eShadow is a digital storytelling platform inspired by traditional Shadow Theatre. It enables the creation of digital stories within a project-based approach that may start from scenario development and include the creation of digital puppets and sceneries, the set-up and recording of story scenes and the final assembly of a digital story. This paper presents how eShadow can be enhanced to solve the problem of creating mixed reality installations to offer rich learning experiences in informal learning settings. This enhanced version is eShadow+ and it is evaluated via two installations which are described and compared. The evaluation results demonstrate the effectiveness of the approach thus offering new learning opportunities that are aligned with current trends in the use of mixed reality technologies.

This paper presents a learning community building framework and how it is being used to establish a learning community on the mathematical foundations of computer hardware, namely the binary system. The work builds on previous research efforts targeting gamification of mathematics and is seen under new light offered by the Theatre in Mathematics (TIM) Methodology. The result is a combination of a theatrical game and a board game to teach the binary system to children. The two games are closely related: The theatrical game uses the children's bodies to enact the mechanism of the board game by employing simple rules for interacting with each other. Following simple rules the participants embody the operation of a calculator that is able to transform integers into their binary representations and compute the result of the four arithmetic operations (addition, subtraction, multiplication and division). A simulator of the theatrical game is also offered so that learners can explore it for themselves and discover how the arithmetic operations are done, even when they are not in the same physical space with their peers. The board game is essentially a binary version of a counting table or abacus. It offers an alternative mechanism for understanding the validity of the rules of the theatrical game and makes these rules more concrete and accessible to the children. This way they can explore on an individual basis the way that the four arithmetic operations are performed. Both games offer new learning opportunities, when compared with previous work related to game-based teaching of the binary system. The games surveyed mainly focus on the binary representation of numbers without engaging students in active exploration of arithmetic operations in the binary system. Another important aspect of this work is its unplugged nature that enables students to engage their body in a playful inquiry of mathematical ideas. The knowledge developed can be transferred to other number systems and in particular to the decimal system, thus contributing to a deeper understanding of the mechanisms of number representations and arithmetic.

The new reality brought about by digital technologies is characterized by new qualities, new opportunities for action, new community affordances, that are captures by the term onlife. This term was initially proposed in the Onlife Manifesto and used in this paper to signify certain qualities that are important in understanding modern digital platforms and applications as well as guide the efforts for effectively extending to provide new capabilities to their users. Specific design principles are presented exemplified by the presentation of the design of a Community of Practice for teachers involved in the pilot activities of the Erasmus+ project TIM - Theatre in Mathematics that promote the adoption of Theatre in teaching Mathematics in Primary and Lower Secondary Education targeting 8-14 years old students.

Block-C is a block-based programming learning tool for C programming language that uses the recognition over recall approach on top of the rigid and complex constructs of C language. It empowers students to learn programming by guiding them to focus on the programming logic rather than the syntax of C language. Novice programmers in introductory programming courses are more productive with the use of Block-C than with regular textual C programming. They can internalize the programming concepts more easily by gradually assigning meaning to the visual models (pertaining to the programming logic) created using the tool. In lab or tutorial sessions, where the presence of facilitators is limited, Block-C can guide the students to complete their assignments easily and effectively. Finally, Block-C promotes the transition to the regular textual C programming by allowing the students to export their code and see how their block-based programs are translated to textual C, but also how textual C is translated to block-based C.

New Media Arts offer opportunities to establish an inclusive educational framework that enables teachers to design and implement project-based learning scenarios where students can engage in deep learning through the preparation, production and refinement of digital artworks resulting in the creation of animated digital stories. The paper presents a combination of New Media Arts with traditional media via eShadow, a dramatized digital storytelling platform inspired by the rich tradition of shadow theatre that enables game-like interventions combining several digital tools for the production of digital stories covering all five phases of filmmaking: scenario development, pre-production, production, post-production and distribution. eShadow can be used (a) to create digital shadow puppets, and (b) to set up, perform and record the scenes of the digital story (production phase). This way, digital story creation is wrapped around interesting game-like decisions, playful improvisations and creative learning. Using eShadow, an intensive project-based learning intervention was undertaken at the Professional Lyceum of Eleftherios Venizelos in Chania for the students of the specialization in “Systems, Applications and Networks” of the Informatics sector where several courses related to the technical background of New Media Arts production are taught: Multimedia Applications, Graphical Programming, Structured Programming and Principles of Digital Technologies.

Coursevo (http://coursevo.com/) is a multilingual multimedia information system for managing courses, supporting learning processes and learning communities through the Web. Its multi-tenant architecture supports multiple instances of the underlying server infrastructure using the same core to serve the needs of multiple communities. An advantage of Coursevo in comparison with other eLearning systems is the emphasis that is given in the use of multimedia as a powerful learning means. Learning activities using multiple media can be more effective than doing it through a single medium (such as text), but what is important is combining media effectively. Coursevo is used in several vocational training and life-long-learning initiatives targeting engineers to establish and continuously support Communities of Practice (CoP). A CoP is a group of people who share an interest, a craft, and/or a profession. The group can evolve naturally because of the members' common interest in a particular domain or area, or it can be created specifically with the goal of gaining knowledge related to their field. We present the establishment of four training frameworks for establishing and supporting distributed CoP across European countries: (1) Computer Science teachers using Python in their courses; (2) Teachers using Arts in teaching all school subjects; (3) Civil protection Communities of Practice; and (4) Communities of Practice in Mechatronics.

Spatiotemporal processes are a generic model for representing various types of content knowledge of physical processes like the ones studied in geosciences, life sciences and diverse specializations of engineering. There is a need to model such content knowledge in a systematic way and provide open exploration environments for learners to interact with the defined spatiotemporal models. ViSTPro provides a generic infrastructure that addresses these needs of science and engineering education, thus fostering active explorations of spatiotemporal processes as rich scenarios authored by educators and offered to learners through a web-based player. Playing a scenario involves graphic representation of formations, movements and interactions on Google maps. Learners interact with graphical entities in an intuitive manner. In contrast, traditional ways of learning depend upon a painful and difficult process to develop abstract mental images with no real-world direct mapping. Using ViSTPro, learners can watch the representation of the processes' evolution in space and time, and actively intervene. To demonstrate the flexibility of ViSTPro and its capability to provide insightful visualizations, a pilot application is elaborated focusing on emergency situations and events with the aim to support the training of civil protection professionals and volunteers. This application enables innovative training methods, through the use of Google maps and complex scenarios pertaining to spatiotemporal processes that model the phenomena under consideration as well as linking to important information that is represented through ViSTPro semantic maps.

We describe SPIM (Spatial Image Management), a framework and a system that allow identification and visualization of the semantics of distant objects in nature, which exist in pictures taken by mobile devices. Semantic objects in nature are represented on 3D maps and tagged with semantic and spatial descriptors. The system functionality creates, on top of pictures, a layer that allows semantic user browsing in augmented geospatial images, semantic object identification in pictures, object interaction, contextual map visualization, and interlinking of information in digital libraries and the web. We present requirements of semantic geospatial descriptions, system functionality, matching algorithms and experimental results.

We describe MoM-NOCS, a Framework and a System that support communities with common interests in nature to capture and share multimedia observations of nature objects or events using mobile devices. The observations are automatically associated with contextual metadata that allow them to be visualized on top of 2D or 3D maps. The observations are managed by a multimedia management system, and annotated by the same and/or other users with common interests. Annotations made by the crowd support the knowledge distillation of the data and data provenance processes in the system. The Framework offers rich functionality for visualizing the observations made by the crowd as function of time. We have designed the MoM-NOCS to be complementary and interoperable with systems that are managed by Natural History museums like MMAT [8] and biodiversity metadata management systems like BIOCASE [4] and GBIF [6] so that they can link to interesting observations in our system, and the statistics on the observations that they manage can be visualized by our software.

The Web of Data is an open environment consisting of very large, inter-linked RDF datasets from various domains (e.g., DBpedia, GeoNames, ACM, PubMed, etc.) accessed through SPARQL queries. Establishing interoperability in this environment has become a major research challenge. This paper presents Sparql--Rw (SPARQL--ReWriting), a framework which provides transparent query access over mapped RDF datasets. The Sparql--Rw provides a generic method for SPARQL query rewriting, with respect to a set of predefined mappings between ontology schemas. To this end, it supports a set of rich and flexible mapping types and it is proved to provide semantics preserving queries.

Modern cameras are powerful devices that can interoperate using international standards with other sensors that can capture the context of each picture taken. Future cameras are expected to integrate such sensors within them. The contextual parameters captured can be interpreted with the help of semantic maps which are maps that integrate semantic information on them. Semantic maps can be used for understanding and visualization of the picture contents as well as for the management of context and content in picture databases. In this paper, we present a model for the management of semantic image information and the contextual knowledge related to the image capture along with a system implementation that manages and exploits this knowledge. Digital picture contents in the database can be interrelated with, and understood based on, contextual semantic geospatial information that the system manages. We describe the integrated camera system, the calculation and visualization of the contextual parameters, and the management of the semantics of the spatial objects. Finally, we present the implementation of SPIM, a SPatial Image Management system that exploits semantic contextual knowledge, its retrieval functionality and the visual user interfaces.

The creation of personalized learning experiences is considered as a necessity to cope with the overwhelming amount of available learning material. This paper presents a personalization framework and an algorithm that allows for the creation of pedagogically sound learning experiences taking into account the variety of the learners and their individual needs.

In this paper, we focus on interoperable semantic multimedia services that are offered in open environments such as the Internet. The use of well-accepted standards is of paramount importance for interoperability support in open environments. In addition, the semantic description of multimedia content utilizing domain ontologies is very useful for indexing, query specification, retrieval, filtering, user Interfaces, and knowledge extraction from audiovisual material. With the MPEG-7 and MPEG-21 standards dominating the multimedia content and service description domain and OWL dominating the ontology description languages, it is important to establish a framework that allows these standards to interoperate. We describe here the DS-MIRF framework, a software engineering framework that facilitates the development of knowledge-based multimedia applications such as multimedia information retrieval, filtering, browsing, interaction, knowledge extraction, segmentation, and content description. DS-MIRF supports interoperability of OWL with the MPEG-7/21 so that domain and application ontologies expressed in OWL can be transparently integrated with MPEG-7/21 metadata. This allows applications that recognize and use the constructs provided by MPEG-7/21 to make use of domain and application ontologies, resulting in more effective retrieval and user interaction with the audiovisual material. We also present a retrieval evaluation methodology and comparative retrieval results

eLearning applications are immensely more valuable when they can use the wealth of information that exists in multimedia digital libraries. However, digital libraries and their standards developed independently on eLearning applications and their standards. It is crucial to bridge the interoperability gap between digital libraries and eLearning applications in order to enable the construction of eLearning applications that easily exploit digital library contents. We present ASIDE, an integrated architecture that supports interoperability between digital libraries and eLearning applications. The architecture is service oriented and supports multiple contexts and views of the digital objects of a library. These views can be utilized by eLearning applications of the digital library for the automatic construction of personalized learning experiences selecting learning objects from the reusable objects of the digital library

Semantic interoperability is usually provided in open environments through standards and domain ontology. The dominant standards for multimedia content and service descriptions are MPEG-7 and MPEG-21. The MPEG-7 semantic DS has powerful semantic description capabilities and supports using semantic entities specified in domain ontology in multimedia content descriptions. However, the MPEG-7/21 usage environment allows neither the specification of semantic user preferences nor the exploitation of domain knowledge and MPEG-7 semantic metadata descriptions. In addition, the users cannot explicitly specify, in the hierarchical MPEG-7/21 filtering and search preferences, the Boolean operators that should be used during content filtering to combine the hierarchy components. We think these as serious limitations and we propose a hierarchical semantic user preference model that allows for the explicit specification of Boolean operators. Then, we present the application of the model in MPEG-7/21 and the model implementation within the DS-MIRF framework

A great challenge in information visualization today is to provide models and software that effectively integrate the graphics content of scenes with domain-specific knowledge so that the users can effectively query, interpret, personalize and manipulate the visualized information [1]. Moreover, it is important that the intelligent visualization applications are interoperable in the semantic web environment and thus, require that the models and software supporting them integrate state-of-the-art international standards for knowledge representation, graphics and multimedia. In this paper, we present a model, a methodology and a software framework for the semantic web (Intelligent 3D Visualization Platform - I3DVP) for the development of interoperable intelligent visualization applications that support the coupling of graphics and virtual reality scenes with domain knowledge of different domains. The graphics content and the semantics of the scenes are married into a consistent and cohesive ontological model while at the same time knowledge- based techniques for the querying, manipulation, and semantic personalization of the scenes are introduced. We also provide methods for knowledge driven information visualization and visualization- aided decision making based on inference by reasoning.

The term t-learning refers to interactive access of video-rich learning materials, primarily within the home, through a digital TV set-top box. The effective development of t-learning systems and applications should be based on existing standardization efforts in the fields of digital TV and e-learning. In this paper we examine the compatibility between the international standard for digital TV (TV-Anytime) and the international standard for e-learning (SCORM). The purpose is to provide a methodology for interoperability between educational applications in digital TV environments and to facilitate the creation of educational metadata for digital TV programs. The approach is also applicable in audiovisual digital libraries providing educational services to their users. We also describe an implementation of the mapping between the two standards. The implementation allows the transformation of TV-Anytime metadata to SCO metadata for the creation of SCORM compatible courses that utilize educational material from TV programs.

The proliferation of interoperability e-learning specifications raises the need of extending existing e-learning platforms so that they can be used efficiently in a distributed environment where material producers, service providers and users (either learners or teachers) exchange information using standard models. This extension is essential to preserve digital learning material and retain the user groups and learning communities already set up. We present a generic architecture and its prototype implementation for addressing this need. This architecture is based on the two assumptions that: (1) the preexistent e-learning platform is implemented on top of a relational database management system, and (2) the interoperability model to be supported is SCORM. The prototype implementation uses a Web-based e-learning platform based on a solid pedagogical framework.

We propose UTML as a high level transaction modeling language to facilitate the complex Web transaction design process. Web transactions may be complex, composed of several sub-transactions and they may access resources with diverse behavior and interfaces like legacy systems and databases. They may also have complex semantics. Thus, transaction design methodologies and tools need to be very flexible, allowing for designing Web applications from scratch (top-down design), as well as using existing systems or services to compose new applications which offer added-value services (bottom-up design) to the user. UTML is based on a transaction meta-model which can describe, in a flexible and extensible manner, most of the known transaction models as well as new ones according to the application's requirements. It provides modeling for transactions that incorporate different behavioral patterns, and it is capable of describing activities with weaker transactional semantics that do not have all the ACID properties. Unlike other models, it can be used to synthesize new transactions from pre-existing transaction systems (like legacy systems), with diverse transactional semantics. UTML provides a rich notation to visualize the transaction design process. This notation has been built on top of UML using its extension mechanisms.

Our goal is to contribute a common theoretical framework for studying the performance of disk-storage devices. Understanding the performance behavior of these devices will allow prediction of the I/O cost in modern applications. Current disk technologies differ in terms of the fundamental modeling characteristics, which include the magnetic/optical nature, angular and linear velocities, storage capacities, and transfer rates. Angular and linear velocities, storage capacities, and transfer rates are made constant or variable in different existing disk products. Related work in this area has studied Constant Angular Velocity (CAV) magnetic disks and Constant Linear Velocity (CLV) optical disks. We present a comprehensive analytical model, validated through simulations, for the random retrieval performance of disk devices which takes into account all the above-mentioned fundamental characteristics and includes, as special cases, all the known disk-storage devices. Such an analytical model can be used, for example, in the query optimizer of large traditional databases as well as in an admission controller of multimedia storage servers. Besides the known models for magnetic CAV and optical CLV disks, our unifying model is also reducible to a model for a more recent disk technology, called zoned disks, the retrieval performance of which has not been modeled in detail before. The model can also be used to study the performance retrieval of possible future technologies which combine a number of the above characteristics and in environments containing different types of disks (e.g., magnetic-disk-based secondary storage and optical-disk-based tertiary storage). Using our model, we contribute an analysis of the performance behavior of zoned disks and we compare it against that for the traditional CAV disks, as well as against that of some possible/future technologies. This allows us to gain insights into the fundamental performance trade-offs.

The problem of optimally placing data on disks (ODP) to maximize disk-access performance has long been recognized as important. Solutions to this problem have been reported for some widely available disk technologies, such as magnetic CAV and optical CLV disks. However, important new technologies such as multizoned magnetic disks, have been recently introduced. For such technologies no formal solution to the ODP problem has been reported. In this paper, we first identify the fundamental characteristics of disk-device technologies which influence the solution to the ODP problem. We develop a comprehensive solution to the problem that covers all currently available disk technologies. We show how our comprehensive solution can be reduced to the solutions for existing disk technologies, contributing thus a solution to the ODP problem for multizoned disks. Our analytical solution has been validated through simulations and through its reduction to the known solutions for particular disks. Finally, we study how the solution for multizoned disks is affected by the disk and data characteristics.

Investigates design principles for placing striped delay-sensitive data on a number of disks in a distributed environment. The cost formulas of our performance model allow us to calculate the maximum number of users that can be supported by n disks, as well as to study the impact of other performance-tuning options. We show that, for fixed probabilities of accessing the delay-sensitive objects, partitioning the set of disks is always better than striping in all of the disks. Then, given a number n of disks and r distinct delay-sensitive objects with access probabilities p/sub 1/, p/sub 2/, ..., p/sub r/ that must be striped across r different disk partitions (i.e. nonoverlapping subsets of the n disks), we use the theory of Schur functions in order to find what is the optimal number of disks that must be allocated to each partition. For objects with different consumption rates, we provide an analytic solution to the problem of disk partitioning. We analyze the problem of grouping the more- and less-popular delay-sensitive objects together in partitions-when the partitions are less than the objects-so that the number of supported users is maximized. Finally, we analyze the trade-off of striping on all the disks versus partitioning the set of the disks when the access probabilities of the delay-sensitive objects change with time.

Article Free Access Share on Data base design principles for striping and placement of delay-sensitive data on disks Authors: Stavros Christodoulakis Laboratory of Distributed Multimedia Information Systems and Applications (MUSIC), Technical University of Crete (TUC), P.O. Box 133, Chania 73100, Greece Laboratory of Distributed Multimedia Information Systems and Applications (MUSIC), Technical University of Crete (TUC), P.O. Box 133, Chania 73100, GreeceView Profile , Fenia A. Zioga Laboratory of Distributed Multimedia Information Systems and Applications (MUSIC), Technical University of Crete (TUC), P.O. Box 133, Chania 73100, Greece Laboratory of Distributed Multimedia Information Systems and Applications (MUSIC), Technical University of Crete (TUC), P.O. Box 133, Chania 73100, GreeceView Profile Authors Info & Claims PODS '98: Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systemsMay 1998 Pages 69–78https://doi.org/10.1145/275487.275496Published:01 May 1998Publication History 4citation258DownloadsMetricsTotal Citations4Total Downloads258Last 12 Months1Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Many current relational database systems use some form of histograms to approximate the frequency distribution of values in the attributes of relations and on this basis estimate query result sizes and access plan costs.The errors that exist in the histogram approximations directly 01993

This paper establishes some fundamental principles for the retrieval and storage of delay-sensitive multimedia data. Delay-sensitive data include digital audio, animations, and video. Retrieval of these data types from secondary storage has to satisfy certain time constraints in order to be acceptable to the user. The presentation is based on digital audio in order to provide intuition to the reader, although the results are applicable to all delay-sensitive data. A theoretical framework is developed for the real-time requirements of digital audio playback. We show how to describe these requirements in terms of the consumption rate of the audio data and the nature of the data-retrieval rate from secondary storage. Making use of this framework, bounds are derived for buffer space requirements for certain common retrieval scenarios. Storage placement strategies for multichannel synchronized data are then categorized and examined. The results presented in this paper are basic to any playback of delay-sensitive data and should assist the multimedia system designer in estimating hardware requirements and in evaluating possible design choices.

yannisQcs.wise.edu Query optimizers of current relational database systems use several statistics maintained by the system on the contents of the database to decide on the most efficient access plan for a given query. These statistics contain errors that transitively affect many estimates derived by the optimizer. We present a formal framework based on which the principles of this error propagation can be studied. Within this framework, we obtain several ana-lytic results on how the error propagates in general, as well as in the extreme and average cases. We also pro-vide results on guarantees that the database system can make based on the statistics that it maintains. Finally, we discuss some promising approaches to controlling the error propagation and derive several interesting proper-ties of them. 1

Optimal data placement on a CLV (Constant Linear Velocity) format optical discs has an objective the minimization of the expected access cost of data retrievals from the disc when the probabilities of access of data items may be different. The problem of optimal data placement for optical discs is both important and more difficult than the corresponding problem on magnetic discs. A good data placement on optical discs is more important because data sets on optical discs such as WORM and CD ROM cannot be modified or moved once they are placed on disc. Currently, even rewritable optical discs are best suited for applications that are archival in nature. The problem of optimal data placement on CLV format optical discs is more difficult, mainly because the useful storage space is not uniformly distributed across the disc surface (along the radius). This leads to a complicated positional performance trade-off not present for magnetic disks. We present a model that encompasses all the important aspects of the placement problem on CLV format optical discs. The model takes into account the nonuniform distribution of useful storage, the dependency of the rotational delay on disc position, a parameterized seek cost function for optical discs, and the varying access probabilities of data items. We show that the optimal placement of high-probability blocks satisfies a unimodality property. Based on this observation, we solve the optimal placement problem. We then study the impact of the relative weights of the problem parameters and show that the optimal data placement may be very different from the optimal data placement on magnetic disks. We also validate our model and analysis and give an algorithm for computing the placement of disc sectors.

A large and important class of optical disc technology are CLV format discs such as CD ROM and WORM. In this paper, we examine the issues related to the implementation and performance of several different file organizations on CLV format optical discs such as CD ROM and WORM. The organizations examined are based on hashing and trees.

Steady progress in the development of optical disc technology over the past decade has brought it to the point where it is beginning to compete directly with magnetic disc technology. WORM optical discs in particular, which permanently register information on the disc surface, have significant advantages over magnetic technology for applications that are mainly archival in nature but require the ability to do frequent on-line insertions.

CLV type optical disks is a very large and important class of optical disk technology, of which CD-ROM disks form a subclass.

In this paper we examine the problem of object and record retrieval from optical disks. General objects (such as images, documents, etc.) may be long and their length may have high variance. We assume that all the components of an object are stored consecutively in storage to speed-up retrieval performance. We first present an optical disk model and an optimal schedule for retrieval of records and objects which qualify in a single query on a file stored on an optical disk device. We then provide exact and approximate analytic results for evaluating the retrieval performance for objects from an optical disk. The analysis provides some basic analytic tools for studying the performance of various file and database organizations for optical disks. The results involve probability distribution of block accesses, probability distributions of span accesses, and probability distribution of seek times. Record retrieval is an important special case. This analysis differs from similar ones in database environments in the following respects: (1) the large size and large variance of the size of objects; (2) crossing of track boundaries by objects; (3) the capability for span access that optical disks provide (e.g., when the optical assembly is located in a given position, information can be read from a number of consecutive tracks (span) with a small additional cost).

Signature files seem to be a promising access method for text and attributes. According to this method, the documents (or records) are stored sequentially in one file ("text file"), while abstractions of the documents ("signatures") are stored sequentially in another file ("signature file"). In order to resolve a query, the signature file is scanned first, and many nonqualifying documents are immediately rejected. We develop a framework that includes primary key hashing, multiattribute hashing, and signature files. Our effort is to find the optimal signature extraction method. The main contribution of this paper is that we present optimal and efficient suboptimal algorithms for assigning words to signatures in several environments. Another contribution is that we use information theory, and study the relationship of the false drop probability F d and the information that is lost during signature extraction. We give tight lower bounds on the achievable F d and show that a simple relationship holds between the two quantities in the case of optimal signature extraction with uniform occurrence and query frequencies. We examine hashing as a method to map words to signatures (instead of the optimal way), and show that the same relationship holds between F d and loss , indicating that an invariant may exist between these two quantities for every signature extraction method.

Signature files have attracted a lot of interest as an access method for text and specifically for messages in the office environment. Messages are stored sequentially in the message file, whereas their hash-coded abstractions (signatures) are stored sequentially in the signature file. To answer a query, the signature file is examined first, and many nonqualifying messages are immediately rejected. In this paper we examine the problem of designing signature extraction methods and studying their performance. We describe two old methods, generalize another one, and propose a new method and its variation. We provide exact and approximate formulas for the dependency between the false drop probability and the signature size for all the methods, and we show that the proposed method (VBC) achieves approximately ten times smaller false drop probability than the old methods, whereas it is well suited for collections of documents with variable document sizes.

Large multimedia data bases become feasible due to recent advances in hardware technology. A very important component of multimedia data base management systems will be the presentation manager which will be responsible for effective multimedia presentation and browsing on the screen of workstations.

MINOS is an object-oriented multimedia information system that provides integrated facilities for creating and managing complex multimedia objects. In this paper the model for multimedia documents supported by MINOS and its implementation is described. Described in particular are functions provided in MINOS that exploit the capabilities of a modern workstation equipped with image and voice input-output devices to accomplish an active multimedia document presentation and browsing within documents. These functions are powerful enough to support a variety of office applications. Also described are functions provided for the extraction of information from multimedia documents that exist in a large repository of information (multimedia document archiver) and functions that select and transform this information. Facilities for information sharing among objects of the archiver are described; an interactive multimedia editor that is used for the extraction and interactive creation of new information is outlined; finally, a multimedia document formatter that is used to synthesize a new multimedia document from extracted and interactively generated information is presented. This prototype system runs on a SUN-3 workstation running UNIX'". An Instavox, directly addressable, analog device is used to store voice segments.

Article Free Access Share on Issues in the architecture of a document archiver using optical disk technology Author: S. Christodoulakis Computer Systems Research Institute, University of Toronto and Computer Research Institute of Crete Computer Systems Research Institute, University of Toronto and Computer Research Institute of CreteView Profile Authors Info & Claims SIGMOD '85: Proceedings of the 1985 ACM SIGMOD international conference on Management of dataMay 1985 Pages 34–50https://doi.org/10.1145/318898.318901Published:01 May 1985Publication History 9citation296DownloadsMetricsTotal Citations9Total Downloads296Last 12 Months6Last 6 weeks4 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my Alerts New Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

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The assumptions of uniformity and independence of attribute values in a file, uniformity of queries, constant number of records per block, and random placement of qualifying records among the blocks of a file are frequently used in database performance evaluation studies. In this paper we show that these assumptions often result in predicting only an upper bound of the expected system cost. We then discuss the implications of nonrandom placement, nonuniformity, and dependencies of attribute values on database design and database performance evaluation.

The signature-file access method for text retrieval is studied.According to this method, documents are stored sequentially in the "text file."Abstractions ("signatures") of the documents are stored in the "signature file."The latter serves as a filter on retrieval: It helps in discarding a large number of nonqualifying documents.In this paper two methods for creating signatures are studied analytically, one based on word signatures and the other on superimposed coding.Closed-form formulas are derived for the false-drop probability of the two methods, factors that affect it are studied, and performance comparisons of the two methods based on these formulas are provided.

In this paper we describe a message server facility for handling large organizational archives of messages in an office information system environment. Messages can be retrieved according to attribute values specified and to some pattern of words appearing in the text of the message. We discuss design decisions and performance considerations in this environment and we derive analytic formulas for the optimal choice of the parameters of the message file organization.

In this paper we provide estimates of the number of sequential and random block accesses required for retrieving a number of records of a file when the distribution of records in blocks of secondary storage is not uniform. We show how these results apply to estimating sizes of joins and semi-joins. We prove that when the uniformity of placement assumption is not satisfied it often leads to pessimistic estimates of performance. Finally we show a recursive estimation of the probability distribution of the number of blocks containing a given number of records.

We describe a message-filing capability which allows for the retrieval of messages according to contents.Messages are organized in large, general files such that frequent reorganization is avoided.The user specifies a filter which restricts the attention to a manageable subset of messages.Messages within the subset are retrieved for a final check.We discuss file organization and access method, as well as performance and implementation considerations.