What is Preprocessing?
Preprocessing encompasses the operations performed on raw text or documents before they are embedded, indexed, or stored in a retrieval system. These operations clean, normalize, and structure the content to improve embedding quality, retrieval accuracy, and system performance. Effective preprocessing is crucial for building high-quality knowledge bases and memory systems, as poor input quality directly degrades output quality regardless of sophisticated downstream processing.
Common preprocessing operations include removing HTML tags and formatting artifacts, normalizing whitespace and special characters, converting to consistent case (typically lowercase), handling or removing special characters and punctuation, correcting encoding issues, removing boilerplate or navigation elements from web pages, and potentially correcting spelling errors or expanding abbreviations. The specific operations depend on the source content and application requirements.
Preprocessing must balance cleaning data to remove noise with preserving information that might be semantically meaningful. Aggressive preprocessing improves consistency but may remove distinctive features that help retrieval. For example, removing all capitalization makes matching more consistent but loses information about proper nouns or emphasis. Domain-specific preprocessing might preserve technical notation, chemical formulas, or code syntax that generic text processing would corrupt. Well-designed preprocessing pipelines are tailored to their content sources and use cases.