666,864 research outputs found
Encoding Classifications as Lightweight Ontologies
Classifications have been used for centuries with the goal of cataloguing and searching large sets of objects. In the early days it was mainly books; lately it has also become Web pages, pictures and any kind of electronic information items. Classifications describe their contents using natural language labels, which has proved very effective in manual classification. However natural language labels show their limitations when one tries to automate the process, as they make it very hard to reason about classifications and their contents. In this paper we introduce the novel notion of Formal Classification, as a graph structure where labels are written in a propositional concept language. Formal Classifications turn out to be some form of lightweight ontologies. This, in turn, allows us to reason about them, to associate to each node a normal form formula which univocally describes its contents, and to reduce document classification to reasoning about subsumption
Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z
The classification of galaxy mergers and isolated disks is key for
understanding the relative importance of galaxy interactions and secular
evolution during the assembly of galaxies. The kinematic properties of galaxies
as traced by emission lines have been used to suggest the existence of a
significant population of high-z star-forming galaxies consistent with isolated
rotating disks. However, recent studies have cautioned that post-coalescence
mergers may also display disk-like kinematics. To further investigate the
robustness of merger/disk classifications based on kinematic properties, we
carry out a systematic classification of 24 local (U)LIRGs spanning a range of
galaxy morphologies: from isolated spiral galaxies, ongoing interacting
systems, to fully merged remnants. We artificially redshift the WiFeS
observations of these local (U)LIRGs to z=1.5 to make a realistic comparison
with observations at high-z, and also to ensure that all galaxies have the same
spatial sampling of ~900 pc. Using both kinemetry-based and visual
classifications, we find that the reliability of kinematic classification shows
a strong trend with the interaction stage of galaxies. Mergers with two nuclei
and tidal tails have the most distinct kinematic properties compared to
isolated disks, whereas a significant population of the interacting disks and
merger remnants are indistinguishable from isolated disks. The high fraction of
late-stage mergers showing disk-like kinematics reflects the complexity of the
dynamics during galaxy interactions. However, the exact fractions of
misidentified disks and mergers depend on the definition of kinematic
asymmetries and the classification threshold when using kinemetry-based
classifications. Our results suggest that additional indicators such as
morphologies traced by stars or molecular gas are required to further constrain
the merger/disk classifications at high-z.Comment: 16 pages, 5 figures, ApJ accepte
On the Breeds of Cattle—Historic and Current Classifications
Classification of cattle breeds contributes to our understanding of the history of cattle and is essential for an effective conservation of genetic diversity. Here we review the various classifications over the last two centuries and compare the most recent classifications with genetic data. The classifications devised during the 19th to the late 20th century were in line with the Linnaean taxonomy and emphasized cranial or horn morphology. Subsequent classifications were based on coat color, geographic origin or molecular markers. Several theories were developed that linked breed characteristics either to a supposed ancestral aurochs subspecies or to a presumed ethnic origin. Most of the older classifications have now been discarded, but have introduced several Latin terms that are still in use. The most consistent classification was proposed in 1995 by Felius and emphasizes the geographic origin of breeds. This is largely in agreement with the breed clusters indicated by a biochemical and molecular genetic analysis, which reflect either groups of breeds with a common geographic origin or single breeds that have expanded by export and/or crossbreeding. We propose that this information is also relevant for managing the genetic diversity of cattl
Bulking II: Classifications of Cellular Automata
This paper is the second part of a series of two papers dealing with bulking:
a way to define quasi-order on cellular automata by comparing space-time
diagrams up to rescaling. In the present paper, we introduce three notions of
simulation between cellular automata and study the quasi-order structures
induced by these simulation relations on the whole set of cellular automata.
Various aspects of these quasi-orders are considered (induced equivalence
relations, maximum elements, induced orders, etc) providing several formal
tools allowing to classify cellular automata
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