Indexing Units

DEFINITION Indexing units refers to the granularity of information in the retrieval system’s index, which can be in principle any document part of a structured text, and as a consequence determines the possible units of retrieval. There are three basic approaches: The first approach is to index every potentially retrievable unit as a whole—the so-called element-based approach [13]. The second approach is to index disjoint nodes—and relying on aggregation or score propagation methods for scoring higher-level nodes [e.g., 1, 12]. The third approach is to index only selected elements, for example by indexing particular element types in separate indexes [10]. Various mixtures of these approaches have also been applied.