Functional Brain Imaging with Multi-Objective Multi-Modal Evolutionary Optimization

Functional brain imaging is a source of spatio-temporal data mining problems. A new framework hybridizing multi-objective and multi-modal optimization is proposed to formalize these data mining problems, and addressed through Evolutionary Computation (EC). The merits of EC for spatio-temporal data mining are demonstrated as the approach facilitates the modelling of the experts' requirements, and flexibly accommodates their changing goals

Penggunaan Algoritma T-Apriori* Untuk Pencarian Association Rule Pada Data Spatio-Temporal

Seiring dengan berkembang pesatnya aplikasi basisdata, obyek data mining juga berkembang untuk menangani tipe data yang kompleks, antara lain data spatio-temporal. Data spatio-temporal menyimpan obyek spasial dan perubahannya, baik perubahan data spasial maupun data atributnya. Pada makalah ini akan dibahas pengembangan algoritma association rule pada data spasial dengan menambahkan batasan waktu. Spatio-temporal association rule terjadi jika terdapat relasi spatio-temporal pada bagian antecedent atau consequent dari sebuah rule. Dua aspek penting dalam pencarian spatio-temporal association rule adalah prapemrosesan data dan algoritma pembangkitan frequent predicate. Metode prapemrosesan data berfungsi untuk memproses data sumber yang berupa data spasial dan non-spasial dengan batasan waktu dan menghasilkan data yang siap untuk di-mining. Pembangkitan frequent predicate dilakukan dengan menggunakan algoritma T-Apriori*, yaitu pengembangan algoritma T- Apriori yang diperluas untuk menangani data spatio-temporal. Selanjutnya, algoritma ini dimanfaatkan untuk mendukung proses pengambilan keputusan dengan cara mengintegrasikannya kedalam sebuah perangkat lunak SIG. Sistem ini mampu melakukan analisis data kesehatan dan demografi yang berbasis spatio-temporal dan menghasilkan knowledge dalam bentuk spatio-temporal association rule. Kata kunci: association rule, spatio-temporal data mining, frequent predicate, T-Apriori

Discovering private trajectories using background information

Trajectories are spatio-temporal traces of moving objects which contain valuable information to be harvested by spatio-temporal data mining techniques. Applications like city traffic planning, identification of evacuation routes, trend detection, and many more can benefit from trajectory mining. However, the trajectories of individuals often contain private and sensitive information, so anyone who possess trajectory data must take special care when disclosing this data. Removing identifiers from trajectories before the release is not effective against linkage type attacks, and rich sources of background information make it even worse. An alternative is to apply transformation techniques to map the given set of trajectories into another set where the distances are preserved. This way, the actual trajectories are not released, but the distance information can still be used for data mining techniques such as clustering. In this paper, we show that an unknown private trajectory can be reconstructed using the available background information together with the mutual distances released for data mining purposes. The background knowledge is in the form of known trajectories and extra information such as the speed limit. We provide analytical results which bound the number of the known trajectories needed to reconstruct private trajectories. Experiments performed on real trajectory data sets show that the number of known samples is surprisingly smaller than the actual theoretical bounds

Challenging Issues of Spatio-Temporal Data Mining

The spatio-temporal database (STDB) has received considerable attention during the past few years, due to the emergence of numerous applications (e.g., flight control systems, weather forecast, mobile computing, etc.) that demand efficient management of moving objects. These applications record objects' geographical locations (sometimes also shapes) at various timestamps and support queries that explore their historical and future (predictive) behaviors. The STDB significantly extends the traditional spatial database, which deals with only stationary data and hence is inapplicable to moving objects, whose dynamic behavior requires re-investigation of numerous topics including data modeling, indexes, and the related query algorithms. In many application areas, huge amounts of data are generated, explicitly or implicitly containing spatial or spatiotemporal information. However, the ability to analyze these data remains inadequate, and the need for adapted data mining tools becomes a major challenge. In this paper, we have presented the challenging issues of spatio-temporal data mining. Keywords: database, data mining, spatial, temporal, spatio-tempora

Human Mobility Mining Using Spatio-Temporal Data

Georuumilised tehnoloogiad on lahutamatu osa meie elust: tehnoloogilise arengu ja positsioneerimiseadmete levikuga on toimunud kiire kasv kättesaadavate georuumiliste andmete mahus. Andmed kogutakse erinevate allikate kaudu, nt GPS ja mobiilseadmete logid, traadita sidevahendid ja asukohapõhised teenused ning teised positsioneerimise süsteemid. Liikumise kohta on võimalik infot koguda suures mõõtkavas ja hea täpsusega - see annab uurijatele võimaluse luua uusi ja innovaatilisi platvorme ja teenuseid georuumilise info analüüsimiseks ning parandada andmete kaevandamise ja visualiseerimise tehnikaid. Selleks, et luua hea nõustamisssüsteem, on väga oluline saada aru inimeste liikumisharjumustest ja käitumisest ning leida igapäevaste tegevuste varjatud mustrid. Magistritöö eesmärgiks on analüüsida andmekaeve meetodeid, uurides, millised mustrid võivad olla liikumise trajektoorides või milliste algoritmidega saab ennustada inimeste käitumist. Töös kontrollitakse nii olemasolevaid metoodikad ja teooriad ruumilise andmekaevandamise valdkonnas kui ka pakutakse arendatud algoritmide jada inimeste liikumise ennustamiseks. Me hindame ja vördleme tulemusi omavahel ning töötame välja metoodika inimeste liikumiskäitumise adaptiivseks andmekaevandamiseks.Geospatial technologies have become an integral part of our lives. With technological progress and rapid increase of geospatial information and inexpensive positioning technologies, more space-related data is becoming available at any time. Data is collected using multiple sources such as GPS and mobile computer logs, wireless communication devices, location-aware services and other positioning systems. This gives scientists the opportunity to create new innovative platforms for spatio-temporal data analysis and improve methods for mining and visualization for decision support. In order to provide a good decision support systems, it is vital to understand people’s movement, mobility behaviour and be able to discover hidden patterns and associations in their daily activities. The aim of this thesis is to analyze and discuss spatial data mining techniques by answering questions like what kinds of patterns can be extracted from spatio-temporal data or which methods are best for predicting human mobility behavior. In this work, we verify existing methodologies and theories about spatio-temporal data mining and propose a sequence of algorithms to achieve good human mobility prediction. We evaluate the results and propose a methodology for adaptive data mining of human mobility behavior

GET_MOVE: An Efficient and Unifying Spatio-Temporal Pattern Mining Algorithm for Moving Objects

International audienceRecent improvements in positioning technology has led to a much wider availability of massive moving object data. A crucial task is to find the moving objects that travel together. Usually, they are called spatio-temporal pat- terns. Due to the emergence of many different kinds of spatio-temporal patterns in recent years, different approaches have been proposed to extract them. However, each approach only focuses on mining a specific kind of pattern. In addition to the fact that it is a painstaking task due to the large number of algorithms used to mine and manage patterns, it is also time consuming. Additionally, we have to execute these algorithms again whenever new data are added to the existing database. To address these issues, we first redefine spatio-temporal patterns in the itemset context. Secondly, we propose a unifying approach, named GeT Move, using a frequent closed itemset-based spatio-temporal pattern-mining algorithm to mine and manage different spatio-temporal patterns. GeT Move is implemented in two versions which are GeT Move and Incremental GeT Move. Experiments are per- formed on real and synthetic datasets and the experimental results show that our approaches are very effective and outperform existing algorithms in terms of efficiency

Periodic pattern mining from spatio-temporal trajectory data

Rapid development in GPS tracking techniques produces a large number of spatio-temporal trajectory data. The analysis of these data provides us with a new opportunity to discover useful behavioural patterns. Spatio-temporal periodic pattern mining is employed to find temporal regularities for interesting places. Mining periodic patterns from spatio-temporal trajectories can reveal useful, important and valuable information about people's regular and recurrent movements and behaviours. Previous studies have been proposed to extract people's regular and repeating movement behavior from spatio-temporal trajectories. These previous approaches can target three following issues, (1) long individual trajectory; (2) spatial fuzziness; and (3) temporal fuzziness. First, periodic pattern mining is different to other pattern mining, such as association rule ming and sequential pattern mining, periodic pattern mining requires a very long trajectory from an individual so that the regular period can be extracted from this long single trajectory, for example, one month or one year period. Second, spatial fuzziness shows although a moving object can regularly move along the similar route, it is impossible for it to appear at the exactly same location. For instance, Bob goes to work everyday, and although he can follow a similar path from home to his workplace, the same location cannot be repeated across different days. Third, temporal fuzziness shows that periodicity is complicated including partial time span and multiple interleaving periods. In reality, the period is partial, it is highly impossible to occur through the whole movement of the object. Alternatively, the moving object has only a few periods, such as a daily period for work, or yearly period for holidays. However, it is insufficient to find effective periodic patterns considering these three issues only. This thesis aims to develop a new framework to extract more effective, understandable and meaningful periodic patterns by taking more features of spatio-temporal trajectories into account. The first feature is trajectory sequence, GPS trajectory data is temporally ordered sequences of geolocation which can be represented as consecutive trajectory segments, where each entry in each trajectory segment is closely related to the previous sampled point (trajectory node) and the latter one, rather than being isolated. Existing approaches disregard the important sequential nature of trajectory. Furthermore, they introduce both unwanted false positive reference spots and false negative reference spots. The second feature is spatial and temporal aspects. GPS trajectory data can be presented as triple data (x; y; t), x and y represent longitude and latitude respectively whilst t shows corresponding time in this location. Obviously, spatial and temporal aspects are two key factors. Existing methods do not consider these two aspects together in periodic pattern mining. Irregular time interval is the third feature of spatio-temporal trajectory. In reality, due to weather conditions, device malfunctions, or battery issues, the trajectory data are not always regularly sampled. Existing algorithms cannot deal with this issue but instead require a computationally expensive trajectory interpolation process, or it is assumed that trajectory is with regular time interval. The fourth feature is hierarchy of space. Hierarchy is an inherent property of spatial data that can be expressed in different levels, such as a country includes many states, a shopping mall is comprised of many shops. Hierarchy of space can find more hidden and valuable periodic patterns. Existing studies do not consider this inherent property of trajectory. Hidden background semantic information is the final feature. Aspatial semantic information is one of important features in spatio-temporal data, and it is embedded into the trajectory data. If the background semantic information is considered, more meaningful, understandable and useful periodic patterns can be extracted. However, existing methods do not consider the geographical information underlying trajectories. In addition, at times we are interested in finding periodic patterns among trajectory paths rather than trajectory nodes for different applications. This means periodic patterns should be identified and detected against trajectory paths rather than trajectory nodes for some applications. Existing approaches for periodic pattern mining focus on trajectories nodes rather than paths. To sum up, the aim of this thesis is to investigate solutions to these problems in periodic pattern mining in order to extract more meaningful, understandable periodic patterns. Each of three chapters addresses a different problem and then proposes adequate solutions to problems currently not addressed in existing studies. Finally, this thesis proposes a new framework to address all problems. First, we investigated a path-based solution which can target trajectory sequence and spatio-temporal aspects. We proposed an algorithm called Traclus (spatio-temporal) which can take spatial and temporal aspects into account at the same time instead of only considering spatial aspect. The result indicated our method produced more effective periodic patterns based on trajectory paths than existing node-based methods using two real-world trajectories. In order to consider hierarchy of space, we investigated existing hierarchical clustering approaches to obtain hierarchical reference spots (trajectory paths) for periodic pattern mining. HDBSCAN is an incremental version of DBSCAN which is able to handle clusters with different densities to generate a hierarchical clustering result using the single-linkage method, and then it automatically extracts clusters from a hierarchical tree. Thus, we modified traditional clustering method DBSCAN in Traclus (spatio-temporal) to HDBSCAN for extraction of hierarchical reference spots. The result is convincing, and reveals more periodic patterns than those of existing methods. Second, we introduced a stop/move method to annotate each spatio-temporal entry with a semantic label, such as restaurant, university and hospital. This method can enrich a trajectory with background semantic information so that we can easily infer people's repeating behaviors. In addition, existing methods use interpolation to make trajectory regular and then apply Fourier transform and autocorrelation to automatically detect period for each reference spot. An increasing number of trajectory nodes leads to an exponential increase of running time. Thus, we employed Lomb-Scargle periodogram to detect period for each reference spot based on raw trajectory without requiring any interpolation method. The results showed our method outperformed existing approaches on effectiveness and efficiency based on two real datasets. For hierarchical aspect, we extended previous work to find hierarchical semantic periodic patterns by applying HDBSCAN. The results were promising. Third, we apply our methodology to a case study, which reveals many interesting medical periodic patterns. These patterns can effectively explore human movement behaviors for positive medical outcomes. To sum up, this research proposed a new framework to gradually target the problems that existing methods cannot handle. These include: how to consider trajectory sequence, how to consider spatial temporal aspects together, how to deal with trajectory with irregular time interval, how to consider hierarchy of space and how to extract semantic information behind trajectory. After addressing all these problems, the experimental results demonstrate that our method can find more understandable, meaningful and effective periodic patterns than existing approaches