In their most basic use virtual corpora are collections of files. But apart from being file grouping devices, they are also designed to support the formulation of queries that take into account and benefit from markup.
With respect to the computational side of markup based searching the primary objective when designing the virtual corpus mechanism was to find a balance between expressive power and efficiency. Section 4.2.1 Virtual corpus views explains views, which are the basic mechanism by which one can teach Abundantia Verborum to recognize markup. Section 4.2.2 The corpus preparation tool describes an additional tool that was built to compensate for some of the limitation of the view mechanism.
With respect to the user side of searching in general and markup based searching in particular, the objective was to maximize the support of encapsulation. Encapsulation is the principle of hiding technical details from users, in this case users of virtual corpora. This topic is discussed in 4.2.3 Users and encapsulation.