The Semantic Web aims at building a foundation of semantic-based data models and languages for not only manipulating data and knowledge, but also in decision making by machines.Naturally, time-varying data and knowledge are required in Semantic Web applications to incorporate time and further reason about it.However, the original specifications of RDF and OWL do not include constructs for handling time-varying data and knowledge.For simplicity, RDF model is confined to binary predicates, hence some form of reification is needed to represent higher-arity predicates.To this date, there are many proposals extending RDF and OWL for handling temporal data and knowledge.They all focus on the valid time.In this paper, we examine each of these proposals and develop a taxonomy to classify them according to the form of reification employed: explicit reification or implicit reification.The implicit reification proposals are further divided into three sub-categories according to semantic constructs

The early development of medical decision support systems (appeared as expert systems (ES)) mainly focused on, among others, rule-based reasoning (RBR) and decision table/tree (DT) methods as problem solving strategies. These efforts were novel at the time; however, as these methodologies applied to more complex situations, the construction of knowledge base (e.g. rules, cases and 'models') for specific problem solving tasks becomes difficult and time consuming. Remedies to these difficulties have been sought, aiming at better knowledge modeling, knowledge acquisition, and extending the problem solving paradigm to distributed architectures. Alternatively, case-based reasoning (CBR) provides a different problem solving paradigm. In CBR, the knowledge is seen as cases that contain explicit and implicit aspects of the knowledge for solving a problem. The CBR methodology works in a practical way, and the reasoning is based on recalled knowledge memory of solved cases. To alleviate the difficulty of knowledge (case) acquisition and construction, this paper presents a design of a template case store, called MedCase. MedCase utilizes the semantic web technologies and supports a distributed CBR system architecture. MedCase promotes an open and accessible architecture for common CBR tasks in a virtual Healthcare Enterprise environment. MedCase will also allow the construction and sharing of cases that facilitate the development of distributed CBR-based medical decision support systems.

Version control systems are an integral part of software development process since their first use in 1970s. And since then, they have been improved with many features and easy-to-use user interfaces. In this paper, we propose a new feature to be implemented into commonly used version control systems, such as CVS and SubVersion. This feature promotes real time collaboration, opening the door towards a social interaction among development team members. This interaction allows software developers to communicate more effectively through an internal social networking site within the context of the version control environment. The new feature demonstrates that it can be effectively utilized to avoid conflicts, which is one of the major challenges not only in version control, but in any collaborative system.

We present an efficient algorithm (UWEP) for updating large itemsets when new transactions are added to the set of old transactions.UWEP employs a dynamic lookahead strategy in updating the existing large itemsets by detecting and removing those that will no longer remain large after the contribution of the new set of transactions.It differs from the other update algorithms by scanning the existing database at most once and the new database exactly once.Moreover, it generates and counts the minimum number of candidates in the new database.The experiments on synthetic data show that UWEP outperforms the existing algorithms in terms of the candidates generated and counted.

This paper incorporates a temporal dimension to nested relations. It combines research in temporal databases and nested relations for managing the temporal data in nontraditional database applications. A temporal data value is represented as a temporal atom; a temporal atom consists of two parts: a temporal set and a value. The temporal atom asserts that the value is valid over the time duration represented by its temporal set. The data model allows relations with arbitrary levels of nesting and can represent the histories of objects and their relationships. Temporal relational algebra and calculus languages are formulated and their equivalence is proved. Temporal relational algebra includes operations to manipulate temporal data and to restructure nested temporal relations. Additionally, we define operations to generate a power set of a relation, a set membership test, and a set inclusion test, which are all derived from the other operations of temporal relational algebra. To obtain a concise representation of temporal data (temporal reduction), collapsed versions of the set-theoretic operations are defined. Procedures to express collapsed operations by the regular operations of temporal relational algebra are included. The paper also develops procedures to completely flatten a nested temporal relation into an equivalent 1 NF relation and back to its original form, thus providing a basis for the semantics of the collapsed operations by the traditional operations on 1 NF relations.

The authors consider the representation of temporal data based on tuple and attribute timestamping. They identify the requirements in modeling temporal data and elaborate on their implications in the expressive power of temporal query languages. They introduce a temporal relational data model where N1NF relations and attribute timestamping are used and one level of nesting is allowed. For this model, a nested relational tuple calculus (NTC) is defined. They follow a comparative approach in evaluating the expressive power of temporal query languages, using NTC as a metric and comparing it with the existing temporal query languages. They prove that NTC subsumes the expressive power of these query languages. They also demonstrate how various temporal relational models can be obtained from the temporal relations by NTC and give equivalent NTC expressions for their languages. Furthermore, they show the equivalence of intervals and temporal elements (sets) as timestamps in their model.

In this paper we describe an implementation of a temporal relational database management system based on attribute timestamping. The algebraic language of the system includes relational algebra operators, restructuring operators and temporal operators. We then use this system to carry out experiments on the performance of different types of temporal databases: databases using attribute timestamping, databases using tuple timestamping where relations are in temporal normal form and databases using tuple timestamping where a single relation is used. We run sample queries against these types of temporal databases and measure the processing time of these queries. This study verifies that the major performance trade off between different types of temporal databases is between the restructuring (unpack) operation needed in temporal databases using attribute timestamping and the join operation needed in temporal databases using tuple timestamping. Furthermore, the experiments show that keepin...

We discuss the issues encountered in the extended algebra and calculus languages for nested relations defined by Roth, Korth, and Silberschatz.[4]. Their equivalence proof between algebra and calculus fails because of the keying problems and the use of extended set operations. Extended set operations also have unintended side effects. Furthermore, their calculus seems to allow the generation of power sets, thus making it more powerful than their algebra.

The paper extends nested relations for managing temporal variation of complex objects. It combines the research in temporal databases and nested relations for nontraditional database applications. The basic modelling construct is a temporal atom as an attribute value. A temporal atom consists of two components, a value and temporal set which is a set of times denoting the validity period of the value. We define algebra operations for nested historical relations. Data redundancy in nested historical relations is also discussed and criteria for well-structured nested relations are established.

The authors propose a graphical query language, Time-by-Example (TBE), which has suitable constructs for interacting with historical relational databases in a natural way. TBE is user-friendly. It follows the graphical, two-dimensional approach of such previous languages as Query-by-Example (QBE), Aggregation-by-Example (ABE), and Summary-Table-by-Example (STBE). TBE also uses the hierarchical window (subquery) concept of ABE and STBE. TBE manipulates triple-valued (set-triple-valued) attributes and historical relations. Set-theoretic expressions are followed to deal with time intervals. The BNF specification for TBE is given.>

A historical database is a vast source of data for statistical analysis. The paper presents a statistical interface for historical relational databases with an underlying data model which uses attribute time-stamping. The statistical interface we propose includes aggregate functions and transformations of data into tabular forms suitable for advanced statistical analysis and is capable of dealing with the subtle semantics of time and various issues associated with it. A new operation, called enumeration, is introduced into historical relational algebra. The enumeration operation derives a table of uniform data, for a set of specified time points or intervals, from a three dimensional historical relation. We also give a method for normalizing historical relations and aligning the time of their attributes.

Article On an algebra for historical relational databases: two views Share on Authors: James Clifford Computer Applications and Information Systems, Graduate School of Business Administration, New York University Computer Applications and Information Systems, Graduate School of Business Administration, New York UniversityView Profile , Abdullah Uz Tansel Baruch College, Statistics and Computer Information Systems, City University of New York Baruch College, Statistics and Computer Information Systems, City University of New YorkView Profile Authors Info & Claims SIGMOD '85: Proceedings of the 1985 ACM SIGMOD international conference on Management of dataMay 1985 Pages 247–265https://doi.org/10.1145/318898.318922Online:01 May 1985Publication History 133citation606DownloadsMetricsTotal Citations133Total Downloads606Last 12 Months12Last 6 weeks0 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 SiteGet Access