The World Wide Web Consortium (W3C) has, after several years of preparation, declared the Indexed Database API as their recommendation, or in other words as the standard. This is a programming interface through which Web applications can access local databases.
The data records may contain both simple values and hierarchical objects, and consist of a key and the associated value. When searching for a particular data set the applications can use either the key or the index of attributes. The index is usually in the form of a persistent B-tree. The access to the data, however, need not pass through the API, but can also run through a higher-level access layer – for example, using a query language such as SQL.