# Specification This document outlines the key elements of the [Contract Negotiation Protocol](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#contract-negotiation-protocol). The used terms are described [here](/ids-knowledgebase/dataspace-protocol/overview/terminology.md). * [Contract Negotiation Protocol](#contract-negotiation-protocol) * [1 Introduction](#1-introduction) * [1.1 States](#11-states) * [1.2 State Machine](#12-state-machine) * [2 Message Types](#2-message-types) * [2.1 Contract Request Message](#21-contract-request-message) * [2.2 Contract Offer Message](#22-contract-offer-message) * [2.3 Contract Agreement Message](#23-contract-agreement-message) * [2.4 Contract Agreement Verification Message](#24-contract-agreement-verification-message) * [2.5 Contract Negotiation Event Message](#25-contract-negotiation-event-message) * [2.6 Contract Negotiation Termination Message](#26-contract-negotiation-termination-message) * [3 Response Types](#3-response-types) * [3.1 ACK - Contract Negotiation](#31-ack---contract-negotiation) * [3.2 ERROR - Contract Negotiation Error](#32-error---contract-negotiation-error) ## 1 Introduction A [Contract Negotiation](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#contract-negotiation) (CN) involves two parties, a [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) that offers one or more [Datasets](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset) under a usage contract and [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) that requests [Datasets](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset). A CN is uniquely identified through an [IRI](https://www.w3.org/International/articles/idn-and-iri/). Each CN requires a newly generated IRI, which may not be used in a CN after a terminal state has been reached. A CN progresses through a series of states, which are tracked by the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) and [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) using messages. A CN transitions to a state in response to an acknowledged message from the counter-party. Both parties have the same state of the CN. In case the states differ, the CN is terminated and a new CN has to be initiated. ### 1.1 States The CN states are: * **REQUESTED**: A contract for a [Dataset](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset) has been requested by the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) based on an [Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer) and the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) has sent an ACK response. * **OFFERED**: The [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) has sent an [Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer) to the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) and the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) has sent an ACK response. * **ACCEPTED**: The [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) has accepted the latest [Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer) and the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) has sent an ACK response. * **AGREED**: The [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) has accepted the latest [Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer), sent an [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) to the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer), and the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) has sent an ACK response. * **VERIFIED**: The [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) has sent an [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) verification to the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) and the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) has sent an ACK response. * **FINALIZED**: The [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) has sent a finalization message including his own [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) verification to the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) and the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) has sent an ACK response. Data is now available to the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer). * **TERMINATED**: The [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) or [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) has placed the CN in a terminated state. A termination message has been sent by either of the [Participants](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#participant) and the other has sent an ACK response. This is a terminal state. ### 1.2 State Machine The CN state machine is represented in the following diagram: ![](/files/zFNlhPjxNeB0X25xztIw) Transitions marked with `C` indicate a message sent by the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer), transitions marked with `P` indicate a [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) message. Terminal states are final; the state machine may not transition to another state. A new CN may be initiated if, for instance, the CN entered the `TERMINATED` state due to a network issue. ## 2 Message Types The CN state machine is transitioned upon receipt and acknowledgement of a message. This section details those messages as abstract message types. * Concrete wire formats are defined by the protocol binding, e.g., [Contract Negotiation HTTPS Binding](/ids-knowledgebase/dataspace-protocol/contract-negotiation/contract.negotiation.binding.https.md).. * All [Policy](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#policy) types ([Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer), [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement)) must contain an unique identifier in the form of a URI. GUIDs can also be used in the form of URNs, for instance following the pattern . * An [ODRL Agreement](https://www.w3.org/TR/odrl-vocab/#term-Agreement) must have a target property containing the [Dataset](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset) id. ### 2.1 Contract Request Message | | | | ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Sent by** | [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) | | **Resulting state** | `REQUESTED`, `TERMINATED` | | **Response** | [ACK](#31-ack---contract-negotiation) or [ERROR](#32-error---contract-negotiation-error) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-request-message-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-request-message-schema.json) | | **Example** | Initiating [Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-request-message_initial.json), [Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-offer-message.json) | | **Diagram(s)** | ![](/files/YRxP3Y6sUK0siC4jDoWZ) | The Contract Request Message is sent by a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) to initiate a CN or to respond to a [Contract Offer Message](#22-contract-offer-message) sent by a [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider). * The [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) must include an `offer` property, which itself must have a `@id` property. If the message includes a `providerPid` property, the request will be associated with an existing CN and a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) [Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer) will be created using either the `offer` or `offer.@id` properties. If the message does not include a `providerPid`, a new CN will be created on [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) side using either the `offer` or `offer.@id` properties and the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) selects an appropriate `providerPid`. * An `offer.@id` will generally refer to an [Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer) contained in a [Catalog](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#catalog). If the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) is not aware of the `offer.@id` value, it must respond with an error message. * The `callbackAddress` is a URL indicating where messages to the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) should be sent in asynchronous settings. If the address is not understood, the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) MUST return an UNRECOVERABLE error. * Different to a [Catalog](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#catalog) or [Dataset](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset), the [Offer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#offer) inside a [Contract Request Message](#21-contract-request-message) must have an `odrl:target` attribute. However, it's contained Rules must not have any `odrl:target` attributes to prevent inconsistencies with the [ODRL inferencing rules for compact policies](https://www.w3.org/TR/odrl-model/#composition-compact). ### 2.2 Contract Offer Message | | | | ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | **Sent by** | [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) | | **Resulting state** | `OFFERED`, `TERMINATED` | | **Response** | [ACK](#31-ack---contract-negotiation) or [ERROR](#32-error---contract-negotiation-error) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-offer-message-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-offer-message-schema.json) | | **Example** | [Example Initial Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-offer-message_initial.json), [Example Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-offer-message.json) | | **Diagram(s)** |

Initial message (note the missing consumerPid)

Message following a Contract Request Message:

| The Contract Offer Message is sent by a [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) to initiate a CN or to respond to a [Contract Request Message](#21-contract-request-message) sent by a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer). * If the message includes a `consumerPid` property, the request will be associated with an existing CN. If the message does not include a `consumerPid`, a new CN will be created on [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) side and the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) selects an appropriate `consumerPid`. * The [Dataset](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset) id is not required but can be included when the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) initiates a CN. * Different to a [Dataset](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset) (see [DCAT Vocabulry Mapping](/ids-knowledgebase/dataspace-protocol/catalog/catalog.protocol.md#11-dcat-vocabulary-mapping)), the Offer inside a ContractOfferMessage must have an `odrl:target` attribute. However, it's contained Rules must not have any `odrl:target` attributes to prevent inconsistencies with the [ODRL inferencing rules for compact policies](https://www.w3.org/TR/odrl-model/#composition-compact). ### 2.3 Contract Agreement Message | | | | ------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Sent by** | [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) | | **Resulting state** | `AGREED`, `TERMINATED` | | **Response** | [ACK](#31-ack---contract-negotiation) or [ERROR](#32-error---contract-negotiation-error) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-agreement-message-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-agreement-message-schema.json) | | **Example** | [Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-agreement-message.json) | | **Diagram(s)** | ![](/files/5A24qjyBHBMLkwPrwE2h) | The Contract Agreement Message is sent by a [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) when it agrees to a contract. It contains the complete [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement). * The message must contain a `consumerPid` and a `providerPid`. * The message must contain an [ODRL Agreement](https://www.w3.org/TR/odrl-vocab/#term-Agreement). * An [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) must contain a `timestamp` property defined as an [XSD DateTime](https://www.w3schools.com/XML/schema_dtypes_date.asp) type. * An [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) must contain an `assigner` and `assignee`. The contents of these properties are a dataspace-specific unique identifier of the [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) parties. Note that these identifiers are not necessarily the same as the identifiers of the [Participant Agents](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#participant-agent) negotiating the contract (e.g., [Connectors](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#connector--data-service-)). * An [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) must contain a `odrl:target` property. None of its Rules, however, must have any `odrl:target` attributes to prevent inconsistencies with the [ODRL inferencing rules for compact policies](https://www.w3.org/TR/odrl-model/#composition-compact). ### 2.4 Contract Agreement Verification Message | | | | ------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Sent by** | [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) | | **Resulting state** | `VERIFIED`, `TERMINATED` | | **Response** | [ACK](#31-ack---contract-negotiation) or [ERROR](#32-error---contract-negotiation-error) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-agreement-verification-message-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-agreement-verification-message-schema.json) | | **Example** | [Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-agreement-verification-message.json) | | **Diagram(s)** | ![](/files/NkMau4oHR2Q12OwoBNmg) | The Contract Agreement Verification Message is sent by a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) to verify the acceptance of an [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement). * A [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) responds with an error if the contract cannot be validated or is incorrect. * The message must contain a `consumerPid` and a `providerPid`. ### 2.5 Contract Negotiation Event Message | | | | ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Sent by** | [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer), [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) | | **Resulting state** | `FINALIZED`, `ACCEPTED`, `TERMINATED` | | **Response** | [ACK](#31-ack---contract-negotiation) or [ERROR](#32-error---contract-negotiation-error) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-negotiation-event-message-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-negotiation-event-message-schema.json) | | **Example** | [Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-negotiation-event-message.json) | | **Diagram(s)** | ![](/files/rugzVepfqlpgiyEKbeBc) | When the Contract Negotiation Event Message is sent by a [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) with an `eventType` property set to `FINALIZED`, an [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) has been finalized and the associated [Dataset](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#dataset) is accessible. The state machine is transitioned to the `FINALIZED` state. * Other event types may be defined in the future. * A [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) responds with an error if the contract cannot be validated or is incorrect. * The message must contain a `consumerPid` and a `providerPid`. * When the message is sent by a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) with an `eventType` set to `ACCEPTED`, the state machine is placed in the `ACCEPTED` state. * It is an error for a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) to send the message with an event type `FINALIZED` to the [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider). * It is an error for a [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) to send the message with an event type `ACCEPTED` to the [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer). Note that CN events are not intended for propagation of an [Agreement](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#agreement) state after a CN has entered a terminal state. It is considered an error for a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) or [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) to send an event after the CN state machine has entered a terminal state. ### 2.6 Contract Negotiation Termination Message | | | | ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Sent by** | [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer), [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) | | **Resulting state** | `TERMINATED` | | **Response** | [ACK](#31-ack---contract-negotiation) or [ERROR](#32-error---contract-negotiation-error) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-negotiation-termination-message-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-negotiation-termination-message-schema.json) | | **Example** | [Message](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-negotiation-termination-message.json) | | **Diagram(s)** | ![](/files/xvgYy9FDp4KuSCJOT7A3) | The Contract Negotiation Termination Message is sent by a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) or [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) indicating it has cancelled the CN sequence. The message can be sent at any state of a CN without providing an explanation. Nevertheless, the sender may provide a description to help the receiver. * The message must contain a `consumerPid` and a `providerPid`. * If an error is received in response to the message, the sending party may choose to ignore the error. Note that a CN may be terminated for a variety of reasons, for example, an unrecoverable error was encountered or one of the parties no longer wishes to continue. A [Connector's](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#connector--data-service-) operator may remove terminated CN resources after it has reached the terminated state. ## 3 Response Types The `ACK` and `ERROR` response types are mapped onto a protocol such as HTTPS. A description of an error might be provided in protocol-dependent forms, e.g., for an HTTPS binding in the request or response body. ### 3.1 ACK - Contract Negotiation | | | | -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Sent by** | [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer), [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-negotiation-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-negotiation-schema.json) | | **Example** | [Process](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-negotiation.json) | | **Diagram(s)** | ![](/files/fpibJ4bmwp02l9NYfkL4) | The Contract Negotiation is an object returned by a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) or [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) indicating a successful state change happened. ### 3.2 ERROR - Contract Negotiation Error | | | | -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Sent by** | [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer), [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) | | **Schema** | [TTL Shape](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/shape/contract-negotiation-error-shape.ttl), [JSON Schema](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/schema/contract-negotiation-error-schema.json) | | **Example** | [Error](https://github.com/International-Data-Spaces-Association/ids-specification/blob/main/negotiation/message/example/contract-negotiation-error.json) | | **Diagram(s)** | ![](/files/nlIohUWtc9M6PmlnWfty) | The Contract Negotiation Error is an object returned by a [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) or [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) indicating an error has occurred. It does not cause a state transition. | Field | Type | Description | | ------------- | -------------- | ------------------------------------------------------------------------------------------------------------ | | `consumerPid` | UUID | The CN unique id on [Consumer](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#consumer) side. | | `providerPid` | UUID | The CN unique id on [Provider](/ids-knowledgebase/dataspace-protocol/overview/terminology.md#provider) side. | | `code` | String | An optional implementation-specific error code. | | `reason` | Array\[object] | An optional array of implementation-specific error objects. | --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.internationaldataspaces.org/ids-knowledgebase/dataspace-protocol/contract-negotiation/contract.negotiation.protocol.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.