Versant reVind

reVind is an Add-on module for the Versant Object Database. The Versant/SQL suite of software modules permits you to use conventional Structured Query Language (SQL) semantics to access data that resides in a Versant object database.

The resulting application architecture can offer the strengths of both the relational and the object database models, such as the openness and interconnectivity of relational tables along with the expressiveness and performance of object collections.

Fluid database definition and natural propagation of data into the database is facilitated by the way that classes and object instances help create the database without the usual constraints of table columns and table rows.

For these reasons, if not purely for performance reasons, object-disciplined storage lays the foundation on which information will sit far into the future. The reVind SQL suite addresses the need to obtain additional connectivity and openness for this information through an SQL-compliant form of object database access.

Interactive SQL commands can be composed as demand dictates, empowering you to access and present data just the way you need it to be, if only for the duration of a fleeting moment.

Features

With the freedom to use SQL semantics, objects are visible through a relational database lens.  However, SQL is not expressive enough to present a complex object model transparently; the Versant/SQL Suite uses some transformation rules to help resolve the treatment of certain difficult-to-represent object provisions. These rules are referred to as model-mapping transformations, or "model mappings" in short. These model mappings permit the object model to be treated entirely as an ER (Entity-Relationship) model. The details of this mapping are described later in this chapter.

reVind provides the following features:

• Dynamic Mapping: Versant/SQL is able to map the object schema in any Versant/ODBMS database and allow SQL and ODBC access from components of the Versant/SQL Suite with minimal user input.
• Query Performance: Versant/SQL uses navigational access based on the associations defined in the object schema whenever joins are attempted between tables based on the object-id columns. This implies that join performance would be within a reasonable range of transparent navigational access for an equivalent query made in C++.
• Standard SQL-92 with no extensions: Instead of extending SQL-92 with object-oriented extensions, Versant/SQL Suite uses standard SQL-92 to present an ER representation of the object schema. This has the benefit of allowing ODBC compliant tools to access Versant databases using the same mechanisms as a user of the Interactive Versant Query Tool.
• Scaleable: Versant/SQL uses cursors to access the Versant database allowing efficient use of resources and enabling a quick response to the query. The object cache is maintained by Versant/SQL engine and the main memory storage system cache size is configurable. In case a sort is requested where the data cannot be accommodated in the main memory storage system, local swap space would be used to satisfy the memory requirements.
• Security: Versant/SQL provides full SQL-92 security over and above the user access list security provided by the ersant object database management system.
  

A "special user" installs and setups reVind. This user will have full access rights over all tables and users. This user could grant and revoke select, insert, update, delete rights for different users. Typically, insert, update, and delete rights should be reserved for a very restricted group of users.

Availability

The reVind add-on module is currently available for following platforms:

• Windows (32-bit)
• Solaris (32-bit)