Abstract Attribute-Based Prediction of File Properties(7)

We present evidence that attributes that are known to the file system when a file is created, such as its name, permission mode, and owner, are often strongly related to future properties of the file such as its ultimate size, lifespan, and access pattern.

DEAS033/24/2003

relative strength of association

first

middle last EECS033/24/2003

relative strength of association

first

middle last uid gid

CAMPUS 10/22/2001

relative strength of association

first

middle last siz e=0

Figure 2:The relative strength of the correlation between the properties “lifetime (lftmd)is one second or shorter”and “size is zero”and several ?le attributes (as indicated by the chi-squared values)for one day of each trace.The chi-squared values are normalized relative to the attribute with the strongest association.The last,middle,and ?rst attributes refer to components of the ?le name,as de-scribed in Section 5.

culty with such a test is distinguishing natural variation from a statistically signi?cant difference;the chi-squared test is used to detect and quantify such differences.The sum of squared differences between the expected and observed number of ?les is our chi-squared statis-tic,and we calculate this statistic for each combination of attribute and property.In statistical terms,we are try-ing to disprove the null hypothesis that ?le attributes are not associated with ?le properties.A chi-squared statis-tic of zero indicates that there is no association (i.e.,the expected and observed values are the same),while the magnitude of a non-zero statistic indicates the degree of association.This value is then used to calculate a p-value which estimates the probability that the difference be-tween the expected and observed values is coincidental.For all of our tests,we have a high chi-square statis-tic,and the p-values are very close to zero.Therefore we may,with very high con?dence,reject the null hy-pothesis and claim that attributes are associated with ?le properties.

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