252,541 research outputs found
NITELIGHT: A Graphical Tool for Semantic Query Construction
Query formulation is a key aspect of information retrieval, contributing to both the efficiency and usability of many semantic applications. A number of query languages, such as SPARQL, have been developed for the Semantic Web; however, there are, as yet, few tools to support end users with respect to the creation and editing of semantic queries. In this paper we introduce a graphical tool for semantic query construction (NITELIGHT) that is based on the SPARQL query language specification. The tool supports end users by providing a set of graphical notations that represent semantic query language constructs. This language provides a visual query language counterpart to SPARQL that we call vSPARQL. NITELIGHT also provides an interactive graphical editing environment that combines ontology navigation capabilities with graphical query visualization techniques. This paper describes the functionality and user interaction features of the NITELIGHT tool based on our work to date. We also present details of the vSPARQL constructs used to support the graphical representation of SPARQL queries
Classification of simple linearly compact Kantor triple systems over the complex numbers
Simple finite dimensional Kantor triple systems over the complex numbers are
classified in terms of Satake diagrams. We prove that every simple and linearly
compact Kantor triple system has finite dimension and give an explicit
presentation of all the classical and exceptional systems.Comment: 46 pages, 3 tables; v2: Major revision of the introduction; v3: Final
version to appear in Journal of Algebr
Exceptional Moufang quadrangles and structurable algebras
In 2000, J. Tits and R. Weiss classified all Moufang spherical buildings of
rank two, also known as Moufang polygons. The hardest case in the
classification consists of the Moufang quadrangles. They fall into different
families, each of which can be described by an appropriate algebraic structure.
For the exceptional quadrangles, this description is intricate and involves
many different maps that are defined ad hoc and lack a proper explanation.
In this paper, we relate these algebraic structures to two other classes of
algebraic structures that had already been studied before, namely to
Freudenthal triple systems and to structurable algebras. We show that these
structures give new insight in the understanding of the corresponding Moufang
quadrangles.Comment: 49 page
Avoiding Unnecessary Information Loss: Correct and Efficient Model Synchronization Based on Triple Graph Grammars
Model synchronization, i.e., the task of restoring consistency between two
interrelated models after a model change, is a challenging task. Triple Graph
Grammars (TGGs) specify model consistency by means of rules that describe how
to create consistent pairs of models. These rules can be used to automatically
derive further rules, which describe how to propagate changes from one model to
the other or how to change one model in such a way that propagation is
guaranteed to be possible. Restricting model synchronization to these derived
rules, however, may lead to unnecessary deletion and recreation of model
elements during change propagation. This is inefficient and may cause
unnecessary information loss, i.e., when deleted elements contain information
that is not represented in the second model, this information cannot be
recovered easily. Short-cut rules have recently been developed to avoid
unnecessary information loss by reusing existing model elements. In this paper,
we show how to automatically derive (short-cut) repair rules from short-cut
rules to propagate changes such that information loss is avoided and model
synchronization is accelerated. The key ingredients of our rule-based model
synchronization process are these repair rules and an incremental pattern
matcher informing about suitable applications of them. We prove the termination
and the correctness of this synchronization process and discuss its
completeness. As a proof of concept, we have implemented this synchronization
process in eMoflon, a state-of-the-art model transformation tool with inherent
support of bidirectionality. Our evaluation shows that repair processes based
on (short-cut) repair rules have considerably decreased information loss and
improved performance compared to former model synchronization processes based
on TGGs.Comment: 33 pages, 20 figures, 3 table
Structurable algebras and groups of type E_6 and E_7
It is well-known that every algebraic group of type F_4 is the automorphism
group of an exceptional Jordan algebra, and that up to isogeny all groups of
type ^1E_6 with trivial Tits algebras arise as the isometry groups of norm
forms of such Jordan algebras. We describe a similar relationship between
groups of type E_6 and groups of type E_7 and use it to give explicit
descriptions of the homogeneous projective varieties associated to groups of
type E_7 with trivial Tits algebras. The underlying algebraic structure for the
relationship considered here are a sort of 56-dimensional structurable algebra
which are forms of an algebra constructed from an exceptional Jordan algebra.Comment: 35 pages, AMSLaTeX -- error in final section correcte
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