> For the complete documentation index, see [llms.txt](https://docs.dh3.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.dh3.io/specs/stream-interceptors/helpers/dictionaries.md). # Dictionaries Dictionaries, also known as associative arrays or hash maps, are essential data structures in modern programming, allowing for the storage and retrieval of key-value pairs. * **Data Mapping**: One primary role of dictionaries in data set building processes is to map unknown or source-specific data fields to known, standardized fields in the target schema. This ensures consistency and eases data integration from various sources. * **Transformations**: Dictionaries can be used to perform data transformations, such as converting abbreviations to full forms or translating codes to readable text. * **Data Cleaning and Validation**: They facilitate cleaning and validating data by mapping incorrect or incomplete data to valid entries. For instance, a dictionary can convert common misspellings or error codes to correct values. * **Extendability**: By maintaining mapping rules in dictionaries, data set building processes become easily extendable. New mappings and transformations can be added or updated without changing the core logic, making the process adaptable to evolving data requirements. * **Efficiency**: Using dictionaries for lookups is computationally efficient, which speeds up data processing, especially with large datasets. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.dh3.io/specs/stream-interceptors/helpers/dictionaries.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.