信息抽取中的权重标注
Weight Annotation in Information Extraction
AI总结：
本文提出文档跨度器的标注器扩展，利用来源半环为信息抽取结果附加权重，研究加权VSet自动机的表达性与计算复杂性，并探讨半环正性对可处理性的影响。
摘要：
文档跨度框架将文本信息抽取任务抽象为一个函数，该函数将每个文档（一个字符串）映射到文档跨度（由其起始和结束索引标识的区间）上的一个关系。例如，正则跨度器是带捕获变量的正则表达式在关系代数（RA）下的闭包，而正则跨度器的表达能力恰好由VSet自动机类所刻画——这是一类受限的转换器，用于标记所选跨度的端点。在本工作中，我们开始研究能够用辅助信息（如置信度、支持度和保密性度量）标注抽取结果的文档跨度器。为此，我们采用Green等人提出的来源半环抽象，其中关系的元组被标注为交换半环的元素，并且标注通过半环算子经由正RA算子传播。因此，所提出的跨度器扩展（称为标注器）将每个字符串映射到跨度上的一个标注关系。作为具体实例，我们探索了加权VSet自动机，其类似于加权自动机和转换器，将半环元素附加到转换上。我们研究了表达性的关键方面，例如在正RA下的闭包性，以及计算复杂性的关键方面，例如标注答案的枚举及其在有序半环情况下的排序枚举。对于其中许多问题，底层半环的基本属性（如正性）对于建立可处理性至关重要。
英文摘要：
The framework of document spanners abstracts the task of information extraction from text as a function that maps every document (a string) into a relation over the document's spans (intervals identified by their start and end indices). For instance, the regular spanners are the closure under the Relational Algebra (RA) of the regular expressions with capture variables, and the expressive power of the regular spanners is precisely captured by the class of VSet-automata -- a restricted class of transducers that mark the endpoints of selected spans. In this work, we embark on the investigation of document spanners that can annotate extractions with auxiliary information such as confidence, support, and confidentiality measures. To this end, we adopt the abstraction of provenance semirings by Green et al., where tuples of a relation are annotated with the elements of a commutative semiring, and where the annotation propagates through the positive RA operators via the semiring operators. Hence, the proposed spanner extension, referred to as an annotator, maps every string into an annotated relation over the spans. As a specific instantiation, we explore weighted VSet-automata that, similarly to weighted automata and transducers, attach semiring elements to transitions. We investigate key aspects of expressiveness, such as the closure under the positive RA, and key aspects of computational complexity, such as the enumeration of annotated answers and their ranked enumeration in the case of ordered semirings. For a number of these problems, fundamental properties of the underlying semiring, such as positivity, are crucial for establishing tractability.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
