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Ran Ziv

Publications and source records attributed to Ran Ziv.

14 recordsLinked to original sources
arXiv2022

CompanyName2Vec: Company Entity Matching Based on Job Ads

Entity Matching is an essential part of all real-world systems that take in structured and unstructured data coming from different sources. Typically no common key is available for connecting records. Massive data cleaning and integration processes require completion before any data analytics, or further processing can be performed. Although record linkage is frequently regarded as a somewhat tedious but necessary step, it reveals valuable insights, supports data visualization, and guides further analytic approaches to the data. Here, we focus on organization entity matching. We introduce CompanyName2Vec, a novel algorithm to solve company entity matching (CEM) using a neural network model to learn company name semantics from a job ad corpus, without relying on any information on the matched company besides its name. Based on a real-world data, we show that CompanyName2Vec outperforms other evaluated methods and solves the CEM challenge with an average success rate of 89.3%.

cs.SI↗
arXiv2017

Representation of large matchings in bipartite graphs

Let $f(n)$ be the smallest number such that every collection of $n$ matchings, each of size at least $f(n)$, in a bipartite graph, has a full rainbow matching. Generalizing famous conjectures of Ryser, Brualdi and Stein, Aharoni and Berger conjectured that $f(n)=n+1$ for every $n>1$. Clemens and Ehrenm{ü}ller proved that $f(n) \le \frac{3}{2}n +o(n)$. We show that the $o(n)$ term can be reduced to a constant, namely $f(n) \le \lceil \frac{3}{2}n \rceil+1$.

math.CO↗
arXiv2017

Fair representation in the intersection of two matroids

For a simplicial complex ${\mathcal C}$ denote by $β({\mathcal C})$ the minimal number of edges from ${\mathcal C}$ needed to cover the ground set. If ${\mathcal C}$ is a matroid then for every partition $A_1, \ldots, A_m$ of the ground set there exists a set $S \in {\mathcal C}$ meeting each $A_i$ in at least $\frac{|A_i|}{β({\mathcal C})}$ elements. We conjecture that a slightly weaker result is true for the intersections of two matroids: if ${\mathcal D}={\mathcal P} \cap {\mathcal Q}$, where ${\mathcal P},{\mathcal Q}$ are matroids on the same ground set $V$ and $β({\mathcal P}), β({\mathcal P}) \le k$, then for every partition $A_1, \ldots, A_m$ of the ground set there exists a set $S \in {\mathcal D}$ meeting each $A_i$ in at least $(\frac{1}{k}-\frac{1}{|V|})|A_i|-1$ elements. We prove this for a partition into two sets.

math.CO↗
arXiv2016

Fair representation by independent sets

For a hypergraph $H$ let $β(H)$ denote the minimal number of edges from $H$ covering $V(H)$. An edge $S$ of $H$ is said to represent {\em fairly} (resp. {\em almost fairly}) a partition $(V_1,V_2, \ldots, V_m)$ of $V(H)$ if $|S\cap V_i|\ge \lfloor\frac{|V_i|}{β(H)}\rfloor$ (resp. $|S\cap V_i|\ge \lfloor\frac{|V_i|}{β(H)}\rfloor-1$) for all $i \le m$. In matroids any partition of $V(H)$ can be represented fairly by some independent set. We look for classes of hypergraphs $H$ in which any partition of $V(H)$ can be represented almost fairly by some edge. We show that this is true when $H$ is the set of independent sets in a path, and conjecture that it is true when $H$ is the set of matchings in $K_{n,n}$. We prove that partitions of $E(K_{n,n})$ into three sets can be represented almost fairly. The methods of proofs are topological.

math.CO↗
arXiv2016

Degree conditions for matchability in $3$-partite hypergraphs

We study conjectures relating degree conditions in $3$-partite hypergraphs to the matching number of the hypergraph, and use topological methods to prove special cases. In particular, we prove a strong version of a theorem of Drisko \cite{drisko} (as generalized by the first two authors \cite{ab}), that every family of $2n-1$ matchings of size $n$ in a bipartite graph has a partial rainbow matching of size $n$. We show that milder restrictions on the sizes of the matchings suffice. Another result that is strengthened is a theorem of Cameron and Wanless \cite{CamWan}, that every Latin square has a diagonal (permutation submatrix) in which no symbol appears more than twice. We show that the same is true under the weaker condition that the square is row-Latin.

math.CO↗
arXiv2016

On a conjecture of Stein

Stein proposed the following conjecture: if the edge set of $K_{n,n}$ is partitioned into $n$ sets, each of size $n$, then there is a partial rainbow matching of size $n-1$. He proved that there is a partial rainbow matching of size $n(1-\frac{D_n}{n!})$, where $D_n$ is the number of derangements of $[n]$. This means that there is a partial rainbow matching of size about $(1- \frac{1}{e})n$. Using a topological version of Hall's theorem we improve this bound to $\frac{2}{3}n$.

math.CO↗
arXiv2015

Uniqueness of the extreme cases in theorems of Drisko and Erdős-Ginzburg-Ziv

Drisko \cite{drisko} proved (essentially) that every family of $2n-1$ matchings of size $n$ in a bipartite graph possesses a partial rainbow matching of size $n$. In \cite{bgs} this was generalized as follows: Any $\lfloor \frac{k+2}{k+1} n \rfloor -(k+1)$ matchings of size $n$ in a bipartite graph have a rainbow matching of size $n-k$. We extend this latter result to matchings of not necessarily equal cardinalities. Settling a conjecture of Drisko, we characterize those families of $2n-2$ matchings of size $n$ in a bipartite graph that do not possess a rainbow matching of size $n$. Combining this with an idea of Alon \cite{alon}, we re-prove a characterization of the extreme case in a well-known theorem of Erdős-Ginzburg-Ziv in additive number theory.

math.CO↗
arXiv2015

Rainbow sets in the intersection of two matroids

Given sets $F_1, \ldots ,F_n$, a {\em partial rainbow function} is a partial choice function of the sets $F_i$. A {\em partial rainbow set} is the range of a partial rainbow function. Aharoni and Berger \cite{AhBer} conjectured that if $M$ and $N$ are matroids on the same ground set, and $F_1, \ldots ,F_n$ are pairwise disjoint sets of size $n$ belonging to $M \cap N$, then there exists a rainbow set of size $n-1$ belonging to $M \cap N$. Following an idea of Woolbright and Brower-de Vries-Wieringa, we prove that there exists such a rainbow set of size at least $n-\sqrt{n}$.

math.CO↗
arXiv2015

Decomposition of bi-colored square arrays into balanced diagonals

Given an $n\times n$ array $M$ ($n\ge 7$), where each cell is colored in one of two colors, we give a necessary and sufficient condition for the existence of a partition of $M$ into $n$ diagonals, each containing at least one cell of each color. As a consequence, it follows that if each color appears in at least $2n-1$ cells, then such a partition exists. The proof uses results on completion of partial Latin squares.

math.CO↗
arXiv2013

Large matchings in bipartite graphs have a rainbow matching

Let $g(n)$ be the least number such that every collection of $n$ matchings, each of size at least $g(n)$, in a bipartite graph, has a full rainbow matching. Aharoni and Berger \cite{AhBer} conjectured that $g(n)=n+1$ for every $n>1$. This generalizes famous conjectures of Ryser, Brualdi and Stein. Recently, Aharoni, Charbit and Howard \cite{ACH} proved that $g(n)\le\lfloor\frac{7}{4}n\rfloor$. We prove that $g(n)\le\lfloor\frac{5}{3} n\rfloor$.

math.CO↗
arXiv2012

On the Length of a Partial Independent Transversal in a Matroidal Latin Square

We suggest and explore a matroidal version of the Brualdi - Ryser conjecture about Latin squares. We prove that any $n\times n$ matrix, whose rows and columns are bases of a matroid, has an independent partial transversal of length $\lceil2n/3\rceil$. We show that for any $n$, there exists such a matrix with a maximal independent partial transversal of length at most $n-1$.

math.CO↗
arXiv2012

On Serial Symmetric Exchanges of Matroid Bases

We study some properties of a serial (i.e. one-by-one) symmetric exchange of elements of two disjoint bases of a matroid. We show that any two elements of one base have a serial symmetric exchange with some two elements of the other base. As a result, we obtain that any two disjoint bases in a matroid of rank 4 have a full serial symmetric exchange.

math.CO↗
arXiv2000

A tree version of Konig's theorem

Konig's theorem states that the covering number and the matching number of a bipartite graph are equal. We prove a generalisation of this result, in which each point in one side of the graph is replaced by a subtree of a given tree. The proof uses a recent extension of Hall's theorem to families of hypergraphs, by the first author and P. Haxell.

math.CO↗