In addition to being a web server, application server and mail server, Domino is also its own database server. The Domino database model is "document-centric" in contrast to the relational model used by Oracle, Microsoft SQL or IBM DB2. This unstructured document-centric data model offers some incredible flexibility in how data is stored. For example, not all documents (records) of a given type need to have the same fields. This allows the database to only store what it needs for any given circumstances. The unstructured database also allows for easy storage of rich text content, attachments, and embedded objects.

An unstructured database is not best suited for every situation. For these occasions, Domino offers the option of attaching to virtually any relational database in a number of ways. For real-time access to relation data, Domino offers the built-in DECS (Domino Enterprise Connection Services) or the more advanced add-on LEI (Lotus Enterprise Integration) server. Both offer real time synchronization of Domino with the back-end data source, but LEI also offers additional features for batch processing. If real-time access to the relational data is not required, Domino offers their LotusScript ODBC or LotusConnectors classes, as well as access through the Domino formula language.

Domino has long been known for its replication capabilities, the ability to maintain synchronized copies of a database on multiple computers - either servers or client workstations. Up until recently, though, for a client to replicate a database from the server to the local workstation and work disconnected, the user had to have the Notes Client software installed. With the introduction of DOLS, though, it is now possible for users with only a web browser to replicate data to their local computer and work with data in a disconnected mode through the web browser. Upon reconnecting to the Domino server, the user can go back "online" and synchronize the local replica with the server replica.

This creates great possibilities for web applications that need to work in a disconnected mode, such as is the case with field technicians using laptop computers. And like so many other Domino features, this is done with little to no additional programming. Combination client-server/web applications Long before the Internet and the Domino web server, Notes had been a robust client-server platform for applications. The introduction of the Domino web server in the mid 90's extended all of the existing capabilities to this new notion of the web. Domino/Notes continues to be a very robust client-server platform. This gives developers the unique option of deploying applications that are a combination of client access and web browser access, or even PDA access. Especially in cases where a business already has an existing Notes application, it is relatively easy to extend this application to have a web front-end as well.

This provides the best of both worlds, while encouraging code re-use. In some cases, the same code may be used for both interfaces. Scalability One of the reasons Domino makes an excellent choice for building web applications is its scalability. Domino has a long history of being supported on many operating systems. In the current version, these include Windows NT, Windows 2000, Linux, Unix (HP, AIX) and OS400. For companies running multiple Domino servers, the servers don't have to be on the same platform; it is common to see a mixed environment. Since IBM purchased Lotus, IBM has positioned Domino as the lower-volume web server choice and WebSphere as the higher-volume choice. However, a Domino server running on a high-end Unix, Linux or OS400 server is quite capable of handling an immense volume of traffic. The additional ability to cluster servers together, even across different operating systems, allows Domino to scale even further.