关键短语提取是文本分析中的一项技术,用于从文档中提取重要的关键短语。借助这些关键短语,人们无需完整阅读文本,就能快速轻松地理解文本内容。关键短语提取最初主要由人工标注者完成,他们详细阅读文本,然后写下最重要的关键短语。其缺点是,如果处理大量文档,此过程可能会耗费大量时间 ⏳。
这正是人工智能 🤖 发挥作用的地方。目前,使用统计和语言特征的经典机器学习方法被广泛应用于提取过程。如今,借助深度学习,相比这些经典方法,我们能够更好地捕捉文本的语义。经典方法关注文本中词语的频率、出现次数和顺序,而这些神经方法则可以捕捉文本中词语的长期语义依赖关系和上下文。
本模型以 KBIR 作为基础模型,并在 semeval2017 数据集上进行微调。KBIR(Keyphrase Boundary Infilling with Replacement,关键短语边界填充与替换)是一个预训练模型,它利用多任务学习设置来优化掩码语言建模(MLM)、关键短语边界填充(KBI)和关键短语替换分类(KRC)的组合损失。 有关该架构的更多信息,请参见此 论文。
关键短语提取模型是经过微调的 transformer 模型,作为一种 token 分类任务,其中文档中的每个词都被分类为是否属于关键短语的一部分。
| 标签 | 描述 |
|---|---|
| B-KEY | 位于关键短语的开头 |
| I-KEY | 位于关键短语的内部 |
| O | 位于关键短语的外部 |
from transformers import (
TokenClassificationPipeline,
AutoModelForTokenClassification,
AutoTokenizer,
)
from transformers.pipelines import AggregationStrategy
import numpy as np
import torch
import torch_npu
# Define keyphrase extraction pipeline
class KeyphraseExtractionPipeline(TokenClassificationPipeline):
def __init__(self, model, *args, **kwargs):
super().__init__(
model=AutoModelForTokenClassification.from_pretrained(model),
tokenizer=AutoTokenizer.from_pretrained(model),
*args,
**kwargs
)
def postprocess(self, all_outputs):
results = super().postprocess(
all_outputs=all_outputs,
aggregation_strategy=AggregationStrategy.SIMPLE,
)
return np.unique([result.get("word").strip() for result in results])
# Load pipeline
device = torch.device('npu:0')
model_name = "ml6team/keyphrase-extraction-kbir-semeval2017"
extractor = KeyphraseExtractionPipeline(model=model_name).to(device)# Inference
text = """
Keyphrase extraction is a technique in text analysis where you extract the
important keyphrases from a document. Thanks to these keyphrases humans can
understand the content of a text very quickly and easily without reading it
completely. Keyphrase extraction was first done primarily by human annotators,
who read the text in detail and then wrote down the most important keyphrases.
The disadvantage is that if you work with a lot of documents, this process
can take a lot of time.
Here is where Artificial Intelligence comes in. Currently, classical machine
learning methods, that use statistical and linguistic features, are widely used
for the extraction process. Now with deep learning, it is possible to capture
the semantic meaning of a text even better than these classical methods.
Classical methods look at the frequency, occurrence and order of words
in the text, whereas these neural approaches can capture long-term
semantic dependencies and context of words in a text.
""".replace("\n", " ")
keyphrases = extractor(text)
print(keyphrases)
# Output
['artificial intelligence']Semeval2017 是一个关键短语抽取/生成数据集,包含 500 篇来自 ScienceDirect 开放获取出版物的英文科学论文摘要,以及来自《纽约时报》的文章和来自《日本时报》的 10K 文章,由专业索引员或编辑进行标注。所选文章在计算机科学、材料科学和物理学领域均匀分布。每篇论文都有一组由学生志愿者标注的关键短语。每篇论文都进行了双重标注,第二次标注由专家标注员完成。
更多信息可参见 论文。
| 参数 | 值 |
|---|---|
| 学习率 | 1e-4 |
| 轮次 | 50 |
| 早停耐心值 | 3 |
数据集中的文档已预处理为带有相应标签的单词列表。唯一需要做的是分词以及重新对齐标签,使其与正确的子词 token 相对应。
from datasets import load_dataset
from transformers import AutoTokenizer
# Labels
label_list = ["B", "I", "O"]
lbl2idx = {"B": 0, "I": 1, "O": 2}
idx2label = {0: "B", 1: "I", 2: "O"}
# Tokenizer
tokenizer = AutoTokenizer.from_pretrained("bloomberg/KBIR")
max_length = 512
# Dataset parameters
dataset_full_name = "midas/semeval2017"
dataset_subset = "raw"
dataset_document_column = "document"
dataset_biotags_column = "doc_bio_tags"
def preprocess_fuction(all_samples_per_split):
tokenized_samples = tokenizer.batch_encode_plus(
all_samples_per_split[dataset_document_column],
padding="max_length",
truncation=True,
is_split_into_words=True,
max_length=max_length,
)
total_adjusted_labels = []
for k in range(0, len(tokenized_samples["input_ids"])):
prev_wid = -1
word_ids_list = tokenized_samples.word_ids(batch_index=k)
existing_label_ids = all_samples_per_split[dataset_biotags_column][k]
i = -1
adjusted_label_ids = []
for wid in word_ids_list:
if wid is None:
adjusted_label_ids.append(lbl2idx["O"])
elif wid != prev_wid:
i = i + 1
adjusted_label_ids.append(lbl2idx[existing_label_ids[i]])
prev_wid = wid
else:
adjusted_label_ids.append(
lbl2idx[
f"{'I' if existing_label_ids[i] == 'B' else existing_label_ids[i]}"
]
)
total_adjusted_labels.append(adjusted_label_ids)
tokenized_samples["labels"] = total_adjusted_labels
return tokenized_samples
# Load dataset
dataset = load_dataset(dataset_full_name, dataset_subset)
# Preprocess dataset
tokenized_dataset = dataset.map(preprocess_fuction, batched=True)
如果不使用流水线函数,您必须筛选出标记为 B 和 I 的 tokens。然后,每个 B 和 I 将合并为一个关键短语。最后,您需要去除关键短语的首尾空格,确保所有不必要的空格都已被删除。
# Define post_process functions
def concat_tokens_by_tag(keyphrases):
keyphrase_tokens = []
for id, label in keyphrases:
if label == "B":
keyphrase_tokens.append([id])
elif label == "I":
if len(keyphrase_tokens) > 0:
keyphrase_tokens[len(keyphrase_tokens) - 1].append(id)
return keyphrase_tokens
def extract_keyphrases(example, predictions, tokenizer, index=0):
keyphrases_list = [
(id, idx2label[label])
for id, label in zip(
np.array(example["input_ids"]).squeeze().tolist(), predictions[index]
)
if idx2label[label] in ["B", "I"]
]
processed_keyphrases = concat_tokens_by_tag(keyphrases_list)
extracted_kps = tokenizer.batch_decode(
processed_keyphrases,
skip_special_tokens=True,
clean_up_tokenization_spaces=True,
)
return np.unique([kp.strip() for kp in extracted_kps])
传统的评估方法包括精确率(precision)、召回率(recall)和 F1 值(F1-score)@k,m,其中 k 代表排名前 k 的预测关键短语数量,m 代表预测关键短语的平均数量。
该模型在 Semeval2017 测试集上取得了以下结果:
| 数据集 | P@5 | R@5 | F1@5 | P@10 | R@10 | F1@10 | P@M | R@M | F1@M |
|---|---|---|---|---|---|---|---|---|---|
| Semeval2017 测试集 | 0.41 | 0.20 | 0.25 | 0.37 | 0.34 | 0.34 | 0.36 | 0.50 | 0.40 |
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