=Paper= {{Paper |id=Vol-2949/paper5 |storemode=property |title=Masked Language Model Entity Matching for Cultural Heritage Data |pdfUrl=https://ceur-ws.org/Vol-2949/paper5.pdf |volume=Vol-2949 |authors=Dominique Piché,Amal Zouaq,Michel Gagnon,Ludovic Font |dblpUrl=https://dblp.org/rec/conf/swodch/PicheZGF21 }} ==Masked Language Model Entity Matching for Cultural Heritage Data== https://ceur-ws.org/Vol-2949/paper5.pdf
    Masked Language Model Entity Matching for
             Cultural Heritage Data

     Dominique Piché1 , Amal Zouaq1 , Michel Gagnon1 , and Ludovic Font1

                        École Polytechnique de Montréal
               2500 chemin de Polytechnique, Montréal, QC, Canada
    {dominique.piche, amal.zouaq, michel.gagnon, ludovic.font}@polymtl.ca




       Abstract. Entity resolution is a well-known issue in Cultural Heritage
       data integration, as existing metadata for cultural works is typically dis-
       tributed across multiple databases maintained by various actors. Identi-
       fying classes of equivalent entities is thus a non-trivial but necessary task.
       Entity linking between heterogeneous data sources is made complex by
       variations in data schemes and cleanliness. In this work, we test masked
       language models (MLM) fine-tuned for entity matching on real-world
       literature data. We examine the impact of pre-processing and input an-
       notation strategies. Our results show that MLMs outperform or match
       our rule-based heuristics in most scenarios. Interestingly, the impact of
       the chosen MLMs language, data pre-processing and input annotation
       all have little to no effect on matching performance in our experiments.

       Keywords: Entity resolution · Knowledge base · Transformers · LRM ·
       Cultural heritage.



1     Introduction

The accumulation of information through dispersed data stores in the past
decades has motivated the development of interlinked knowledge graphs able
not only to represent complex information through graph-based structures, but
also to link information hosted on servers operated by unrelated entities. The
translation of various data stores describing a given domain into one unified
knowledge graph requires the detection of duplicate representations of the same
real world entities, as each real-world entity having a single unique identifier
allows for the aggregation of data describing it, and references to be made to it
from external sources. This problem is known as entity matching, alignment or
resolution. Several issues complicate matching entities between data sets, notably
the absence of preexisting global identifiers and variations in data cleanliness,
data schemes and database scopes. Cultural heritage (CH) data is particularly
prone to these types of problems due to the way it is collected and maintained,
as discussed below. Our aim is to determine to which extent neural solutions
mitigate the need for data cleaning and restructuring before match prediction.




Copyright © 2021 for this paper by its authors. Use permitted under Creative Commons
License Attribution 4.0 International (CC BY 4.0).
2       D. Piché et al.

1.1   Cultural heritage data integration
The integration of CH metadata into linked knowledge bases has been the fo-
cus of various initiatives, as various cultural domain actors such as national
libraries, museums and publishers. Cultural Heritage (CH) data describes ob-
jects and works of cultural significance and their contents, as well as the context
of their creation. Most existing data sets focus on physical items, e.g. museum
data describing artefacts. These data sets are typically constituted through man-
ual cataloging. As CH data focuses heavily on physical manifestations of works,
matching identical conceptual works realized in separate manifestations is re-
quired. For example, two separate data sets may describe separate editions of
the book Don Quixote in different languages, yet the thematic information of the
original conceptual work should be aggregated in a single entity through entity
matching.
    A recurring problem for translation of collections of real-world CH data sets
into unified knowledge bases is the absence of global unique identifiers for entities.
The ideal method for matching entities between sources would be the use of
identifiers such as an International Standard Book Number, or ISBN, for book
editions. In practice, however, most entity types are only described with internal
unique identifiers, requiring alternatives for cross-source matching. In the case
of literary data, it is rare to find a global unique identifier for entities such
as authors, even though ISNI and VIAF is slowly becoming more widespread.
Existing data sources rarely make the distinction between conceptual works and
their manifestations, and, consequently, works are left without global identifiers.
Evolving cataloging standards and data entry practices often mean that not only
do sources often use different naming and encoding conventions for information
such as titles and dates, but that data sets contain internal inconsistencies.
    In the absence of identifiers, the next best method for resolving entity duplica-
tion is the detection of similar entity representations, i.e. entities with enough at-
tribute similarity for confident matching. Implementation of rule-based matching
has its challenges, notably data cleanliness and heterogeneity in data schemes.
Evaluating the entity similarity within or between sources is difficult, as impor-
tant attributes such as titles and names are formatted according to different
rules from record to record, even within one data set.
    Extraction and cleaning of source record data before translation into a single
model can do much to solve this "dirty entity" problem, allowing for compari-
son of pre-processed and clean representations of entitiesThis process is labour
intensive, and requires extensive domain knowledge in order to map information
between models, as multiple versions of a cataloging standard present within
single source, duplicated attributes, typos and mislabeled values are frequent
occurrences. Thus, finding solutions less reliant on pre-processing may speed up
development time.

1.2   Neural solutions for matching dirty entities
As these challenges are a frequent occurrence amongst most CH data integration
initiatives, the development of a generalizable solution for entity matching with-
       Masked Language Model Entity Matching for Cultural Heritage Data         3

out the need for domain-specific extraction, cleaning and matching rules could
help speed future knowledge base creation efforts, especially in cases with incon-
sistent source data. Tools leveraging neural methods for entity matching have
been developed in the past years, with graph-embedding based neural models
such as [2] currently some of the best performing on Knowledge Graphs.
    On the other hand, pre-trained Masked Language Models (MLMs) taking
texts as inputs, such as BERT, have outperformed existing state-of-the-art meth-
ods on various language understanding tasks, and their application to the entity
matching problem has beaten records on benchmark data sets [1,9]. As CH data
often contains large amounts of textual descriptions, the application of MLMs
to the matching task could potentially accelerate development and increase per-
formance.

    We explore how MLM methods can be used to unify four literature metadata
sets from various actors of Quebec’s literary world into a homogeneous knowledge
base. As our source data are mostly in French, pre-trained French language
models are among those leveraged to generate entity pair embeddings for match
prediction. In particular, we focus on Work and Author entities, central types
in literary metadata. We compare MLMs to a string similarity baseline on fully
cleaned and labeled data. We then test language models on various input formats
in order to determine how much data pre-processing and annotation is required
for peak performance. Our key research questions are:

1. How do masked language models compare to rule-based and domain-related
   heuristics in the context of CH data?
2. What is the impact of pre-processing and input formats on MLM matcher
   performance?

The paper is structured as follows. We present an overview of our source data
and target ontology in section 3, our global information extraction, cleaning,
matching and translation process in section 4.1, with particular focus on the
entity matching phase. Our MLMs are described in section 4.2, and our training
sets and baselines in sections 4.3 and 4.4 respectively. We present and analyse
our results in sections 5.


2   Related Work

Alignment of instances between data sets is a well known research problem [1,3,
9, 11, 12, 14]. Initial approaches were mostly rule-based but they require domain
expertise and maintenance in order to be adapted to new data [3]. Probabilistic
matching of instances then remained the primary method for alignment, notably
in Semantic Web applications, as in [14].
    Further development of neural deep learning approaches has seen them ap-
plied successfully for entity matching, with some top performing models using
4       D. Piché et al.

Recurrent Neural Networks with Long Short Term Memory [5, 6]. Recent sur-
veys [11] mention these types of architectures as achieving state-of-the-art per-
formance on benchmark entity matching data sets such as DBLP-ACM and
Walmart-Amazon [4].
    More recently, Natural Language Processing (NLP) techniques using transfer
learning through transformers pre-trained on masked language modeling tasks
demonstrated state-of-the-art performance on language-related downstream tasks.
As entity matching can be seen as the binary classification of two sequences as
identical or not, these models can be easily fine-tuned on this task. Two exist-
ing works [1, 9] using this method have already outperformed existing models
on the Magellan alignment benchmarks. The second, Ditto [9], makes use of
data augmentation and attribute annotation strategies challenging the language
model to learn nuances for embedding similar sequences. Both solutions add a
fully connected layer and a SoftMax classification layer for match predictions on
top of pre-trained English language models (BERT, DistilBERT, RoBERTa or
XLNet).
    In this work, given that our data sources are in French, we propose a matching
architecture based on French pre-trained MLMs. Two MLMs built on RoBERTa’s
architecture are of interest. CamemBERT [10] is trained on the French portion of
the OSCAR corpus, a pre-filtered version of Common Crawl, while FlauBERT [8]
trains on a combination of French sets, including WMT19, OPUS, Wikimedia
and Project Gutenberg.


3     Data overview

Our experiments are performed in the context of a project headed by the Min-
istry of Culture and Communications of Quebec (MCCQ), which aims to create
a knowledge base for Quebec’s literary data, sourced from the domain’s stake-
holders. Data stems from four sets, provided by the Quebec national library and
archives (BAnQ), Messageries ADP (a book distributor), the Infocentre Lit-
téraire des écrivains du Québec (ILE), and Les Éditions Hurtubise, a Quebec
publisher.


3.1   Source records

The provided sets describe literary entities organized in records. Records consist
of book metadata descriptions, with one entry generally describing a specific
edition of a book, its content, physical description, publication and author.
    Our sources present the typical challenges for entity resolution in CH data.
Although the sets have similar scopes, there are minor differences regarding the
content of a single record. A book series may be described in a single record, as is
the case in BAnQ, or be distributed over multiple records, as is the case in ADP’s
data. Conventions for encoding titles and names also vary: some sources remove
leading pronouns, some place last names before first names for authors, some
split titles and subtitles into separate fields, etc. Records have varying degrees
       Masked Language Model Entity Matching for Cultural Heritage Data          5

of quality; some only contain uppercase text, some are cut off after a certain
number of characters. Entity attributes vary, with, for example, BAnQ being
the only set containing authors’ dates of birth. Frequently, attributes defined in
a source’s data scheme are absent a large part of records. Finally, some sources
have separate collections of records for authors and books, while other sources
concatenate author and book information into single records.
    To train our MLM matchers, labeled training sets of positive and negative
matches must be generated. One unique global identifier, the ISBN, is available
across data sets and can be used to generate these sets. We present the generation
and content of these sets further in this section.


3.2   Ontological Model

Our final model uses a linked data structure, defined in an ontology, with data
being stored in RDF triples. As we are working with literary data, we chose
to implement an IFLA Library Reference Model (LRM) [13] based knowledge
graph as a target model.
    LRM is an implementation-agnostic conceptual model for representing li-
brary data, and was conceived to replace a series of previous reference models,
including the Functional Requirements for Bibliographic Records (FRBR) [7].
LRM defines 11 types of entities in a hierarchical structure, with some schema
elements retained from the previous reference models.
    Works, Expressions and Manifestations represent different layers of ab-
straction for intellectual works and their physical manifestations. The Work is
the higher conceptual level, representing the work of art as created by the writer
(the story of “Alice in Wonderland”); the Expression represents the embodi-
ment of that work in a written form (the French translation by André Gagnon);
the Manifestation represents the creation of a series of physical entities that
correspond to published editions of that text (the 2012 edition published by
Hurtubise). The Item is disregarded, as our model is not being developed for
inventory management.
    Nomen entities encompass identifiers, names, titles, terms, descriptors and
subject headings. The existence of this type is justified by the necessity to rep-
resent assignation relationships between Agents and Nomens and identification
of other characteristics of individual Nomens such as schemes and encoding lan-
guage. In the context of fusing data sets using varied classification schemes, this
functionality is crucial.


4     Methodology

We describe the data model in section 4.1 and the structure of our transformer-
based matching model in section 4.2. The structure of and generation strategy
for our labeled training data sets is laid out in subsection 4.3, and heuristic
matching baseline, experiments and metrics in 4.4.
6       D. Piché et al.

4.1   General Architecture for Knowledge Base Extraction
The creation of a unified knowledge base from disparate sources generally in-
volves a set of data processing steps. These steps have an incidence on the per-
formance of the subsequent modules (e.g. entity matching). Particularly, cleaning
attributes and aligning schemas across data sets can help facilitate rule-based
entity matching. However, the success of each of these steps is highly depen-
dent on data characteristics as outlined in section 3.1. We developed a multi-
stage pipeline for extracting, cleaning, enriching, aligning and translating entities
from source records into our LRM-based model, with experiments focusing on
the alignment phase.
    Six main phases compose our pipeline. Records are extracted from sources
and given unique identifiers in Phase 1. Entities contained in records are ex-
tracted in Phase 2. A record typically contains one Work entity, with associ-
ated Expression and Manifestation, one Author and one Publisher. The entities
are restructured into a common intermediate representation based on our LRM
model. For example, a publication description containing "354 p." is assigned
to a Manifestation entity’s page number attribute. In Phase 3 that the con-
tent of attributes is cleaned and standardized. Errors or special filing characters
are identified and removed. Sub-attributes, such as first names and surnames
for names, are extracted. In Phase 4, entities are enriched through external
resources; language strings are replaced with links to WikiData language pages,
place names are replaced with place entities with unique codes and organized into
hierarchies, etc. Classes of equivalent entities are identified in Phase 5. These
equivalence classes’ canonical representations, generated from merging entities
that make up the classes, are translated into the target graph in Phase 6.

The matching phase in more detail. Conceptually, the task is to identify
clusters of local entities representing the same real-world entity, with the entity
matcher - the MLM - determining whether representations of two clusters imply
these clusters should be merged. Once a cluster is newly modified, it is then
compared to other clusters once more to check for new possible matches. This
process allows for gradual integration of further data sets. Once the pool of
clusters reaches a stable state (no link between clusters can be found), translation
to the final graph can start.

4.2   Masked Language Model for Entity Matching
Our architecture is inspired by recent works [9] and [1], but differs by the nature
of data (database records, semi-structured data), the language (French) and
our experiments on the impact of input formats and pre-processing strategies.
The MLM is enriched with a fully connected layer and a SoftMax classification
layer added in the output layers. Fine-tuning and evaluation is performed on the
train, test and validation sets presented in section 4.3. The pre-trained models
selected for generating sequence embeddings for entities are CamemBERT [10]
and FlauBERT [8], both based on RoBERTa. Both models are pre-trained on
       Masked Language Model Entity Matching for Cultural Heritage Data             7

a masked language modeling task on large French corpora. We use parameters
from previous works [1] for batch size (32) and learning rate (3e-5).

Input format. BERT-like language models, such as the ones we use, take text
as input, composed of one or two sequences, and, for a classification task, a
label to be predicted. In our case, each entry represents a pair of entities to be
aligned, composed of two entity strings and a label identifying whether they are
to be aligned or not. Our labeled sets represent entries on one line, with a tab
separating each of the three elements: the string for entities 1 and 2, and the
label.

    Table 1. Input formats for different pre-processing and annotation strategies

           Pre-processing and annotation        Structure
         1 RegEx cleaning and data annotation [C] attribute1 [V] value1 [C]
           with LRM attribute names, values attribute2 [V] value2 [...]
           and special tokens                   [C] attributeN [V] valueN
         2 Data annotation with original        [C] attribute1 [V] value1 [C]
           schema names, values                 attribute2 [V] value2 [...]
           and special tokens, without cleaning [C] attributeN [V] valueN
         3 Data annotation with original        attribute1 value1
           schema names and values,             attribute2 value2 [...]
           without cleaning or special tokens   attributeN valueN
         4 Raw data values without              value1 value2 [...] valueN
           cleaning or annotation



     We experiment with four input formats differing in pre-processing and anno-
tation strategies, in our training sets. These input formats concatenate extracted
attribute values into strings as entity representations. Annotation strategies add
special tags (e.g. [C]) that indicate the schema/meaning of a given text token
to help the matcher identify the various elements in the string. The first format
is based on what was proposed by Li et al, 2020 [9]. The data in this format
is cleaned with regular expressions normalizing punctuation, removing special
characters and structuring strings in the same way (e.g. firstname then last-
name) among data sets. The data is restructured to follow our LRM schema.
Input strings consist of alternating pairs of attribute names and values, separated
by special tokens indicating whether the following substring is the name of an
attribute ([C]) or its value ([V]). Attribute names are one or two characters long:
t for title, st for subtitle, a for Author name, etc. The second format is similar,
but with the special tokens removed. Attribute names and values are separated
by a space only. The third format does away with cleaning and restructuring.
Entries are created from original attribute names and values, only separated by
a space. Attribute names can thus be a textual label or a standardized field iden-
tifier, such as a MARC21 code, depending on the source. The final input format
omits attribute names and cleaning entirely, and is a concatenation of original
8         D. Piché et al.

attribute values only. Examples of complete entries for these formats are shown
in Table 2.


Table 2. Examples for input formats of a positive match, with sequence 1 from BAnQ
and sequence 2 from Hurtubise ([C]: Column identifier token, [V]:Value identifier token,
t: title, a: author, 245a: MARC21 subfield for title, etc.)


    #           Value
    1   Seq 1 : [C] t [V] Être un héros [C] e [V] La Courte échelle [C] st [V]
                des histoires de gars [C] lp [V] Montréal [C] np [V] 218
        Seq 2 : [C] t [V] Être un héros [C] ap [V] 2011 [C] a [V] Simon Boulerice
                [C] e [V] La Courte échelle [C] st [V] des histoires de gars
                [C] lp [V] Montréal [C] np [V] 218
    2   Seq 1 : [C] 245a [V] Être un héros : [C] 245b [V] des histoires de gars /
                [C] 260b [V] La Courte échelle, [C] 300a [V] 1 ressource en ligne
                (218 p.) : [C] 260a [V] Montréal :
        Seq 2 : [C] 0 [V] Être un héros : des histoires de gars
                [C] 2 [V] Boulerice, Simon [C] 3 [V] La Courte échelle, 2011, 218 p.
                [C] 1 [V] 2011 [C] 4 [V] Montréal
    3   Seq 1 : 245a Être un héros : 245b des histoires de gars /
                260b La Courte échelle, 300a 1 ressource en ligne (218 p.) :
                260a Montréal :
        Seq 2 : 0 Être un héros : des histoires de gars 2 Boulerice, Simon
                3 La Courte échelle, 2011, 218 p. 1 2011 4 Montréal
    4   Seq 1 : Être un héros : des histoires de gars / La Courte échelle,
                1 ressource en ligne (218 p.) : Montréal :
        Seq 2 : Être un héros : des histoires de gars Boulerice, Simon La Courte
                échelle, 2011, 218 p. 2011 Montréal




4.3     Training and evaluation sets

We need evaluation sets for the entities we seek to align, in our case Works and
Authors. Each set used, shown in Table 3, is comprised of pairs of entities with
labels 1 for positive pairs and 0 for negative pairs.

    Positive pairs for Works are identified using the only unique ID available
across sources: the ISBN of the Manifestations associated with the Works. The
cardinality of the relations between Works and Manifestations allots the inference
that Works having Manifestations with the identical ISBNs are refer to the same
entity. As for Authors, without a unique identifier (only one source contains ISNI
or VIAF IDs), we must assume that two Author records that have written the
same Work and have similar names (using Levenshtein ratio 1) are the same.
        Masked Language Model Entity Matching for Cultural Heritage Data              9

        Table 3. Descriptive statistics of our training, validation and test sets


      Entity    Train (80%)    Valid (10%)     Test (10%)    Positives   Negatives
       Work       44 573          5 572          5 574        18 573      37 146
      Author      34 645          4 331          4 332        14 436      28 872




                                                                        
                                               string edit distance
       Levenshtein(str1, str2) =      1−                                     ∗ 100   (1)
                                             max(len(str1), len(str2))

    For negative pairs, pairs of records are chosen at random. If two selected
records do not have a shared ISBN and there is a large edit distance between
their names or titles or they have similar titles yet fundamentally incompatible
characteristics such as different volume numbers, then they are not considered to
be identical entities in the real world. To avoid too great an imbalance between
the amount of positive and negative pairs, we limit the amount of negatives
to twice the number of positives. Negative and positive pairs are acquired and
separated into training, validation and tests sets containing identical proportions
of positive and negative pairs.
    As ISBNs were used as a key for the creation of the training, validation and
test sets, they cannot be part of entity encodings, as since the task at hand is
finding pairs of entities that do not have shared unique identifiers, this would
unduly influence our results.



4.4    Baselines and evaluation metrics


Our baseline alignment method is based on string similarity between attributes
describing the entities. Using only entity names may be problematic, as some
non-matches may share more similar names than some true matches (as shown
in Fig. 1, which plots Levenshtein ratios. 1 between Work titles). The left fig-
ure shows a global view of ratios, while the right one illustrates the overlap
between similarities of positive and negative pairs in the 60-80 range that make
determining a clean threshold impossible.
    Relying only on titles will cause false positives; comparing the names of the
authors of each candidate entity eliminates these cases. If two works have very
similar author names in addition to having similar titles, then the rule-based
method considers them to be a match. Similarly, authors are matched if they are
similarly named (L1 > 95) and wrote similar books (L1 > 90). Standard recall,
precision, accuracy and F1 score metrics are employed. Results are presented in
section 5, examined in section 6.
10                    D. Piché et al.

          0.10                                                                     0.010
                        Positive                                                                                                    Positive
          0.08          Negative                                                   0.008                                            Negative

          0.06                                                                     0.006
Density




                                                                         Density
          0.04                                                                     0.004

          0.02                                                                     0.002

          0.00                                                                     0.000
                 20     30     40   50     60       70   80   90   100                     40   45   50   55 60 65 70          75     80       85
                                     Levenshtein ratio                                                     Levenshtein ratio


Fig. 1. Density estimate of Levenshtein ratios of titles of identical (positive) and dis-
tinct (negative) Works using format 1 (Table 1)


5            Results
Table 4 shows our experimental results for each of our research questions. In sec-
tion A, we compare the performance of our best matching model (determined in
later experiments B, C and D) with our heuristic-based baseline on completely
cleaned, LRM-structured data, annotated with special tokens (see example in
Table 2). These results show MLMs combined with SoftMax classifiers can vastly
outperform domain-aware rules, while illustrating that Author matching is triv-
ial in comparison with the Work matching task; a more challenging test set
is required for better comparisons. However, our best heuristics are unable to
achieve this perfect result, with MLMs having better performance on edge cases.

    Training separate models for different entity types, however, uses more com-
putational resources. We test whether a single model trained on joint Author-
Work sets can reach similar levels of performance. Section B of demonstrates that
a single model performs just as split models. Section C compares the performance
of both pre-trained French MLMs. CamemBERT outperforming FlauBERT on
every metric except precision, we use this model on all input formats 2 in section
D. Given the equal or higher F1 scores (Table 4’s section D) for drastically re-
duced pre-processing, these costly steps may be omitted without significant risk.
More pre-processing steps require developing domain-specific rules with poor
reusability and require active maintenance in the case of addition of data. Our
results show that MLMs allow us to avoid this problem for entity matching in
our context, as shown by format 4’s results.


6            Conclusion and Further Research
We propose a MLM entity matching model for matching digital cultural records
expressed in French, confirming that transformer-based pre-trained masked lan-
guage models are a powerful tool for entity matching for cultural heritage data.
We conclude that high performances can be achieved through fine-tuning even on
very limited, unprocessed and heterogeneous labeled data. Even if our heuris-
tic methods obtain very high scores, their comparable labour cost and poor
       Masked Language Model Entity Matching for Cultural Heritage Data        11

                           Table 4. Aggregated results

 A. Best matcher versus baseline                  Evaluation on test set
 Model Type    Peak Ep.    Entity            F1     Recall Precision Accuracy
 Rule-based                Author        0.9955     0.9965     0.9945     0.9970
                              Work       0.9119     0.8407     0.9962     0.9458
 CamemBERT            4    Author       0.9986     0.9979     0.9993     0.9991
                      4       Work      0.9978     0.9968     0.9989     0.9986
 B. Joint Author-Work matcher
 Model name    Peak Ep. Max Ep.
 Rule-based                              0.9501     0.9088     0.9954     0.9682
 CamemBERT           10      10         0.9991     0.9988     0.9994     0.9994
 C. MLM arch. on Author-Work set
 Model name   Peak Ep. Max Ep.
 CamemBERT          10        10        0.9991      0.9988    0.9994     0.9994
 FlauBERT           10        10         0.9989    0.9991      0.9988     0.9993
 D. Pre-processing formats
 Input format   Peak Ep. Max Ep.
 1                    10      10         0.9991     0.9988     0.9994     0.9994
 2                     4      10         0.9992     0.9988    0.9997      0.9995
 3                     4      10         0.9993     0.9991     0.9994     0.9995
 4                    10      10        0.9994     0.9994      0.9994    0.9996




reuse make MLM matching models a competitive alternative, leaning match-
ing rules automatically. The use of heterogeneous data models has little impact
on MLM performance in our tests, facilitating integration of new data sets. Fur-
thermore, our results show that pre-processing does not improve MLM matching
over unprocessed data, meaning development cost may be significantly reduced.
Performance differences between unprocessed data sets and those annotated as
suggested in Li et al. [9] were minimal; tagging of values with column names and
special tokens may not yield performance substantial improvements.

    One limitation is the use of ISBNs for positive pair generation. Correlated
ISBNs mean correlated publication data; this may hamper the model’s ability
to correctly match works published in different places, times or languages. As
positive pair generation for authors also relies on shared publications, they may
suffer the same issue. Another possible bias is introduced by negative pair gener-
ation, as in order to generate high confidence negative matches, very strict rules
are employed, precluding the presence edge-cases training sets.

    In future work, we will further investigate the results of the English MLM
for our task and we will try to replicate our results on data pre-processing and
annotation on other entity matching data sets, rework negative pair annotation
for more challenging examples, as well as test competing graph-based entity
clustering methods.
12      D. Piché et al.

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