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Active object-oriented database systems are a commonly accepted solution for capturing the time- and context-dependent knowledge of non-standard applications. Several attempts have been made already to integrate active concepts into object-oriented database systems and to increase the expressive power of event specification languages. However, this has often been done without considering the consequences...
This paper proposes an approach to building event services for active database applications. It introduces dimensions to characterize distributed event definition, detection, production and notification. The core of our approach is a parametric event service called QUETZAL that has three interfaces, each of them implementing the given dimensions as parameters. Therefore, different event (detection)...
Current needs of industry required the development of advanced database models like mobile databases, active databases, and fuzzy databases. Fuzzy concepts are adapted to the field of databases in order to deal with ambiguous, uncertain data. Fuzziness comes into picture in mobile databases especially with moving objects. Incorporating fuzziness into rules would improve the effectiveness of active...
To avoid OID index retrieval becoming a bottleneck, efficient buffering strategies are needed to minimize the number of disk accesses. In this paper, we develop analytical cost models which we use to find optimal sizes of the index page buffer and the index entry cache, for different memory sizes, index sizes, and access patterns. Because existing buffer hit estimation models are not applicable for...
DO2 is a deductive object-oriented database developed at the National University of Singapore. The system aims to integrate deductive and object-oriented paradigms and use their advantages to overcome both the paradigms’ respective weaknesses. DO2 differs from conventional deductive object-oriented databases in its' key-based approach for OIDs, pro-active approach to resolving inheritance...
This paper studies the problem of selecting rules to fire in real-time active databases in order to avoid missing action deadlines. We give an algorithm that executes at every fixed time interval (called the Rule Selection Period), and satisfies three properties, namely, the Completion Property, the Duration Property, and the Priority Property. We develop a probabilistic model, and an inexpensive...
The main argument of the paper is that database understanding (or reverse engineering) requires sophisticated program understanding techniques, and conversely. Database reverse engineering (DBRE) can be carried out following a generic methodology, one of the phases of which consists in eliciting all the implicit and untranslated data structures and constraints. Evidences of these hidden constructs...
A new method for schema analysis is described in which reasoning is based upon the real-world semantics of schema elements. The method distinguishes between intrinsic and in-context semantics, which respectively provide a basis for shallow and deep semantic comparisons between element. The method provides a basis for more accurate integration of component schemas within a federated database system.
Many organizations nowadays own several information systems which represent a mine of possible information resources whose effective exploitation is becoming a key issue in many application contexts. A major problem to be faced within such contexts is the semantic normalization of scheme objects used in heterogeneous, independent and pre-existing databases as to single out differences and similitudes...
Extending the usability of merged database and text-retrieval systems by building on an object-oriented database management system (OODBMS) can offer better and complementary advantages to both database and information retrieval systems (IRS). In this paper, we present a new approach for integrating OODBMSs and IRSs that maintains the flexibility and avoids overheads of mapping process, by means of...
Signature file acts as a filter to eliminate the unqualified data items for an information request. The contribution of this paper is two-fold. First, we propose a methodology for structured database. The main idea of decomposition amounts to dividing the relations of database into subrelations called ’rectangle’. Owing to the reduction of storage overhead, rectangular decomposition has a direct benefit...
The focus of this paper is information brokers within Information Discovery (ID). We describe Cumulative Duality matrices, an instrument to deal with design criteria for such information brokers. ID is the synthesis of Information Retrieval and Information Filtering, where information brokers act as middle-agents. There are numerous design criteria for information brokers. Since these stem from ID,...
This paper describes an agent based architecture to manage workflows. The agents, rather than predefined rules, determine the flow of work, enabling them to cater for unexpected inputs. The agents in this distributed system use organisational rules, as well as the state of the decision making environment to control the flow of work. An experimental agent-based workflow system based on the World Wide...
In the paper a particular approach to transaction management in databases supporting collaborative applications is proposed. It is based on a new transaction model which allows practically unrestricted collaboration among members of the same team. The basic assumption of this model is that collaborating users try to solve their access conflicts on a higher level than the level of a database management...
This paper focuses on the database modeling of spatiotemporal phenomena. Their components and behavior are analyzed and a formal framework with a small set of concepts-namely objects, attributes, relationships, fields, and constraints, with spatial and temporal dimension-for their definition is provided. A mathematical model for the expression of spatiotemporal constraints, based on the aforementioned...
In this paper we describe an approach to rule base V&V founded on a N-dimensional tesseral representation of space. The advantages offered by the representation are that it is simple, concise and lends itself to computationally effective manipulation of objects (defined in the representation) using standard integer addition and subtraction. The encapsulation of a rulebase in this tesseral representation...
In this paper, we propose a temporal link mechanism for ’time-dependent’ hypermedia. It has become a serious problem to maintain link information at all times according to updating. It is very important to keep consistency and maintain the updates, especially for broadcast hypermedia, which are transmitted from a server to a client via the internet or a broadcasting system. The mechanism we propose...
We extend the relational data model to incorporate linear orderings into data domains, which we call the ordered relational model. We formally define Ordered Functional Dependencies (OFDs) for the extended model by means of two possible extensions of domains, pointwise-orderings and lexicographical orderings. We first present a sound and complete axiom system for OFDs in the case of pointwise-orderings...
Prototype databases are needed in any information system development process to support data-intensive applications development. It is common practice to populate these databases using synthetic data. This data usually bears little relation to the application's domain and considers only a very reduced subset of the integrity constraints the database will hold during operation. This paper claims...
A reuse based approach to construct software tool supporting a specific method built ≪ on the fly ≫ is presented in this paper. Its originality is to apply a process view on the reusable component which is either method chunk or software chunk. Our process view leads to construct method and software tool by assembling chunks. Chunks which are either method or software ones can be assembled in different...
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