As an open license project, Open Street Map (OSM) aims to make the collectively produced geographic data freely available to be used for various purposes. Routing engines frequently take advantage of this data set. Nonetheless, providing routing services on top of OSM requires the full connectivity of the OSM road network graph in the interest area. This connectivity needs to be achieved individually at every level of the road network graph: the motorway, trunk, primary, secondary, tertiary, and residential roads. However, due to its open-editing nature, the OSM data often contains faults attributed to issues like missing road network connections or mistakenly attributed road segments.

As any other type of data, GPS traces contain noise, anomaly, and sometimes unexpected values. Normally, researchers and data engineers analysts would start dealing with GPS data by removing those noises and outliers. However, in this work, we take the opposite direction. We focus on analyzing those unexpected values rather than discarding them. Interestingly, we discovered useful findings from an insight look at the noise in GPS trajectories. The intuition behind those discoveries is that when unexpected GPS readings are observed several times around a specific location, we study the nature of that location rather than thrown away those reading. By doing so, we are able to tell the type of area around those readings. For example, we can infer that a driver is passing by a tall building or through a forest based on the pattern of noise in the GPS readings. We are also able to question the quality of the underlying road map. Our findings and discoveries are based on the analysis of real GPS data for the Microsoft shuttles.

In this demo, we present a system for managing location uncertainty in moving objects' data and refining their uncertain trajectories. Therefore, users are able to query objects' past, present, and predicted location more precisely. In the absence of precise location data, i.e. exact lat and long, the uncertain location is defined by an uncertainty region that overlaps multiple nodes in the underlying road network graph. Imprecise location comes from various causes such as inaccurate GPS readings, cloaked region for privacy, or communication issues. The main idea is to find a maximum likelihood connected path of nodes across consecutive regions of uncertainty. By doing so, we narrow down the possible paths and hence prune out a considerable number of nodes in the uncertain regions which in turn leads to a smaller and more precise region. Finally, using the latest location data received from a given object, following refinements, we predict its future movements. Due to the uncertain nature of the problem, there are always multiple possible locations for a moving object. This is only amplified when we try to predict future movements. The refinement steps narrow down possible locations significantly and hence reduces the computation cost. During the demo, the audience will be able to interact with the system to define the size of the uncertainty region, examine the refinement process, and visually experience how the system narrows down the possible locations of the objects' past, current, and future trajectory segments.

GPS data is noisy by nature. A typical location-based service would start by filtering out the noise from the raw GPS points that are generated by moving objects. Once the locations of the objects are identified, the location-based service is provided. In this paper, we decide not to throw away the noise. Instead, we consider the noise as an asset. We analyze the various noise patterns under different conditions and region characteristics. More specifically, we focus on one example where a lot of GPS noise is experienced; which is urban canyons. We believe that learning the GPS noise patterns in a supervised environment enables us to discover knowledge about new areas or areas where we have little knowledge. This paper is based on the analysis of GPS traces that are collected from the shuttle service within the Microsoft campuses around Seattle, Washington.

It is a fact that there are tons of GPS traces generated every minute by the millions of in-road vehicles over the world. Naturally, those traces contain imprecise readings, and most of the time they include noise and outliers. Therefore, there is a real need for a tool to allow users, companies, and researchers to get a deep insight into those raw traces and discover potential knowledge out of it. This knowledge would uncover the quality level of the GPS traces and, indeed, the quality level of the underlying map. It would also help discover interesting facts about the surrounding environment such as the type and height of buildings, the landscape cover, the weather conditions, and the nature of businesses and activities. This demo presents a system that allows users to interactively explore their collected GPS traces. Users can visually inspect the precision of their raw GPS traces, and snap these traces to the underlying road network map. Furthermore, users have the ability to clean their traces by applying various types of spatio-temporal filters. Users can perform noise analysis and produce statistics over regions of interest on the map. Last but not least, the system gives suggestions or guesses on the surrounding environment by comparing the perceived noise patterns to a database of pre-stored noise patterns. For the demo purpose, the system is initially populated with a rich data set of trajectories generated from the Microsoft shuttle service around the Greater Area of Seattle.

NoSQL data-stores are commonly used to provide flexibility and availability for big data handling. However, there is a lack of comprehensive studies about which NoSQL data-store performs the best from the two scalability aspects, (scale-up, and scale-out), in a distributed and parallel processing environment. This paper compares the popular NoSQL data-stores (Cassandra, HBase, and MongoDB) and analyzes the resulting performance. Our experiments measure throughput, latency, and run-time of the evaluated data-stores on a big data set that consist of standard benchmarking workloads. Our results provide that the performance of each NoSQL data-store varies according to two main factors, (a) the type of executed operation, (read, scan, update, write, and insert), and (b) the level of distribution.

Locating spatial data sources for a specific area of interest (AOI) is a difficult task, because of constantly updating server locations (URLs), specific layer location changes within that server location, and the relative unpopularity of a specific spatial data source. The proposed system, named Pine attempts to remedy the issue using automatic, yet user-led discovery of data sources by utilizing a web plug-in that discovers spatial data sources as users browse the web. The web plug-in has a two-fold function, (1) immediately presenting the spatial data source and all of the layers contained within that server discovered by the plug-in, (2) sending those layers and servers into a centralized, search-able repository that is accessible via the web. By utilizing the users browsing habits, and their machines as the discoverers of spatial data, Pine avoids the very high computational overhead of discovery of spatial data sources from a central server using a web crawling approach. As with any user-contributed data set, Pine must get users to actually contribute to the central repository, and it achieves this by including functionality that is useful to the user on its own by displaying a search-able list in the web plug-in of spatial data sources that the user has discovered themselves, a previously difficult task. The system implements a push based approach for discovering data sources, as the plug-in sends the data directly to the central repository, it is always up to date with the newest data sources discovered by any of the many instances of the web plug-in running on users computers

This poster presents the PreGo system for smart touring services. PreGo is smart in the sense that it enables its users to consider many preferences, (e.g., distance, travel time, services, attractions, safety), in their routing queries. The recommended route is completely personalized based on each user's weights for each of the routing preferences.

Connected moving objects with location sensors form the world of the Internet of Moving Things. This world includes people, animals, vehicles, drones, and vessels, to name a few. The conventional spatial libraries including Microsoft SQL Server Spatial (SqlSpatial) are primarily developed to evaluate spatial operations on stationary things. When it comes to real-world applications for the Internet of Moving Things that require realtime tracking and processing, the limitations of these libraries float to the surface. Unfortunately, the SqlSpatial library has very limited operations in this domain. This paper presents the Reactive eXtension Spatial (RxSpatial) library developed to provide real-time processing of spatio-temporal operations on moving objects connected through the Internet of Things. The superiority of the RxSpatial over the basic SqlSpatial is demonstrated throughout extensive experimental evaluations on real and synthetic data sets.

In smart cities, commuters have the opportunities for smart routing that may enable selecting a route with less car accidents, or one that is more scenic, or perhaps a straight and flat route. Such smart personalization requires a data management framework that goes beyond a static road network graph. This paper introduces PreGo, a novel system developed to provide real time personalized routing. The recommended routes by PreGo are smart and personalized in the sense of being (1) adjustable to individual users preferences, (2) subjective to the trip start time, and (3) sensitive to changes of the road conditions. Extensive experimental evaluation using real and synthetic data demonstrates the efficiency of the PreGo system.

A few decades ago, the Internet was created. Since then, searching for information and services has increased exponentially. With the introduction of GPS-enabled devices, a special type of search appeared offering location-aware services. These services customize search results based on users' location. This includes, but not limited to, (1) service finding, e.g., "find the nearest pizza restaurant", (2) routing, e.g., "obtain the shortest path from a user's home to the airport", (3) transportation, e.g., "what are the bus links to get a user from downtown to the mall", and (4) monitoring, e.g., "alert a parent if their child school-bus deviates from its regular route". Though new hardware and software technologies such as smart watches, voice search, and big-data platforms have been introduced and widely used, each single type of the above services has benefited very little from these technologies. On the local level of each service (the micro level), a full-fledged view is still missing. On the global level of all service types (the macro level), all Location-aware services are still acting as isolated islands and a global optimized service is not available. This paper presents our vision of how to provide an integrated macro location-aware service that acts harmoniously, and how each micro service can be further improved by better incorporation of novel technologies. We also overview the key challenges associated with these suggested improvements. Then, we highlight the potential value-added by the application of our vision.

The spatial libraries that have been developed by Microsoft, IBM and Oracle have substantially changed the capabilities of geospatial computing. These libraries implement several functionalities that include intersection, distance, and area for various geospatial objects. These libraries came out to address a wealth of use cases that were challenging in that era. As time goes by, GPS devices and location-aware mobile technologies increased the demand for geospatial computing, in general, and for real time geostreaming, in particular. Existing commercial spatial libraries were originally designed to support operations on stationary objects with limited or no capabilities for moving objects. In this paper, we introduce the RxSpatial library, a real time reactive spatial library for spatiotemporal stream query processing. RxSpatial provides, (1) a front-end, which is a programming interface for developers who are familiar with the Microsoft. NET Reactive framework and the Microsoft SQL Server Spatial Library, and (2) a back-end for processing spatial operations in a streaming fashion. RxSpatial provides the programming convenience at the front end and the query processing efficiency at the back end.

Existing routing services calculate the best route from source to destination over a road network graph. Most commercial routing services offer the best route in terms of either the shortest travel distance or the shortest travel time (with or without considering current traffic conditions). While travel distance and travel time are crucial route preferences for the commuter, other preferences are equally, or even more, important. Examples of other route preferences include fuel consumption, gas emissions, road safety, points of interest along the route, construction activities, open shops and restaurants. While some route preferences are static (e.g., travel distance and points of interests), other route preferences are dynamic and vary according to the time of the day (e.g., traffic-dependent travel time and the number of open shops/restaurants). Volunteered Geographic information (VGI) has been proposed as an approach to collect massive amounts of route information and, more specifically, the time varying parameters. This demo presents PreGo, a time-dependent multi-preference routing engine. During the demo, audience would interact with the PreGo routing engine to (1) find the optimal route w.r.t. The user's personal preferences for a given start time, (2) dynamically obtain the best start time for a trip given a set of preferences, (3) feed the system with VGI and examine their effect on the chosen route at real time, and (4) examine the correctness and efficiency of the PreGo selected routes compared to routes chosen by other commercial systems.

Current commercial spatial libraries implemented strong support on functionalities like intersection, distance, and area for various stationary geospatial objects. The missing point is the support for moving object. Performing moving object real-time location tracking and computation on server side of GIS application is challenging because of high user volume of moving object to track, time complexity of analysis and computation, and requirement of real-timing. In this Demo, we present the RxSpatial, a real time reactive spatial library that consists of (1) a front-end, a programming interface for developers who are familiar with the Reactive framework and the Microsoft Spatial Library, and (2) a back-end for processing spatial operations in a streaming fashion. Then we provide the demonstration scenarios that show how RxSpatial is employed in real-world applications. The demonstration scenarios include criminal activity tracking, collaborative vehicle system, performance analysis and an interactive internal inspection.

Predictive queries on moving objects offer an important category of location-aware services based on the objects' expected future locations. A wide range of applications utilize this type of services, e.g., traffic management systems, location-based advertising, and ride sharing systems. This paper proposes a novel index structure, named Predictive tree (P-tree), for processing predictive queries against moving objects on road networks. The predictive tree: (1) provides a generic infrastructure for answering the common types of predictive queries including predictive point, range, KNN, and aggregate queries, (2) updates the probabilistic prediction of the object's future locations dynamically and incrementally as the object moves around on the road network, and (3) provides an extensible mechanism to customize the probability assignments of the object's expected future locations, with the help of user defined functions. The proposed index enables the evaluation of predictive queries in the absence of the objects' historical trajectories. Based solely on the connectivity of the road network graph and assuming that the object follows the shortest route to destination, the predictive tree determines the reachable nodes of a moving object within a specified time window T in the future. The predictive tree prunes the space around each moving object in order to reduce computation, and increase system efficiency. Tunable threshold parameters control the behavior of the predictive trees by trading the maximum prediction time and the details of the reported results on one side for the computation and memory overheads on the other side. The predictive tree is integrated in the context of the iRoad system in two different query processing modes, namely, the precomputed query result mode, and the on-demand query result mode. Extensive experimental results based on large scale real and synthetic datasets confirm that the predictive tree achieves better accuracy compared to the existing related work, and scales up to support a large number of moving objects and heavy predictive query workloads.

In this seminar, we address spatial predictive queries both in Euclidian spaces and over road networks. We provide a definition for various types of spatial predictive queries, describe current research trends, and envision future directions. We present practical application scenarios and emphasize the roadblocks that are holding industry back from the commercialization of spatial predictive queries. This seminar targets audience in mobile data management, spatiotemporal query processing, mobile crowd sourcing, and tracking of moving objects.

This demo presents the Panda system for efficient support of a wide variety of predictive spatio-temporal queries. These queries are widely used in several applications including traffic management, location-based advertising, and store finders. Panda targets long-term query prediction as it relies on adapting a long-term prediction function to: (a) scale up to large number of moving objects, and (b) support predictive queries. Panda does not only aim to predict the query answer, but, it also aims to predict the incoming queries such that parts of the query answer can be precomputed before the query arrival. Panda maintains a tunable threshold that achieves a trade-off between the predictive query response time and the system overhead in precomputing the query answer. Equipped with a Graphical User Interface (GUI), audience can explore the Panda demo through issuing predictive queries over a moving set of objects on a map. In addition, they are able to follow the execution of such queries through an eye on the Panda execution engine.

Road-network data compression reduces the size of the network to occupy lesser storage with the aim to fit small form-factor routing devices, mobile devices, or embedded systems. Compression (1) reduces the storage cost of memory and disks, and (2) reduces the I/O and communication overhead. There are several road network compression techniques proposed in literature. These techniques are evaluated by their compression ratios. However, none of these techniques takes into consideration the possibility that the generated compressed data can be used directly in map-matching. Map-matching is an essential component of routing services that matches a measured latitude and longitude of an object to an edge in the road network graph. In this paper, we propose a novel compression technique, named COMA, that significantly reduces the size of a given road network data. Another advantage of the proposed technique is that it enables the generated compressed road network graph to be used directly in map-matching without a need to decompress it beforehand. COMA smartly deletes those nodes and edges that will not affect neither the graph connectivity nor the accuracy of map-matching objects' location. COMA is equipped with an adjustable parameter, termed conflict factor C, by which location-based services can achieve a trade-off between the compression gain and map-matching accuracy. Extensive experimental evaluation on real road network data demonstrates competitive performance on compression-ratio and the high mapmatching accuracy achieved by the proposed technique.

We demonstrate a novel location aware services framework termed COMA for efficient compression and map-matching of road-network graph data. Key innovations include working demonstration of a new compression algorithm to eliminate nodes and edges that do not affect graph connectivity while ensuring object location map-matching accuracy. The demonstration features: (1) Algorithm to leverage compressed versions of road-network graphs for map-matching of objects locations to correct road edges without decompression, (2) Upwards of 75% compression ratio implying significant savings for road network data transmission costs, a key constraint for internet of things (IOT) devices, and (3) Use of a new controllable parameter, termed conflict factor C, whereby location aware services can trade the compression efficiency with map-matching accuracy at varying granularity. In addition to above features the demonstration features an extensible framework that enables experimentation and comparison between various compression and map-matching algorithms in a rich interactive interface. In this paper we outline data management challenges for location aware services using various scenarios for compression of a real road-network map of a large region of United States, along with both real and synthetic moving object trajectories distributed over this map. We describe the COMA framework through its map-based Graphical User Interface, ability to select the area of interest from the road-network map, and submit a compression request. COMA can export and save the compact versions of the selected area in different formats and plot the compressed graph over the original map for visual inspection to study the differences between compressed and uncompressed versions and various related statistics.

Traditional routing services aim to save driving time by recommending the shortest path, in terms of distance or time, to travel from a start location to a given destination. However, these methods are relatively static and to a certain extent rely on traffic patterns under relatively normal conditions to calculate and recommend an appropriate route. As such, they do not necessarily translate effectively during severe weather events such as tornadoes. In these scenarios, the guiding principal is not, optimize for travel time, but rather, optimize for survivability of the event, i.e., can we recommend an evacuation route to those users inside the hazardous areas. In this demo, we present a framework for routing services for evacuating and avoiding real world severe weather threats that is able to: (1) Identify the users inside the dangerous region of a severe weather event (2) Recommend an evacuation route to guide the users out to a safe destination or shelter (3) Assure the recommended route to be one of the shortest paths after excluding the risky area (4) Maintain the flow of traffic by normalizing the evacuation on the possible safe routes. During the demo, attendees will be able to use the system interactively through its graphical user interface within a number of different scenarios. They will be able to locate the severe weather events on real time basis in any area in USA and examine detailed information about each event, to issue an evacuation query from an existing dangerous area by identifying a destination location and receiving the routing direction on their mobile devices, to issue an avoidance routing query to ask for a shortest path that avoids the dangerous region, to have an inside look into the internal system components and finally, to evaluate the overall system performance.

The 21st ACM SIGSPATIAL Conference on Advances in Geographic Information Systems (GIS) was held in November of 2013 in Orlando, Florida. Following the success of last year's event, we organized the second programming contest associated with the conference, called the SIGSPATIAL GIS Cup 2013. The subject of the competition was Geo-fencing, which identifies the qualified point and area pairs using a virtual perimeter for a real-world geographic area. We describe the contest details, and the results, as well as the lessons learned during the process.

The 20th ACM SIGSPATIAL Conference on Advances in Geographic Information Systems (GIS) was held in November of 2012. In conjunction with this conference, we organized the conference's first competition, called the SIGSPATIAL GIS Cup 2012. The subject of the competition was map matching, which is the problem of correctly matching a sequence of noisy GPS points to roads. We describe the details of the contest, the results of the competition, and the lessons we learned in running a contest like this.

Microsoft StreamInsight (StreamInsight, for brevity) is a platform for developing and deploying streaming applications, which need to run continuous queries over high-data-rate streams of input events. StreamInsight leverages a well-defined temporal stream model and operator algebra, as the underlying basis for processing long-running continuous queries over event streams. This allows StreamInsight to handle imperfections in event delivery and to provide correctness guarantees on the generated output. StreamInsight natively supports a diverse range of off-the-shelf streaming operators. In order to cater to a much broader range of customer scenarios and applications, StreamInsight has recently introduced a new extensibility infrastructure. With this infrastructure, StreamInsight enables developers to integrate their domain expertise within the query pipeline in the form of user defined modules (functions, operators, and aggregates). This paper describes the extensibility framework in StreamInsight; an ongoing effort at Microsoft SQL Server to support the integration of user-defined modules in a stream processing system. More specifically, the paper addresses the extensibility problem from three perspectives: the query writer's perspective, the user defined module writer's perspective, and the system's internal perspective. The paper introduces and addresses a range of new and subtle challenges that arise when we try to add extensibility to a streaming system, in a manner that is easy to use, powerful, and practical. We summarize our experience and provide future directions for supporting stream-oriented workloads in different business domains.

Microsoft StreamInsight (StreamInsight, for brevity) is a platform for developing and deploying streaming applications that run continuous queries over high-rate streaming events. StreamInsight adopts a temporal stream model to handle imperfections in event delivery and define consistency guarantees on the output. This demo highlights the ability of StreamInsight to monitor, analyze and correlate spatio-temporal stream data that is generated by moving objects. The demo scenario is based on the Microsoft Shuttle Service where GPS readings are generated and streamed by shuttles as they move around the Microsoft main campus in Redmond, WA. The demo presents a set of relational continuous queries as well as various real-time analytics that help improve the efficiency of the shuttle service in terms of the average wait time per passenger and the average daily mileage per shuttle.

Similarity joins have been studied as key operations in multiple application domains, e.g., record linkage, data cleaning, multimedia and video applications, and phenomena detection on sensor networks. Multiple similarity join algorithms and implementation techniques have been proposed. They range from out-of-database approaches for only in-memory and external memory data to techniques that make use of standard database operators to answer similarity joins. Unfortunately, there has not been much study on the role and implementation of similarity joins as database physical operators. In this paper, we focus on the study of similarity joins as first-class database operators. We present the definition of several similarity join operators and study the way they interact among themselves, with other standard database operators, and with other previously proposed similarity-aware operators. In particular, we present multiple transformation rules that enable similarity query optimization through the generation of equivalent similarity query execution plans. We then describe an efficient implementation of two similarity join operators, ¿-Join and Join-Around, as core DBMS operators. The performance evaluation of the implemented operators in PostgreSQL shows that they have good execution time and scalability properties. The execution time of Join-Around is less than 5% of the one of the equivalent query that uses only regular operators while ¿-Join's execution time is 20 to 90% of the one of its equivalent regular operators based query for the useful case of small ¿ (0.01% to 10% of the domain range). We also show experimentally that the proposed transformation rules can generate plans with execution times that are only 10% to 70% of the ones of the initial query plans.

Microsoft SQL Server spatial libraries contain several components that handle geometrical and geographical data types. With advances in geo-sensing technologies, there has been an increasing demand for geospatial streaming applications. Microsoft SQL Server StreamInsight ( StreamInsight , for brevity) is a platform for developing and deploying streaming applications that run continuous queries over high-rate streaming events. With its extensibility infrastructure, StreamInsight enables developers to integrate their domain expertise within the query pipeline in the form of user defined modules. This demo utilizes the extensibility infrastructure in Microsoft StreamInsight to leverage its continuous query processing capabilities in two directions. The first direction integrates SQL spatial libraries into the continuous query pipeline of StreamInsight. StreamInsight provides a well-defined temporal model over incoming events while SQL spatial libraries cover the spatial properties of events to deliver a solution for spatiotemporal stream query processing. The second direction extends the system with an analytical refinement and prediction layer. This layer analyzes historical data that has been accumulated and summarized over the years to refine, smooth and adjust the current query output as well as predict the output in the near future. The demo scenario is based on transportation data in Los Angeles County.

Geographically co-located sensors tend to participate in the same environmental phenomena. Phenomenon-aware stream query processing improves scalability by subscribing each query only to a subset of sensors that participate in the phenomena of interest to that query. In the case of sensors that generate readings with a multi-attribute schema, phenomena may develop across the values of one or more attributes. However tracking and detecting phenomena across all attributes does not scale well as the dimensions increase. As the size of sensor network increases, and as the number of attributes being tracked by a sensor increases this becomes a major bottleneck. In this paper, we present a novel n-dimensional Phenomenon Detection and Tracking mechanism (termed as nd-PDT) over n-ary sensor readings. We reduce the number of dimensions to be tracked by first dropping dimensions without any meaningful phenomena, and then we further reduce the dimensionality by continuously detecting and updating various forms of functional dependencies amongst the phenomenon dimensions.

Group-by is a core database operation that is used extensively in OLTP, OLAP, and decision support systems. In many application scenarios, it is required to group similar but not necessarily equal values. In this paper we propose a new SQL construct that supports similarity-based group-by (SGB). SGB is not a new clustering algorithm, but rather is a practical and fast similarity grouping query operator that is compatible with other SQL operators and can be combined with them to answer similarity-based queries efficiently. In contrast to expensive clustering algorithms, the proposed similarity group-by operator maintains low execution times while still generating meaningful groupings that address many application needs. The paper presents a general definition of the similarity group-by operation and gives three instances of this definition. The paper also discusses how optimization techniques for the regular group-by can be extended to the case of SGB. The proposed operators are implemented inside PostgreSQL. The performance study shows that the proposed similarity-based group-by operators have good scalability properties with at most only 25% increase in execution time over the regular group-by.

In this demo, we present the Microsoft Complex Event Processing (CEP) Server, Microsoft CEP for short. Microsoft CEP is an event stream processing system featured by its declarative query language and its multiple consistency levels of stream query processing. Query composability, query fusing, and operator sharing are key features in the Microsoft CEP query processor. Moreover, the debugging and supportability tools of Microsoft CEP provide visibility of system internals to users. Web click analysis has been crucial to behavior-based online marketing. Streams of web click events provide a typical workload for a CEP server. Meanwhile, a CEP server with its processing capabilities plays a key role in web click analysis. This demo highlights the features of Microsoft CEP under a workload of web click events.

Spatio-temporal data streams that are generated from mobile stream sources (e.g., mobile sensors) experience similar environmental conditions that result in distinct phenomena. Several research efforts are dedicated to detect and track various phenomena inside a data stream management system (DSMS). In this paper, we use the detected phenomena to reduce the demand on the DSMS resources. The main idea is to let the query processor observe the input data streams at the phenomena level. Then, each incoming continuous query is directed only to those phenomena that participate in the query answer. Two levels of indexing are employed, a phenomenon index and a query index. The phenomenon index provides a fine resolution view of the input streams that participate in a particular phenomenon. The query index utilizes the phenomenon index to maintain a query deployment map in which each input stream is aware of the set of continuous queries that the stream contributes to their answers. Both indices are updated dynamically in response to the evolving nature of phenomena and to the mobility of the stream sources. Experimental results show the efficiency of this approach with respect to the accuracy of the query result and the resource utilization of the DSMS.

A phenomenon appears in a sensor network when a group of sensors persist to generate similar behavior over a period of time. PhenomenaBases (or databases of phenomena) are equipped with phenomena detection and tracking (PDT) techniques that continuously run in the background of a sensor database system to detect new phenomena and to track already existing phenomena. The process of phenomena detection and tracking is initiated by a multi-way join operator that comes at the core of PDT techniques to report similar sensor readings. With the increase in the sensor network size, the join operator (and, consequently, query processing in the PhenomenaBase) face several scalability challenges. In this paper, we present a join operator for PhenomenaBases (the SNJoin operator) that is specially-designed for dynamically-configured large-scale sensor networks with distributed processing capabilities. Experimental studies illustrate the scalability of the proposed join operator in PhenomenaBases with respect to the number of detected phenomena and the output delay

We present the demonstration of the design of "STEAM", Purdue Boiler Makers' stream database system that allows for the processing of continuous and snap-shot queries over data streams. Specifically, the demonstration focuses on the query processing engine, "Nile". Nile extends the query processor engine of an object-relational database management system, PREDATOR, to process continuous queries over data streams. Nile supports extended SQL operators that handle sliding-window execution as an approach to restrict the size of the stored state in operators such as join.