If history provides any guidance, new vendors are more likely sources of effective post-relational database. Let's look at the transition from technology-centric to user-centric computing, from proprietary network/hierarchical to open relational DBMS. Only IBM would successfully transition from a leader in the proprietary DBMS arena (with IMS and DL/1) to a leader in relational DBMS (with DB/2). Many of the major proprietary network/hierarchical vendors have disappeared - two of the largest, ADR (Datacom) and Cullinane (IDMS), through acquisition by Computer Associates.

Datacom, IDMS and others offered relational-like capabilities. The relational-market leaders, however, were new companies that specialized in relational database, such as Oracle, Sybase and Informix and Ingres (an RDBMS pioneer and former giant no longer viewed as a top tier RDBMS.). Unencumbered by the baggage of legacy technology and customers these vendors could build and deliver market-winning relational products.

Of course, the software industry is different today than it was at the time of transition to relational from proprietary DBMS. The relational database vendors are larger companies and, thanks in great measure to a buoyant stock market, have much greater resources.

Some of the vendors, notably Oracle, are better diversified in areas such as applications and services. These vendors may well be able to build new post-relational technologies or at least acquire them, although this would represent a significant shift from their commitment to the SQL engine.

While hybrids of proprietary and relational did not fare well in the market, hybrid relational/post-relational may well do so. Certainly we would expect to see OO appear widely in database and tool technologies.

The obvious concern of many developers is the potential risk in dealing with a "new vendor" to acquire leading post-relational technologies. However, buying the next generation post-relational technologies does not necessitate buying from a brand new start-up vendor. Because technology waves take so long to mature, many post-relational vendors have been in business for years and have revenue in the comfortable tens-of-millions-of-dollars range. This should come as no surprise since relational vendors were around for years growing slowly until the time came for the relational market to explode.

Of course for these richer data models to succeed in the marketplace, they must also support traditional interoperability standards such as SQL. Increasingly, SQL as an interoperable query language will begin to be differentiated from an RDBMS as SQL is extended to incorporate some object features that don't fit well with the RDBMS model.

While RDBMS vendors will be incorporating aspects of objects and other technologies into their offerings, the most likely scenario is that they will fundamentally retain their strong RDBMS nature with its older data model as the low level basis for their products. This strategy may pay off in marketing as it allows them to talk about hybrid models, but it fails to reap many of the technology rewards as they try to shoehorn richer technologies into a highly limited data model. Much stronger products will be those that incorporate a much richer and more sophisticated data model into the core of the product. It is much easier for them to then provide an access path for older technology interoperability without stunting the opportunities inherent in a more sophisticated and advanced technology.

As with the car industry of the 1970s and 1980s, it will be interesting to see what happens as entrenched large companies become challenged by more technologically advanced and cost effective alternatives.

有一篇是中文的，鼓吹如何替代RDB：

http://www.intersystems.cn/cache/analysts/reviews/idcbreakthrough.htm