Allegiance Telecom Chooses DSET Solutions for Increasing Sales-Force Productivity

Bridgewater, NJ and Dallas, TX - May 22, 2000 - DSET Corporation (NASDAQ: DSET) and Allegiance Telecom, Inc. (NASDAQ: ALGX) announced today that Allegiance has selected the DSET ezSubscribe solutions suite for automating sales operations and increasing sales-force productivity. Allegiance is a major competitive local exchange carrier (CLEC) based in Dallas, Texas. DSET is a leading supplier of business-to-business e-commerce connectivity solutions for the telecom industry.

ezSubscribe solutions electronically retrieve customer service records (CSRs) from an incumbent local exchange carrier, translate them into easy-to-understand service descriptions, and generate comparative sales quotes demonstrating the savings customers could realize by switching their service to the CLEC, in this case Allegiance. The translated CSR data can also be exported to an order management system, significantly reducing the amount of manual data entry required for the customer migration process.

Allegiance Telecom, which has also deployed DSET's ezLocal ordering gateway, will use ezSubscribe to obtain CSRs from trading partners that include Ameritech, Bell South, US West, Pacific Bell, SBC, and Bell Atlantic. ezSubscribe will be operationally integrated with Allegiance's Consolidated Order Entry System.

"The ezSubscribe suite will enable us to be substantially more efficient when it comes to interacting with potential customers," said Jerry Sklar, senior vice president of operations support systems and customer implementation for Allegiance Telecom. "Additionally, ezSubscribe will help us achieve greater automation by pre-populating data in the orders sent to MetaSolv's Telecom Business Solution^TM(TBS^TM) software that we use in combination with our Consolidated Order Entry System. With ezSubscribe, we're continuing the evolution of our operations towards flow-through automation of all major processes basic to winning customers, turning on services for new customers, and maintaining the quality of our services."

"Using the ezSubscribe application, Allegiance Telecom recently completed a successful retrieval of a customer service request (CSR) directly from Bell Atlantic's production environment," said Sklar. "This flow-through provisioning of CSR information for service address, billing address, directory, and service detail information automates the ordering process and greatly diminishes the chance of a data entry error."

"Bell Atlantic's operations support systems help competitors process orders quickly and accurately. This helps build a robust wholesale business to serve this important client base in New York and elsewhere across our region," said Tony Yanez, vice president - account management for wholesale markets at Bell Atlantic. "By building our industry-standard interfaces, we can provide easy access to our OSS and enhance our capability as a wholesale provider."

"The increased productivity that Allegiance can achieve as a result of deploying ezSubscribe to bond with Bell Atlantic and other ILECs reflects the growing range of benefits that DSET products offer to all competitive carriers," stated Paul Smith, DSET's senior vice president of strategic planning and product management. "ezSubscribe can cut the time required to generate sales quotes from days to minutes. It also cuts the manual effort that CLEC personnel have to expend by automatically populating much of the information in service orders for customers migrating from the incumbents. Typically, more than 90 percent of the orders that a CLEC has to process involve migration from an incumbent. The potential savings are substantial."

About Allegiance Telecom

Based in Dallas, Texas, Allegiance Telecom is a facilities-based CLEC that offers businesses a complete package of telecommunications services, including local, long distance, international calling, high-speed data transmission, and Internet services. The company is targeting 36 major metropolitan areas in the U.S. with its "one-stop shopping" approach. Allegiance is currently operational in the following 21 markets: Atlanta, Baltimore, Boston, Chicago, Dallas, Denver, Detroit, Fort Worth, Houston, Long Island, Los Angeles, New York, Northern New Jersey, Oakland, Orange County, Philadelphia, San Diego, San Francisco, San Jose, St. Louis and Washington D.C. Allegiance's Web address is: www.allegiancetele.com.

About DSET

DSET Corporation is a leading provider of business-to-business e-commerce connectivity solutions for the global telecommunications marketplace. The DSET suite of electronic-bonding gateways is designed to interconnect the operations support systems (OSSs) of service providers that must exchange information and share network capabilities as trading partners to provision and maintain a growing range of services for customers in the competitive telecom market. DSET's local number portability solutions play a key role in enabling business and residential customers to change service providers without changing their local phone numbers. DSET is headquartered in Bridgewater, New Jersey, and the company's Web site can be viewed at www.dset.com.

Statements regarding financial matters contained in this press release, other than historical facts, are forward-looking. Since all statements about DSET's plans, estimates, and expectations are based on current projections that involve risks and uncertainties, and are subject to change at any time, the company's actual results may differ materially from expected results. Investors should consider these risks and uncertainties, which are discussed in documents filed by DSET with the Securities and Exchange Commission. These documents identify important factors that could cause the actual results to differ materially from those contained in the projections or forward-looking statements. DSET expressly disclaims any obligation to update any forward-looking statements.

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DSET Contacts:

Media Relations: Dean Maskevich, DSET Marketing Communications, 908-526-7500 Ext. 1366, e-mail: dmaskevi@dset.com

Investor Relations: John P. Murphy, Westfield Investor Relations, 908-233-1558, e-mail: westfieldir@worldnet.att.net

Allegiance Contact:

Jerry Ostergaard, Public Relations Manager, 708-836-5261, e-mail: jerry.ostergaard@algx.com

DSET and the DSET logo are registered trademarks of DSET Corporation.

MetaSolv is a registered trademark, and MetaSolv Software and TBS are trademarks of MetaSolv Software, Inc.

All other trademarks are the property of their respective owners.