@conference {812, title = {Persona Finetuning for Online Gaming using Personalisation Techniques}, booktitle = {Proceedings of the 2022 HCII Conference}, year = {2022}, abstract = {

Automatic persona generation has been shown to have specific measurable benefits for application creators and users. In most situations, personas are adequately descriptive and diversified to achieve user type accuracy and coverage. For specific market segments, such as online gaming, using personas may accurately describe existing user base but not changing habit and need that are introduced by the fluidity of the offerings and the delivery methods. Changes in the ways that applications are marketed, such as new payment methods, for example, subscription models, pay-to-play and pay-to-win, payment-driven-gamification, seriously affect user needs and result in direct impact on user acceptance. This work utilises structured user needs from online gaming players to augment personas using personalisation techniques. The personas are finetuned and dediversified to result in concise personas, based on user needs that successfully convey information for creators and users alike.

}, keywords = {collaborative filtering, Data-driven methods, Diversification, Online Gaming, Persona, Personalisation, Usability evaluation, User study}, author = {Dimitris Spiliotopoulos and Dionisis Margaris and Kostas N. Koutrakis and Panos Philippopoulos and Costas Vassilakis} } @article {813, title = {On Producing Accurate Rating Predictions in Sparse Collaborative Filtering Datasets}, journal = {Information}, volume = {13}, year = {2022}, month = {jun}, pages = {302}, abstract = {

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{\textendash}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{\textquoteright}s success. An extensive evaluation is conducted using sparse collaborative filtering datasets. It is found that the number of near neighbours used for the prediction formulation, the rating average of the user for whom the prediction is generated and the rating average of the item concerning the prediction can indicate, in many cases, whether the rating prediction produced is reliable or not.

}, keywords = {accuracy, collaborative filtering, Evaluation, Personalisation, Rating prediction, Recommender Systems, reliability, Sparse Datasets}, doi = {https://doi.org/10.3390/info13060302}, author = {Dionisis Margaris and Costas Vassilakis and Dimitris Spiliotopoulos} } @conference {786, title = {Policy Making Analysis and Practitioner User Experience}, booktitle = {Proceedings of the 22nd International Conference on Human-Computer Interaction}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

This article presents the work on social media analysis-driven policy-making platforms that are powered by classic social media analysis technologies, such as policy modelling, linguistic analysis, opinion mining, sentiment analysis and information visualization. The approach examines the user design perspective towards user experience in policymaking for all the innovative modules used. The technology behind such complex task is presented while the resulting platform is appraised on the potential for real world application. The findings drive the development and the requirements for the summative usability assessment tests. We also report on the level the practitioners adopted the policy formulation tools.

}, keywords = {Content Analysis, natural language interfaces, opinion mining, policy making, social network analysis, User Experience}, doi = {10.1007/978-3-030-60114-0_29}, author = {Dimitris Koryzis and Fotios Fitsilis and Dimitris Spiliotopoulos and Theocharis Theocharopoulos and Dionisis Margaris and Costas Vassilakis} } @conference {714, title = {PaloAnalytics project concept, scope and outcomes: an opportunity for culture}, booktitle = {Proceedings of the Workshop on Cultural Informatics, co-located with the 14th International Workshop On Semantic And Social Media Adaptation And Personalization (SMAP 2019)}, year = {2019}, abstract = {This paper describes the national funded project entitled PaloAnalytics, which develops an innovative platform that allows companies and organizations, that operate in several countries, to monitor and analyze, in depth, the markets{\textquoteright} interest to their products and successfully plan their marketing and communication strategy, with data and insights collected from all the local media, and focuses on its application to cultural spaces and museums. In this notion, we examine the effect that this project can have in cultural spaces or companies related to arts and culture. PaloAnalytics platform allows organizations to investigate the impact of their products on consumers across different countries and this is achieved with the analysis of content from sites, blogs, social networks and open data. This implies that cultural organization can benefit by adopting the implemented services, so that the can recognize and analyze their audience, their online marketing campaigns as well as examine the impact of their messages and the spread of their messages on the Internet. In this paper, we briefly describe the project and discuss on the impact on cultural related organizations.}, keywords = {big data, data monitoring, Data visualization, deep learning, influencers, infographics, trending topics}, url = {http://ceur-ws.org/Vol-2412/paper7.pdf}, author = {Vassilis Poulopoulos and Manolis Wallace and Costas Vassilakis and George Lepouras}, editor = {Angeliki Antoniou and Manolis Wallace} } @conference {vacilosEuromed18, title = {Personality Analysis of Social Media Influencers as a Tool for Cultural Institutions}, booktitle = {Digital Heritage. Progress in Cultural Heritage: Documentation, Preservation, and Protection}, year = {2018}, pages = {236{\textendash}247}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {Nowadays, more and more cultural venues tend to utilize social media as a main tool for marketing, spreading their messages, engaging public and raising public awareness towards culture. It comes to a point where the massive of content in social media makes it a tedious procedure to contact the appropriate audience, the people that would really be stimulated by cultural information. In this notion, we assume that establishing conversations of high impact can possibly guide the cultural venues to audiences that can benefit more. These conversations usually include the so called influencers, users whose opinion can affect many people on social media; the latter usually referred to as followers. In this research paper we examine the characteristics of the influencers that can affect the procedures of a cultural venue on social media. The research is done within the scope of "CrossCult" EU funded project.}, keywords = {cultural informatics, influencers, personality traits, social media, user modeling}, doi = {10.1007/978-3-030-01762-0_20}, author = {Vassilis Poulopoulos and Costas Vassilakis and Angela Antoniou and Giorgos Lepouras and Manolis Wallace} } @article {Poulopoulos2018Heritage, title = {The personality of the influencers, the characteristics of qualitative discussions and their analysis for recommendations to cultural institutions}, journal = {Heritage}, volume = {1}, number = {2}, year = {2018}, month = {oct}, pages = {239-253}, abstract = {Social media usage is affecting peoples{\textquoteright} 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{\textquoteright} 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{\textquoteright}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 character of the influencer and the substances of a {\textquotedblleft}serious{\textquotedblright} conversation. {\textquotedblleft}Serious{\textquotedblright} conversations are regarded the ones in which a cultural organization can participate actively and benefit from the participation. We present the results of our experimental evaluation and analyze how cultural institutions can benefit from the outcomes of our research.}, keywords = {cultural informatics, digital humanities, personality traits, personalization, serious conversations, social media influencers, user modeling}, issn = {2571-9408}, doi = {10.3390/heritage1020016}, url = {https://doi.org/10.3390/heritage1020016}, author = {Vassilis Poulopoulos and Costas Vassilakis and Angela Antoniou and Giorgos Lepouras and Anastasios Theodoropoulos and Manolis Wallace} } @conference {theodorakopoulos-smap2017, title = {Personalized Augmented Reality Experiences in Museums using Google Cardboards}, booktitle = {2017 12th International Workshop on Semantic and Social Media Adaptation and Personalization (SMAP)}, year = {2017}, month = {07}, publisher = {IEEE CPS}, organization = {IEEE CPS}, abstract = {In this short paper we examine the suitability of the Google Cardboard as a means for the delivery of personalized cultural experiences. Specifically, we develop the content and create the application required in order to provide highly personalized visits to the Archaeological Museum in Tripolis, Greece. We also examine the usability issues related to the use of Google Cardboards. Early results are promising, and based on them we also outline the next steps ahead.}, doi = {10.1109/smap.2017.8022676}, url = {https://ieeexplore.ieee.org/document/8022676/}, author = {Marinos Theodorakopoulos and Nikos Papageorgopoulos and Andriana Mourti and Angela Antoniou and Manolis Wallace and Giorgos Lepouras and Costas Vassilakis and Nikos Platis} } @conference {marg2016-ssci, title = {Pruning and Aging for User Histories in Collaborative Filtering}, booktitle = {Proceedings of the 2016 IEEE Symposium Series on Computational Intelligence}, year = {2016}, month = {12}, abstract = {In this paper, we introduce algorithms for pruning and aging user ratings in collaborative filtering systems, based on their oldness, under the rationale that aged user ratings may not accurately reflect the current state of users regarding their preferences. The aging algorithm reduces the importance of aged ratings, while the pruning algorithm removes them from the database. The algorithms are evaluated against various types of datasets. The pruning algorithm has been found to present a number of advantages, namely (1) reducing the rating database size, (2) achieving better prediction generation times and (3) improving prediction quality by cutting off predictions with high error. The algorithm can be used in all rating databases that include a timestamp and has been proved to be effective in any type of dataset, from movies and music, to videogames and books.}, doi = {10.1109/ssci.2016.7849920}, url = {https://ieeexplore.ieee.org/document/7849920/}, author = {Dionisis Margaris and Costas Vassilakis} } @conference {556, title = {A Platform for the Presentation and Dissemination of Cultural Heritage Information for Mobile Devices Enriched with Augmented Reality}, booktitle = {Proceedings of the Greek Conference for the Digitization of Cultural Information (EUROMED)}, year = {2015}, month = {September}, address = {Volos, Greece}, author = {K. Masselos and Costas Vassilakis and Giorgos Lepouras and Christos Tryfonopoulos and N. Tselikas and N. Platis} } @article {Vasiliadis-2013x, title = {Performance Tuning of Dual-priority Delta Networks through Queuing Scheduling Disciplines}, journal = {Journal of Communications Software and Systems}, volume = {9(4)}, number = {4}, year = {2013}, month = {12/2013}, pages = {222-235}, publisher = {Croatian Communications and Information Society}, abstract = {Differentiated Services (DiffServ) and other scheduling strategies are now widespread in the traditional, {\textquotedblleft}best effort{\textquotedblright} 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.}, doi = {10.24138/jcomss.v9i4.143}, url = {https://hrcak.srce.hr/180111}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis} } @article {vasiliadis2011a, title = {Performance Analysis of Dual-Priority Multilayer Multistage Interconnection Networks under Multicast Environment}, journal = {Journal of Networks}, volume = {June}, year = {2011}, pages = {858{\textendash}871}, abstract = {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{\textlnot}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.}, keywords = {banyan networks, multicast traffic, multilayer networks, Multistage interconnection networks, performance analysis}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis} } @article {vasiliadis11, title = {Performance Analysis of Multi-Layered Multi-Priority Asymetric-Sized Delta Networks}, journal = {Journal of Computer Systems, Networks, and Communications}, volume = {to appear}, year = {2011}, pages = {12}, abstract = {In this paper the performance of multi-layered asymmetric-sized finite-buffered Delta Networks supporting multi-class routing traffic is presented and analyzed in the uniform traffic conditions under various loads using simulations. The rationale behind introducing asymmetric-sized buffered systems is to have a better exploitation of available buffer spaces, while the implementation of multi-layered architecture is applied in order to further improve the overall performance of network. The findings of this performance evaluation can be used by network designers for drawing optimal configurations while setting up the network, so as to best meet the performance and cost requirements under the anticipated traffic load and quality of service specifications.}, doi = {10.1155/2011/723102}, url = {https://www.hindawi.com/journals/jcnc/2011/723102/}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis} } @article {vasiliadis2011b, title = {Performance Study of Multi-Layered Multistage Interconnection Networks under Hotspot Traffic Conditions}, journal = {Journal of Computer Systems, Networks, and Communications}, volume = {2010}, year = {2010}, pages = {11 pages}, abstract = {The performance of Multistage Interconnection Networks (MINs) under hotspot traffic, where some percentage of the traffic is targeted at single nodes, which are also called hot-spots, is of crucial interest. The prioritizing of packets has already been proposed at previous works as alleviation to the tree saturation problem, leading to a scheme that natively supports 2-class priority traffic. In order to prevent hotspot traffic from degrading uniform traffic we expand previous studies by introducing multi-layer Switching Elements (SEs) at last stages in an attempt to balance between MIN performance and cost. In this paper the performance evaluation of dual-priority, double-buffered, multi-layer MINs under single hotspot setups is presented and analyzed using simulation experiments. The findings of this paper can be used by MIN designers to optimally configure their networks}, keywords = {Hotspot traffic, multi-layer networks, Multistage interconnection networks, Performance evaluation}, doi = {10.1155/2010/403056}, url = {https://www.hindawi.com/journals/jcnc/2010/403056/}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis} } @conference {Vasiliadis2009395, title = {Performance evaluation of multicast routing over multilayer multistage interconnection networks}, booktitle = {Proceedings of the 2009 5th Advanced International Conference on Telecommunications, AICT 2009}, year = {2009}, note = {cited By (since 1996) 0}, month = {5}, pages = {395-403}, abstract = {Multilayer MINs have emerged mainly due to the increased need for routing capacity in the presence of multicast and broadcast traffic, their performance prediction and evaluation however has not been studied sufficiently insofar. In this paper, we use simulation to evaluate the performance of multilayer MINs with switching elements of different buffer sizes and under different offered loads. The findings of this paper can be used by MIN designers to optimally configure their networks. Β{\textcopyright} 2009 IEEE.}, keywords = {Broadcast traffic, Buffer sizes, Interconnection networks, Multicast routing, Multicasting, Multicasts, Multilayers, Multistage interconnection network, Network routing, Performance evaluation, Performance prediction, Switching elements}, doi = {10.1109/AICT.2009.72}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-70349732883\&partnerID=40\&md5=e85525a7b36de8d84ea1ae52110ff1f9}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis and E. Glavas} } @conference {Vasiliadis200890, title = {Performance Evaluation of Distance Vector Routing Protocol on a Wireless Circular Model}, booktitle = {Proceedings of the IEEE sponsored International Joint Conference CISSE 2007}, year = {2008}, month = {12}, pages = {323-328}, publisher = {Springer Netherlands}, organization = {Springer Netherlands}, abstract = {In this paper, a wireless Circular Model over a generic distance-vector routing protocol is presented and analyzed. The performance of this model over the Distance Vector protocol, which is an implementation of Distributed Bellman-Ford algorithm, has been evaluated by using the simulation environment of NS-2. We conducted an extensive evaluation study for various mobility schemes in order to incorporate the behavior of nodes and the routing protocol in a real-life hotspot situation In the test-bed model, while the number of source nodes was allowed to arbitrarily vary, there was exactly one destination node, closely modeling thus real-life situations where a single hotspot/access point exists. Finally, different constant bit rates (CBR) were used in order to estimate the throughput of receiving, dropping rates, the number of lost packets, as well as the average packet delay under various traffic conditions. This study is aimed to help wireless network designers in choosing the best suited routing protocols for their networks, through making explicit performance figures for common network setups.}, doi = {10.1007/978-1-4020-8737-0}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis}, editor = {Tarek Sobh and Khaled Elleithy and Ausif Mahmood and Mohammad A. Karim} } @conference {Katifori2008a1, title = {Personal Ontology Creation and Visualization for a Personal Interaction Management System}, booktitle = {Proceedings of PIM, CHI 2008}, year = {2008}, month = {4}, abstract = {Ontologies offer a flexible and expressive layer of abstraction, very useful for capturing the semantics of information repositories and facilitating their retrieval either by the user or by the system to support user tasks. This work presents an ontology-based user profiler, in the context of a Personal Interaction Management System (PIMS). The profiler, based on an ontology of the users? domain, enables them to create their personal ontology by initially choosing one of the available template ontologies as a starting point, which they subsequently populate and customize. The profiler employs a web interface which allows users to populate their personal ontology through forms, hiding ontology complexities and peculiarities. Forms are dynamically generated through ontology views, which are specified by ontology designers.}, author = {Akrivi Katifori and Costas Vassilakis and I. Daradimos and Giorgos Lepouras and Yannis Ioannidis and Alan Dix and Antonella Poggi and Tiziana Catarci} } @conference {Vasiliadis2007, title = {Performance Analysis of dual priority single-buffered blocking Multistage Interconnection Networks}, booktitle = {3rd International Conference on Networking and Services, ICNS 2007}, year = {2007}, month = {6}, publisher = {IEEE}, organization = {IEEE}, abstract = {In this paper a novel architecture of dual priority single-buffered blocking Multistage Interconnection Networks (MINs) is presented. We analyzed their performance in the uniform traffic condition under various loads using simulations. We compared the dual priority architecture against a single priority MIN, 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 demonstrated the gain of the high priority packets against the low priority packets under different configuration schemas. In this paper we focus on studying the influence of the priority bit in the header field of transmitted packets on the performance of high and low priority traffic of a MIN. Performance prediction before actual network implementation and understanding the impact of parameter settings in a MIN setup are valuable assets for network designers for minimizing overall deployment costs and delivering efficient networks. Β{\textcopyright} 2007 IEEE.}, keywords = {Computer architecture, Interconnection networks, International conferences, Low priority (LP), Metrics (CO), Multistage interconnection networks Multistage interconnection netowrk (MIN), Network architecture, Network designers, Network performances, Novel architecture, Packet throughput, Parameter estimation, Parameter settings, Performance analyses, Performance predictions, Schemas, Systems engineering, telecommunication, Telecommunication networks, Uniform traffic}, doi = {10.1109/ICNS.2007.92}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-47049115567\&partnerID=40\&md5=148ac10a4b9facdaf1066911f87f5bb5}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis} } @conference {Vasiliadis2007a, title = {Performance evaluation of two-priority network schema for single-buffered delta networks}, booktitle = {IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC}, year = {2007}, note = {cited By (since 1996) 0}, month = {9}, abstract = {In this paper a novel two-priority network schema is presented, and exemplified through its application on singlebuffered Delta Networks in packet switching environments. Network operations considered include conflict resolution and communication strategies. The proposed scheme is evaluated and compared against the single-priority scheme. Performance evaluation was conducted through simulation, due to the complexity of the model, and uniform traffic conditions were considered. Metrics were gathered for the two most important network performance factors, namely packet throughput and the mean time a packet needs to traverse the network. The model can also be uniformly applied to several representative networks providing a basis for fair comparison and the necessary data for network designers to select optimal values for network operation parameters. Β{\textcopyright} 2007 IEEE.}, keywords = {Computer simulation, Mobile radio systems, Network operations, Packet switching, Single-buffered delta networks, Telecommunication networks, Telecommunication traffic}, doi = {10.1109/PIMRC.2007.4394153}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-44349140122\&partnerID=40\&md5=d8cd4384e09916ce753625ec5f2c8549}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis and E. Glavas} } @conference {Vasiliadis2006b, title = {Performance analysis of blocking banyan switches}, booktitle = {Proceedings of the IEEE sponsored International Joint Conference on Computer, Information and System Sciences and Engineering - CIS2E 06}, year = {2006}, month = {12}, abstract = {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.}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis} } @conference {Vasiliadis2006a, title = {Performance Analysis of Multistage Interconnection Networks determining optimal parameters for data-intensive business applications}, booktitle = {Proceedings of the 7th IBIMA Conference}, year = {2006}, month = {12}, abstract = {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.}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis} } @article {1993-spiliopoulou-cai, title = {Parallel Optimisation of Join Queries Using a Technique of Exhaustive Nature}, journal = {Computers and Artificial Intelligence}, volume = {12}, number = {2}, year = {1993}, pages = {145{\textendash}166}, abstract = {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.}, keywords = {databases}, author = {M. Spiliopoulou and M. Hatzopoulos and Costas Vassilakis} }