There is a text based query expression editor for very entity set inside the virtual database (namely the ones corresponding to the 61 virtual tables). The query expression editor can be used to build arbitrarily complex query expressions. The said editor is backed by a sub-SQL DSL generator that can guide the user to construct expressions without been too smart (namely make decisions for the user). Most of the input inside the query expression editor can be accomplished by using four keys, namely the right, up and down arrow keys and the back delete key to select or delete. The expression constructed can be saved and recalled later to re-used or edited.