Information Management Università degli Studi di Copyright By PowCoder代写 加微信 powcoder Why Information Management – 1 • We live today in a society that is generating a huge amount of heterogeneous data • Data can be used to extract information for decision making • Data can be organized in different ways • Relational data • […]
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Information Management Università degli Studi di Databases (slides partially provided by Prof. Samarati) Copyright By PowCoder代写 加微信 powcoder Paradigms for data distribution • Client-server architectures • Separation between the database server and the client • Distributed databases • Several database servers used by the same application • Parallel databases • Several storage devices and processors
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Question 1) Information Management Prof. June 18, 2020 Time available 2:00 hours Copyright By PowCoder代写 加微信 powcoder 1. Describe how ACID properties are affected by data distribution. 2. Illustrate the working of Vector clocks. 3. Consideringtheattachedschema,indicatethetimestampassociatedwitheachoperationofeachprocess.Fortheexercise, assume to adopt Vector clocks and that all the timestamps are initialized to 0. Operations are denoted with a
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Question 1) Information Management Prof. , Prof. September 2, 2021 Time available 2:00 hours 1. Illustrate the problem of global serializability in a distributed system. Copyright By PowCoder代写 加微信 powcoder 2. Illustrate the concept of happened before characterizing logical clocks. 3. Fill the attached schema indicating the timestamp associated with each operation of each process.
A bit of history • 1970/1980: Rela%onal databases • Storage is expensive Copyright By PowCoder代写 加微信 powcoder • Dara are normalized • Data are stored regardless of how they will be used • RDBMS become popular • Client/server model • SQL becomes a standard for querying databases • 1990: WWW and Internet • 2000: Web
Question 1) Information Management July 21, 2020 Time available 2:00 hours (1:30 hours for students who do not answer to question 5) Copyright By PowCoder代写 加微信 powcoder 1. Illustrate the concept of happened before characterizing logical clocks. 2. Describe the differences between Lamport clocks and Vector clocks. 3. Fill the attached schema indicating the timestamp
Causal consistency (1) • Causal consistency is a weaker version of sequential consistency • If event a caused or influenced event bàeveryone should see a and then b • Writes that are potentially causally related must be seen by all the processes in the same order Copyright By PowCoder代写 加微信 powcoder • Concurrent writes may
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Clustering Chapter 10 Clustering Copyright By PowCoder代写 加微信 powcoder • Clustering is the process of grouping a set of data objects into multiple groups or clusters so that objects within a cluster • have high similarity • are very dissimilar to objects in other clusters • Clustering is called data segmentation because it partitions large
Tree-based indexes (3) • B-trees and B+-trees support searches along one dimension only • Not suited for multi-dimensional data like DWs • Multidimensional trees are an evolution of B-trees for multidimensional data • Describe sets of points through geometric regions containing clusters of points Copyright By PowCoder代写 加微信 powcoder • Clusters are used for search
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Frequent itemset mining Frequent patterns • Frequent patterns: patterns (e.g., itemsets, subsequences, or substructures) that appear frequently in a data set Copyright By PowCoder代写 加微信 powcoder • Example: a set of items, such as milk and bread, that appear frequently together in a transaction data set is a frequent itemset • Finding frequent patterns plays
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