Krawler aims at making the automated process of extracting and processing (geographic) data from heterogeneous sources easy. It can be viewed as a minimalist Extract, Transform, Load (ETL). ETL refers to a process where data is
- extracted from heterogeneous data sources (e.g. databases or web services);
- transformed in a target format or structure for the purposes of querying and analysis (e.g. JSON or CSV);
- loaded into a final target data store (e.g. a file system or a database).
ETL naturally leads to the concept of a pipeline: a set of processing functions (called hooks in krawler) connected in series, often executed in parallel, where the output of one function is the input of the next one. The execution of a given pipeline on an input dataset to produce the associated output is a job performed by krawler.
A set of introduction articles to krawler have been written and detail: