1,720,981 research outputs found
Preferences in Temporal Relational Databases
Full text linkDespite the huge amount of work devoted to the treatment of time within the relational context, some relevant phenomena remain to be fully addressed. We focus on one of them, i.e., temporal indeterminacy with preferences. In several domains (e.g., workflows, guidelines) and tasks (e.g., planning, scheduling), the exact time of occurrence of facts is not known: only an interval of possible values for their starting time, and a range of possible durations is available. Additionally, preferences can be assigned to the different temporal possibilities. We propose the first relational temporal database approach coping with such issues. We introduce a new data model to cope with indeterminate time with preferences, considering a family of preference functions, and we propose new definitions of relational algebraic operators to query the new data model. We also ascertain the properties of the new model and algebra, with emphasis on reducibility, and on the correctness of the algebraic operators
A Knowledge Server for Reasoning about temporal constraints between classes and instances of events
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An intensional approach to qualitative and quantitative periodicity-dependent temporal constraint
No full textManaging proposals and evaluations of updates to medical knowledge: Theory and applications
No full textAbstractThe process of keeping up-to-date the medical knowledge stored in relational databases is of paramount importance. Since quality and reliability of medical knowledge are essential, in many cases physicians’ proposals of updates must undergo experts’ evaluation before possibly becoming effective. However, until now no theoretical framework has been provided in order to cope with this phenomenon in a principled and non-ad hoc way. Indeed, such a framework is important not only in the medical domain, but in all Wikipedia-like contexts in which evaluation of update proposals is required. In this paper we propose GPVM (General Proposal Vetting Model), a general model to cope with update proposal⧹evaluation in relational databases. GPVM extends the current theory of temporal relational databases and, in particular, BCDM – Bitemporal Conceptual Data Model – “consensus” model, providing a new data model, new operations to propose and accept⧹reject updates, and new algebraic operators to query proposals. The properties of GPVM are also studied. In particular, GPVM is a consistent extension of BCDM and it is reducible to it.These properties ensure consistency with most relational temporal database frameworks, facilitating implementation on top of current frameworks and interoperability with previous approaches
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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