Naturally, the system has its limits. It doesn't assist IRS agents in the process of actually conducting audits. And it isn't the system that returns information to individuals or corporations seeking answers about particular returns.

"We aren't open to the public. And we don't manage any transactional data stores. The way we deliver value is behind the scenes," he said.

Putting it together
Like any large federal agency or corporation, the IRS stores data from many sources -- from legacy mainframe databases to Oracle databases, to flat files and others. Linking them together to do any sort of business intelligence work a decade ago was a "nightmare," Butler said.

For the CDW, Butler's research group chose ten years ago to adopt Sybase's then-new IQ Analytics Server. Unlike most horizontally minded databases, IQ stores data in column-based tables, which can make it slow for writing data, but quick at reading it -- making it perfect for applications such as data warehousing.

Sybase's IQ has more than 1,000 customers today, including 200 banks . But going with a radical technology from a vendor bleeding money at the time, as Sybase was, was very risky .

"We were met with a lot of skepticism," Butler recalled. "Why don't you go with IBM or Informix's people asked me. It looked a little risky, too, since Sybase IQ wasn't part of the approved enterprise architecture. Eventually, I was told that we could use IQ for research, but we were going to keep on mostly using Oracle and IBM DB2 ."

Restricted access
Actually, the research division also uses Microsoft's SQL Server to store all of the metadata for the data warehouse and the rest of the agency. Managing and cleaning all of that metadata -- 10,000 labels for 150 databases -- is a huge task in itself, Butler said.

Better hardware, improvements to IQ, and most of all, faster and cheaper storage have combined to boost the CDW's performance.

"When we started, it took us six to eight weeks to load one year's worth (15TB to 20TB) of tax returns. It takes four hours today," Butler said.

Today, only about 500 researchers -- mostly from the IRS, some from the Department of the Treasury -- are allowed direct access to the CDW, using Hyperion BI query tools.

But Butler's team is starting to build analysis services that would calculate and publish summary and trend statistics to wikis, blogs and SharePoint sites inside the IRS. That would make it easier for the IRS to fulfill data requests from federal agencies.

The ultimate goal is to make the information available to the public, similar to the way the Census Bureau publishes copious demographic data to its Web site. That, Butler says, would be "the pot of gold at the end of the rainbow."