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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>Recommender Systems, October</journal-title>
      </journal-title-group>
      <issn pub-type="ppub">1613-0073</issn>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>Contrastive Learning for Multilingual Job Recom mendation</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Daniel Deniz</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Federico Retyk</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Laura García-Sardiña</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Hermenegildo Fabregat</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Luis Gasco</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Recommender Systems</institution>
          ,
          <addr-line>Deep Learning, Contrastive Learning, Multilingual Semantic Textual Similarity</addr-line>
          ,
          <country>Job Title Ranking</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2024</year>
      </pub-date>
      <volume>1</volume>
      <fpage>4</fpage>
      <lpage>18</lpage>
      <abstract>
        <p>The transformative power of artificial intelligence is revolutionizing the talent acquisition domain. Automatic job recommendation systems are emerging as a key component of this transformation. This study presents a new multilingual job recommendation solution that leverages combined unsupervised and contrastive learning to efectively model the semantic similarity between job titles across 11 languages. Our approach pre-trains a multilingual encoder using unsupervised learning on co-occurrence information of skills and job titles, followed by fine-tuning via contrastive learning on a dataset of similar and dissimilar job pairs based on the European Skills, Competences, Qualifications and Occupations (ESCO) taxonomy. This sequential learning strategy significantly enhances representation quality. Our novel multilingual job title encoder achieves strong ranking results across all languages, with 4.3% improvement in mean Average Precision (mAP) for English compared to previous state-of-the-art monolingual solutions. The proposed method also ofers very good cross-lingual capabilities, enabling the ranking of jobs in diferent languages with improved alignment and uniformity properties in the representation space.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <sec id="sec-1-1">
        <title>In today’s fast-paced job market, organizations face an</title>
        <p>
          increased competitive pressure to find and retain the best
suitable skilled candidates [1]. The introduction of
Information and Communication Technologies (ICTs) in
Human Resources (HR) processes in recent years, and
especially with more recent advancements in artificial
intelligence (AI) has helped in alleviating this pressure
in time-sensitive recruitment processes, especially those
that have relied heavily on human specialists [2]. The
integration of AI and machine learning has been
transforming the recruitment process by allowing companies
to rapidly process and analyze large amounts of candidate
and supporting data-driven decisions to optimize and
refine recruitment strategies [
          <xref ref-type="bibr" rid="ref12">3, 4</xref>
          ]. A key aspect of this
transformation is the emergence of automatic job
recommendation systems. Job seekers also benefit from
these innovations, as they can find better tailored job
recommendations within the large amount of job postings
available on online platforms, making it easier for them
to find and apply to opportunities that suit their skills
and their career goals.
        </p>
      </sec>
      <sec id="sec-1-2">
        <title>Driven by recent technical advancements in semantic textual similarity (STS), automatic job recommenda</title>
        <sec id="sec-1-2-1">
          <title>RecSys in HR’24: The 4th Workshop on Recommender Systems for</title>
        </sec>
        <sec id="sec-1-2-2">
          <title>Human Resources, in conjunction with the 18th ACM Conference on</title>
          <p>Workshop
Proce dings
htp:/ceur-ws.org
ISN1613-073</p>
          <p>CEUR</p>
          <p>Workshop Proceedings (CEUR-WS.org)
manager
gerente
directour
engineer</p>
          <p>Cosine Similarity</p>
          <p>Loss Function
Train Job Title Encoder
(Multilingual) Stage 1</p>
          <p>Trained weights</p>
          <p>Fine-tune Job Title Encoder
(Multilingual)</p>
          <p>Stage 2</p>
          <p>Loss Function</p>
          <p>Normalized
Temperature-scaled
Cross Entropy</p>
          <p>Job Title Encoder</p>
          <p>Text Ranking
software
engineer
application
programmer
animal
osteopath
textile
inspector
to build a multilingual Job Title Encoder for intelligent job
recommendation. The process starts from a pre-trained
encoder, and we propose two steps: 1) Unsupervised training:
we define target representations ( 1) for every job based on
jobs into these representations. 2) Contrastive training: we
use synonyms and relations from ESCO ( 2) to fine-tune the
encoder with contrastive learning techniques.
tion systems are increasingly relying on this task to
develop matching algorithms that accurately pair job
vacancies with candidates based on their skills and
experience [5, 6, 7]. Novel STS approaches leverage neural
networks to automatically generate vector
representations that efectively capture the semantic nuances of text
elements, thus significantly enhancing matching
performance compared to traditional methods [8].</p>
        </sec>
      </sec>
      <sec id="sec-1-3">
        <title>The methods for training encoders for STS can be ods, and unsupervised methods that do not require any</title>
        <p>CEUR</p>
        <p>ceur-ws.org</p>
        <p>© 2024 Copyright for this paper by its authors. Use permitted under Creative Commons License broadly divided into two approaches: supervised
methlabeled data. Examples of unsupervised procedures ap- ters [17, 18]. However, these approaches sufer from data
plied to the HR domain were proposed by Zbib et al. [6] sparsity and the cold start problem, especially when
makand Lavi et al. [9]. They do not rely on human anno- ing recommendations in the case where a user has few
tations, and instead, they use noisy data automatically interactions with other items [19].
collected from resumes and job listings. Conversely, su- Recent advancements in this field leverage techniques
pervised methods rely on large amounts of labelled data from machine learning, natural language processing
to train, which can be sometimes hard to obtain in terms (NLP), and AI. The incorporation of content-based
emof quality and quantity [10]. Contrastive learning has bedding strategies in recommendation systems has led
shown very strong results for STS as a technique that to the development of eficient and reliable item retrieval
helps improve the learned representations and increase methods, ofering significant benefits in terms of
generthe training data eficiency [ 11, 12, 13]. alization, scalability, and cold start capabilities [20].</p>
        <p>Our paper builds upon these advances and presents
a multi- and cross-lingual intelligent job recommenda- 2.1. Content-based Job Recommender
tion solution that relies on STS to measure the
similarity between job titles across 11 languages (English, Ger- Systems
man, French, Spanish, Italian, Dutch, Portuguese, Polish, In the existing literature, numerous studies on
Japanese, Chinese, and Korean). We introduce a novel embedding-based recommender systems are based
two-stage methodology for training an encoder focused on Deep Learning techniques. For instance, Zhao et
on job title semantic similarity for text ranking (see Fig- al. [20] proposed a Convolutional Neural Network
ure 1). (CNN) with an attention layer as a key component in</p>
        <p>In the first stage we pre-train a multilingual encoder their recommendation system to encode job titles, skills,
following an unsupervised approach using noisy data and other context-aware elements into a dense-vector
automatically collected from job postings and resumes. representation for ranking candidates with job vacancies.
In the second stage we fine-tune the encoder via con- In [7], authors propose a method to train a job title
trastive learning on a dataset with pairs of relevant and encoder in which they fine-tune a pre-trained language
non-relevant jobs based on the European Skills, Compe- model with an auxiliary classification loss, using job-skill
tences, Qualifications and Occupations taxonomy (ESCO) co-occurrence statistics extracted from vacancies. Zbib
[14, 15]. The ESCO occupations taxonomy is a hierar- et al. [6] first build dense-vector representations for jobs
chically structured standard classification that organizes based on their distribution of skills (also extracted from
jobs into groups and concepts based on their similarity vacancies), which are expected to encode the semantics
in terms of skill level and required specialization. For of the job. Then, they train the encoder to map job title
instance, ESCOXLM-R [16] work has demonstrated the surface forms to such representations. At inference time,
efectiveness of using the ESCO taxonomy for adapting a the encoder only sees the surface form of (potentially
multilingual language model to the job market domain. new) jobs, and cosine similarity is used to measure the</p>
        <p>We study the efectiveness of the proposed methodol- semantic distance between encoded occupations. These
ogy by training various encoders with diferent backbone approaches are based on the premise that skills are
esarchitectures (Transformer-based vs. CNN-based) and sential to understand the meaning of a job, and therefore,
original pre-training objectives (semantic-similarity vs. semantically similar job titles should exhibit similar skill
masked language modeling). We find that trained en- profiles.
coders outperform state-of-the-art benchmarks on the Similarly, [21] develops a novel approach to train an
job title ranking task. Moreover, the proposed solution encoder derived from BERT [22] to link skills with
occushows very good multi- and cross-lingual capabilities, pations by leveraging co-occurrence information via a
achieving ranking performance results for each language contrastive learning method.
that are remarkably close to English, the language with
the best results. Notably, the encoders exhibit strong 2.2. Contrastive Learning methods for
alignment and uniformity properties in cross-lingual
evaluations. Semantic Textual Similarity</p>
      </sec>
      <sec id="sec-1-4">
        <title>In recent years, contrastive learning has emerged as a</title>
        <p>2. Related Methods powerful technique for learning high-quality sentence
embeddings. This technique was initially popularized in
Job recommendation systems are a vital component of computer vision [23]. It focuses on learning
representamodern employment platforms that help match job seek- tions by distinguishing positive pairs (similar data points)
ers with relevant opportunities. Traditional systems against negative pairs (dissimilar data points). Models
are based on matrix factorization and collaborative fil- are trained to bring the representations of positive pairs
caltoivseerptaoigrsetfhaertrhwerhialpeaprutsihninthgetehmerbeepdrdeisnegntsaptaiocnes[2o4f,n2e5g]-. NJooibssy+(SEkNil)ls PDVo-Dc2BVOeWc acmecnaognuianngteaeenrrt</p>
        <p>Contrastive learning techniques can help alleviate the
amnainsocteroinpySTpSrotabslekms[a2n6,d1i1m, 1p3ro].vTehreeparneisseontrtoatpiyonprpoebrlfeomr- T(Jr1ao0nbslTlaainttilgoe.sn)s rmeMpurleatispleinanugtaxutiailolianjroyfbosr dmgeirneaergnceiatnnogteueeerrr
refers to the issue where the vector representations do
not uniformly occupy the embedding space. Instead, they Figure 2: Creation of Multilingual Dataset from Noisy Skills
might cluster in a narrow cone of the space, leading to an (ing1)pfroorceUsnssfuopre
rv1iseisdstirmaiinlainrgtoofthJoeboTnietledeEpniccotedderi.nT[h6e].builduneven distribution that diminishes the model’s ability
to distinguish between diferent data points [ 27, 28].</p>
        <p>The adaptation of contrastive learning to NLP has led
to the development of several solutions in the context of the multilingual encoder obtained in the previous step.
STS for measuring how closely the meaning of two sen- In this case, we use pairs of similar and dissimilar jobs
tences align. Works in this area often rely on pre-trained derived from the ESCO taxonomy.
language models, such as BERT [22] or RoBERTa [29], as Below we describe how the data used in the diferent
the backbone for generating initial sentence embeddings stages of this approach was prepared. Then, we describe
[30]. As in SimCSE [11] or ConSERT [31], contrastive the procedure for training the neural network in each
learning is then applied to fine-tune these embeddings, stage to build the Multilingual Job Title Encoder for
improving their ability to capture semantic similarity, in automatic job title ranking.</p>
        <p>STS tasks.</p>
        <p>The design of the loss function is crucial in contrastive 3.1. Data Preparation
learning, and has undergone a significant evolution from
Siamese pair loss [32], triplet loss [33], to alternatives
with multiple negatives such as N-pair loss function [34],
or NT-XENT (Normalized Temperature-scaled Cross
Entropy) [23], which can lead to improved representation
learning [11].</p>
        <p>In this work, we leverage the relationship between
jobs and skills to build auxiliary representations that
later guide the training of the multi- and cross-lingual
job title encoder. Then, we fine-tune the encoder using
a contrastive learning loss with multiple negatives to
improve matching and text ranking between candidates
and job vacancies.</p>
      </sec>
      <sec id="sec-1-5">
        <title>In the first place, we build the diferent datasets that will take part in the training of the multilingual encoder. These datasets have diferent origins, structure, and properties.</title>
        <p>We construct  1, a multilingual dataset of job
positions by linking the surface form of job occupations to a
dense-vector representation. These representations are
based on the distribution of noisy skills related to each
job title collected from a collection of job postings and the
work experience sections of anonymized resumes. In this
dataset we include data from 11 diferent languages:
English (en), German (de), Spanish (es), French (fr), Italian
(it), Japanese (ja), Korean (ko), Dutch (nl), Portuguese
(pt), Polish (pl), and Chinese (zh). Bear in mind that we
3. Our Approach do not require any manual annotation for building this
dataset (unsupervised).</p>
        <p>In this work, we propose a novel approach for training The other dataset is  2, which we compile as a
cola semantic textual similarity solution for intelligent job lection of multilingual pairs of similar and dissimilar
recommendation. Then, we describe how we build an job titles, based on relations extracted from the ESCO
encoder model for multilingual job title ranking that taxonomy. This dataset includes the same languages as
operates across 11 languages. the ones described before, except for the three Asian</p>
        <p>Our main contribution is the two-step training pro- languages (Japanese, Korean, and Chinese) since they
cedure depicted in Figure 1. In Step 1, similarly to the are not included in ESCO. Our experiments show that
process presented in [6], we use doc2vec [35] and the the contrastive learning step benefits these languages
skills distribution for every job title to create auxiliary through cross-lingual transfer despite not being included
dense-vector representations. These are in turn used to in the training data of that stage.
train an encoder that maps the surface form of each job
title to its reference doc2vec representation. Since auxil- 3.1.1. Job Title Similarity from Noisy Skills Dataset
iary representations encode language-agnostic semantics,
we expose the encoder to job surface forms in various The  1 dataset described above is used to learn the
selanguages, all mapped to the same point in the representa- mantic relations between job occupations based on the
tion space, resulting in a multi- and cross-lingual encoder. co-occurrence distribution of skills for each job title. The
Then, in Step 2, we use contrastive learning to fine-tune knowledge provided by the skills is transferred to an
ebnetcwodeeern, ethneasbeli njogbuosctcoucpaaptitounres tbhaesesdemoanntthiceisrims uilrafraictye 0 - 1 - 2 - 6 7 - 8 - 9
forms. SGurobu-mpajor 61 - 62 63</p>
        <p>The process of creating this dataset consists of two Minor Group 621 - 622
steps. In the first one, we start from a collection of job
titles and associated noisy skills for each occupation. We Unit Group 6221 - 6222 - 6223 6224
consider these skills as noisy since they are retrieved in Occupation 6223.1 + 6223.2 +
agnlisahujtoobmpaotsetdinwgsayanbdyasnimonpylmesizteridnrgesmuamtcehs.inTghefrdoamtaEsent-, NOaccrruopwation 6223.2.1 +
sourced from proprietary real data, covers a broad range Figure 3: ESCO groups for job occupations. For creating the
of industries, including manufacturing, healthcare, tech, positive pairs, we do all possible combinations of synonyms
ifnance, or banking, among others. Next, we follow a for each occupation concept. Also, we retrieve positive pairs
similar procedure to that presented in Zbib et al. [6], us- from parent occupations and from other occupations from
ing PV-DBOW Doc2vec to create a dataset with pairs the same Unit Group. Negatives are retrieved from concepts
of job titles and fixed-length vectors (512 dimensions). outside of the selected for the positives ones.
These vectors are the auxiliary representations that will
be used as synthetic targets in the first training stage. We
refer to the resulting dataset as  1 . minor, sub-major and major groups, based on their
sim</p>
        <p>As shown in Figure 2, the next step is to expand the ilarity in terms of the skill specialization and skill level
pairs of job titles and fixed-length vectors to the other required for the job. ESCO therefore includes
occupalanguages. To do this, we translate a subset of the English tions located at level 5 and lower of this classification
job titles (starting with around 2.3 Million) to the target structure. All occupation concepts contain one preferred
languages using Machine Translation1. Afterwards, we label and a number of alternative labels.
include in the previous dataset new pairs with the surface We use these hierarchically structured groups of
oclexical form of the resulting translations, but with the cupation concepts to extract a collection of multilingual
same vector representation as the corresponding source (positive and negatives) job title pairs (see Figure 3).
English. We create the positive pairs by including all possible</p>
        <p>The same job title in diferent languages will have the combinations without repetition of the preferred and
alsame auxiliary representation (Eg. manager (en), gerente ternative labels of each occupation concept. In addition,
(es), and directeur (fr) will share the same doc2vec vector). to ensure lexical diversity among similar jobs, we
generBy this, we aim to foster the multi- and cross-lingual ate a small subset of positive pairs by retrieving labels
capabilities of the proposed solution for text retrieval in from parent occupations (30%) only if the concept is a
Human Resource applications based on job title semantic narrow occupation. Finally, we retrieve more positive
similarity. We refer to this multilingual dataset as  1. pairs from other occupations of the same Unit Group
The final dataset has 14.5 Million English job titles and (10%2).
an average of 2.3 Million job occupations per each of the Regarding the negative pairs, we retrieve the samples
other languages. for each occupation concept from labels of a diferent
Major Group (50%), from another Sub-major Group (25%),
3.1.2. Similarity Pairs from ESCO Dataset from another Minor Group (15%), and from another Unit
Secondly, we prepare the  2 dataset used for further Group (10%).
ifne-tuning the encoder using multilingual pairs (English, The process described above is performed for each
German, French, Spanish, Italian, Dutch, Portuguese, and language independently, and once more to create
crossPolish) of similar and dissimilar job titles, aiming to ex- lingual pairs selecting job occupations from any language.
tract relations between job occupations that can help The final dataset includes around 136 K of diferent job
improve the matching performance for automatic job occupations, detailed into around 1 M diferent positive
recommendations. pairs (anchor + positive elements) and about 128 negative</p>
        <p>
          We build this collection of pairs using the ESCO Tax- samples per unique job title.
onomy (version 1.2.0). The ESCO occupations taxonomy
is built on ISCO-08 [
          <xref ref-type="bibr" rid="ref1">36</xref>
          ], a four-level hierarchically struc- 3.2. Training Methodology
tured classification that can be used to classify jobs into
436 unit groups. These groups are the most detailed ones Below, we describe the end-to-end process carried out to
of the classification structure, and are aggregated into train the model for multilingual job occupation ranking.
1Google Translate
2These two percentages are with respect to the number of positive
pairs from each occupation concept.
contable
        </p>
        <p>accountant
tecnico
del eluci
technicien
lumière
técnicade
restauração
abgeordnete
directorade
hotel
gerentede
alojamiento
treedoctor
kierownikds
operacyjnych
huishoudhulp
clerical
assistant
3.2.1. Unsupervised training from Noisy Skills</p>
        <p>representations
the batch size.</p>
        <p>First, we train the multilingual encoder to align the
output representation for each job occupation with the
doc2vec auxiliary representation generated in  1</p>
        <p>. With
this aim, we train the encoder receiving as inputs pairs
of job title (  ) and fixed-length auxiliary embedding (   )
from  1. In Equation 1 we show the cosine similarity
function used for training the model based on the
representation generated from distribution of noisy skills
related to every job, where ℎ refers to the output of the
model after processing the surface text form   , and  to</p>
        <p>1
 =1
ℒ
= −
∑ (ℎ
 ,   )</p>
        <p>(1)
3.2.2. Contrastive Learning from Similarity Pairs</p>
      </sec>
      <sec id="sec-1-6">
        <title>In the second stage, we fine-tune the multilingual en</title>
        <p>coder following a contrastive method using a NT-Xent
loss function without in-batch negatives (see Equation 3).</p>
      </sec>
      <sec id="sec-1-7">
        <title>This function uses several negative pairs for each anchor</title>
        <p>sample, which helps the model to better discriminate
between similar and dissimilar examples, and provides
more stability during training (see Figure 4).</p>
        <p>In the following (  ,  
that are fed as input to the
+,  ,1.. ) represents the tuples
−
model during training.  
refers to the anchor element,  + to the positive sample,
−
and  ,1.. to each negative element. On the other hand,
 refers to the output embedding of the model for a
particular input, resulting in (  ,  
+,  ,1.. ).  stands for the
−
number of negatives per anchor element,  is equal to the
batch size, and  is the temperature value used in the
function. To compare vectors, we use the cosine similarity
( ) function.</p>
        <p>(, ) =  (,)/
ℒ = −
∑ log (

1
 =1
 (  ,  +)</p>
        <p>(  ,  +) +∑=1  (  ,  ,−)
)
(2)
(3)</p>
      </sec>
      <sec id="sec-1-8">
        <title>The temperature  calibrates the intensity of the energy</title>
        <p>to push away the representation of the negative pairs
with respect to the anchor and positive element. During
training, the tuples of inputs are built dynamically from
the collection of positive and negative pairs of  2.</p>
      </sec>
    </sec>
    <sec id="sec-2">
      <title>4. Results and Discussion</title>
      <p>In this Section, we describe the implementation details
and report on results obtained from experiments using
the proposed methodology for training a multilingual
encoder to develop an intelligent job occupation
recommendation solution. First, we introduce the Multilingual
Language Models selected to study the proposed approach,
these architectures are studied in terms of their eficiency
(performance on job title ranking vs. model size).</p>
      <sec id="sec-2-1">
        <title>Next, we do an ablation analysis of the diferent stages</title>
        <p>for training the model with the introduced solution to
assess the benefits that each stage provides. Finally, we
analyze the performance of the trained encoder for
crosslingual job title ranking.</p>
        <p>To evaluate the matching performance of the proposed
method, we use the English job titles similarity dataset3
from Zbib et al. [6]. This set includes more than 2,500
job occupations distributed between query and corpus
document elements. Each pair of query-document is
labeled for binary relevance. We replicate this dataset for
the other languages by using Human Translation (de,
fr, ja, and zh) or Machine Translation (for the
remaining languages). These datasets are publicly available at
GitHub4.</p>
      </sec>
      <sec id="sec-2-2">
        <title>We evaluate models using the Mean Average Preci</title>
        <p>
          sion (mAP) of the output of the ranked lists. We use the
trec_eval software library to compute this metric 5.
Architecture approach using the selected architectures. We start with
Pm.UMSuEl-tCi.NMNP[N3e7t][
          <xref ref-type="bibr" rid="ref3">38</xref>
          ] comparing the evaluation performance with respect to
XMLuMlt-i.REo5BELRarTgae[[3490]] other models without any fine-tuning. We observe that
EB5ERMTi†stral 7B Instr. [
          <xref ref-type="bibr" rid="ref6">41</xref>
          ] pre-trained models without any additional fine-tuning
mUSE-CNN (ours) struggle to match the performance of fine-tuned
alternaPX.LMMu-lRtio.BMEPRNTeat ((oouurrss)) tives in job title similarity ranking. Even the E5 Mistral 7B
Instruct fails to outperform the fine-tuned BERT model
TJoabbTleitl1e Ranking comparison. Mean Average Precision (mAP) on English despite having 64 times more parameters.
results are shown. The English test set is from [6]. The test Our method achieves the best results, with 0.7386
sets for the other languages are built by translating them from mAP (XLM-RoBERTa) for English, which is 4.3% higher
the English one. Result with † is from our previous work in [6]. compared to the current state-of-the-art on the English
We highlight in bold the candidate architecture with the best job title similarity test set with monolingual BERT model
average results on all languages. In addition, we highlight the from [6]. In addition, we get the best average results for
best result for each collection of languages. AvgEU={de, es, fr, all languages with 0.6900 mAP using the XLM-RoBERTa
it, nl, pl, pt}. AvgAS={ja, ko, zh}. architecture.
        </p>
        <p>We observe that the best results for European
languages (de, es, fr, it, nl, pl, pt) are obtained with the
4.1. Text Ranking with Multilingual ifne-tuned Transformer-based architectures. Also, the
Encoder XLM-RoBERTa architecture obtains the best results on
the Asian languages (ja, ko, zh). We select this
architecWe perform an analysis of state-of-the-art Multilingual ture as the best candidate for building the multilingual
Language Models by testing them on text ranking for job intelligent job recommendation system.
title recommendation. In particular, we selected three We also find that the eficient mUSE-CNN encoder
candidate architectures based on their size in terms of pa- delivers competitive results with significantly lower
comrameters and their zero-shot performance on the ranking putational costs, making it an optimal choice for
deploytask. ment in resource-limited environments. Refer to
Ap</p>
        <p>It is worth noting that in this paper, our aim is not pendix A for details on the configuration for training the
solely to identify the base model with the best results, but selected encoder architectures.
also to study the efectiveness of models in terms of their
size and computational cost, with the goal of providing 4.2. Ablation Analysis
the practitioner with a practical guide for accuracy vs.
eficiency trade-ofs. In the ablation analysis we examine the contribution of</p>
        <p>
          With that in mind, we select two Transformer-based every stage of the proposed approach to the final ranking
architectures: XLM-RoBERTa [
          <xref ref-type="bibr" rid="ref4">39</xref>
          ] and Paraphrase Mul- performance of job recommendation.
tilingual MPNet [
          <xref ref-type="bibr" rid="ref3">38</xref>
          ]. Both architectures have around First, we carry out the pre-training of the selected
278 M of parameters and are based on XLM-RoBERTa architectures solely with the first training stage (see
base models. The main diference between them is that §3.2.1) on  1. In Table 2 we observe how the most
simXLM-RoBERTa is pre-trained on multilingual masked ple architecture mUSE-CNN achieves very competitive
language modeling objective, while Paraphrase Multilin- results compared to the Transformer-based alternatives
gual MPNet is a multilingual model that has been distilled for all languages. In addition, the performance in English
from the monolingual MPNet v26 model, a sentence em- (0.7028) is comparable with the results presented in Zbib
bedding model built from MPNet [
          <xref ref-type="bibr" rid="ref7">42</xref>
          ] and fine-tuned on et al. [6] (0.7077).
sentence pairs. Next, we do an additional ablation by training the
        </p>
        <p>
          On the other hand, we choose the Multilingual Uni- architecture directly on the second training stage (see
versal Sentence Encoder model CNN-based (mUSE-CNN ) §3.2.2) using only contrastive learning on similar and
[
          <xref ref-type="bibr" rid="ref2">37</xref>
          ]. This model generates good quality sentence em- dissimilar pairs of jobs from  2. The results show that
beddings in multiple languages and is very computation- when applying only contrastive learning for training,
ally eficient compared to the previous two models, with we can improve the mAP compared to not applying any
around only 69M parameters. Despite its smaller size, it fine-tuning. However, the results stay significantly lower
ofers reasonable zero-shot performance on job ranking. than those obtained in the previous stage.
        </p>
        <p>Table 1 shows the results obtained with our proposed Also, note the diference for ranking performance in
Korean for the Paraphrase Multilingual MPNet
architecture. This is because this architecture without fine-tuning
ofers very poor results for this language compared to
the other alternatives (with mAP values below 0.05).
mUSE-CNN
P. Multi. MPNet
XLM-RoBERTa
mUSE-CNN
P. Multi. MPNet
XLM-RoBERTa
mUSE-CNN
P. Multi. MPNet
XLM-RoBERTa</p>
        <p>Fine-Tuning
Unsup. Contr.</p>
        <p>1 7
 1 7
 1 7
7  2
7  2
7  2
 1  2
 1  2
 1  2</p>
        <p>Finally, the combination of both stages sequen- Architecture Fine-tuned
tially leads to the best mAP values. For the mUSE-CNN, mUSE-CNN 7
we observe an average improvement of 4.29% with re- PX.LMMu-Rltoi.BMERPTNaet 77
spect to results from Stage 1. Also, improvements of 9.01% mUSE-CNN  1 +  2
and 7.18% are observed for the Paraphrase Multilingual P. Multi. MPNet  1 +  2
MPNet v2 and XLM-RoBERTa architectures respectively. XLM-RoBERTa  1 +  2
We remark that, after this stage, Transformer-based ar- Table 3
chitectures surpass the eficient mUSE-CNN for job title Cross-lingual Evaluation. Each column represents a test set
ranking for up to 1.3 points on average. indicating the language of the queries and corpus elements</p>
        <p>
          To evaluate the statistical significance of the improve- respectively. For example, in the en-de set, the queries are in
ments achieved by the two-stage approach compared to English and corpus documents in German.
applying only the first-stage method, we employed the
Wilcoxon signed-rank test [
          <xref ref-type="bibr" rid="ref8">43</xref>
          ]. The results indicate that
the diference in performance between these methods is the cross-lingual capabilities with respect to German and
statistically significant at a significance level of 0.05 for Chinese.
all variants. Table 3 shows the cross-lingual ranking performance
        </p>
        <p>It is relevant to note that the contrastive learning stage of our solution. We significantly improve the ranking
brings gains for ranking in European languages (which performance for German and Chinese with respect to
are included in the dataset used for training -  2). How- English compared to the architectures without any
fineever, all Asian languages also benefit from this training tuning. For example, for the encoder based on
XLMprocedure, as the cross-lingual capabilities of these archi- RoBERTa after fine-tuning, we improve mAP when
testtectures (see §4.3) can contribute in improving ranking ing using Chinese queries and English corpus samples
on languages not seen during this training stage. from only 0.0414 for up to 0.7226. Our cross-lingual</p>
        <p>In short, training the models for semantic-similarity analysis reveals improved performance on non-English
based on the skills of each job occupation leads to a rea- languages compared to monolingual results in Table 2.
sonable solution for multilingual job title ranking. In This can be attributed to two key factors: the better
repreaddition, fine-tuning this alternative using relations of sentation quality for English job titles and the encoder’s
job titles from the ESCO Taxonomy furthers adjust the ability to align representations of job occupations across
embedding space to improve the ranking performance languages.
of the final solution on each language. This shows that In Figure 5, we investigate the representation quality
both stages of our proposed method are beneficial. of encoders trained on cross-lingual occupation pairs,
consisting of pairs of the same job title in two
difer4.3. Cross-lingual Evaluation ent languages. For simplicity, we focus on a subset of
languages and on two of the presented encoders. To
Finally, we conducted a cross-lingual evaluation of the evaluate this, we employ the alignment (ℒ ) and
proposed method on the selected architectures. For this uniformity (ℒ  ) metrics introduced by Wang et
purpose, we created several datasets where the language al. [26]. The alignment metric evaluates how close the
of the query elements difered from that of the corpus. features from positive pairs (i.e., same occupation in
difIn particular, we studied the ranking performance when ferent languages) are positioned in the feature space. On
English was fixed as one of the languages and assessed the other hand, the uniformity metric measures how</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>5. Conclusions</title>
      <p>evenly the normalized features are distributed over the
unit hypersphere, allowing for the analysis of features
density. Refer to Wang et al. [26] for a detailed definition In this paper we presented a methodology for
developof these metrics. ing a solution for intelligent multilingual job occupation</p>
      <p>
        A good encoder is one with very good alignment (fea- recommendation, resulting in a job title encoder model
tures of the same occupation in diferent languages are for text ranking based on semantic similarity across 11
very close), and good uniformity (otherwise, the learned languages.
representations would occupy a narrow cone in the vec- This method optimizes the neural network
architector space, which severely limits their expressiveness [
        <xref ref-type="bibr" rid="ref9">44</xref>
        ]). tures in two steps. First, a pre-trained multilingual
lanFor both metrics, lower numbers are better, which is con- guage model is adapted as an encoder to obtain the vector
sistent with the literature. representation of every job occupation by learning their
      </p>
      <p>Figure 5-left shows that the XLM-RoBERTa without any similarity based on the distribution of skills linked to
ifne tuning (pre-trained on masked language modeling) each job. This stage provides large insights to the trained
ofers very good alignment. However, the uniformity is model about the semantic similarity of the diferent
mulvery poor, which means that the vector space is quite tilingual occupations, resulting in a good solution for job
compressed and limited when encoding job occupations. title ranking.</p>
      <p>However, after our fine-tuning, the uniformity is signif- Secondly, we take advantage of the ESCO taxonomy
icantly improved from 0 to around -3.4 at the expense and its hierarchically structured classification of jobs
of slightly worse alignment, which results in an encoder based on their similarity in terms of skill level and skill
that is very competitive at recommending cross-lingual specialization, to extract similar and dissimilar pairs of
jobs, ofering mAP values for up to 0.72 points. job occupations. This information together with
con</p>
      <p>Figure 5-right shows the same analysis for the mUSE- trastive learning techniques helps to further optimize the
CNN encoder. In this case, the model without fine-tuning embedding representation obtained with the models, and
ofers reasonable uniformity with low alignment. Both can improve the average mAP for ranking for up to 9%
properties are significantly improved after our training with respect to only carrying out the first training stage.
procedure, resulting in an encoder that is better at rank- To the best of our knowledge, the contrastive
learning cross-lingual occupations. Note, too, that when com- ing stage introduced in this study contributes to surpass
paring with the XLM-RoBERTa trained model, better job title ranking performance in English by 4.3% over
alignment values lead to better mAP values. state-of-the-art monolingual approaches. Finally, we
observe that the presented solution exhibits remarkable
cross-lingual capabilities, enabling the ranking of jobs in
diferent languages, ofering good alignment and
uniformity properties.</p>
      <p>Our work presents limitations that open promising job titles similarity from noisy skill labels, 2022.
directions for future research. In particular, our solution arXiv:2207.00494.
does not leverage contextual information, which might [7] J. Decorte, J. V. Hautte, T. Demeester, C. Develder,
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      <sec id="sec-3-1">
        <title>In this appendix, we provide information about the se</title>
        <p>lected encoders used for doing the analysis of the
proposed methodology for multilingual job recommendation. Table 4</p>
      </sec>
      <sec id="sec-3-2">
        <title>We also describe details about the hyperparameters and</title>
        <p>training configuration for each architecture.</p>
        <p>• mUSE-CNN: Multilingual Universal Sentence</p>
        <p>
          Encoder CNN [
          <xref ref-type="bibr" rid="ref2">37</xref>
          ]. This model is based on
Convolutional Neural Networks for eficient
inference at the cost of reduced accuracy. This model
is trained using 16 languages on multiple tasks:
question-answer prediction, translation ranking,
and natural language inference. The
architecture is implemented in Tensorflow and is publicly
available at Kaggle7. This model has 69 M
parameters.
• XLM-RoBERTa [
          <xref ref-type="bibr" rid="ref4">39</xref>
          ]: This architecture is a
        </p>
        <p>
          Transformer-based model pre-trained on 100
languages using masked language modeling. We use
the model implemented in Tensorflow available
at Kaggle8. This model has 278 M parameters.
• Paraphrase Multilingual MPNet [
          <xref ref-type="bibr" rid="ref3">38</xref>
          ]: This
model is a multilingual encoder that has been
distilled from the monolingual MPNet v29 model, a
sentence embedding model built from MPNet [
          <xref ref-type="bibr" rid="ref7">42</xref>
          ]
and fine-tuned on a dataset with 1 billion
English sentence pairs. The model backbone is
XLMP. Multi. MPNet
(§3.2.1)
# Steps
        </p>
        <p>500 K
Training configuration on Stage 1 with unsupervised method</p>
        <p>RoBERTa, and it is distilled to mimic the vector- for each encoder with the contrastive learning method
dense representation of English sentences on +50
languages. This architecture is implemented in
(Stage 2). Due to its reduced size in terms of parameters,
for mUSE-CNN encoder, we use a bigger batch size and
PyTorch and is publicly available at Hugging- larger number of negatives per anchor element compared
to Transformer-based architectures. As for
Transformerbased solutions, due to the limitation in terms of the</p>
      </sec>
      <sec id="sec-3-3">
        <title>Tensorflow implementation, we have to reduce the batch</title>
        <p>size of XLM-RoBERTa encoder, consequently, we increase
the number of training steps. Lastly, regarding the
temperature ( ), we do a grid search with the following values</p>
      </sec>
      <sec id="sec-3-4">
        <title>The training configuration difers between CNN-based</title>
        <p>vs. Transformer-based encoders, due to the diferent
nature of their backbone architecture. Also, training for</p>
      </sec>
      <sec id="sec-3-5">
        <title>Transformer-based architecture is diferent given that</title>
        <p>modeling, and the other on sentence similarity. These
configurations are the result of preliminary experiments
in which we compared the impact of the diferent
hyperparameters for every encoder model.</p>
        <p>
          A common element shared by all variants is the use
of the AdamW [
          <xref ref-type="bibr" rid="ref10">45</xref>
          ] optimizer, which employs a learning
rate decay mechanism that gradually reduces the learning
rate to zero.
one of the architectures is trained on masked language  = {0.01, 0.05, 0.1, 0.2, 0.25, 0.3} .
        </p>
      </sec>
    </sec>
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</article>