
operational parameters, including buffer length, MIN size, offered
load and ratios of high priority packets which are varied across
experiments to gain insight on how each parameter affects the overall
MIN performance. The 2-class priority MIN performance is compared
against the performance of single priority MINs, detailing the performance
gains and losses for packets of different priorities. Performance
is assessed by means of the two most commonly used factors, namely
packet throughput and packet delay, while a performance indicator
combining both individual factors is introduced, computed and discussed.
The findings of this study can be used by network and interconnection
system designers in order to deliver efficient systems while minimizing
the overall cost. The performance evaluation model can also be applied
to other network types, providing the necessary data for network
designers to select optimal values for network operation parameters.
Wireless Local Area Networks (WLANs) have developed into a viable
technology to support multimed... more Wireless Local Area Networks (WLANs) have developed into a viable
technology to support multimedia traffic and are expected to support
multimedia services with guaranteed Quality of Service (QoS) for
diverse traffic types (video, audio, and data). In this paper, we
consider the incorporation of prediction into a generic distance-vector
routing protocol for WLANs, evaluate the performance of the resulting
routing scheme. Our study considers the enhancement of Distributed
Bellman-Ford algorithm, which is a widely used algorithm, and assesses
the effectiveness of the enhanced version on top of a fourth generation
system (4-G). In order to compare the performance of the standard
protocol against that of the prediction-enhanced version, we gather
metrics for the two most important network performance factors, namely
packet throughput and delay under different mobility and traffic
conditions, using the simulation environment of NS-2. Both medium-
and high-mobility configurations have been considered in this study.
Differentiated Services (DiffServ) and other scheduling strategies
are now widespread in the tra... more Differentiated Services (DiffServ) and other scheduling strategies
are now widespread in the traditional, “best effort” Internet. These
Internet Architectures offer Quality of Service (QoS) guarantees
for important customers at the same time as supporting less critical
applications of lower priority. Strict priority queuing (PQ), weighted
round robin (WRR), and class-based weighted fair queuing (CBWFQ)
are three common scheduling disciplines for differentiation of services
in telecommunication networks. In this paper, a comparative performance
study of the above PQ, WRR and CBWFQ queuing scheduling policies
applied on a double-buffered, 6-stage Multistage Interconnection
Network (MIN) that natively supports a 2-class priority mechanism
is presented and analyzed using simulation experiments. We also consider
a 10-stage MIN, to validate that the conclusions drawn from the 6-stage
MIN apply to MINs of different sizes. The findings of this paper
can be used by MIN designers to optimally configure their networks.
Historic research involves finding, using, and correlating informationwithin
primary and seconda... more Historic research involves finding, using, and correlating informationwithin
primary and secondary sources, in order to communicate an understanding
of past events. In this process, historians employ their scientific
knowledge, experience, and intuition to formulate queries (who was
involved in an event, when did an event occur etc.), and subsequently
try to locate the pertinent information from their sources. In this
article, the authors investigate how historians formulate queries,
which query terms are chosen, and how historians proceed in searching
for related information in sources. The insight gained from this
investigation can be subsequently used for organizing documentswithin
historical source repositories and building tools that will enable
historians to access the needed informationmore rapidly and fully.
In this study we present a technique for the parallel optimisation
of join
queries that uses th... more In this study we present a technique for the parallel optimisation
of join
queries that uses the offered coarse-grain parallelism of the underlying
architecture in
order to reduce the CPU-bound optimisation overhead. The optimisation
technique
performs an almost exhaustive search of the solution space for small
join queries and
gradually, as the number of joins increases, it diverges towards iterative
improvement.
This technique has been developed on a low-parallelism transputer-based
architecture,
where its behaviour is studied for the optimisation of queries with
many tens of joins.
In this work, the usage of ontologies for meeting requirements related
to e-service composition,... more In this work, the usage of ontologies for meeting requirements related
to e-service composition, e-service cataloguing, change management
and administrative responsibility is examined. An ontology for e-government
services is presented, covering various aspects of services, including
administrative responsibility, meta-data, involved documents and
legislation. Both the development and usage phase of the ontology
are covered and directions for further exploitation of the potential
offered by the ontological representation are given.
Transactional services are an indispensible part of e-government,
since provision of services to... more Transactional services are an indispensible part of e-government,
since provision of services to citizens and enterprises,as well as
the interaction between the government and citizens-enterprises are
modelled mainly through such services. Latest quantifications, however,
show that the development of such services lags behind as compared
both to the expectations of citizens-enterprises and to the efforts
made by governments. This can be attributed, amongst other reasons,
to the "traditional" approach to electronic service development,
which treats each electronic service as an isolated software project.
In this paper, we propose an e-service development platform, which
covers the whole lifecycle of transactional services and facilitates
the analysis, development, deployment and maintenance of these services.
We introduce a novel knowledge-based recommendation algorithm for
leisure time information to be... more We introduce a novel knowledge-based recommendation algorithm for
leisure time information to be used in social networks, which enhances
the state-of-the-art in this algorithm category by taking into account
(a) qualitative aspects of the recommended places (restaurants, museums,
tourist attractions etc.), such as price, service and atmosphere,
(b) influencing factors between social network users, (c) the semantic
and geographical distance between locations and (d) the semantic
categorization of the places to be recommended. The combination of
these features leads to more accurate and better user-targeted leisure
time recommendations.
Firms and organizations are increasingly exploiting electronic channels
to reach their customers... more Firms and organizations are increasingly exploiting electronic channels
to reach their customers and create new business opportunities. To
this end, electronic shops have been developed, either offering products
from a single firm or encompassing multiple individual electronic
stores, comprising thus electronic shopping malls. Two main concerns
for e-commerce are personalization and enhancement of user experience.
Personalization addresses the ability to offer content tailored to
the preferences of each user or user group. Preferences may be explicitly
declared by the user, or derived by the system through inspecting
user interaction; if the system dynamically reacts to changes of
visitor behavior, it is termed as adaptive. Enhancement of user experience
is another major issue in e-commerce, given that 2D-images and texts
on the screen are not sufficient to provide information on products
aspects such as physical dimensions, textures and manipulation feedback.
Multimedia presentations can also be used as a means for .information
acceleration. for promoting "really new" products. This article aims
to specify a system that exploits capabilities offered by adaptation
and VR technologies to offer e-shoppers personalized and enhanced
experiences, while addressing challenges related to the cost, complexity
and effort of building and maintaining such a system.
This chapter presents an architecture for supporting the creation
of adaptive virtual reality mu... more This chapter presents an architecture for supporting the creation
of adaptive virtual reality museums on the web. It argues whether
the task of developing adaptive virtual reality museums is a complex
one, presenting key challenges, and should thus be facilitated by
means of a supporting architecture and relevant tools. The proposed
architecture is flexible enough to cater for a variety of user needs,
and modular promoting extensibility, maintainability and tailorability.
Adoption of this architecture will greatly simplify the development
of adaptive virtual reality museums, reducing the needed effort to
exhibit digitisation and user profile specification; user profiles
are further refined dynamically through the user data recorder and
the user modelling engine, which provide input for the virtual environment
generator.
Reusability is the degree to which a software component or other work
can be used in more than o... more Reusability is the degree to which a software component or other work
can be used in more than one programs or software systems. e-Government
is a prosperous area for the application of reusability, since the
services offered to citizens from the same administration, or even
different administrations, have common portions that can be developed
only once and reused wherever appropriate. In this paper we present
the design and implementation of an electronic service development
environment which offers the potential to reuse components that have
already been implemented, for the realization of new services.
Real-world information, knowledge and procedures after which information
systems are modeled are... more Real-world information, knowledge and procedures after which information
systems are modeled are generally of dynamic nature and subject to
changes, due to the emergence of new requirements or revisions to
initial specifications. E-government information systems (eGIS) present
a higher degree of volatility in their environment, since requirement
changes may stem from multiple sources, including legislation changes,
organizational reforms, end-user needs, interoperability and distribution
concerns etc. To this end, the design and implementation of eGIS
must adhere to paradigms and practices that facilitate the accommodation
of changes to the eGIS as they occur in the real world. In this work,
we present a role-based model for designing and implementing eGIS
that can dynamically accomodate changes, providing the necessary
facilities for modeling multiple aspects of the same real-world entities
and delivering context-specific behaviour.
Novel and intelligent visualization methods are being developed in
order to accommodate user sea... more Novel and intelligent visualization methods are being developed in
order to accommodate user searching and browsing tasks, including
new and advanced functionalities. Besides, research in the field
of user modeling is progressing in order to personalize these visualization
systems, according to its users’ individual profiles. However, employing
a single visualization system, may not suit best any information
seeking activity. In this paper we present a visualization environment,
which is based on a visualization library, i.e. is a set of visualization
methods, from which the most appropriate one is selected for presenting
information to the user. This selection is performed combining information
extracted from the context of the user, the system configuration
and the data collection. A set of rules inputs such information and
assigns a score to all candidate visualization methods. The presented
environment additionally monitors user behavior and preferences to
adapt the visualization method selection criteria.
In the mobile and pervasive computing environment, software engineering
should not treat diversi... more In the mobile and pervasive computing environment, software engineering
should not treat diversity and mobility as problems to overcome,
but seek methods of which it could take advantage instead. In these
environments, the selection of purpose-oriented and timely information,
tailored to user preferences and media characteristics will ensure
an optimised information delivery. To this end, the context .the
information that surrounds the human-computer interaction. plays
a key role and is rapidly changing in mobile settings, and the understanding
of it is indispensable for the application designers in order to
choose, capture and exploit it. In this work, we present an architecture
facilitating the collection of context information and its exploitation
for optimized information delivery, within mobile and pervasive computing
environments.
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Papers by Costas Vassilakis