Dimitar Iliyanov Dimitrov
Also published as: Dimitar Dimitrov
2026
FMISUYotkovaKastreva at SemEval-2026 Task 13: Lightweight Detection of LLM-Generated Code via Stylometric Signals
Elitsa Yotkova | Violeta Kastreva | Dimitar Dimitrov | Ivan Koychev | Preslav Nakov
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
Elitsa Yotkova | Violeta Kastreva | Dimitar Dimitrov | Ivan Koychev | Preslav Nakov
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
SemEval-2026 Task 13 investigates machine-generated code detection across multiple programming languages and application scenarios, asking participating systems to generalize to unseen languages and domains. This paper describes our participation in Subtask A (binary classification) and explores both pretrained code encoders and lightweight feature-based methods.We design ratio-based features that are less sensitive to snippet length. To support the extraction of descriptiveness-related signals, we use parsing engines and a programming-language classifier. Additionally, we train a separate code-vs-text line classifier to identify raw natural language segments embedded within samples. We combine a shallow decision tree with heuristic rules derived from data analysis to produce the final predictions. Our approach is computationally efficient, requires only CPU resources for training, and achieves near-instant inference time, offering a lightweight alternative to large pretrained models.
2025
SemEval 2025 Task 10: Multilingual Characterization and Extraction of Narratives from Online News
Jakub Piskorski | Tarek Mahmoud | Nikolaos Nikolaidis | Ricardo Campos | Alipio Mario Jorge | Dimitar Dimitrov | Purificação Silvano | Roman Yangarber | Shivam Sharma | Tanmoy Chakraborty | Nuno Guimaraes | Elisa Sartori | Nicolas Stefanovitch | Zhuohan Xie | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 19th International Workshop on Semantic Evaluation (SemEval-2025)
Jakub Piskorski | Tarek Mahmoud | Nikolaos Nikolaidis | Ricardo Campos | Alipio Mario Jorge | Dimitar Dimitrov | Purificação Silvano | Roman Yangarber | Shivam Sharma | Tanmoy Chakraborty | Nuno Guimaraes | Elisa Sartori | Nicolas Stefanovitch | Zhuohan Xie | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 19th International Workshop on Semantic Evaluation (SemEval-2025)
We introduce SemEval-2025 Task 10 on Multilingual Characterization and Extraction of Narratives from Online News, which focuses on the identification and analysis of narratives in online news media. The task is structured into three subtasks: (1) Entity Framing, to identify the roles that relevant entities play within narratives, (2) Narrative Classification, to assign documents fine-grained narratives according to a given, topic-specific taxonomy of narrative labels, and (3) Narrative Extraction, to provide a justification for the dominant narrative of the document. To this end, we analyze news articles across two critical domains, Ukraine-Russia War and Climate Change, in five languages: Bulgarian, English, Hindi, Portuguese, and Russian. This task introduces a novel multilingual and multifaceted framework for studying how online news media construct and disseminate manipulative narratives. By addressing these challenges, our work contributes to the broader effort of detecting, understanding, and mitigating the spread of propaganda and disinformation. The task attracted a lot of interest: 310 teams registered, with 66 submitting official results on the test set.
NarratEX Dataset: Explaining the Dominant Narratives in News Texts
Nuno Guimarães | Purificação Silvano | Ricardo Campos | Alipio Jorge | Ana Filipa Pacheco | Dimitar Iliyanov Dimitrov | Nikolaos Nikolaidis | Roman Yangarber | Elisa Sartori | Nicolas Stefanovitch | Preslav Nakov | Jakub Piskorski | Giovanni Da San Martino
Findings of the Association for Computational Linguistics: EMNLP 2025
Nuno Guimarães | Purificação Silvano | Ricardo Campos | Alipio Jorge | Ana Filipa Pacheco | Dimitar Iliyanov Dimitrov | Nikolaos Nikolaidis | Roman Yangarber | Elisa Sartori | Nicolas Stefanovitch | Preslav Nakov | Jakub Piskorski | Giovanni Da San Martino
Findings of the Association for Computational Linguistics: EMNLP 2025
We present NarratEX, a dataset designed for the task of explaining the choice of the Dominant Narrative in a news article, and intended to support the research community in addressing challenges such as discourse polarization and propaganda detection. Our dataset comprises 1,056 news articles in four languages, Bulgarian, English, Portuguese, and Russian, covering two globally significant topics: the Ukraine-Russia War (URW) and Climate Change (CC). Each article is manually annotated with a dominant narrative and sub-narrative labels, and an explanation justifying the chosen labels. We describe the dataset, the process of its creation, and its characteristics. We present experiments with two new proposed tasks: Explaining Dominant Narrative based on Text, which involves writing a concise paragraph to justify the choice of the dominant narrative and sub-narrative of a given text, and Inferring Dominant Narrative from Explanation, which involves predicting the appropriate dominant narrative category based on an explanatory text. The proposed dataset is a valuable resource for advancing research on detecting and mitigating manipulative content, while promoting a deeper understanding of how narratives influence public discourse.
Annotating the Annotators: Analysis, Insights and Modelling from an Annotation Campaign on Persuasion Techniques Detection
Davide Bassi | Dimitar Iliyanov Dimitrov | Bernardo D’Auria | Firoj Alam | Maram Hasanain | Christian Moro | Luisa Orrù | Gian Piero Turchi | Preslav Nakov | Giovanni Da San Martino
Findings of the Association for Computational Linguistics: ACL 2025
Davide Bassi | Dimitar Iliyanov Dimitrov | Bernardo D’Auria | Firoj Alam | Maram Hasanain | Christian Moro | Luisa Orrù | Gian Piero Turchi | Preslav Nakov | Giovanni Da San Martino
Findings of the Association for Computational Linguistics: ACL 2025
Persuasion (or propaganda) techniques detection is a relatively novel task in Natural Language Processing (NLP). While there have already been a number of annotation campaigns, they have been based on heuristic guidelines, which have never been thoroughly discussed. Here, we present the first systematic analysis of a complex annotation task -detecting 22 persuasion techniques in memes-, for which we provided continuous expert oversight. The presence of an expert allowed us to critically analyze specific aspects of the annotation process. Among our findings, we show that inter-annotator agreement alone inadequately assessed annotation correctness. We thus define and track different error types, revealing that expert feedback shows varying effectiveness across error categories. This pattern suggests that distinct mechanisms underlie different kinds of misannotations. Based on our findings, we advocate for an expert oversight in annotation tasks and periodic quality audits. As an attempt to reduce the costs for this, we introduce a probabilistic model for optimizing intervention scheduling.
Entity Framing and Role Portrayal in the News
Tarek Mahmoud | Zhuohan Xie | Dimitar Iliyanov Dimitrov | Nikolaos Nikolaidis | Purificação Silvano | Roman Yangarber | Shivam Sharma | Elisa Sartori | Nicolas Stefanovitch | Giovanni Da San Martino | Jakub Piskorski | Preslav Nakov
Findings of the Association for Computational Linguistics: ACL 2025
Tarek Mahmoud | Zhuohan Xie | Dimitar Iliyanov Dimitrov | Nikolaos Nikolaidis | Purificação Silvano | Roman Yangarber | Shivam Sharma | Elisa Sartori | Nicolas Stefanovitch | Giovanni Da San Martino | Jakub Piskorski | Preslav Nakov
Findings of the Association for Computational Linguistics: ACL 2025
We introduce a novel multilingual and hierarchical corpus annotated for entity framing and role portrayal in news articles. The dataset uses a unique taxonomy inspired by storytelling elements, comprising 22 fine-grained roles, or archetypes, nested within three main categories: protagonist, antagonist, and innocent. Each archetype is carefully defined, capturing nuanced portrayals of entities such as guardian, martyr, and underdog for protagonists; tyrant, deceiver, and bigot for antagonists; and victim, scapegoat, and exploited for innocents. The dataset includes 1,378 recent news articles in five languages (Bulgarian, English, Hindi, European Portuguese, and Russian) focusing on two critical domains of global significance: the Ukraine-Russia War and Climate Change. Over 5,800 entity mentions have been annotated with role labels. This dataset serves as a valuable resource for research into role portrayal and has broader implications for news analysis. We describe the characteristics of the dataset and the annotation process, and we report evaluation results on fine-tuned state-of-the-art multilingual transformers and hierarchical zero-shot learning using LLMs at the level of a document, a paragraph, and a sentence.
SlavicNLP 2025 Shared Task: Detection and Classification of Persuasion Techniques in Parliamentary Debates and Social Media
Jakub Piskorski | Dimitar Dimitrov | Filip Dobranić | Marina Ernst | Jacek Haneczok | Ivan Koychev | Nikola Ljubešić | Michal Marcinczuk | Arkadiusz Modzelewski | Ivo Moravski | Roman Yangarber
Proceedings of the 10th Workshop on Slavic Natural Language Processing (Slavic NLP 2025)
Jakub Piskorski | Dimitar Dimitrov | Filip Dobranić | Marina Ernst | Jacek Haneczok | Ivan Koychev | Nikola Ljubešić | Michal Marcinczuk | Arkadiusz Modzelewski | Ivo Moravski | Roman Yangarber
Proceedings of the 10th Workshop on Slavic Natural Language Processing (Slavic NLP 2025)
We present SlavicNLP 2025 Shared Task on Detection and Classification of Persuasion Techniques in Parliamentary Debates and Social Media. The task is structured into two subtasks: (1) Detection, to determine whether a given text fragment contains persuasion techniques, and (2) Classification, to determine for a given text fragment which persuasion techniques are present therein using a taxonomy of 25 persuasion technique taxonomy. The task focuses on two text genres, namely, parliamentary debates revolving around widely discussed topics, and social media, in five languages: Bulgarian, Croatian, Polish, Russian and Slovene. This task contributes to the broader effort of detecting and understanding manipulative attempts in various contexts. There were 15 teams that registered to participate in the task, of which 9 teams submitted a total of circa 220 system responses and described their approaches in 9 system description papers.
PolyNarrative: A Multilingual, Multilabel, Multi-domain Dataset for Narrative Extraction from News Articles
Nikolaos Nikolaidis | Nicolas Stefanovitch | Purificação Silvano | Dimitar Iliyanov Dimitrov | Roman Yangarber | Nuno Guimarães | Elisa Sartori | Ion Androutsopoulos | Preslav Nakov | Giovanni Da San Martino | Jakub Piskorski
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Nikolaos Nikolaidis | Nicolas Stefanovitch | Purificação Silvano | Dimitar Iliyanov Dimitrov | Roman Yangarber | Nuno Guimarães | Elisa Sartori | Ion Androutsopoulos | Preslav Nakov | Giovanni Da San Martino | Jakub Piskorski
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
We present polyNarrative, a new multilingual dataset of news articles, annotated for narratives. Narratives are overt or implicit claims, recurring across articles and languages, promoting a specific interpretation or viewpoint on an ongoing topic, often propagating mis/disinformation. We developed two-level taxonomies with coarse- and fine-grained narrative labels for two domains: (i) climate change and (ii) the military conflict between Ukraine and Russia. We collected news articles in four languages (Bulgarian, English, Portuguese, and Russian) related to the two domains and manually annotated them at the paragraph level. We make the dataset publicly available, along with experimental results of several strong baselines that assign narrative labels to news articles at the paragraph or the document level. We believe that this dataset will foster research in narrative detection and enable new research directions towards more multi-domain and highly granular narrative related tasks.
2024
SemEval-2024 Task 4: Multilingual Detection of Persuasion Techniques in Memes
Dimitar Dimitrov | Firoj Alam | Maram Hasanain | Abul Hasnat | Fabrizio Silvestri | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 18th International Workshop on Semantic Evaluation (SemEval-2024)
Dimitar Dimitrov | Firoj Alam | Maram Hasanain | Abul Hasnat | Fabrizio Silvestri | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 18th International Workshop on Semantic Evaluation (SemEval-2024)
The automatic identification of misleading and persuasive content has emerged as a significant issue among various stakeholders, including social media platforms, policymakers, and the broader society. To tackle this issue within the context of memes, we organized a shared task at SemEval-2024, focusing on the multilingual detection of persuasion techniques. This paper outlines the dataset, the organization of the task, the evaluation framework, the outcomes, and the systems that participated. The task targets memes in four languages, with the inclusion of three surprise test datasets in Bulgarian, North Macedonian, and Arabic. It encompasses three subtasks: (i) identifying whether a meme utilizes a persuasion technique; (ii) identifying persuasion techniques within the meme’s ”textual content”; and (iii) identifying persuasion techniques across both the textual and visual components of the meme (a multimodal task). Furthermore, due to the complex nature of persuasion techniques, we present a hierarchy that groups the 22 persuasion techniques into several levels of categories. This became one of the attractive shared tasks in SemEval 2024, with 153 teams registered, 48 teams submitting results, and finally, 32 system description papers submitted.
Dissecting Paraphrases: The Impact of Prompt Syntax and supplementary Information on Knowledge Retrieval from Pretrained Language Models
Stephan Linzbach | Dimitar Dimitrov | Laura Kallmeyer | Kilian Evang | Hajira Jabeen | Stefan Dietze
Proceedings of the 2024 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Stephan Linzbach | Dimitar Dimitrov | Laura Kallmeyer | Kilian Evang | Hajira Jabeen | Stefan Dietze
Proceedings of the 2024 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Pre-trained Language Models (PLMs) are known to contain various kinds of knowledge.One method to infer relational knowledge is through the use of cloze-style prompts, where a model is tasked to predict missing subjects orobjects. Typically, designing these prompts is a tedious task because small differences in syntax or semantics can have a substantial impact on knowledge retrieval performance. Simultaneously, evaluating the impact of either prompt syntax or information is challenging due to their interdependence. We designed CONPARE-LAMA – a dedicated probe, consisting of 34 million distinct prompts that facilitate comparison across minimal paraphrases. These paraphrases follow a unified meta-template enabling the controlled variation of syntax and semantics across arbitrary relations.CONPARE-LAMA enables insights into the independent impact of either syntactical form or semantic information of paraphrases on the knowledge retrieval performance of PLMs. Extensive knowledge retrieval experiments using our probe reveal that prompts following clausal syntax have several desirable properties in comparison to appositive syntax: i) they are more useful when querying PLMs with a combination of supplementary information, ii) knowledge is more consistently recalled across different combinations of supplementary information, and iii) they decrease response uncertainty when retrieving known facts. In addition, range information can boost knowledge retrieval performance more than domain information, even though domain information is more reliably helpful across syntactic forms.
EXAMS-V: A Multi-Discipline Multilingual Multimodal Exam Benchmark for Evaluating Vision Language Models
Rocktim Das | Simeon Hristov | Haonan Li | Dimitar Dimitrov | Ivan Koychev | Preslav Nakov
Proceedings of the 62nd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Rocktim Das | Simeon Hristov | Haonan Li | Dimitar Dimitrov | Ivan Koychev | Preslav Nakov
Proceedings of the 62nd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
We introduce EXAMS-V, a new challenging multi-discipline multimodal multilingual exam benchmark for evaluating vision language models. It consists of 20,932 multiple-choice questions across 20 school disciplines covering natural science, social science, and other miscellaneous studies, e.g., religion, fine arts, business, etc. EXAMS-V includes a variety of multimodal features such as text, images, tables, figures, diagrams, maps, scientific symbols, and equations. The questions come in 11 languages from 7 language families. Unlike existing benchmarks, EXAMS-V is uniquely curated by gathering school exam questions from various countries, with a variety of education systems. This distinctive approach calls for intricate reasoning across diverse languages and relies on region-specific knowledge. Solving the problems in the dataset requires advanced perception and joint reasoning over the text and the visual content in the image. Our evaluation results demonstrate that this is a challenging dataset, which is difficult even for advanced vision–text models such as GPT-4V and Gemini; this underscores the inherent complexity of the dataset and its significance as a future benchmark.
2021
SemEval-2021 Task 6: Detection of Persuasion Techniques in Texts and Images
Dimitar Dimitrov | Bishr Bin Ali | Shaden Shaar | Firoj Alam | Fabrizio Silvestri | Hamed Firooz | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 15th International Workshop on Semantic Evaluation (SemEval-2021)
Dimitar Dimitrov | Bishr Bin Ali | Shaden Shaar | Firoj Alam | Fabrizio Silvestri | Hamed Firooz | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 15th International Workshop on Semantic Evaluation (SemEval-2021)
We describe SemEval-2021 task 6 on Detection of Persuasion Techniques in Texts and Images: the data, the annotation guidelines, the evaluation setup, the results, and the participating systems. The task focused on memes and had three subtasks: (i) detecting the techniques in the text, (ii) detecting the text spans where the techniques are used, and (iii) detecting techniques in the entire meme, i.e., both in the text and in the image. It was a popular task, attracting 71 registrations, and 22 teams that eventually made an official submission on the test set. The evaluation results for the third subtask confirmed the importance of both modalities, the text and the image. Moreover, some teams reported benefits when not just combining the two modalities, e.g., by using early or late fusion, but rather modeling the interaction between them in a joint model.
MOMENTA: A Multimodal Framework for Detecting Harmful Memes and Their Targets
Shraman Pramanick | Shivam Sharma | Dimitar Dimitrov | Md. Shad Akhtar | Preslav Nakov | Tanmoy Chakraborty
Findings of the Association for Computational Linguistics: EMNLP 2021
Shraman Pramanick | Shivam Sharma | Dimitar Dimitrov | Md. Shad Akhtar | Preslav Nakov | Tanmoy Chakraborty
Findings of the Association for Computational Linguistics: EMNLP 2021
Internet memes have become powerful means to transmit political, psychological, and socio-cultural ideas. Although memes are typically humorous, recent days have witnessed an escalation of harmful memes used for trolling, cyberbullying, and abuse. Detecting such memes is challenging as they can be highly satirical and cryptic. Moreover, while previous work has focused on specific aspects of memes such as hate speech and propaganda, there has been little work on harm in general. Here, we aim to bridge this gap. In particular, we focus on two tasks: (i)detecting harmful memes, and (ii) identifying the social entities they target. We further extend the recently released HarMeme dataset, which covered COVID-19, with additional memes and a new topic: US politics. To solve these tasks, we propose MOMENTA (MultimOdal framework for detecting harmful MemEs aNd Their tArgets), a novel multimodal deep neural network that uses global and local perspectives to detect harmful memes. MOMENTA systematically analyzes the local and the global perspective of the input meme (in both modalities) and relates it to the background context. MOMENTA is interpretable and generalizable, and our experiments show that it outperforms several strong rivaling approaches.
Detecting Harmful Memes and Their Targets
Shraman Pramanick | Dimitar Dimitrov | Rituparna Mukherjee | Shivam Sharma | Md. Shad Akhtar | Preslav Nakov | Tanmoy Chakraborty
Findings of the Association for Computational Linguistics: ACL-IJCNLP 2021
Shraman Pramanick | Dimitar Dimitrov | Rituparna Mukherjee | Shivam Sharma | Md. Shad Akhtar | Preslav Nakov | Tanmoy Chakraborty
Findings of the Association for Computational Linguistics: ACL-IJCNLP 2021
Detecting Propaganda Techniques in Memes
Dimitar Dimitrov | Bishr Bin Ali | Shaden Shaar | Firoj Alam | Fabrizio Silvestri | Hamed Firooz | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing (Volume 1: Long Papers)
Dimitar Dimitrov | Bishr Bin Ali | Shaden Shaar | Firoj Alam | Fabrizio Silvestri | Hamed Firooz | Preslav Nakov | Giovanni Da San Martino
Proceedings of the 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing (Volume 1: Long Papers)
Propaganda can be defined as a form of communication that aims to influence the opinions or the actions of people towards a specific goal; this is achieved by means of well-defined rhetorical and psychological devices. Propaganda, in the form we know it today, can be dated back to the beginning of the 17th century. However, it is with the advent of the Internet and the social media that propaganda has started to spread on a much larger scale than before, thus becoming major societal and political issue. Nowadays, a large fraction of propaganda in social media is multimodal, mixing textual with visual content. With this in mind, here we propose a new multi-label multimodal task: detecting the type of propaganda techniques used in memes. We further create and release a new corpus of 950 memes, carefully annotated with 22 propaganda techniques, which can appear in the text, in the image, or in both. Our analysis of the corpus shows that understanding both modalities together is essential for detecting these techniques. This is further confirmed in our experiments with several state-of-the-art multimodal models.
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- Preslav Nakov 12
- Giovanni Da San Martino 8
- Jakub Piskorski 5
- Roman Yangarber 5
- Firoj Alam 4
- Nikolaos Nikolaidis 4
- Elisa Sartori 4
- Shivam Sharma 4
- Purificação Silvano 4
- Nicolas Stefanovitch 4
- Tanmoy Chakraborty 3
- Nuno Guimarães 3
- Ivan Koychev 3
- Fabrizio Silvestri 3
- Md. Shad Akhtar 2
- Bishr Bin Ali 2
- Ricardo Campos 2
- Hamed Firooz 2
- Maram Hasanain 2
- Tarek Mahmoud 2
- Shraman Pramanick 2
- Shaden Shaar 2
- Zhuohan Xie 2
- Ion Androutsopoulos 1
- Davide Bassi 1
- Rocktim Das 1
- Stefan Dietze 1
- Filip Dobranić 1
- Bernardo D’Auria 1
- Marina Ernst 1
- Kilian Evang 1
- Jacek Haneczok 1
- Abul Hasnat 1
- Simeon Hristov 1
- Hajira Jabeen 1
- Alipio Jorge 1
- Laura Kallmeyer 1
- Violeta Kastreva 1
- Haonan Li 1
- Stephan Linzbach 1
- Nikola Ljubešić 1
- Michał Marcińczuk 1
- Alípio Mario Jorge 1
- Arkadiusz Modzelewski 1
- Ivo Moravski 1
- Christian Moro 1
- Rituparna Mukherjee 1
- Luisa Orrù 1
- Ana Filipa Pacheco 1
- Gian Piero Turchi 1
- Elitsa Yotkova 1