North American Directory Assistance Automation

December 18, 2001

North American Directory Assistance Automation

A varetis White Paper

An Overview of varetis’ Directory Automation Solutions

varetis Communications is pleased to announce a new standard in Directory Assistance (DA) automation solutions. ADIS (Automated Directory Inquiry System), our flagship DA automation solution, and NDIS (National Directory Inquiry System), our world-class search technology, have been built to usher the North America Directory Assistance market into the next generation of both fully automated and attendant-backed call center solutions.  With these solutions come new possibilities for lowering operational costs and introducing new services while at the same time protecting existing investments in Operator Services infrastructure.

This paper provides a brief overview of varetis’ DA automation solutions, covering technology, architecture, integration with existing systems, operator fallback, and possibilities for the development of new, enhanced services based on varetis’ core technology.

Reducing the Cost of Directory Assistance

Of the many challenges facing today’s directory assistance providers, the most well known and perhaps most difficult to address has been that of cost reduction.  Automated solutions of all kinds have been employed by the DA industry now for decades in service to cost reduction, with varying results.  The ultimate goal of these efforts has been the realization of the full automation of a call to directory assistance, in which no human intervention of any kind is necessary for completion of the call.  That goal was realized for certain types of calls several years ago; the difficulty, however, has been in automating a large enough volume of calls to justify the expense of installing and maintaining the automation systems.

varetis has solved this problem with ADIS – our Automated Directory Inquiry System.  In partnership with IBM, Telelogue, and others, varetis has architected a standards-based, highly scalable DA automation system that can dramatically reduce the cost of providing Directory Assistance.  ADIS automates a large volume of these calls in an intelligent, intuitive fashion, while allowing service providers to enjoy excellent customer satisfaction metrics through the use of the most natural human/machine interface possible – voice.

Respecting Call Types

At first blush, a DA dialog would appear to be quite simple – and therefore simple to automate – but this is deceptive.  Calls to DA can vary widely in character – so widely, in fact, that a technology ideally suited for one type of call may be inappropriate for another.  The success rate of an automated system turns out to be strongly dependent on an optimal combination of technologies for telephony interconnection, dialog management, data search, speech recognition, speech synthesis, and computer telephony.  For these reasons, varetis has chosen to divide DA calls into three broad categories – Residential Search, Business Search, and Reverse Search calls – and to address specific technologies to each in order to maximize the resulting automation percentages.  Each solution is integrated into the IBM DirecTalk audio processing platform, and each automates the three elements of a directory assistance call – call arrival, data search and customer report delivery.  Callers are prompted for search arguments, and receive the listing information verbally via an SMS message or call completion.  The entire process is fully automated, with no need for operator intervention.  If necessary, however, an operator fallback feature can connect the caller to a live operator for further assistance.

varetis’ DA Automation System

  • Residential Search calls are automated by varetis’ Automated Directory Inquiry System - Residential (ADIS-R), which excels at providing both full and partial automation for directories as large as 160 million listings.  ADIS-R is a world-class DA automation solution that enables service providers to fully automate DA calls for residential white pages listings through the speech recognition of search arguments such as first name, last name and locality.
  • Business Search calls are automated by Telelogue’s Voice Business FinderTM, which excels at automating calls to businesses through the recognition of arguments such as company name and locality, as well as the complex requirements of caption set navigation and disambiguation.
  • Reverse Search calls are automated by varetis’ Reverse Automated Directory Inquiry System (R-ADIS), which provides the capability to search the listings database via the telephone number.  Continuous-digit speech recognition technology is used to capture the telephone number, and integrated DTMF fallback allows for digit entry via the touchtone keypad.

These sophisticated technologies together are designed to provide a complete, integrated system for an automated directory assistance service.

User-Centered Design

Much of the difficulty in building automation systems lies in the area of effective dialog design.  Even with today’s advanced speech recognition technology, the central challenge remains -- to guide the consumer to be as concise and accurate as possible in the dialog.  Even with the limited amount of information that must be collected for a Directory Assistance inquiry – City, State, Name, and sometimes Address – this challenge is daunting, not because of the behavior of individuals, but because of the scale of behavioral variation implicit in large populations.  varetis addresses this challenge with a variety of techniques designed to produce a human/machine interface that is at once intuitive and accurate.  

The key technology here is the adaptive dialog, in which the concepts of flexibility and graduated heuristics are integral.  ADIS dialogs adapt in an extremely flexible manner to the behavior of an individual caller.  Prompting is based upon the information needs of the dialog at any given moment, and can be configured according to the business needs of the DA service provider.  Dialogs, for example, can be configured to omit arguments such as street name or first name if desired – information that is often unknown to the caller, and that might confuse an otherwise straightforward interaction.  Callers, further, are required to respond to each prompt only once; there is no mandatory verification step as can sometimes be observed in competitive solutions.  This effectively shortens and simplifies the dialog without necessarily impacting system accuracy.

Technology Highlights

The core technology in automation systems is speech recognition, and to date, most systems have been constrained in their performance by the constraints of the speech recognizer itself.  Today, this technology has evolved to levels unthinkable just a few short years ago.  Yet even the best speech recognition engine will rarely identify a user response as a unique recognition result. This is because the process of recognizing a spoken language is a highly statistical matter; recognition results are always produced within a range of uncertainty.  This fact is inherent to the technology, and is not so different from what we humans do in listening to each other – occasionally we fail to understand a word, or need clarification, or ask for a statement to be repeated.  It is in the nature of spoken communications.

varetis technology circumvents this fact through the use of what are called ‘N-best’ lists.  An N-best list is a list produced by the recognizer containing the N most likely spoken words to any prompt utterance.  The word that was actually spoken by the user is sometimes the first entry in that list, but it is usually necessary to consider entries further down the list in order of probability as well.  Since the recognizer can never be certain exactly where in the list the correct utterance is, these long lists must be queried for every utterance.

How does this work?  This functionality is provided by varetis’ remarkable search technology NDIS (National Directory Inquiry System).  After the N-best lists (one for each utterance) have been produced by the recognizer, the NDIS search engine is instructed to retrieve all listings that match at least one element from each list.  With three search arguments, and N=50, this results in 503 or 125,000 combinations to search. NDIS will then search within these 125,000 combinations to find the correct listing.  To do so, every entry in each N-best list is augmented with a recognition confidence value, and the combined confidence value for every subscriber record found is computed. Finally, the resulting subscriber records are sorted by this combined confidence value, so that ADIS will read out the most likely listing result first.

The most remarkable aspect of this process is not the size of the effort, nor even its complexity.  The most interesting and distinguishing factor – the aspect that most differentiates varetis technology from that of its competitors, is the speed and accuracy at which this process takes place.  ADIS must operate in essentially real time; responses to these kinds of search requirements must complete in under a single second.  ADIS is able to combine all recognized search arguments in each N-best list and to retrieve the subscriber listing with only a single database transaction to the NDIS search engine in sub-second response time. varetis’ NDIS search engine technology, in fact, is capable of satisfying this requirement in under 1/2 second even with four N-best lists of 50 items each.  This level of performance is simply unmatched by any other database search technology in existence. NDIS, therefore, is a key element in providing an efficient, scalable, nationwide automated DA system.

Infrastructure Modularity

Architecturally, varetis automation solutions have been designed from the ground up to support heterogeneous technologies from best-of-breed suppliers, and to integrate them with a minimum of effort.  This is made possible in large measure by the VoiceXML specification – a key ingredient to understanding varetis’ competitive advantage.  

As the name suggests, VoiceXML is similar to the XML (extensible Markup Language) specification, extending XML-style capabilities into the domain of voice communications.  VoiceXML, like XML, is a semantic specification, meaning that it is designed to convey meaning as well as specific instructions.  This is important, because it allows system designers to specify instructions at a high level of abstraction.  In practice, this means that VoiceXML is used to convey what is to be done, rather than how to do it.  For the designer, this leads to well-defined, modular system development.

This means that varetis can utilize best of breed technology as it evolves, and can implement technical solutions according to the specific needs of our customers – a practice that was at best difficult in the audio processing domain until now.   The result is better value, greater flexibility, and the ability to ride the technology curve without the need to constantly reinvest in technology infrastructure.

Data Quality Considerations

Even the best DA automation system is only as good as the data upon which it operates.  Data quality is of paramount importance in providing accurate, reliable DA service.  DA service providers work hard to ensure that their data is of the highest possible quality, and this must be reflected in the automation of these systems as well.  The trick is to maintain data quality as the scope of coverage increases.  

The diagram at right is an exploded view of the previous diagram, and includes varetis’ optional National Directory Assistance capabilities, which are provided in partnership with LSSI.  As traditional service providers expand into long distance services, the ability to provide DA services with national or international reach is growing in tandem.  In this diagram, you’ll notice that the NDIS search engine occurs twice – first, as an integral part of the DA system, and second, as an integral part of the NDA system, which is optionally provided by LSSI.  

This turns out to be important for reasons of consistency in providing automation services, because the same database can be used both for automated directory inquiries and for traditional operator-assisted inquiries.  This kind of consistency is important in providing high-quality service to consumers in both automated and non-automated domains, and is one of the factors that we regard as an important competitive advantage for varetis in providing an automated solution to our customers.  Moving forward, customers can even choose to extend this consistency, and the associated service quality, into the search domain through the use of NDIS in both automation and white pages environments.

Involving the Operator

Directory assistance automation has the capacity to entirely change the nature of operator interaction.  While users are provided with a consistent, friendly, intuitive dialog, operators are freed to handle more complex queries that do not lend themselves to automation so readily.  This provides a more satisfying working environment for the operator, and permits the service provider to focus operator assistance on higher-revenue inquiries, such as those for Enhanced DA, international DA, or even for concierge services.  In an automated environment, an operator is only involved in a call when necessary.  This is referred to as operator fallback, and it occurs only when the requested number cannot be found or if the caller experiences difficulties in using the system.  Operator fallback does not negate the use of automation, however; operators are also assisted by partial automation of the calls.  Any unambiguous responses that have been successfully recognized are used to populate the operator’s screen as the operator is connected to the call, resulting in improved search accuracy and shortened call holding times.  As the operator is connected, call control is automatically transferred from the automation system to the existing operator services infrastructure. 

Operator integration of this type is a challenging business; it requires the seamless interaction of the listings database, the operator position, and the operator services switching fabric.  varetis technology has been designed to accommodate this complexity by integrating with existing operator services infrastructure through the use of the Nortel Networks’ OPP and OAP protocol standards.  These standards permit a heterogeneous vendor environment to interact with TOPS, Directory One, Volt Delta

, and ISx switching and database infrastructure -- infrastructure that today dominates the existing North American Operator Services market.  The result is that much of the existing technology investment is protected even as varetis enhances its functionality -- good news for existing DA service providers.

Investment in Future Solutions

Perhaps the most important aspect of varetis’ technology, surprisingly, lies outside of the specific domain of DA automation.  It can be found instead in the unprecedented solutions flexibility that NDIS technology places in the hands of the DA service provider.  Unlike every solution that precedes it, NDIS is not a single-purpose search engine.  It can be exploited in a wide variety of database-driven applications for which outstanding speed and scalability are a prerequisite.  Beyond DA automation, for example, NDIS can be used to drive new services such as Internet Directory Assistance, Location Based Services, 511 Information Services and of course operator assisted DA.  An investment in NDIS is more than just an investment in DA automation; it represents a framework from within which a variety of new, revenue-generating services can be built.

These capabilities are supported by a variety of tools that allow service providers to acquire, scrub, and organize listing data in an efficient and cost-effective manner.  New data, such as location or namespace information can be merged with existing subscriber data accurately and quickly, expanding the possibilities for enhanced services development and deployment.  As the core of an end-to-end information services infrastructure, NDIS technology can help varetis customers to differentiate their services offerings in both breadth and depth, and can dramatically expand the business possibilities for network-based call center services.


varetis enters the North American Directory Assistance marketplace as more than just the leading supplier of DA systems throughout the world.  varetis also brings world-class technology, strong business partnerships, and a deep understanding of the technical requirements for integration with existing Operator Services infrastructure.  These capabilities are simply unmatched by any competitive vendor offering DA automation solutions today.

The Directory Company and Market Leader

varetis AG is the world leader in the production of professional directory solutions for providers of telecommunications and information services. More than 240 Call Centers and nearly 18,000 agent positions worldwide use products and solutions from varetis AG. Leading providers on all five continents, including AT&T, BT, Deutsche Telekom AG, Telkom South Africa, TOT Thailand and Telecom New Zealand, profit from varetis' nearly 20 years of experience. varetis AG currently employs a total of 280 people at its headquarters in Munich, at subsidiaries in Great Britain, Hungary and the United States, and at branch offices in Switzerland, France and Brazil. varetis AG (WKN 691 190) has been listed on the German Neuer Markt since February 7, 2000. Further information can be found at:

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