Temporal Object Research Articles

Semantics-based time-alignment operations in temporal query processing and optimization

In a temporal database, object properties and associations evolve very irregularly in time. Different evaluations of data objects with different valid intervals need to be recorded and processed for different temporal instances and their associations. Their intervals need to be aligned in order to find the common intervals in which the combined data are valid. Efficiency can be gained if, in every step of the traversals and manipulations, a minimal number of temporal instances is produced. This paper presents a set of semantics-based time-alignment operations defined as time-computation construct. They can be used as guides to determine the proper alignment operations that should be used to achieve efficient query processing. Five primitive time-alignment operations are defined in this paper. They can be combined and used to efficiently support different temporal query situations. As a byproduct of implementing a parallel temporal query processor on an nCUBE2 computer, we found that these time-alignment primitives and their combinations can be implemented efficiently using a memory mapping technique. We present this implementation technique and analyze its order of complexity.

Modeling medical trials in pharmacoeconomics using a temporal object model

Time is an inherent feature of many medical applications. These applications can also benefit from the support of object database management systems which better capture the semantics of the complex objects that arise in the medical domain. In this paper, we present a uniform behavioral temporal object model which includes a rich and extensible set of types and behaviors to support the various features of a medical application. We concentrate here on the application of pharmacoeconomic medical trials. Pharmacoeconomics is a field of medical economics in which the costs and outcomes of alternative treatments are assessed and compared, in order to establish which is the most appropriate treatment for a particular illness in a particular setting. We describe in detail the histories and timelines features of our temporal model and show how they can effectively be used to model a pharmacoeconomic trial. We then give an instance of a pharmacoeconomic trial as it would appear in the temporal object model and show, using queries, how a series of different behaviors could be used to retrieve various components of the instance. These components could then be used to assess the alternative treatments involved in the trial and determine their cost-effectiveness.

Temporal Contexts for Discourse Representation: An Extension of the Conceptual Graph Approach

A discourse is composed of a sequence of sentences that must be interpreted with respect to the context in which they are uttered and to the actions that produce them: locutors‘ speech acts. The analysis of discourse content must be based on a pragmatic approach to the study of language in use. Some of the most obvious linguistic elements that require contextual information for their representation are deictic forms such as here, now, I, you, this , and verb tenses. Several authors have recognized a need for introducing contextual structures in knowledge representation models such as semantic networks. Sowa‘s Conceptual Graph Theory is a powerful approach to conceptually represent knowledge contained in discourses. However, it must be extended in order to represent several semantic and pragmatic mechanisms related to the expression of time in natural language. In this paper we present such an extension as a framework for modeling temporal knowledge in discourses integrating several features borrowed from speech act theory. First, we introduce the notions of time interval, temporal object, temporal situation, and temporal relation. Then, we discuss the importance of explicitly introducing the concept of time coordinate system in a discourse representation and we present different kinds of temporal contexts: narrator‘s perspective, agent‘s perspective and temporal localization. We show how this conceptual framework can be used to represent various referential mechanisms in discourse such as anaphoras, indexicals, direct and indirect styles. We also discuss how to model several linguistic phenomena such as speech act characteristics and the specification of performative and attitude utterances. Finally, we briefly discuss how verb tenses can be determined in a discourse on the basis of this temporal approach.

A temporal extension to a generic object data model

We present a temporal object model capable of representing the lifespan of objects and also the history of the roles and associations in which they participate We advocate an approach of temporal generalisation rather than temporal extension in which a model in its entirety is given a temporal semantics through an orthogonal generalisation of all concepts of the model Our model allows objects to participate in several roles simultaneously Further metadata may also have temporal properties allowing the lifespan of the object roles themselves and constraints over these roles to be modelled The model is based on the generic object data model OM and the associated algebra has been generalised into a full temporal algebra over object roles

Combining qualitative and quantitative constraints in temporal reasoning

This paper presents a general model for temporal reasoning that is capable of handling both qualitative and quantitative information. This model allows the representation and processing of many types of constraints discussed in the literature to date, including metric constraints (restricting the distance between time points) and qualitative, disjunctive constraints (specifying the relative position of temporal objects). Reasoning tasks in this unified framework are formulated as constraint satisfaction problems and are solved by traditional constraint satisfaction techniques, such as backtracking and path consistency. New classes of tractable problems are characterized, involving qualitative networks augmented by quantitative domain constraints, some of which can be solved in polynomial time using arc and path consistency.

Representing temporal musical objects and reasoning in the MusES system

Abstract We describe a representation framework for temporal objects and reasoning in the MusES system. The framework is claimed to be use‐neutral within the context of tonal music. It is based on the use of an object‐oriented programming language, Smalltalk, and makes full use of two main representation mechanisms: class inheritance and delegation. We describe the kernel of the representation framework and explain the main design choices. We show how the kernel can be used and extended to represent important temporal concepts related to tonal music. The framework is validated by the realization of two substantial applications: an automatic analyzer for chord sequences, and a simulator of jazz improvisations.

Frontal and inferior temporal cortical activity in visual target detection: Evidence from high spatially sampled event-related potentials

Visual event-related potential (ERP) studies show effects due to target detection in the P3 and in earlier negativities over posterior recording sites. The topography of these earlier components suggests contributions from both anterior and posterior neural generators, however these studies were performed with sparse recording arrays and may not have provided a full description of the scalp topography of the visual ERP. The current study employed a high-density recording array (64 channels) and spherical spline interpolated topographic voltage and current density maps to describe the scalp distribution of the major deflections in the visual ERP from a visual oddball paradigm: the P1, N1, N2/P2a (a temporally coincident posterior negativity and anterior positivity) and P3. A modified difference wave analysis was also performed to track the time-course of target detection effects in the ERP. Target detection effects were found in the N2/P2a and P3 components. The scalp distribution of the N2/P2a was consistent with separate frontal and posterior neural generators and this is discussed in reference to human hemodynamic and nonhuman primate studies of neural activity in the inferior temporal visual object recognition system and in frontal systems of selective attention and working memory in visual target detection tasks.

A logic programming framework for modeling temporal objects

We present a general approach for modeling temporal aspects of objects in a logic programming framework. Change is formulated in the context of a database which stores explicitly a record of all changes that have occurred to objects and thus (implicitly) all states of objects in the database. A snapshot of the database at any given time is an object-oriented database, in the sense that it supports an object-based data model. An object is viewed as a collection of simple atomic formulas, with support for an explicit notion of object identity, classes and inheritance. The event calculus is a treatment of time and change in first-order classical logic augmented with negation as failure. The paper develops a variant of the event calculus for representing changes to objects, including change in internal state of objects, creation and deletion of objects, and mutation of objects over time. The concluding sections present two natural and straightforward extensions, to deal with versioning of objects and schema evolution, and a sketch of implementation strategies for practical application to temporal object-oriented databases.

Modeling the temporal complexities of symptoms.

To analyze the temporal aspects of symptoms, including their temporal uncertainty, in order to develop a high-level conceptual data model representation of this domain. A basic tenet of existing temporal models is that events occur not only relative to a particular date or time, but also relative to the time of some other event. The time an event occurs, particularly when the event is a symptom being recalled by a patient or collected by a busy provider, is frequently incomplete or uncertain, and this uncertainty must also be represented in a temporal data model. The object-oriented modeling technique used in this study is becoming popular among U.S. medical informatics standards developers. A conceptual data model for the temporal aspects of symptom data, including temporal uncertainty, has been developed. The object-oriented modeling approach used enables the temporal objects and attributes defined in this model to be inherited by other medical objects, such as problems. The temporal comparators presented here have previously been defined, and may serve as the basis for standardizing the terms used to describe how one event temporally relates to another. In an attempt to achieve domain completeness, this study concentrated more on developing a model that is highly expressive than on developing one that is easily queried. This trade-off in representation versus "queryability" will require further analysis and may require modifications to the underlying model.

Iterative maximum likelihood displacement field estimation in quantum-limited image sequences

We develop an algorithm for obtaining the maximum likelihood (ML) estimate of the displacement vector field (DVP) from two consecutive image frames of an image sequence acquired under quantum-limited conditions. The estimation of the DVF has applications in temporal filtering, object tracking, stereo matching, and frame registration in low-light level image sequences as well as low-dose clinical X-ray image sequences. In the latter case, a controlled X-ray dosage reduction may be utilized to lower the radiation exposure to the patient and the medical staff. The quantum-limited effect is modeled as an undesirable, Poisson-distributed, signal-dependent noise artifact. A Fisher-Bayesian formulation is used to estimate the DVF and a block component search algorithm is employed in obtaining the solution. Several experiments involving a phantom sequence and a teleconferencing image sequence with realistic motion demonstrate the effectiveness of this estimator in obtaining the DVF under severe quantum noise conditions (20-25 events/pixel).

A coherent architecture for a temporal object data base management system

The last decade has witnessed the emergence of practical general-purpose data base management systems (DBMS) as “state of the art” technology. In consequence, these systems are now widely used in a variety of application environments. However, many such systems were designed to capture current data, i.e., a snapshot of reality, but are insufficient for those applications in which past or future data are also required. Even so, there has been little effort to design temporal DBMS, and currently there are no prominent commercial temporal DBMS. This article identifies, explores, and provides an approach to designing a coherent architecture for a temporal object DBMS (TODBMS). It specifically involves the design, development, and implementation of TODBMS. We introduce the basic features of our system and provide an overview of the functionalities supported. In addition, we identify the major components of TODBMS and define the types of services each component should offer, as well as common abstractions and interfaces for these components. Application environments include management and geographic information systems, data base visualization, and robotics.

TOS

In the areas of sciences, engineering and design, the entities experience both structural and state changes. Existing database models allow changes in the structure and state through the techniques of schema evolution and version management, respectively, but fail to capture and represent both of these changes together and at the same time. In this paper we formally introduce the Temporal Object-Oriented System (TOS) which allows simultaneous changes in both the structure and state of the objects. An object in TOS is called a temporal object (TO). An aggregation of different TOs of the system can give rise to a new object which is then referred to as a temporal complex object (TCO). Both temporal objects and temporal complex objects can replace and refresh their knowledge through a process called renovation. The paper also discusses the process of renovations for both TOs and TCOs and enumerate their temporal parameters (i.e., timespan, life-span and life-sequence). A query language for the TOS, called Temporal Object Query Language (TOQL), is also proposed which is a super-set of the relational query language SQL.

A Petri net model for temporal knowledge representation and reasoning

This paper presents a general model based on timed Petri net, capable of handling both qualitative and quantitative temporal information. Both metric relations between time points and qualitative relations between time interval can be encoded in a model. This model also allows the representation of higher-order expression and repeated activities which constitute a large part of the normal schedule. In addition, graphical representation of a timed Petri net gives a straightforward view of relations between temporal objects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

How inferior temporal cortex became a visual area.

The origins of contemporary work on the temporal cortex and object recognition are traced from their roots in phrenology through the search for a cortical visual area to the discovery of the Klüver-Bucy syndrome and its fractionation, finally ending with early single-neuron recording studies.

Figure–ground discrimination from temporal information

The separation of figures from ground is achieved by the visual system based on differences in features such as luminance, colour, depth, orientation, texture or motion. Temporal information, namely phase differences between groups of spatially homogeneous points, can also lead to a clear discrimination of an object shape. The time difference needed to separate figure and ground is around 5 ms over a range of temporal frequencies between 1.3 Hz and 30 Hz, both for sharply focused and for blurred points. These short delays are clearly below the temporal integration time of the visual system. The results have implications for theories on temporal binding and object recognition.

A metric time-point and duration-based temporal model

Constraint-based formalisms are a useful and common way to deal with temporal reasoning tasks. Assertions represent temporal constraints between temporal objects, time-points or intervals: Metric temporal constraints between time points permit us to express a minimum and maximum temporal distance between two time points and to define a valid temporal interval for each one. However, existing approaches have limited expressiveness for representing non-disjunctive qualitative constraints of point algebra and the empirical results do not seem very adequate for managing a great number of time points or when the time for management is limited.In this paper, an efficient and expressive time point and duration-based temporal representation model with metric constraints is presented. The main features of the model refer to the formal properties of the internal time model and the specific representation of temporal constraints, which integrates constraints on time-points and on durations and is more adequate for their computational management. Sound and complete management processes are specified on the basis of model properties. From this specification, two choices for management are proposed: (i) with neither propagation nor preprocessing techniques, complete management algorithms have an O(e*n) complexity, but a linear empirical cost is obtained; (ii) with complete propagation an O(n 2 ) complexity is achieved.

A UNIFIED MODEL AND METHODOLOGY FOR TEMPORAL OBJECT DATABASES

This paper identifies, explores and provides an approach to handling temporal information in object databases. It specifically involves the design and development of the Temporal Three Dimensional Information Space model that integrates time with objects. The model is based on a small number of simple temporal object constructs and provides a user with the basic primitives for temporal object definition, manipulation and retrieval. This research presents a step towards defining the concepts and techniques for incorporating time in object databases, and provides concrete experimental framework for demonstration thereof. Target Application environments include management and geographic information systems, database visualization and robotics.

Tactus: toolkit-level support for synchronized interactive multimedia

Tactus addresses problems of synchronizing and controlling various interactive continuous-time media. The Tactus system consists of two main parts. The first is a server that synchronizes the presentation of multiple media, including audio, video, graphics, and MIDI at a workstation. The second is a set of extensions to a graphical user interface toolkit to help compute and/or control temporal streams of information and deliver them to the Tactus Server. Temporal toolkit objects schedule computation events that generate media. Computation is scheduled in advance of real time to overcome system latency, and timestamps are used to allow accurate synchronization by the server in spite of computation and transmission delays. Tactus supports precomputing branches of media streams to minimize latency in interactive applications.

A Conceptual Description Method of Spatio-temporal Objects

The modelling of geometric and image-based data is a main aspect of spatial data handling in GIS. And the modelling of time is also very important to consider history and prediction of the real world. Frist, this paper introduces a topological model for spatial objects, applying SDTS(Spatial Data Transfer Specification) and an object oriented approach.Next, the structure of temporal object types is discussed, which consists of three parts. The first is the life period of objects. The second is pointer sequence to show previous objects. The third is pointer sequence to show objects occured from this object. This model can describe occurrence, change, and extinction of entities.Finally, the spatio-temporal object type is derived from spatial and temporal object types.

A study of regional cerebral blood flow and cognitive performance in Alzheimer's disease.

Thirty five patients with dementia of the Alzheimer type (DAT) and 35 controls matched for age, sex and handedness were investigated using single photon emission computer tomography (SPECT) with 99m technetium HMPAO. Regional cerebral blood flow (rCBF) was assessed semi-quantitatively in 18 cortical and 4 subcortical areas by normalising mean information density in each region to cerebellar mean information density. Analysis revealed significantly reduced rCBF to temporal, parietal, frontal and left occipital cortex in the patients whilst blood flow to subcortical areas showed no differences between the 2 groups. In addition, significant left-sided cortical hypoperfusion was seen in the DAT group but not in controls. When patients were sub-divided on the basis of disease severity, those with mild disease showed temporal, parietal and left frontal changes with more severely affected patients also showing right frontal and left occipital involvement. rCBF patterns did not distinguish between presenile and senile onset cases once duration and severity of illness were controlled. Eight cortical areas were also rated visually for perfusion deficits on a simple 4 point scale. Perfusion deficits were detected in 34 of 35 patients but in only 4 of 35 controls. In the DAT group significant correlations were found between many of the neuropsychological tests used and rCBF. Memory correlated with left temporal activity, praxis, perception, object assembly and block design with right parietal activity and language with activity throughout the left hemisphere. Significant correlations were also seen between subcortical and cortical blood flow, possibly explaining the correlations observed between many of the neuropsychological tests and thalamic blood flow.