In the real-estate biz, an "old charmer" is usually an ugly shack in need of serious repair. Well, it looks like the term "open house" may be a euphemism, too.

Last week, a group of 17 companies involved in the complex world of online real estate uncorked the Alliance for Advanced Real Estate Transaction Technology (AARTT), a new consortium that plans to develop a standard called comprehensive real-estate transaction markup language, or CRTML. The language will outline a common way to exchange data between the myriad transactions--from title searches to mortgage applications--that take place during the sale of a home.

CRTML could make life easier for Web integrators and developers that target the real-estate market. The vertical already has several disparate and incompatible standards, including the Real Estate Transaction Standard (RETS) and Legal XML. "The industry itself is very fragmented, and there are many different standards efforts," says Ari Vidali, CTO of iproperty.com, and the man who spearheaded AARTT's formation.

Where the various standards overlap, like in fields for a home address, they often don't agree on ways to format data, says Vidali. "The overarching goal of the AARTT is to create standards for seamless interchange between all these different standards."

But, initially at least, AARTT didn't include one of the industry's largest players, Homestore.com, which didn't attend the group's coming-out party. "I'm not sure why we weren't invited," says Errol Samuelson, director of product strategy at Homestore.com. "We were quite surprised. I sat on a panel with Ari just weeks earlier, and he never mentioned the consortium to me."

Retorts Vidali: "NAR, a major owner of Homestore.com, was at the earliest meetings of the group," NAR, or the National Association of Realtors, is at the center of another controversy involving Homestore.com. The U.S. Department of Justice is investigating Homestore.com for possible antitrust violations. The investigation reportedly was triggered by Homestore.com's ties to NAR, as well as Homestore.com's pending US$1 billion acquisition of Move.com.

But Samuelson thinks there's another reason Homestore.com was not invited to AARTT's open house: Homestore.com's new service, called e-realtor.com, may compete with iproperty in the B2B marketplace, Samuelson says.

Whatever the reason for Homestore.com's initial exclusion, the popular real-estate site is now on board the AARTT bandwagon, "as long as the group is an open group and not slanted toward any one participant," says Samuelson.

AARTT members include AppraisalHub, Bowstreet, Deloitte & Touche, Homeadvisor Technologies, Homebid, iLumin, InteliTouch and Interealty. CRTML 1.0 is expected sometime in 2001, says Vidali.

The online real-estate industry already has determined standards for the multiple-listing service (MLS), says Howard Latham, COO of Vistainfo, an MLS service provider and an AARTT member. "The next step is to do the same thing for transactions."

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