Reducing the View Selection Problem through Code Modeling: Static and Dynamic approaches

2015 - 2016Data  warehouse  systems aim to support decision making by providing users with the appropriate  information  at  the right time. This task is particularly challenging in business contexts where large  amount of data is produced at a high speed. To this end, data warehouses have been equipped with  Online Analytical Processing tools that help users to make fast and precise decisions througt the  execution of complex queries. Since the computation of these queries is time consuming, data   warehouses precompute a set of materialized views answering to the workload  queries.   This thesis work defines a process to determine the minimal set of workload queries and the set of views to materialize. The set of queries is represented by an optimized lattice structure used to select  the views to be materialized according to the processing time costs and the view storage space. The minimal set of required Online Analytical Processing queries is computer by analyzing the data model defined with the visual language CoDe (Complexity Design). The latter allows to conceptually organizatio  the visualization of data reports and to generate visualizations of data obtained from data-­‐mart queries. CoDe adopts a hybrid modeling process combining two main methodologieser-­‐driven and data-­ driven. The first aims to create a model according to  the  user  knowledge,  re-quirements, and analysis needs, whilst the latter has in  charge to concretize data  and their relationships in the model through Online Analytical Processing queries. Since the materialized views change over time, we also propose a dynamic process that allows users to upgrade the CoDe model with a context-­‐aware editor, build an optimized lattice structure able to  minimize the effort to recalculate it,and propose the new set of views  to  materialize  Moreover,  the  process applies a Markov strategy to predict whether the views need to be recalculate or not  according to the changes of the model. The effectiveness of the proposed  techniques has  been  evaluated on a real world data warehouse. The results  revealed that the Markov strategy gives a better set of solutions in term of storage space and total processing cost. [edited by author]  XV n.

Exploiting CoDe modeling for the optimization of OLAP queries

The visualization of big-data represents a hard challenge due to the sheer amount of information contained in data warehouses. Thus, the accuracy on data relationships in a representation becomes one of the most crucial aspects to perform business knowledge discovery. A tool that allows to model and visualize information relationships between data is CoDe, which by processing several queries on a data-mart, generates a visualization of such data. However on a large data warehouse, the computation of these queries increases the response time by the query complexity. A common approach to speed up data warehousing is precompute a set of materialized views, store in the warehouse and use them to compute the workload queries. In this paper, we define a process exploiting the CoDe modeling to determine the minimal number of required OLAP queries and to mitigate the problem of view selection, i.e., select the optimal set of materialized views. The results of an experiment on a real data warehouse show an improvement in the range of 62-98% with respect the approach that does not consider materialized views, and 5% wrt. an approach that exploits them

A Mobile Application for Supporting Archaeologists in the Classification and Recognition of Petroglyphs

In this paper we present a mobile application, named PetroSketch, for supporting archaeologists in the classification and recognition of petroglyph symbols. PetroSketch is a virtual notebook enabling users to draw a petroglyph symbol on a white page, or by following the contour of a symbol captured with the camera, and to obtain its classification and the list of symbols more similar to it. The latter is performed by a flexible image matching algorithm that measures the similarity between petroglyph by using a distance, derived from the image deformation model, which is computationally efficient and robust to local distortions

A Mobile Application for Supporting Archaeologists in the Classification and Recognition of Petroglyphs

In this paper we present a mobile application, named PetroSketch, for supporting archaeologists in the classification and recognition of petroglyph symbols. PetroSketch is a virtual notebook enabling users to draw a petroglyph symbol on a white page, or by following the contour of a symbol captured with the camera, and to obtain its classification and the list of symbols more similar to it. The latter is performed by a flexible image matching algorithm that measures the similarity between petroglyph by using a distance, derived from the image deformation model, which is computationally efficient and robust to local distortions