XML semantic constraint validation for XML updates: A survey

XML databases are commonly used for representing data with more complex structures than traditional relational data. Like in any data model, it is very important to ensure that the contents of the database always valid even after any attempt of updates. XML Updates validation is a process of checking the correctness of XML documents, in terms of satisfying their constraints, after updates operations. The validation can be generally categorized into structural and semantic validation. The first validation is to ensure that all XML nodes in the documents conform to structural information in its associated schema. Meanwhile, the second validation checks the integrity constraints of the documents, and it involve various factors such as the functional dependencies, domain constraint, inheritance, etc. In this paper, we provide a preliminary survey of semantic validation w.r.t XML Updates. The work of validation usually applied either upon any attempt of updates or in a scheduled period. We compare the output gain by works in terms of operation of update, the composition, types of constraint, etc. It shows that even though there are abundant of studies in this area, not much work has investigated a complete semantic validation of different semantic constraints. The constraints are still strongly dependent on structural information of documents and lied only on the data access tier of application architecture.