Abstract

This document details the general architecture of Intelligent Personal Assistants as described in Architecture and Potential for Standardization Version 1.3 with regard to interface definitions. The architectural descriptions focus on intent-based voice-based personal assistants and chatbots. Current LLM intent-less chatbots may have other interface needs.

Status of This Document

This specification was published by the Voice Interaction Community Group. It is not a W3C Standard nor is it on the W3C Standards Track. Please note that under the W3C Community Contributor License Agreement (CLA) there is a limited opt-out and other conditions apply. Learn more about W3C Community and Business Groups.

Table of Contents

1. Introduction
2. Problem Statement
3. Architecture
4. High Level Interfaces
5. Low Level Interfaces

1. Introduction

Intelligent Personal Assistants (IPAs) are now available in our daily lives through our smart phones. Apple’s Siri, Google Assistant, Microsoft’s Cortana, Samsung’s Bixby and many more are helping us with various tasks, like shopping, playing music, setting a schedule, sending messages, and offering answers to simple questions. Additionally, we equip our households with smart speakers like Amazon’s Alexa or Google Home which are available without the need to pick up explicit devices for these sorts of tasks or even control household appliances in our homes. As of today, there is no interoperability among the available IPA providers. Especially for exchanging learned user behaviors this is unlikely to happen at all.

Furthermore, in addition to these general-purpose assistants, there are also specialized virtual assistants which are able to provide their users with in-depth information which is specific to an enterprise, government agency, school, or other organization. They may also have the ability to perform transactions on behalf of their users, such as purchasing items, paying bills, or making reservations. Because of the breadth of possibilities for these specialized assistants, it is imperative that they be able to interoperate with the general-purpose assistants. Without this kind of interoperability, enterprise developers will need to re-implement their intelligent assistants for each major generic platform.

This document is the second step in our strategy for IPA standardization. It is based on a general architecture of IPAs described in Architecture and Potential for Standardization Version 1.3 which aims at exploring the potential areas for standardization. It focuses on voice as the major input modality. We believe it will be of value not only to developers, but to many of the constituencies within the intelligent personal assistant ecosystem. Enterprise decision-makers, strategists and consultants, and entrepreneurs may study this work to learn of best practices and seek adjacencies for creation or investment. The overall concept is not restricted to voice but also covers purely text based interactions with so-called chatbots as well as interaction using multiple modalities. Conceptually, the authors also define executing actions in the user's environment, like turning on the light, as a modality. This means that components that deal with speech recognition, natural language understanding or speech synthesis will not necessarily be available in these deployments. In case of chatbots, speech components will be omitted. In case of multimodal interaction, interaction modalities may be extended by components to recognize input from the respective modality, transform it into something meaningful and vice-versa to generate output in one or more modalities. Some modalities may be used as output-only, like turning on the light, while other modalities may be used as input-only, like touch.

In this second step we describe the interfaces of the general architecture of IPAs in Architecture and Potential for Standardization Version 1.3. We believe it will be of value not only to developers, but to many of the constituencies within the intelligent personal assistant ecosystem. Enterprise decision-makers, strategists and consultants, and entrepreneurs may study this work to learn of best practices and seek adjacencies for creation or investment.

In order to cope with such use cases as those described above an IPA follows the general design concepts of a voice user interface, as can be seen in Figure 1.

Interfaces are described with the help of UML diagrams. We expect the reader to be familiar with that notation, although most concepts are easy to understand and do not require in-depth knowledge. The main diagram types used in this document are component diagrams and sequence diagrams. The UML diagrams are provided as Enterprise Architect Model pa-architecture.EAP. They can be viewed with the free of charge tool EA Lite

2. Problem Statement

2.1 Use Cases

This section describes potential usages of IPAs that will be used later in the document to illustrate the usage of the specified interfaces.

2.1.1 Weather Information

A user located in Berlin, Germany, is planning to visit her friend a few kilometers away, the next day. As she considers taking the bike, she asks the IPA for weather conditions.

2.1.2 Flight Reservation

A user located in Berlin, Germany, would like to plan a trio to an international conference and she wants to book a flight to the conference in San Francisco. Therefore, she approaches the IPA to help her with booking the flight,

3. Architecture

3.1 Architectural Principle

The architecture described in this document follows the SOLID principle introduced by Robert C. Martin to arrive at a scalable, understandable and reusable software solution.

Single responsibility principle

The components should have only one clearly-defined responsibility.

Open closed principle

Components should be open for extension, but closed for modification.

Liskov substitution principle

Components may be replaced without impacts onto the basic system behavior.

Interface segregation principle

Many specific interfaces are better than one general-purpose interface.

Dependency inversion principle

High-level components should not depend on low-level components. Both should depend on their interfaces.

This architecture aims at following both, a traditional partitioning of conversational systems, with separate components for speech recognition, natural language understanding, dialog management, natural language generation, and audio output, (audio files or text to speech) as well as newer LLM (Large Language Model) based approaches. This architecture does not rule out combining some of these components in specific systems.

3.2 Main Use Cases

Among others, the following most popular high-level use cases for IPAs are to be supported

1. Question Answering or Information Retrieval
2. Executing local and/or remote services to accomplish tasks

This is supported by a flexible architecture that supports dynamically adding local and remote services or knowledge sources such as data providers. Moreover, it is possible to include other IPAs, with the same architecture, and forward requests to them, similar to the principle of a Russian doll (omitting the Client Layer). All this describes the capabilities of the IPA. These extensions may be selected from a standardized marketplace. For the reminder of this document, we consider an IPA that is extendible via such a marketplace.

The following table lists the IPA main use cases and related examples that are used in this document

These main use cases are shown in the following figure

Not all components may be needed for actual implementations, some may be omitted completely. Especially, LLM-based architectures may combine the functionality of multiple components into only one or few components. However, we note them here to provide a more complete picture.

The architecture comprises three layers that are detailed in the following sections

1. Client Layer
2. Dialog Layer
3. External Data / Services / IPA Providers

Actual implementations may want to distinguish more or fewer than these layers. The assignment to the layers is not considered to be strict so that some of the components may be shifted to other layers as needed. This view only reflects a view that the Community Group regard as ideal and to show the intended separation of concerns.

According to these components they are assigned to the packages shown below.

4. High Level Interfaces

This section details the interfaces from the figure shown in the architecture. The interfaces are described with the following attributes

name

Name of the attribute

type

Hint if this attribute is a single data item or a category. The exact data types of the attributes are left open for now. A category may contain other categories or data items.

description

A short description to illustrate the purpose of this attribute.

required

Flag, if this attribute is required to be used in this interface.

A typical flow for the high level interfaces is shown in the following figure.

This sequence supports the major use cases stated above.

4.1 Interface Client Input

This interface describes the data that is sent from the IPA Client to the IPA Service. The following table details the data that should be considered for this interface in the method processInput

The session id can be created by the IPA Service. In case a session id is provided, it must be used for subsequent calls.

The IPA Client maintains request id for each request that is being sent via this interface. These ids must be unique within a session.

Audio data can be delivered mainly in two ways

1. Endpointed audio data
2. Streamed audio data

For endpointed audio data the IPA Client determines the end of speech, e.g., with the help of voice activity detection. In this case only that portion of audio is sent that contains the potential spoken user input.In terms of user experience this means that processing of the user input can only happen after the end of speech has been detected.

For streamed audio data, the IPA Client starts sending audio data as soon as it has been detected that the user is speaking to the system with the help of the Client Activation Strategy. In terms of user experience this means that processing of the user input can happen while the user is speaking.

An audio codec may be used, e.g., to reduce the amount of data to be transferred. The selection of the codec is not part of this specification.

Optionally, multimodal input can be transferred that has been captured as input from a specific modality recognizer. Modalities are all other modalities but audio, e.g., text for a chat bot, or gestures.

Optionally, meta data may be transferred augmenting the input. Examples of such data include user identification, timestamp and location.

The IPA Service may maintain a session id, e.g., to serve multiple clients and allow them to be distinguished.

As a return value this interface describes the data that is sent from the IPA Service to the IPA Client. The following table details the data that should be considered for this interface in the ClientResponse.

In case the parameter multimodal output contains commands to be executed, they are expected to follow the specification of the Interface Service Call.

The following sections will provide examples using the JSON format to illustrate the interfaces. JSON is only chosen as it is easy to understand and read. This specification does not make any assumptions about the underlying programming languages or data format. They are just meant to be an illustration of how responses may be generated with the provided data. It is not required that implementations follow exactly the described behavior.

4.1.2 Example Weather Information for Interface Client Input

The following request to processInput sends endpointed audio data with the user's current location to query for tomorrow's weather with the utterance What will the weather be like tomorrow".

{
	"sessionId": "0d770c02-2a13-11ed-a261-0242ac120002",
	"requestId": "42",
	"audio": {
		"type": "Endpointed",
		"data": "ZmhhcGh2cGF3aGZwYWhuZ...zI0MDc4NDY1NiB5dGhvaGF3",
		"encoding": "PCM-16BIT"
	}
	"multimodal": {
		"location": {
			"latitude": 52.51846213843821,
			"longitude": 13.37872252544883338.897957
		}
		...
	},
	"meta": {
		"timestamp": "2022-12-01T18:45:00.000Z"
		...
	}
}

In this example endpointed audio data is transfered as a value. There are other ways to send the audio data to the IPA, e.g., as a reference. This way is chosen as it is easier to illustrate the usage.

In return the the IPA may send back the following response Tomorrow there will be snow showers in Berlin with temperatures between 0 and -1 degrees via ClientResponse to the Client.

{
	"sessionId": "0d770c02-2a13-11ed-a261-0242ac120002",
	"requestId": "42",
	"audio": {
		"type": "Endpointed",
		"data": "Uvrs4hcGh2cGF3aGZwYWhuZ...vI0MDc4DGY1NiB5dGhvaRD2",
		"encoding": "PCM-16BIT"
	}
	"multimodal": {
		"text": "Tomorrow there will be snow showers in Berlin with temperatures between 0 and -1 degrees."
		...
	},
	"meta": {
		...
	}
}

4.1.3 Example Flight Reservation for Interface Client Input

The following request to processInput sends endpointed audio data with the user's current location to book a flight with the utterance I want to fly to San Francisco.

{
	"sessionId": "0c27895c-644d-11ed-81ce-0242ac120002",
	"requestId": "15",
	"audio": {
		"type": "Endpointed",
		"data": "ZmhhcGh2cGF3aGZwYWhuZ...zI0MDc4NDY1NiB5dGhvaGF3",
		"encoding": "PCM-16BIT"
	}
	"multimodal": {
		"location": {
			"latitude": 52.51846213843821,
			"longitude": 13.37872252544883338.897957
		}
		...
	},
	"meta": {
		"timestamp": "2022-11-14T19:50:00.000Z"
		...
	}
}

In return the the IPA may send back the following response When do you want to fly from Berlin to San Francisco? via ClientResponse to the Client

{
	"sessionId": "0d770c02-2a13-11ed-a261-0242ac120002",
	"requestId": "42",
	"audio": {
		"type": "Endpointed",
		"data": "Uvrs4hcGh2cGF3aGZwYWhuZ...vI0MDc4DGY1NiB5dGhvaRD2",
		"encoding": "PCM-16BIT"
	}
	"multimodal": {
		"text": "When do you want to fly from Berlin to San Francisco?"
		...
	},
	"meta": {
		...
	}
}

4.2 External Client Input

This interface describes the data that is sent from t the Provider Selection Service. The input is a copy of the data that is sent from the IPA Client to the IPA Service in Interface Client Input. This interface mainly differs in the return value. The following table details the data that should be considered for this interface in the method processInput.

As a return value this interface describes the data that is sent from the Provider Selection Service and the NLU and Dialog Management. The following table details the data that should be considered for this interface in the method ExternalClientResponse.

The parameters name, session id and request id are copies of the data received from the Interface Client Input.

This call is optional depending if external IPAs are used or not.

Depending on the capabilities of the external IPA the return value may be one of the following options

• multimodal output
• interpretation

The category interpretation may be one of the following options, depending on the capabilities of the external IPA

• single-intent, i.e. provide multiple intents in a single utterance
• multi-intent, i.e. provide one intent in a single utterance

With single-intent the user provides a single intent per utterance. An example for single-intent is "Book a flight to San Francisco for tomorrow morning." The single intent is here book-flight. With multi-intent the user provides multiple intents in a single utterance. An example for multi-intent is "How is the weather in San Francisco and book a flight for tomorrow morning." Provided intents are check-weather and book-flight. In this case the IPA needs to determine the order of intent execution based on the structure of the utterance. If not to be done in parallel, the IPA will trigger the next intent in the identified order.

As multi-intent is not very common in today's IPAs the focus for now is on single-intent as detailed in the following table

4.2.1 Example Weather Information for Interface External Client Input

The following request to processInput is a copy of Example Weather Information for Interface Client Input.

In return the the external IPA may send back the following response via ExternalClientResponse to the Dialog.

{
    "sessionId": "0d770c02-2a13-11ed-a261-0242ac120002",
    "requestId": "42",
    "callResult": "success",
    "interpretation": [
        {
            "intent": "check-weather",
            "intentConfidence": 0.9,
            "entities": [
                {
                    "location": "Berlin",
                    "entityConfidence": 1.0
                },
                {
                    "date": "2022-12-02",
                    "entityConfidence": 0.94
                },
            ]
        },
        ...	
    ]
}

The external speech recognizer converts the obtained audio into text like How will be the weather tomorrow. The NLU then extracts the following from that decoded utterance, other multimodal input and metadata.

• intent: check-weather from, e.g., utterance part How will the weather…
• entity: date from utterance part …tomorrow…
• entity: location, e.g., from the multimodal input of location

This is illustrated in the following figure.

4.2.2 Example Flight Reservation for Interface External Client Input

The following request to processInput is a copy of Example Flight Reservation for Interface Client Input.

In return the the IPA may send back the following response When do you want to fly from Berlin to San Francisco? via ClientResponse to the Client. In this case, empty entities, like date indicate that there are still slots to be filled and no service call can be made right now.

{
    "sessionId": "0d770c02-2a13-11ed-a261-0242ac120002",
    "requestId": "42",
    "callResult": "success",
    "interpretation": [
        {
            "intent": "book-flight",
            "intentConfidence": 0.87,
            "entities": [
                {
                    "origin": "Berlin",
                    "entityConfidence": 1.0
                },
                {
                    "destination": "San Francisco",   
                    "entityConfidence": 0.827
                },
                {
                    "date": "",   
                },
                ...
            ]
        },
        ...	
    ]
}

The external speech recognizer converts the obtained audio into text like I want to fly to San Francisco. The NLU then extracts the following from that decoded utterance, other multimodal input and metadata.

• intent: book-fligh from, e.g., utterance part I want to fly…
• entity: location from utterance part …San Francisco…
• entity: location, e.g., from the multimodal input of location

This is illustrated in the following figure.

Further steps will be needed to convert both location entities to origin and destination in the actual reply. This may be either done by the flight reservation IPA directly or by calling external services beforehand to determine the nearest airports from these locations.

4.3 External Service Call

This interface describes the data that is sent from the Dialog to the Provider Selection Service. The following table details the data that should be considered for this interface in the method callService.

As a return value the result of this call is sent back in the ClientResponse.

This call is optional depending on the result of the next dialog step if an external service should be called or not.

4.3.1 Example Weather Information for Interface Service Call

The following request to callService may be made to call the weather information service. Although calling the weather service is not a direct functionality of the IPA, it may help to understand how the entered data may be processed to obtain a spoken reply to the user's input.

{
    "sessionId": "0d770c02-2a13-11ed-a261-0242ac120002",
    "requestId": "42",
    "services": [
        {
            "serviceId": "weather-service",
            "parameters": [
                {
                    "location": "Berlin",
                    "date": "2022-12-02"
                }
            ]
        },
        ...	
    ]
}

In return the the external service may send back the following response via ExternalClientResponse to the Dialog

{
    "sessionId": "0d770c02-2a13-11ed-a261-0242ac120002",
    "requestId": "42",
    "callResult": "success",
    "services": [
        {
            "serviceId": "weather-information",
            "callResult": "success",
            "callResultDetails": [
                {
                    "location": "Berlin",
                    "date": "2022-12-02",
                    "forecast": "snow showers",
                    "minTemperature": -1,
                    "maxTemperature": 0,
                    ...
                }
            ]
        },
        ...	
    ]
}

This information is the used to actually create a reply to the user as described in ExternalClientResponse to the Client.

4.4.Error Handling

Errors may occur anywhere in the processing chain of the IPA. The following gives an overview of how they are suggested to be handled.

Along the processing path errors may occur

1. in the response of a call to another component
2. inside this component to be further processed by subsequent components

Error messages carry the following information

5. Low Level Interfaces

This section is still under preparation.

5.1. Client Layer

The Client Layer contains the main components that interface with the user.

5.1.1 IPA Client

Clients enable the user to access the IPA via voice. The following diagram provides some more insight.

5.1.1.1 Modality Manager

The modality manager enables access to the modalities that are supported by the IPA Client. Major modalities are voice and text in case of chatbots. The following interfaces are supported

• Client Interaction
• Handle-xxx-Modality

5.1.1.2 Client Activation Strategy

The Client Activation Strategy defines how the client gets activated to be ready to receive spoken commands as input. In turn the Microphone is opened for recording. Client Activation Strategies are not exclusive but may be used concurrently. The most common activation strategies are described in the table below.

The usage of hotwords includes privacy aspects as the microphone needs to be always active. Streaming to the components outside the user's control should be avoided, hence detection of hotwords should ideally happen locally. With regard to nested usage of IPAs that may feature their own hotwords, the detection of hotwords might be required to be extensible.

5.2 Dialog Layer

The Dialog Layer contains the main components to drive the interaction with the user.

5.2.1 IPA Service

5.2.2 ASR

5.2.3 NLU

5.2.4 Dialog Management

5.3 External Data / Services / IPA Providers

5.3.1 Provider Selection Service