[1] Most XML retrieval approaches do so based on techniques from the information retrieval (IR) area, e.g. by computing the similarity between a query consisting of keywords (query terms) and the document.
The aim is to find the smallest retrieval unit that is highly relevant.
Relevance can be defined according to the notion of specificity, which is the extent to which a retrieval unit focuses on the topic of request.
Often, they are very formal, concentrate more on searching than on ranking, and are used by experienced users able to formulate complex queries.
[8] For data-centric XML datasets, the unique and distinct keyword search method, namely, XDMA[9] for XML databases is designed and developed based on dual indexing and mutual summation.