A temporal database contains time-varying data. In a real-time database transactions have deadlines or timing constraints. In this paper we review the substantial research in these two heretofore separate research areas. We first characterize the time domain, then investigate temporal and real-time data models. We evaluate temporal and real-time query languages along several dimensions. Temporal and real-time DBMS implementation is examined. We conclude with a summary of the major accomplishments of the research to date, and list several research questions that should be addressed next. Keywords: object-oriented database, relational databases, query language, temporal data model, time-constrained database, transaction time, user-defined time, valid time 1 Introduction Time is an important aspect of all real-world phenomena. Events occur at specific points in time; objects and the relationships among objects exist over time. The ability to model this temporal dimension of the real worl...

this paper, we propose a sound and complete axiomatic model for DSE in OBSs. The main benefit of the model is the formalization of DSE characteristics into a welldefined set of axioms. The axioms automatically maintain complex schema relationships and properties from two input sets associated with each type in a schema. The elements of these sets can be provided by the user, schema designer, system, or a combination of sources. One set is called the essential supertypes and contains the types that must be maintained as supertypes of a type for as long as it is consistently possible. The other set is called the essential properties and contains the properties that must be maintained in the type for as long as it is consistently possible. The correct properties and relationships within the schema are automatically derived by the axiomatic model using the essential supertypes and essential properties as a basis. The derivations performed by the axiomatic model have a proven soundness, completeness, and termination. The inclusion/exclusion of axioms in the model leads to a design space that categorizes OBSs into object-based, type-based, and object-oriented systems. The last category is further refined into several distinct subcategories that vary in functionality and expressiveness. To illustrate the power and practical usefulness of the model, the DSE operations of several existing OBSs are reduced to the axiomatic model and compared within this common framework. In recent years, researchers have addressed the problem of defining DSE policies for OBSs. These studies approach the issue from the perspective of individual systems. The axiomatic model is unique in this respect in that it captures and formalizes the salient features of DSE in OBSs and can be adopted as a commo...

We describe a general multimedia query language, called MOQL, based on ODMG's Object Query Language (OQL). In contrast to previous multimedia query languages that are either designed for one particular medium (e.g. images) or specialized for a particular application (e.g., medical imaging), MOQL is general in its treatment of multiple media and different applications. The language includes constructs to capture the temporal and spatial relationships in multimedia data as well as functions for query presentation. We illustrate the language features by query examples. The language is implemented for a multimedia database built on top of ObjectStore.

A key aspect in video modeling is spatial relationships. In this paper we propose a spatial representation for specifying the spatial semantics of video data. Based on such a representation, a set of spatial relationships for salient objects is defined to support qualitative and quantitative spatial properties. The model captures both topological and directional spatial relationships. We present a novel way of incorporating this model into a video model, and integrating the abstract video model into an object database management system which has rich multimedia temporal operations. The integrated model is further enhanced by a spatial inference engine. The powerful expressiveness of our video model is validated by some query examples.

Modeling moving objects has become a topic of increasing interest in the area of video databases. Two key aspects of such modeling are spatial and temporal relationships. In this paper we introduce an innovative way to represent the trajectory of a single moving object and the relative spatio-temporal relations between multiple moving objects. The representation supports a rich set of spatial topological and directional relations. It also supports both quantitative and qualitative user queries about moving objects. Algorithms for matching trajectories and spatio-temporal relations of moving objects are designed to facilitate query processing. These algorithms can handle both exact and similarity matches. We also discuss the integration of our moving object model, based on a video model, in an object-oriented system. Some query examples are provided to further validate the expressiveness of our model.

One of the key aspects of videos is the temporal relationship between video frames. In this paper we propose a tree-based model for specifying the temporal semantics of video data. We present a unique wayofintegrating our video model into an object database management system which has richmultimedia temporal operations. We further showhow temporal histories are used to model video data, explore the video objectbase using object-oriented techniques. Such a seamless integration gives a uniform interface to end users. The integrated video objectbase management system supports a broad range of temporal queries.

The schema of a system consists of the constructs that model its entities. Schema evolution is the timely change and management of the schema. Dynamic schema evolution is the management of schema changes while the system is in operation. We propose a sound and complete axiomatic model for dynamic schema evolution in objectbase management systems (OBMSs) that support subtyping and property inheritance. The model is formal, which distinguishes it from the traditional approach of informally defining a number of invariants and rules to enforce them. By reducing systems to the axiomatic model, their functionality with respect to dynamic schema evolution can be compared within a common framework. 1 Introduction Object-oriented computing is emerging as the predominant technology for providing database services in advanced application domains such as engineering design, CAD/CAM systems, multimedia, medical imaging, and geo-information systems, to name a few. An important characteristic of t...

Most of the work in modeling time in information systems has concentrated on issues such as support for historical information and providing query facilities to manipulate such information. In doing so, some simplistic view of the underling nature of time has been assumed. However, the domain of time is far from being simplistic. In this paper, we outline the various issues which arise in modeling basic temporal entities and propose solutions to these issues. More specifically, we note that the nature of temporal information can either be anchored (e.g., October 25; 1995) or unanchored (e.g., 1 week), and is usually available in multiple granularities (e.g., the airline flight departure and arrival times are usually given in minutes, while the history of the salary of an employee is usually recorded in days). Physical temporal information also needs to be represented in a manner so as to be human readable. This is achieved using calendars. In this work, we show how both anchored and un...

In this paper we present a formal model for the support of temporal schema versions in object-oriented databases. Its definition is partially based on a generic (ODMG compatible) object model and partially introduces new concepts. The proposed model supports all the schema changes which are usually considered in the OODB literature, for which an operational semantics and a formal analysis of their correct behaviour is provided. Semantic issues arising from the introduction of temporal schema versioning in a conventional or temporal database (concerning the interaction between the intensional and extensional levels of versioning and the management of data in the presence of multiple schema versions) are also considered.

Abstract. This paperpresents the DT Framework, a collection of object-oriented classes representing a generalized framework for inheritance management and table-based method dispatch. It demonstrates how most existing table-based dis-patch techniques can be generalized and made incremental, so that relevant en-tries in the dispatch table are modified each time a selector or class hierarchy link is added or removed. The incremental nature makes the framework highly efficient, with low millisecond average modification time, and supports table-based dispatch even in schema-evolving languages. During table maintenance, the framework detects and records inheritance conflicts, and maintains informa-tion useful during compile-time optimizations. 1