View maintenance for hierarchical semistructured data

The problem of incremental view maintenance in materialized data warehouses has been studied extensively for relational select-project-join (SPJ) views. Many new data sources, however, are highly irregular and views often perform complex restructuring operations. This paper describes WHAX (Warehouse Architecture for XML), an architecture for defining and maintaining views over hierarchical semistructured data sources with key constraints. The WHAX model is a variant of the deterministic model [5], but is more reminiscent of XML, The view definition language is it variation of XML-QL and supports selections, joins, and important restructuring operations such as regrouping and aggregation. The incremental maintenance is based on the notion of mufti-linearity and generalizes well-known techniques from SPJ-views.