Frequently Asked Questions

What is a standard?
What is the Real Estate Transaction Specification?
What is the Real Estate Transaction DTD (RETML)?
What can this standard do for me?
When will I see any of theses benefits?
What does it mean to say that software complies with the standard?
How will I know if a product complies with standard?
Will I need to change my MLS system to use the standard?
Will I need to change my listing form?
Will the standard let me update information in the MLS?
Will RETS require new software or hardware?
Will this standard work on my Macintosh?
Does this standard have capablilities for international support?
How much will it cost an MLS to implement?
Will my local MLS lose control of the data?
Why should I sign on now before the standard has been proven?
Why believe this standard will succeed when DxM failed?
Do I need to understand all the technical details?
What steps do I need to take if I'm interested?
How was the standard developed?
Who can make changes to the standard?
Where can I get the full standard?


What is a standard, anyway?

When someone brings a new toaster home from the store, he or she never worries whether the plug will fit in the kitchen outlet or if the house has the right kind of electricity. That person is relying on a set of standards adopted by the appliance manufacturers and power companies to assure that things work together.

In the software industry, standards perform a similar function. They are not programs themselves and they do not get installed on any computer. Rather, standards are sets of rules that independent developers can follow to create software that will work together with other software built using the same rules. But they do not define what the program should do, just as the electrical standards do not specify whether a new appliance should make toast or brew coffee.

There are two ways standards can come into existence. Many companies in an industry may be solving a particular problem in a certain way. Perhaps they are copying a market leader or going along with a tradition. That solution has become a de facto standard, whether or not it's been officially sanctioned. The other option is for an organization or consortium to create a solution to a particular problem and to publish it as a standard for others to use. It only becomes a true standard, however, when enough other people actually start using it.

RETS has been developed taking the second route.

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What is the Real Estate Transacation Specification?

The Real Estate Transaction Specification is a document that defines a series of computer interactions called "transactions" and serves as the definitive reference source for developers who implement them. It establishes the parameters for each specified transaction, both upload and download, as well as the expected behaviors and results that compliant hosts and clients must be able to manage, including error codes.

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What is are the RETS2 Payload XSDs and the RETS 1.7 and 1.5 Real Estate Transaction DTD (RETML)?

The RETS2 Payload XSDs and the RETS 1.7 and 1.5 Real Estate Transaction DTD relates to XML (for eXtensible Mark-up Language), a technology that many observers believe has the flexibility and power to transform electronic commerce. The key capability of XML is to make data self-describing - that is, it sends "tags" with the data to tell the receiving computer what the information is, how it relates to other information and what to do with it.

For instance, a search result may report a value of "3" for one feature of a house. To know whether that means three bathrooms or three bedrooms or three acres in a traditional MLS system, the receiving computer must be told about the database structure on that particular host. In XML, the specific host is immaterial. By reading the attached XML tags, the receiving computer could recognize that "3" means the house has three bedrooms, a bedroom is a type of room, and the number of bedrooms can be included in the total number of rooms.

In addition, XML allows a data hierarchy, so that values from several fields can be combined under one label. As an example, the label "street address" could be defined as including the information for house number, street directional prefix, street name, and street direction suffix.

XSD is an acronym for XML Schema Definition used to formally describe the elements in an Extensible Markup Language Document. RETS2 uses XSD because it has the following advantages over DTDs: it is more direct, written entirely in XML (no need for intermediary parsers), includes self-documentation, and has the ability to be queried through XML Transformations (XSLT).

DTD is an acronym for Document Type Definition, a document that describes the tags and hierarchy structure for a particular set of XML data such as RETML, the RETS DTD that relates to real property listings.

RETS 1.x RETML incorporates approximately 140 commonly used fields that are found in some variation on most MLS systems, providing a substantial subset of the property information that will be highly useful for a number of typical applications.

However, RETML does not attempt to be comprehensive or to provide a basis for a stand-alone XML-based MLS system, nor does it support the update transaction that is part of RETS. In fact, a RETS 1.x compliant system need not even maintain all of the fields in RETML, although in response to a query it must pass meaningful data to inform the client that the requested field is absent.

RETS2 Payloads are designed to be more comprehensive and support the functionality of the Real Estate Transaction Lifecycle. MLS Payloads, which have inherited many of the standard names from RETML, are smaller and targeted at certain functions or resources. RETS2 XSDs also include Transaction Management System (TMS) Payloads and NRDS Payloads.

RETS2 is designed to accommodate the continued development of XML in two ways. Payloads are intended to be a minimum common set of fields. They can be locally extended to add information of particular importance in a given market area. Although a client is not required to interpret those extensions to be compliant, competitive pressures will move software companies to include that feature in their products if it proves to have market value. Also, RETS2 allows providers to develop and publish their own Schema, DTD or other custom payload.

Even more fundamentally, the RETS Transactions (Search, Update, etc.) do not depend technically or functionally on either the RETS2 Payloads or the RETS 1.x RETML. This means that the payloads and the transaction sets will be able to develop at their respective speeds along parallel paths without disrupting the integrity of either.

The XML format will be most useful to client software that prefers to deal with the standardized subset of fields described by a XML Schema or DTD. For the benefit of being more generic, that type of application will be willing to forego some of the information available on a host and to accept what it does receive in a different format than the host employs (for example, in plain English expressions instead of coded values). Sample applications that might benefit from XML data transfer would include CMA and flyer generation programs that produce consistent documents from different host systems.

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What can this standard do for me?

A well-defined, well-accepted standard has the potential to benefit different industry groups in different ways.

Agents: A standard will make it easier for software vendors to enter the real estate arena and to sell their wares into a national market. That should result in more choices for agents and more powerful tools that are better integrated with the MLS data. It should also increase competition in local market areas.

Brokers: Broker office systems will be able to exchange information much more easily with local MLS hosts, both upload and download. This will be particularly beneficial for companies that need to manage listings in more than one MLS. RETS can also encourage the creation of enterprise-wide solutions that link functions such as inventory control, transaction management and agent productivity. Under the standard, tasks like populating web sites, generating print advertisements and organizing transaction services will be easier and more accurate.

MLSs: Having the standard will improve the price/performance ratio for property information systems. Software developed using RETS will give MLS operators more options to offer the membership, such as a wider variety of access software, data export services, Internet/web services and other value-added service integration options. It will open up possible new business opportunities, such as functioning as a service bureau to provide fee-based technical capabilities to local brokerage firms.

Client software programs will enjoy more reliable and consistent connections with the MLS server, reducing support for applications that 'break' when MLS changes are implemented. Additionally, clients can be written to work across different MLS systems, allowing agents to retain their familiar software when MLS vendors change and reducing training costs. RETS will also facilitate the use of Internet-based systems that run in parallel with current dial-up access to ease the transition period.

NAR: NAR benefits when its members are served. By facilitating the development process and sponsoring adoption of RETS, NAR is promoting the technology environment that will prepare REALTORS® to become managers of the electronic transaction.

Vendors: RETS will allow software vendors to use a single interface across many compliant systems rather than creating and maintaining multiple custom interfaces. That will save development time and resources that can be applied to lower costs or improve features. In addition, development and distribution of software to a large variety of MLS systems in different geographic locations can be dramatically easier, encouraging new products by opening larger market opportunities.

Industry: RETS will assist the real estate business climate in several ways. Introducing Internet-based technology such as XML will allow more profitable integration of the Internet into business. Creating a common communications protocol will establish a framework for the electronic real estate transaction and supply a core technology around which industry sectors can collaborate. The standards change process will introduce an accepted process for technological initiatives in the industry. Most significantly, the entire standards effort will provide a platform for improved service offerings to consumers.

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When will I see the benefits?

Brokers, Agents and MLSs have been seeing the benefits of using RETS for the past several years. For details on how RETS benefits users, and some innovative RETS success stories, you can refer to the Comprehensive Overview document on this site.

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What does it mean to say that software fully complies with the standard

In saying that a piece of software fully complies with RETS, the vendor is claiming that the programming code properly follows all of the rules laid out in the standard, that the product performs all of the functions mandated by the standard, and that the program will successfully execute the RETS transaction sets when used in conjunction with another piece of software that also complies with the standard.

Two fully compliant products, however, will not necessarily be equal. Programs will still compete on issues such as their range of features, the quality of their screen designs and the intuitiveness of their operations.

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How will I know if a product complies with standard?

Besides comparing a products functionality against the requirements set forth in the RETS2,
RETS 1.7 and 1.5 Specification documents, you can determine a product's compliance by either
looking for it on the list of compliant products or test your own product against one of the
compliance checkers (Server or
Client). Please refer to the
compliance section of this site
for more information on RETS compliance.

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