1 Introduction

1.1 IPR Policy

This specification is provided under the RF on Limited Terms Mode of the OASIS IPR Policy, the mode chosen when the Technical Committee was established. For information on whether any patents have been disclosed that may be essential to implementing this specification, and any offers of patent licensing terms, please refer to the Intellectual Property Rights section of the TC’s web page (https://www.oasis-open.org/committees/dss-x/ipr.php).

1.2 Terminology

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119] and [RFC8174].

1.2.1 Terms and Definitions

For the purposes of this document no specific terms or definitions have been identified as deviating from the usual meaning in the context of XML / JSON schema, digital signatures or transport.

1.2.2 Abbreviated Terms

JSON — JavaScript Object Notation

URI — (IETF) Uniform Resource Identifier according to [RFC3986]

URL — Uniform Resource Locator

XML — (W3C) Extensible Markup Language

XSD — (W3C) XML Schema

1.3 Normative References

[DSS2JSON] A. Kuehne, S. Hagen. DSS 2.0 Core JSON Schema. OASIS, oasis-dss-core-schema-v2.0-schema.json

[DSS2-XSD] A. Kuehne, S. Hagen. DSS 2.0 Core XML Schema. OASIS, oasis-dss-core-schema-v2.0.xsd

[DSSMD-JSON] D. Hühnlein, A. Kuehne. Digital Signature Service Metadata JSON Schema. OASIS.

[DSSMD-XML] D. Hühnlein, A. Kuehne. Digital Signature Service Metadata XML Schema. OASIS, oasis-dss-metadata-schema.xsd

[ISO3166-1] ISO 3166-1:2013: "Codes for the representation of names of countries and their subdivisions — Part 1: Country codes".

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, http://www.rfc-editor.org/info/rfc2119.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, https://www.rfc-editor.org/info/rfc3986.

[RFC5646] Phillips, A., Ed., and M. Davis, Ed., "Tags for Identifying Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, September 2009, https://www.rfc-editor.org/info/rfc5646

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, http://www.rfc-editor.org/info/rfc8174.

1.4 Non-Normative References

[BDX-SMP-v1.0] Service Metadata Publishing (SMP) Version 1.0. Edited by Jens Aabol, Kenneth Bengtsson, Erlend Klakegg Bergheim, Sander Fieten, and Sven Rasmussen. 01 August 2017. OASIS Standard. http://docs.oasis-open.org/bdxr/bdx-smp/v1.0/os/bdx-smp-v1.0-os.html

[BDX-SMP-v2.0] Service Metadata Publishing (SMP) Version 2.0. Edited by Kenneth Bengtsson, Erlend Klakegg Bergheim, Sander Fieten, and G. Ken Holman. 30 January 2019. OASIS Committee Specification Draft 02 / Public Review Draft 02. https://docs.oasis-open.org/bdxr/bdx-smp/v2.0/csprd02/bdx-smp-v2.0-csprd02.html. Latest version: https://docs.oasis-open.org/bdxr/bdx-smp/v2.0/bdx-smp-v2.0.html

[CSC-v1.0] Cloud Signature Consortium, “Architectures and protocols for remote signature applications”, Published version 1.0.3.0, 2018

[DSS-v1.0] Digital Signature Service Core Protocols, Elements, and Bindings Version 1.0. Edited by Stefan Drees. 11 April 2007. OASIS Standard. http://docs.oasis-open.org/dss/v1.0/oasis-dss-core-spec-v1.0-os.html.

[DSS-v2.0] Digital Signature Service Core Protocols, Elements, and Bindings Version 2.0. Edited by Andreas Kuehne and Stefan Hagen. 20 February 2019. OASIS Committee Specification 02. http://docs.oasis-open.org/dss-x/dss-core/v2.0/cs02/dss-core-v2.0-cs02.html. Latest version: http://docs.oasis-open.org/dss-x/dss-core/v2.0/dss-core-v2.0.html.

[eIDAS] Regulation (EU) No 910/2014 of the European Parliament and of the Council of of 23 July 2014 on electronic identification and trust services for electronic transactions in the internal market and repealing Directive 1999/93/EC, http://data.europa.eu/eli/reg/2014/910/oj.

[OIDC-MD] OpenID Connect Discovery 1.0. Edited by N. Sakimura, J. Bradley, M. Jones and E. Jay, 8 November 2014, https://openid.net/specs/openid-connect-discovery-1_0.html

[OpenAPI] The OpenAPI Specification, https://github.com/OAI/OpenAPI-Specification

[RFC8414] M. Jones, N. Sakimura, J. Bradley. OAuth 2.0 Authorization Server Metadata. IETF RFC 8414, June 2018.
http://www.ietf.org/rfc/rfc8414.txt.

[SAML-MD] Metadata for the OASIS Security Assertion Markup Language (SAML) V2.0. Edited by Scott Cantor, Jahan Moreh, Rob Philpott and Eve Maler. 15 March 2005, OASIS Standard. https://docs.oasis-open.org/security/saml/v2.0/saml-metadata-2.0-os.pdf

[TS119432] ETSI, “Electronic Signatures and Infrastructures (ESI); Protocols for remote digital signature creation”, ETSI TS 119 432, V1.1.1 (2019-03), https://www.etsi.org/deliver/etsi_ts/119400_119499/119432/01.01.01_60/ts_119432v010101p.pdf

[TS119442] ETSI, “Electronic Signatures and Infrastructures (ESI); Protocol profiles for trust service providers providing AdES digital signature validation services”, ETSI TS 119 442, V1.1.1 (2019-02), https://www.etsi.org/deliver/etsi_ts/119400_119499/119442/01.01.01_60

[TS119512] ETSI, “Electronic Signatures and Infrastructures (ESI); Protocols for trust service providers providing long-term data preservation services”, Draft ETSI TS 119 512, V0.0.9 (2019-05).

[TS119612] ETSI, “Electronic Signatures and Infrastructures (ESI); Trusted Lists”, ETSI TS 119 612, V2.2.1 (2016-04), https://www.etsi.org/deliver/etsi_ts/119600_119699/119612/02.02.01_60/.

[WSDL] Web Services Description Language (WSDL) 1.1, W3C Note 15 March 2001, https://www.w3.org/TR/2001/NOTE-wsdl-20010315

1.5 Typographical Conventions

Keywords defined by this specification use this monospaced font.

Normative source code uses this paragraph style.

Text following the special symbol («) – an opening Guillemet (or French quotation mark) – within this specification identifies automatically testable requirements to aid assertion tools. Every such statement is separated from the following text with the special end symbol (») – a closing Guillemet and has been assigned a reference that follows that end symbol in one of the three patterns:

1. [DSS-section#-local#] if it applies regardless of syntax

2. [JDSS-section#-local#] if it applies only to JSON syntax

3. [XDSS-section#-local#] if it applies only to XML syntax

Some sections of this specification are illustrated with non-normative examples.

Example 1: text describing an example uses this paragraph style

Non-normative examples use this paragraph style.

All examples in this document are non-normative and informative only.

Representation-specific text is indented and marked with vertical lines.

Representation-Specific Headline

Normative representation-specific text

All other text is normative unless otherwise labelled e.g. like:

Non-normative Comment:

This is a pure informative comment that may be present, because the information conveyed is deemed useful advice or common pitfalls learned from implementer or operator experience and often given including the rationale.

1.6 Motivation and related work (Non-normative)

Based on existing [DSS-v1.0] and emerging [DSS-v2.0] standards for digital signature services as well as the [eIDAS] regulation on electronic identification and trust services, there is a growing ecosystem consisting of providers and consumers of a variety of digital signature related services, which raises the demand for a normalised discovery and provision of service-related metadata.

While there are already standards for the handling of service-related metadata for services for exchanging business documents (see [BDX-SMP-v1.0] and [BDX-SMP-v2.0]) or identity management services (see [SAML-MD], [RFC8414] and [OIDC-MD]), there is currently no comprehensive metadata standard for digital signature services, but only first steps towards filling this gap (see [CSC-v1.0], [TS119432] and [TS119512]).

Against this background, the present document aims at providing a generic and extensible structure (see clauses 2 and 3) and simple discovery mechanism (see clause 4) for digital signature service-related metadata, which is intended to be used in conjunction with [DSS-v2.0] and related profiles and extensions, such as [TS119432], [TS119442] and [TS119512] for example.

2 Overview

As depicted in Figure 1, the main components of the service-related metadata structure specified in the present document comprise Provider, Protocol, Profile, Operation and Policy.

Figure 1: Overview of main components within the service-related metadata structures

The main component is the Provider element (see clause 3.1.1), which contains general metadata related to the provider of the service(s). As a service provider may support one or more protocols, for signature generation, signature validation or long-term preservation for example, and a provider may support different profiles of the supported protocols, the Provider element may contain one or more Protocol elements (see clause 3.1.2), which in turn may contain one or more Profile elements (see clause 3.1.3), which describe the supported profiles. A Profile element may in turn contain among other elements one or more Operation elements (see clause 3.1.4) and zero or more Policy elements (see 3.1.7), in which the applicable policies are specified or referenced.

3 Data Structure Models

3.1 Data Structure Models defined in this document

The XML elements of this section are defined in the XML namespace 'http://docs.oasis-open.org/dss-x/ns/metadata'.

3.1.1 Component Provider

The component Provider is the main element of the metadata structure and contains information about the provider of the digital signature services. The structure of this component has been inspired by the content provided by the info call defined in [CSC-v1.0].

Below follows a list of the sub-components that constitute this component:

The Name element MUST contain one instance of a string, which contains the commercial name of the service provider. It is RECOMMENDED to limit the size of this string to 255 characters.

The Logo element MUST contain one instance of a URI, which refers to an image file containing the logo of the service provider. This image file MUST be published online and SHOULD either be in JPEG or PNG format and SHOULD NOT be larger than 256x256 pixels.

The Region element MUST contain one instance of a string with the [ISO3166-1] Alpha-2 code of the country in which the service provider is established.

The OPTIONAL SupportedLanguage element, if present, MAY occur zero or more times in order to signal the set of supported languages in line with [RFC5646].

The OPTIONAL Description element, if present, MAY occur zero or more times containing a sub-component, which provides additional information which describes the service. If present each instance MUST satisfy the requirements specified in [DSS-v2.0] for the InternationalString component, whereas it is RECOMMENDED to limit the size of the value component to 255 characters.

The OPTIONAL AuthInfo element, if present, MUST contain a URI, which provides information on the authentication and authorisation mechanisms required to access the provided services. This URI SHOULD point to OAuth 2.0 [RFC8414] or SAML 2.0 [SAML-MD] specific metadata.

The Protocol element MUST occur 1 or more times containing a sub-component, which provides information about the supported protocols of the service. Each instance MUST satisfy the requirements specified in this document in section 3.1.2.

The OPTIONAL Extension element, if present, MAY occur zero or more times containing a sub-component, which extends the semantic of the Provider component. If present each instance MUST satisfy the requirements specified in this document in section 3.1.9.

3.1.1.1 Provider – JSON Syntax

The ProviderType JSON object SHALL implement in JSON syntax the requirements defined in the Provider component.

Properties of the JSON object SHALL implement the sub-components of Provider using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
Name	name
Logo	logo
Region	region
SupportedLanguage	lang
Description	description
AuthInfo	authinfo
Protocol	protocol
Extension	ext

The ProviderType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-ProviderType": {

"type": "object",

"properties": {

"name": {

"type": "string"

"logo": {

"type": "string"

"region": {

"type": "string"

"lang": {

"type": "array",

"items": {

"type": "string"

}

"description": {

"type": "array",

"items": {

"$ref": "#/definitions/dsb-InternationalStringType"

}

"authinfo": {

"type": "string"

"protocol": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ProtocolType"

}

"ext": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ExtensionType"

}

"required": ["name", "logo", "region", "protocol"]

}

3.1.1.2 Provider – XML Syntax

The XML type ProviderType SHALL implement the requirements defined in the Provider component.

The ProviderType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="ProviderType">

<xs:sequence>

<xs:element name="Name" type="xs:string"/>

<xs:element name="Logo" type="xs:anyURI"/>

<xs:element name="Region" type="xs:string"/>

<xs:element name="SupportedLanguage" type="xs:language" maxOccurs="unbounded" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Description"/>

<xs:element name="AuthInfo" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

<xs:element name="Protocol" type="md:ProtocolType" maxOccurs="unbounded" minOccurs="1"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Extension"/>

</xs:sequence>

</xs:complexType>

Each child element of ProviderType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.2 Component Protocol

The Protocol component is part of the Provider component specified in clause 3.1.1 and provides information about a digital signature related protocol supported by the service provider.

Below follows a list of the sub-components that constitute this component:

The OPTIONAL Server element, if present, MUST contain one instance of a URI, which SHOULD be the URL of the target host of the service supporting the protocol. For REST-based services this is the URL of Server Object component within [OpenAPI] and for SOAP-based services this is the soap:address within [WSDL].

The OPTIONAL Specification element, if present, MAY occur zero or more times containing a URI, which points to a specification document describing the digital signature related protocol. Examples of digital signature related protocols include the generation [DSS-v1.0, DSS-v2.0, TS119432], validation [TS119442] and preservation [TS119512] of digital signatures.

The OPTIONAL Version element, if present, MUST contain a string, which indicates the version of the protocol specification, if it is not specified within the specification document mentioned above.

The OPTIONAL Description element, if present, MAY occur zero or more times containing a sub-component, which provides additional information with respect to the supported protocol. If present, each instance MUST satisfy the requirements specified in [DSS-v2.0] for the InternationalString component.

The Profile element MUST occur 1 or more times containing a sub-component, which further describes the specific profile of the supported digital signature related protocol. Each instance MUST satisfy the requirements specified in this document in section 3.1.3.

The OPTIONAL Extension element, if present, MAY occur zero or more times containing a sub-component, which extends the semantics of the Protocol component. If present each instance MUST satisfy the requirements specified in this document in section 3.1.9.

3.1.2.1 Protocol – JSON Syntax

The ProtocolType JSON object SHALL implement in JSON syntax the requirements defined in the Protocol component.

Properties of the JSON object SHALL implement the sub-components of Protocol using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
Server	srv
Specification	spec
Version	version
Description	description
Profile	profile
Extension	ext

The ProtocolType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-ProtocolType": {

"type": "object",

"properties": {

"srv": {

"type": "string"

"spec": {

"type": "array",

"items": {

"type": "string"

}

"version": {

"type": "string"

"description": {

"type": "array",

"items": {

"$ref": "#/definitions/dsb-InternationalStringType"

}

"profile": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ProfileType"

}

"ext": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ExtensionType"

}

"required": ["profile"]

}

3.1.2.2 Protocol – XML Syntax

The XML type ProtocolType SHALL implement the requirements defined in the Protocol component.

The ProtocolType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="ProtocolType">

<xs:sequence>

<xs:element name="Server" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

<xs:element name="Specification" type="xs:anyURI" maxOccurs="unbounded" minOccurs="0"/>

<xs:element name="Version" type="xs:string" maxOccurs="1" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Description"/>

<xs:element name="Profile" type="md:ProfileType" maxOccurs="unbounded" minOccurs="1"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Extension"/>

</xs:sequence>

</xs:complexType>

Each child element of ProtocolType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.3 Component Profile

The Profile component is part of the Protocol component specified in clause 3.1.2 and provides information about the specific profile of the supported digital signature related protocol.

Below follows a list of the sub-components that constitute this component:

The ProfileIdentifier element MUST contain one instance of a URI, which uniquely identifies the profile of the digital signature related protocol.

The OPTIONAL Specification element, if present, MAY occur zero or more times containing a URI, which points to a specification document describing the specific profile of the digital signature related protocol.

The OPTIONAL Description element, if present, MAY occur zero or more times containing a sub-component, which satisfies the requirements specified in [DSS-v2.0] for the InternationalString component and can be used to provide descriptions of the profile in multiple languages.

The Operation element MUST occur 1 or more times containing a sub-component, which describes a specific operation supported by the profile of the digital signature related protocol. For each supported operation there MUST be an Operation component and each instance MUST satisfy the requirements specified in this document in section 3.1.4.

The OPTIONAL Policy element, if present, MAY occur zero or more times containing a sub-component, which specifies the set of policies, which are applicable for the specific profile of the digital signature related protocol. If present each instance MUST satisfy the requirements specified in this document in section 3.1.7.

The OPTIONAL Extension element, if present, MAY occur zero or more times containing a sub-component, which extends the semantics of the Profile component.. If present each instance MUST satisfy the requirements specified in this document in section 3.1.9.

3.1.3.1 Profile – JSON Syntax

The ProfileType JSON object SHALL implement in JSON syntax the requirements defined in the Profile component.

Properties of the JSON object SHALL implement the sub-components of Profile using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
ProfileIdentifier	pid
Specification	spec
Description	description
Operation	op
Policy	pol
Extension	ext

The ProfileType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-ProfileType": {

"type": "object",

"properties": {

"pid": {

"type": "string"

"spec": {

"type": "array",

"items": {

"type": "string"

}

"description": {

"type": "array",

"items": {

"$ref": "#/definitions/dsb-InternationalStringType"

}

"op": {

"type": "array",

"items": {

"$ref": "#/definitions/md-OperationType"

}

"pol": {

"type": "array",

"items": {

"$ref": "#/definitions/md-PolicyType"

}

"ext": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ExtensionType"

}

"required": ["pid", "op"]

}

3.1.3.2 Profile – XML Syntax

The XML type ProfileType SHALL implement the requirements defined in the Profile component.

The ProfileType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="ProfileType">

<xs:sequence>

<xs:element name="ProfileIdentifier" type="xs:anyURI"/>

<xs:element name="Specification" type="xs:anyURI" maxOccurs="unbounded" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Description"/>

<xs:element name="Operation" type="md:OperationType" maxOccurs="unbounded" minOccurs="1"/>

<xs:element name="Policy" type="md:PolicyType" maxOccurs="unbounded" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Extension"/>

</xs:sequence>

</xs:complexType>

Each child element of ProfileType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.4 Component Operation

The Operation component is part of the Profile component specified in clause 3.1.3 and provides information about an operation supported by a specific profile of the supported digital signature related protocol.

Below follows a list of the sub-components that constitute this component:

The Name element MUST contain one instance of a string, which MUST reflect the name of the request to invoke the operation. For REST-based services this corresponds to the Paths Object component within [OpenAPI] and the Name element SHOULD contain the relative path the endpoint at which the operation can be invoked, which is appended to the URL of the Server component within the Protocol element specified in clause 3.1.2. For SOAP-based services the Name element corresponds to the soap:operation within [WSDL].

The OPTIONAL Specification element, if present, MUST contain a URI, which points to a specification document describing the specific operation under consideration.

The OPTIONAL Input element, if present, MAY occur zero or more times containing a sub-component, which specifies details of a specific input parameter. If present each instance MUST satisfy the requirements specified in this document in section 3.1.5.

The OPTIONAL Option element, if present, MAY occur zero or more times containing a sub-component, which specifies details of a specific optional input parameter. If present each instance MUST satisfy the requirements specified in this document in section 3.1.5.

The OPTIONAL Output element, if present, MAY occur zero or more times containing a sub-component, which specifies details of a specific output parameter. If present each instance MUST satisfy the requirements specified in this document in section 3.1.5.

The OPTIONAL Schema element, if present, MUST contain a URI, which points to the applicable schema document, which defines the detailed syntax of the component implementing the operation under consideration.

The OPTIONAL Extension element, if present, MAY occur zero or more times containing a sub-component, which extends the semantics of the Operation element. If present each instance MUST satisfy the requirements specified in this document in section 3.1.9.

3.1.4.1 Operation – JSON Syntax

The OperationType JSON object SHALL implement in JSON syntax the requirements defined in the Operation component.

Properties of the JSON object SHALL implement the sub-components of Operation using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
Name	name
Specification	spec
Description	desc
Input	in
Option	opt
Output	out
Schema	xsd
Extension	ext

The OperationType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-OperationType": {

"type": "object",

"properties": {

"name": {

"type": "string"

"spec": {

"type": "string"

"desc": {

"type": "array",

"items": {

"$ref": "#/definitions/dsb-InternationalStringType"

}

"in": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ParameterType"

}

"opt": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ParameterType"

}

"out": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ParameterType"

}

"xsd": {

"type": "string"

"ext": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ExtensionType"

}

"required": ["name"]

}

3.1.4.2 Operation – XML Syntax

The XML type OperationType SHALL implement the requirements defined in the Operation component.

The OperationType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="OperationType">

<xs:sequence>

<xs:element name="Name" type="xs:string"/>

<xs:element name="Specification" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Description"/>

<xs:element name="Input" type="md:ParameterType" maxOccurs="unbounded" minOccurs="0"/>

<xs:element name="Option" type="md:ParameterType" maxOccurs="unbounded" minOccurs="0"/>

<xs:element name="Output" type="md:ParameterType" maxOccurs="unbounded" minOccurs="0"/>

<xs:element name="Schema" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Extension"/>

</xs:sequence>

</xs:complexType>

Each child element of OperationType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.5 Component Parameter

The Parameter component defines the syntax and semantics of the child components Input, Option and Output of the Operation component specified in clause 3.1.4 and allows to provide additional information with respect to specific input and output parameters as well as the available options for an operation, if this is not yet unambiguously specified by the document referenced in the child element Specification of the Operation according to clause 3.1.4.

Below follows a list of the sub-components that constitute this component:

The Name element MUST contain one instance of a string, which reflects the name of the paramter under consideration.

The OPTIONAL Specification element, if present, MUST contain a URI, which points to a specification document describing additional details with respect to the parameter under consideration.

The OPTIONAL Format element, if present, MAY occur zero or more times containing a sub-component, which can be used to specify the format of the (optional) input or output parameter under consideration. If present each instance MUST satisfy the requirements specified in this document in section 3.1.6.

The OPTIONAL Extension element, if present, MAY occur zero or more times containing a sub-component, which extends the semantis of the Parameter component. If present each instance MUST satisfy the requirements specified in this document in section 3.1.9.

3.1.5.1 Parameter – JSON Syntax

The ParameterType JSON object SHALL implement in JSON syntax the requirements defined in the Parameter component.

Properties of the JSON object SHALL implement the sub-components of Parameter using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
Name	name
Specification	spec
Description	desc
Format	form
Schema	xsd
Extension	ext

The ParameterType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-ParameterType": {

"type": "object",

"properties": {

"name": {

"type": "string"

"spec": {

"type": "string"

"desc": {

"type": "array",

"items": {

"$ref": "#/definitions/dsb-InternationalStringType"

}

"form": {

"type": "array",

"items": {

"$ref": "#/definitions/md-FormatType"

}

"xsd": {

"type": "string"

"ext": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ExtensionType"

}

"required": ["name"]

}

3.1.5.2 Parameter – XML Syntax

The XML type ParameterType SHALL implement the requirements defined in the Parameter component.

The ParameterType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="ParameterType">

<xs:sequence>

<xs:element name="Name" type="xs:string"/>

<xs:element name="Specification" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Description"/>

<xs:element name="Format" type="md:FormatType" maxOccurs="unbounded" minOccurs="0"/>

<xs:element name="Schema" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Extension"/>

</xs:sequence>

</xs:complexType>

Each child element of ParameterType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.6 Component Format

The Format component is part of the Parameter component specified in clause 3.1.5 and allows to provide additional information with respect to format of the specific input and output parameters or options of an operation, if this is not yet unambiguously specified by the document referenced in the child element Specification of the Operation according to clause 3.1.4.

Below follows a list of the sub-components that constitute this component:

The FormatID element MUST contain one instance of a URI, which identifies the format of the parameter.

The OPTIONAL Specification element, if present, MUST contain a URI, which points to a specification document describing additional details with respect to the format under consideration.

The OPTIONAL Parameter element, if present, MAY occur zero or more times containing a sub-component, which provides more information with respect to a specific parameter under consideration. If present each instance MUST satisfy the requirements specified in this document in section 3.1.5.

The OPTIONAL Extension element, if present, MAY occur zero or more times containing a sub-component, which extends the semantic of the Format component. If present each instance MUST satisfy the requirements specified in [DSS-v2.0] for the Any component.

The OPTIONAL IsDefault element, if present, MUST contain one instance of a boolean and indicates whether the format under consideration is the default format. Its default value is 'false'. The precise semantics what it means that a format is considered to be “the default format” MUST be defined by profiles or extensions of [DSS-v2.0].

3.1.6.1 Format – JSON Syntax

The FormatType JSON object SHALL implement in JSON syntax the requirements defined in the Format component.

Properties of the JSON object SHALL implement the sub-components of Format using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
FormatID	fid
Specification	spec
Description	desc
Parameter	format
Extension	ext
IsDefault	def

The FormatType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-FormatType": {

"type": "object",

"properties": {

"fid": {

"type": "string"

"spec": {

"type": "string"

"desc": {

"type": "array",

"items": {

"$ref": "#/definitions/dsb-InternationalStringType"

}

"format": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ParameterType"

}

"ext": {

"type": "array",

"items": {

"$ref": "#/definitions/dsb-AnyType"

}

"def": {

"type": "boolean",

"default": "false"

}

"required": ["fid"]

}

3.1.6.2 Format – XML Syntax

The XML type FormatType SHALL implement the requirements defined in the Format component.

The FormatType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="FormatType">

<xs:sequence>

<xs:element name="FormatID" type="xs:anyURI"/>

<xs:element name="Specification" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Description"/>

<xs:element name="Parameter" type="md:ParameterType" maxOccurs="unbounded" minOccurs="0"/>

<xs:element name="Extension" type="dsb:AnyType" maxOccurs="unbounded" minOccurs="0"/>

</xs:sequence>

<xs:attribute name="IsDefault" type="xs:boolean" default="false" use="optional"/>

</xs:complexType>

Each child element of FormatType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.7 Component Policy

The Policy component appears within the Profile component specified in clause 3.1.3 and provides information about an applicable policy of the profile of the supported digital signature related protocol.

Below follows a list of the sub-components that constitute this component:

The OPTIONAL PolicyByRef element, if present, MUST contain one instance of a sub-component, which provides a reference to a human readible policy document. This element MUST satisfy the requirements specified in this document in section 3.1.8.

The OPTIONAL PolicyByDef element, if present, MUST contain one instance of a sub-component, which contains a machine readible policy document. This element MUST satisfy the requirements specified in [DSS-v2.0] for the Any component. The detailed syntax and semantics of the machine readibly policy document MUST be defined by profiles or extensions of [DSS-v2.0] or specifications referenced in such documents.

The OPTIONAL EarlierPolicy element, if present, MAY occur zero or more times containing a URI, which refers to an earlier policy document.

The OPTIONAL Extension element, if present, MAY occur zero or more times containing a sub-component, which extends the semantics of the Policy component. If present each instance MUST satisfy the requirements specified in this document in section 3.1.9.

The OPTIONAL Type element, if present, MUST contain one instance of a URI. The admissible or recommended values for the policy types SHOULD be defined by profiles or extensions of [DSS-v2.0].

3.1.7.1 Policy – JSON Syntax

The PolicyType JSON object SHALL implement in JSON syntax the requirements defined in the Policy component.

Properties of the JSON object SHALL implement the sub-components of Policy using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
PolicyByRef	pbref
PolicyByDef	pbdef
EarlierPolicy	ep
Extension	ext
Type	type

The PolicyType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-PolicyType": {

"type": "object",

"properties": {

"type": {

"type": "string",

"format": "uri"

"pbref": {

"$ref": "#/definitions/md-PolicyByRefType"

"pbdef": {

"$ref": "#/definitions/dsb-AnyType"

"ep": {

"type": "array",

"items": {

"type": "string"

}

"ext": {

"type": "array",

"items": {

"$ref": "#/definitions/md-ExtensionType"

}

3.1.7.2 Policy – XML Syntax

The XML type PolicyType SHALL implement the requirements defined in the Policy component.

The PolicyType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="PolicyType">

<xs:sequence>

<xs:choice>

<xs:element name="PolicyByRef" type="md:PolicyByRefType"/>

<xs:element name="PolicyByDef" type="dsb:AnyType"/>

</xs:choice>

<xs:element name="EarlierPolicy" type="xs:anyURI" maxOccurs="unbounded" minOccurs="0"/>

<xs:element maxOccurs="unbounded" minOccurs="0" ref="md:Extension"/>

</xs:sequence>

<xs:attribute name="Type" type="xs:anyURI" use="optional"/>

</xs:complexType>

Each child element of PolicyType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.8 Component PolicyByRef

The PolicyByRef component appears within the Policy component specified in clause 3.1.7 and provides a reference to a human readible policy document, which is applicable for a profile of the supported digital signature related protocol.

Below follows a list of the sub-components that constitute this component:

The PolicyID element MUST contain one instance of a URI, which uniquely identifies the policy under consideration.

The OPTIONAL PolicyLocation element, if present, MUST contain a URI, which SHOULD refer to the location where the policy document can be retrieved. If the PolicyID is already a retrievable URL, the PolicyLocation MAY be omitted.

3.1.8.1 PolicyByRef – JSON Syntax

The PolicyByRefType JSON object SHALL implement in JSON syntax the requirements defined in the PolicyByRef component.

Properties of the JSON object SHALL implement the sub-components of PolicyByRef using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
PolicyID	polid
PolicyLocation	polloc

The PolicyByRefType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-PolicyByRefType": {

"type": "object",

"properties": {

"polid": {

"type": "string"

"polloc": {

"type": "string"

}

"required": ["polid"]

}

3.1.8.2 PolicyByRef – XML Syntax

The XML type PolicyByRefType SHALL implement the requirements defined in the PolicyByRef component.

The PolicyByRefType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="PolicyByRefType">

<xs:sequence>

<xs:element name="PolicyID" type="xs:anyURI"/>

<xs:element name="PolicyLocation" type="xs:anyURI" maxOccurs="1" minOccurs="0"/>

</xs:sequence>

</xs:complexType>

Each child element of PolicyByRefType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.1.9 Component Extension

The Extension component defined in the present document is used in several other components and provides a lightweight possibility for extending the semantics of other components.

Below follows a list of the sub-components that constitute this component:

The Name element MUST contain one instance of a string and specifies the name of the extension element.

The Value element MUST contain one instance of a string and specifies the value of the extension element.

NOTE: In contrast to the Any component defined in [DSS-v2.0], the Extension element defined here only consists of a simple Name and Value pair, which maintains the direct readability by humans, but is less powerful than the Any component, which also allows features transformations for example.

3.1.9.1 Extension – JSON Syntax

The ExtensionType JSON object SHALL implement in JSON syntax the requirements defined in the Extension component.

Properties of the JSON object SHALL implement the sub-components of Extension using JSON-specific names mapped as shown in the table below.

Element	Implementing JSON member name
Name	name
Value	value

The ExtensionType JSON object is defined in the JSON schema [DSSMD-JSON] and is provided below as a service to the reader.

"md-ExtensionType": {

"type": "object",

"properties": {

"name": {

"type": "string"

"value": {

"type": "string"

}

"required": ["name", "value"]

}

3.1.9.2 Extension – XML Syntax

The XML type ExtensionType SHALL implement the requirements defined in the Extension component.

The ExtensionType XML element is defined in XML Schema [DSSMD-XML], and is copied below for information.

<xs:complexType name="ExtensionType">

<xs:sequence>

<xs:element name="Name" type="xs:string"/>

<xs:element name="Value" type="xs:string"/>

</xs:sequence>

</xs:complexType>

Each child element of ExtensionType XML element SHALL implement in XML syntax the sub-component that has a name equal to its local name.

3.2 Element / JSON name lookup tables

The subsequent table allows to find the names of a component's element for a given JSON member name.

JSON member name	mapped from element name
authinfo	AuthInfo
def	IsDefault
ep	EarlierPolicy
ext	Extension
fid	FormatID
form	Format
format	Parameter
ID	Id
in	Input
lang	SupportedLanguage
logo	Logo
name	Name
op	Operation
opt	Option
out	Output
pbdef	PolicyByDef
pbref	PolicyByRef
pid	ProfileIdentifier
pol	Policy
polid	PolicyID
polloc	PolicyLocation
pre	NamespacePrefix
profile	Profile
protocol	Protocol
region	Region
spec	Specification
uri	NamespaceURI
value	Value
version	Version
xsd	Schema

The subsequent table allows to find the abbreviated JSON member names for a given element name.

Element	Implementing JSON member name
AuthInfo	authinfo
DigestMethod	alg
DigestValue	val
EarlierPolicy	ep
Extension	ext
Format	form
FormatID	fid
Id	ID
Input	in
IsDefault	def
Logo	logo
Name	name
NamespacePrefix	pre
NamespaceURI	uri
Operation	op
Option	opt
Output	out
Parameter	format
Policy	pol
PolicyByDef	pbdef
PolicyByRef	pbref
PolicyID	polid
PolicyLocation	polloc
Profile	profile
ProfileIdentifier	pid
Protocol	protocol
Region	region
Schema	xsd
Specification	spec
SupportedLanguage	lang
Value	value
Version	version

4 Metadata Discovery

Unless other discovery mechanisms are specified (by profiles or extensions of [DSS-v2.0] for example), it is RECOMMENDED that digital signature service providers make available a JSON or XML document using the appropriate content type (i.e. application/json or application/xml) with the digital signature service metadata at the path formed by concatenating the string /.well-known/dss-info to a suitable “basic information URL” of the service provider, which is intended to provide relevant information about the provided services (see also “TSP information URI” in clause 5.4.4 of [TS119612]).

Appendix A. Acknowledgments

The following individuals have participated in the creation of this specification and are gratefully acknowledged:

Andreas Kuehne, Individual

Detlef Hühnlein, Individual

Ernst Jan van Nigtevecht, Sonnenglanz Consulting

Appendix B. List of Figures

Figure 1: Overview of main components within the service-related metadata structures. 8

Appendix C. Revision History

Revision	Date	Editor	Changes Made
WD01	2019-03-17	Detlef Hühnlein and Andreas Kuehne	Draft for discussion within DSS-X and potential ballot public review
CSD01	2019-03-18	Detlef Hühnlein and Andreas Kuehne	Version for public review
CS01	2019-05-07	Detlef Hühnlein and Andreas Kuehne	Committee Specification
CSD02	2019-09-09	Andreas Kuehne	Version for public review, no changes within this document but in the related schema files
CS02	2019-10-27	Andreas Kuehne	Version for publication as CS. Only editorial changes, as no comments received for CSD02.