Abstract
The importance of automated document understanding in terms of today’s businesses’ speed, efficiency, and cost reduction is indisputable. Although structured and semi-structured business documents have been studied intensively within the literature, information extraction from the unstructured ones remains still an open and challenging research topic due to their difficulty levels and the scarcity of available datasets. Transactional documents occupy a special place among the various types of business documents as they serve to track the financial flow and are the most studied type accordingly. The processing of unstructured transactional documents requires the extraction of complex relations (i.e., n-ary, document-level, overlapping, and nested relations). Studies focusing on unstructured transactional documents rely mostly on textual information. However, the impact of their visual compositions remains an unexplored area and may be valuable on their automatic understanding. For the first time in the literature, this article investigates the impact of using different visual representations and their fusion on information extraction from unstructured transactional documents (i.e., for complex relation extraction from money transfer order documents). It introduces and experiments with five different visual representation approaches (i.e., word bounding box, grid embedding, grid convolutional neural network, layout embedding, and layout graph convolutional neural network) and their possible fusion with five different strategies (i.e., three basic vector operations, weighted fusion, and attention-based fusion). The results show that fusion strategies provide a valuable enhancement on combining diverse visual information from which unstructured transactional document understanding obtains different benefits depending on the context. While different visual representations have little effect when added individually to a pure textual baseline, their fusion provides a relative error reduction of up to 33%.
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The data consisting monetary transactions of real customers are confidential.
Notes
There exist also semi-structured money transfer orders which are processed with table-detection algorithms, which are beyond the scope this article.
In the original study, Oral et al. [2] also use character embeddings next to pretrained textual word embeddings and report that this helps the performances at very low levels (0.2 percentage points) for NER. To alleviate this complexity, we dropped the character BiLSTM layer from textual representations to better observe the effects of the visual representations.
The term Layout embedding is also used by Xu et al. [22], but the approach that we introduce here should not be confused with it which is more similar to our Grid Embedding approach.
We also tested with an attention-based fusion approach using textual features as our attention context, but could not obtain good results.
Although there could appear semi-structured documents in this domain containing well-formed forms and tables, the authors state that these are not included in this dataset.
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Acknowledgements
The authors would like to thank Onur Deniz, Mehmet Yasin Akpınar, Erdem Emekligil, and Mustafa İşbilen for their valuable support.
Funding
This work is funded by the Scientific and Technological Research Council of Turkey (TUBITAK) and by Yapı Kredi Technology with a TUBITAK 1505 (University - Industry Cooperation Support Program) project Grant No. 5190073.
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Both authors contributed equally to methodology, conceptualization, formal analysis, investigation, visualization, writing—original draft, review and editing. [Berke Oral] helped in software and data curation; [Gülşen Eryiǧit] contributed to supervision and funding acquisition.
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Oral, B., Eryiğit, G. Fusion of visual representations for multimodal information extraction from unstructured transactional documents. IJDAR 25, 187–205 (2022). https://doi.org/10.1007/s10032-022-00399-3
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DOI: https://doi.org/10.1007/s10032-022-00399-3