Probably because the term data virtualization is relatively young, some think it's also young technology and thus immature and only usable in small environments. This is a misunderstanding. Therefore, I decided to give a feeling of the long and rich history of data virtualization, making use of extracts from my book "Data Virtualization for Business Intelligence Systems."
Fundamental to data virtualization are the concepts abstraction and encapsulation. These concepts have their origin in the early 1970s. Exactly forty years ago, in 1972, David L. Parnas wrote a groundbreaking article "On the Criteria to be Used in Decomposing Systems into Modules." In this to me legendary article, Parnas explains how important it is that applications are developed in such a way that they become independent of the structure of the stored data. The big advantage of this concept is that if one changes, the other may not have to change. In addition, by hiding technical details, applications become easier to maintain, or to use more modern terms, they become more agile. Parnas calls this information hiding and worded it as follows: "... the purpose of [information] hiding is to make inaccessible certain details that should not affect other parts of a system."
Information hiding eventually became the basis for popular concepts, such as, object-orientation, component based development, and more currently service oriented architectures. All three have encapsulation and abstraction as foundation. No one questions the values of those three concepts anymore.
But Parnas was not the only one who saw the value of encapsulation and abstraction. The most influential paper in the history of data management "A Relational Model of Data for Large Shared Data Banks", written by E.F. Codd, founder of the relational model, started as follows: "Future users of large data banks must be protected from having to know how the data is organized [...] application programs should remain unaffected when the internal representation of data is changed and even when some aspects of the external representation are changed." He used different terms as Parnas, but he clearly had the same vision. This illustrates one fundamental principle of computer science which is at the root of data virtualization: applications should be independent of the complexities of accessing data.
At the end of the 1970s, a concept called the three schema approach (or concept) was introduced and thoroughly researched. G.M. (Sjir) Nijssen was one of the driving forces behind most of the research in this area. Nijssen wrote numerous articles on this topic. Again, abstraction and encapsulation were the driving forces.
A personal note: In 1979 I started my IT career working for Nijssen in Brussels, Belgium, when all that research was going on. I didn't realize it at that time, but obviously data virtualization has played a role in my career from day one.
Technologically, data virtualization owes a lot to distributed database technology and federation servers. Most of the initial research for data federation was done by IBM in their famous System R* project which started way back in 1979. Another project that contributed heavily to distributed queries, was the Ingres project which eventually led to the open source SQL database server called Ingres, now distributed by Actian Corporation. System R* was a follow-up project to IBM's System R project--the birth place of SQL. Eventually, System R led to the development of most of IBM's commercial SQL database servers, including SQL/DS and DB2.
The forerunners of data virtualization servers can not be omitted here. The first products that deserve the label data federation server are IBM's DataJoiner and Information Builder's EDA/SQL (Enterprise Data Access). The former was introduced in the early 1990s and the latter in 1991. Both were not database servers, but were primarily products for integrating data from different data sources. Besides being able to access most SQL database servers, they were the first products to provide a SQL interface to non-SQL databases. Both products have matured and have undergone several name changes. After being part of IBM DB2 Information Integrator, DataJoiner is currently called IBM InfoSphere Federation Server, and EDA/SQL has been renamed into iWay Data Hub and is part of Information Builders' Enterprise Information Integration Suite.
I could list more technologies, research projects, and products that have been fundamental to the development of data virtualization, but I will stop here. This already impressive list clearly shows the long history and the serious amount of research that has gone into data virtualization and its forerunners. So, maybe the term data virtualization is young, but the technology definitely isn't. Therefore, classifying data virtualization as young and immature, would not be accurate.
Note: If you have questions related to data virtualization, send them in. I am more than happy to answer them.
Posted November 12, 2012 7:50 AM
Permalink | No Comments |