clarifying an N[X]-BIDB

master
Oliver Kennedy 2021-09-17 23:21:37 -04:00
parent 03875a7cd9
commit f08a03c990
Signed by: okennedy
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2 changed files with 7 additions and 3 deletions

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@ -91,7 +91,7 @@ Two important subclasses of \abbrNXPDB\xplural that are of interest to us are th
The probability of such a world is the product of the probabilities of all tuples present in the world. %and one minus the sum of the probabilities of all tuples from blocks for which no tuple is present in the world.
For bag \tis and \bis, we define the probability of a tuple to be the probability that the tuple exists with multiplicity at least $1$.
As already noted above, in this work, we define \tis and \bis as subclasses of \abbrNXPDB\xplural.
In this work, we define \tis and \bis as subclasses of \abbrNXPDB\xplural defined over variables $\vct{X}$ (\Cref{def:semnx-pdbs}) where $\vct{X}$ can be partitioned into blocks that satisfy the conditions of a \ti or \bi (stated formally in \Cref{subsec:tidbs-and-bidbs}).
In this work, we consider one further deviation from the standard: We use bag semantics for queries.
Even though tuples cannot occur more than once in the input \ti or \bi, they can occur with a multiplicity larger than one in the result of a query.
Since in \tis and \bis, there is a one-to-one correspondence between tuples in the database and variables, we can interpret a vector $\vct{w} \in \{0,1\}^n$ as denoting which tuples exist in the possible world $\assign_{\vct{w}}(\pxdb)$ (the ones where $\vct{w}[j] = 1$).

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@ -100,10 +100,14 @@ This text is an informal proof of \Cref{prop:expection-of-polynom} originally in
We agree that this should not be part of the proof of the later, and have removed the text.
\RCOMMENT{l.686 "The closure of ... over K-relations": you should give more details on this part. It is not obvious to me that the relations from l.646 hold.}
\AH{This too needs to be looked at.}
The core of this (otherwise trivial) argument, that semiring homomorphisms commute through queries, was already proven in \cite{DBLP:conf/pods/GreenKT07}. We now make this reference explicit.
\RCOMMENT{l.711 "As already noted...": ah? I don't see where you define which subclass of N[X]-PDBs define bag version of TIDBs. If this is supposed to be in Section 2.1.1 this is not clear, since the world "bag" does not even appear there (and as already mentioned everything seems to be set semantics in this section). I fact, nowhere in the article can I see a definition of what are bag TIDBs/BIDBs}
\AH{This needs to be taken care of in the appendix.}
The new text precisely defines TIDBs (\Cref{sec:intro}), and the BIDB generalization (\Cref{subsec:tidbs-and-bidbs}). The specific text referenced in this comment has now been restructured to reference \Cref{def:semnx-pdbs} (which defines an \abbrNXPDB defined over variables $\vct{X}$) and relate it to the formal structure of BIDBs in \Cref{subsec:tidbs-and-bidbs}.
\RCOMMENT{- l.707 "the sum of the probabilities of all the tuples in the same block b is 1": no, traditionally it can be less than 1, which means that there could be no tuple in the block.}
The reviewer is correct and we have updated our appendix text accordingly.