| Internet-Draft | OneDM SDF | November 2020 |
| Koster & Bormann | Expires 19 May 2021 | [Page] |
The Semantic Definition Format (SDF) is a format for domain experts to use in the creation and maintenance of data and interaction models in the Internet of Things. It was created as a common language for use in the development of the One Data Model liaison organization (OneDM) definitions. Tools convert this format to database formats and other serializations as needed.¶
An SDF specification describes definitions of SDF Objects and their associated interactions (Events, Actions, Properties), as well as the Data types for the information exchanged in those interactions.¶
A JSON format representation of SDF 1.0 is defined in this document.¶
(This is a republication of draft-onedm-t2trg-sdf-00 as an IETF ASDF Working Group document, with no technical changes, a superfluous figure removed, and some tool version induced reformatting.)¶
Recent versions of this document are available at its GitHub repository https://github.com/ietf-wg-asdf/SDF -- this also provides an issue tracker as well as a way to supply "pull requests".¶
General discussion of this SDF Internet-Draft happens on the mailing list of the IETF ASDF Working Group, asdf@ietf.org (subscribe at https://www.ietf.org/mailman/listinfo/asdf).¶
The IETF Note Well applies (https://www.ietf.org/about/note-well/).¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
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The Semantic Definition Format (SDF) is a format for domain experts to use in the creation and maintenance of data and interaction models in the Internet of Things. It was created as a common language for use in the development of the One Data Model liaison organization (OneDM) definitions. Tools convert this format to database formats and other serializations as needed.¶
An SDF specification describes definitions of SDF Objects and their associated interactions (Events, Actions, Properties), as well as the Data types for the information exchanged in those interactions.¶
A JSON format representation of SDF 1.0 is defined in this document.¶
sdf.¶
Conventions:¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
We start with an example for the SDF definition of a simple Object called "Switch" (Figure 1).¶
{
"info": {
"title": "Example file for OneDM Semantic Definition Format",
"version": "2019-04-24",
"copyright": "Copyright 2019 Example Corp. All rights reserved.",
"license": "https://example.com/license"
},
"namespace": {
"cap": "https://example.com/capability/cap"
},
"defaultNamespace": "cap",
"sdfObject": {
"Switch": {
"sdfProperty": {
"value": {
"description": "The state of the switch; false for off and true for on."
"type": "boolean"
}
},
"sdfAction": {
"on": {
"description": "Turn the switch on; equivalent to setting value to true."
},
"off": {
"description": "Turn the switch on; equivalent to setting value to false."
},
"toggle": {
"description": "Toggle the switch; equivalent to setting value to its complement."
}
}
}
}
}
This is a model of a switch.
The state value declared in the sdfProperty group, represented by a Boolean, will be true for "on" and will be false for "off".
The actions on or off declared in the sdfAction group are redundant with setting the value and are in the example to illustrate that there are often different ways of achieving the same effect.
The action toggle will invert the value of the sdfProperty value, so that 2-way switches can be created; having such action will avoid the need for first retrieving the current value and then applying/setting the inverted value.¶
The sdfObject group lists the affordances of instances of this object.
The sdfProperty group lists the property affordances described by the model; these represent various perspectives on the state of the object.
Properties can have additional qualities to describe the state more precisely.
Properties can be annotated to be read, write or read/write; how this is actually done by the underlying transfer protocols is not described in the SDF model but left to companion protocol bindings.
Properties are often used with RESTful paradigms [I-D.irtf-t2trg-rest-iot], describing state.
The sdfAction group is the mechanism to describe other interactions in terms of their names, input, and output data (no data are used in the example), as in a POST method in REST or in a remote procedure call.
The example toggle is an Action that
changes the state based on the current state of the Property named value.
(The third type of affordance is Events, which are not described in this example.)¶
The SDF language uses seven predefined Class Name Keywords for modeling connected
Things, six of which are illustrated in Figure 2 (the seventh class sdfProduct is exactly like sdfThing).¶
The seven main Class Name Keywords are discussed below.¶
Objects, the items listed in an sdfObject group, are the main "atom" of reusable semantics for model construction.
It aligns in scope with common definition items from many IoT modeling
systems, for example ZigBee Clusters [ZCL], OMA SpecWorks LwM2M
Objects [OMA], and
OCF Resource Types [OCF].¶
An sdfObject contains a set of sdfProperty, sdfAction, and
sdfEvent definitions that describe the interaction affordances
associated with some scope of functionality.¶
For the granularity of definition, sdfObject definitions are meant
to be kept narrow enough in scope to enable broad reuse and
interoperability.
For example, defining a light bulb using separate sdfObject
definitions for on/off control, dimming, and color control affordances
will enable interoperable functionality to be configured for diverse
product types.
An sdfObject definition for a common on/off control may be used to
control may different kinds of Things that require on/off control.¶
sdfProperty is used to model elements of state within sdfObject instances.¶
An instance of sdfProperty may be associated with some protocol
affordance to enable the application to obtain the state variable and,
optionally, modify the state variable.
Additionally, some protocols provide for in-time reporting of state
changes.
(These three aspects are described by the qualities readable,
writable, and observable defined for an sdfProperty.)¶
Definitions in sdfProperty groups look like definitions in sdfData groups, however, they actually also declare a Property with the given qualities to be potentially present in the containing Object.
(Qualities beyond those of sdfData definitions could be defined for sdfProperty declarations
but currently aren't; this means that even Property qualities
such as readable and writable can be associated with definitions in sdfData groups, as well.)¶
For definitions in sdfProperty and sdfData, SDF provides qualities that can
constrain the structure and values of data allowed in an instance of
these data, as well as qualities that associate semantics to these
data, for engineering units and unit scaling information.¶
For the data definition within sdfProperty or sdfData, SDF borrows
a number of elements proposed for the drafts 4 and 7 of the json-schema.org "JSON Schema"
format [I-D.handrews-json-schema-validation], enhanced by qualities that are specific to SDF.
However, for the current version of SDF, data are constrained to be of
simple types (number, string, Boolean) and arrays of these types.
Syntax extension points are provided that can be used to provide
richer types in future versions of this specification (possibly more
of which can be borrowed from json-schema.org).¶
Note that sdfProperty definitions (and sdfData definitions in
general) are not intended to constrain the formats of data used for
communication over network interfaces.
Where needed, data definitions for payloads of protocol messages are
expected to be part of the protocol binding.¶
The sdfAction group contains declarations of Actions, model affordances that, when triggered,
have more effect than just reading, updating, or observing Thing
state, often resulting in some outward physical effect (which, itself,
cannot be modeled in SDF). From a programmer's perspective, they
might be considered to be roughly analogous to method calls.¶
Actions may have multiple data parameters; these are modeled as input
data and output data (using sdfData definitions, i.e., the same entries as for
sdfProperty declarations).
Actions may be long-running, that is to say that the effects may not
take place immediately as would be expected for an update to an
sdfPoperty; the effects may play out over time and emit action
results.
Actions may also not always complete and may result in application
errors, such as an item blocking the closing of an automatic door.¶
Actions may have (or lack) qualities of idempotency and side-effect safety.¶
The current version of SDF only provides data constraint modeling and semantics for the input and output data of definitions in sdfAction groups.
Again, data definitions for payloads of protocol messages, and
detailed protocol settings for invoking the action, are expected to be
part of the protocol binding.¶
The sdfEvent group contains declarations of Events, which can model
affordances that inform about "happenings" associated with an instance
of an Object; these may result in a signal being stored or emitted as
a result.¶
Note that there is a trivial overlap with sdfProperty state changes,
which may also be defined as events but are not generally required to
be defined as such.
However, Events may exhibit certain ordering, consistency, and
reliability requirements that are expected to be supported in various
implementations of sdfEvent that do distinguish sdfEvent from
sdfProperty.
For instance, while a state change may simply be superseded by another
state change, some events are "precious" and need to be preserved even
if further events follow.¶
The current version of SDF only provides data constraint modeling and semantics for the output data of Event affordances. Again, data definitions for payloads of protocol messages, and detailed protocol settings for invoking the action, are expected to be part of the protocol binding.¶
Definitions in sdfData groups are provided separately from those in
sdfProperty groups to enable common
modeling patterns, data constraints, and semantic anchor concepts to
be factored out for data items that make up sdfProperty items and
serve as input and output data for sdfAction and sdfEvent items.¶
It is a common use case for such a data definition to be shared
between an sdfProperty item and input or output parameters of an
sdfAction or output data provided by an sdfEvent.
sdfData definitions also enable factoring out extended application
data types such as mode and machine state enumerations to be reused
across multiple definitions that have similar basic characteristics
and requirements.¶
Back at the top level, the sdfThing groups enables definition of models for
complex devices that will use one or more sdfObject definitions.¶
A definition in an sdfThing group can refine the metadata of the definitions it
is composed from: other definitions in sdfThing groups definitions in sdfObject groups.¶
sdfThing has a derived class sdfProduct, which can be used to
indicate a top level inventory item with a Stock-Keeping Unit (SKU)
identifier and other particular metadata.
Structurally, there is no difference between definitions in either
group; semantically, a definition in an sdfProduct group is intended
to describe a class of complete Things.¶
SDF definitions are contained in SDF files. One or more SDF files can work together to provide the definitions and declarations that are the payload of the SDF format.¶
A SDF definition file contains a single JSON map (JSON object). This object has three sections: the information block, the namespaces section, and the definitions section.¶
The information block contains generic meta data for the file itself and all included definitions.¶
The keyword (map key) that defines an information block is "info". Its value is a JSON map in turn, with a set of entries that represent qualities that apply to the included definition.¶
Qualities of the information block are shown in Table 1.¶
| Quality | Type | Required | Description |
|---|---|---|---|
| title | string | yes | A short summary to be displayed in search results, etc. |
| version | string | yes | The incremental version of the definition, format TBD |
| copyright | string | yes | Link to text or embedded text containing a copyright notice |
| license | string | yes | Link to text or embedded text containing license terms |
While the format of the version string is marked as TBD, it is intended to be lexicographically increasing over the life of a model: a newer model always has a version string that string-compares higher than all previous versions.
This is easily achieved by following the convention to start the version with an [RFC3339] date-time or, if new versions are generated less frequently than once a day, just the full-date (i.e., YYYY-MM-DD); in many cases, that will be all that is needed (see Figure 1 for an example).¶
The license string is preferably either a URI that points to a web page with an unambiguous definition of the license, or an [SPDX] license identifier. (For models to be handled by the One Data Model liaison group, this will typically be "BSD-3-Clause".)¶
The namespaces section contains the namespace map and the defaultNamespace setting.¶
The namespace map is a map from short names for URIs to the namespace URIs themselves.¶
The defaultNamespace setting selects one of the entries in the namespace map by giving its short name. The associated URI (value of this entry) becomes the default namespace for the SDF definition file.¶
| Quality | Type | Required | Description |
|---|---|---|---|
| namespace | map | no | Defines short names mapped to namespace URIs, to be used as identifier prefixes |
| defaultNamespace | string | no | Identifies one of the prefixes in the namespace map to be used as a default in resolving identifiers |
The following example declares a set of namespaces and defines cap as the default namespace.¶
"namespace": {
"cap": "https://example.com/capability/cap",
"zcl": "https://zcl.example.com/sdf"
},
"defaultNamespace": "cap",
¶
If no defaultNamespace setting is given, the SDF definition file does not contribute to a global namespace. As the defaultNamespace is set by giving a namespace short name, its presence requires a namespace map that contains a mapping for that namespace short name.¶
If no namespace map is given, no short names for namespace URIs are set up, and no defaultNamespace can be given.¶
The Definitions section contains one or more groups, each identified by a Class Name Keyword (there can only be one group per keyword; the actual grouping is just a shortcut and does not carry any specific semantics). The value of each group is a JSON map (object), the keys of which serve for naming the individual definitions in this group, and the corresponding values provide the qualities (name-value pairs) for the individual definition.¶
Each group may contain zero or more definitions. Each identifier defined creates a new type and term in the target namespace. Declarations have a scope of the current definition block.¶
A definition may in turn contain other definitions. Each definition consists of the newly defined identifier and a set of key-value pairs that represent the defined qualities and contained definitions.¶
An example for an Object definition is given in Figure 3:¶
"sdfObject": {
"foo": {
"sdfProperty": {
"bar": {
"type": "boolean"
}
}
}
}
This example defines an Object "foo" that is defined in the default namespace (full address: #/sdfObject/foo), containing a property that can be addressed as
#/sdfObject/foo/sdfProperty/bar, with data of type boolean.¶
Some of the definitions are also declarations: the definition of the entry "bar" in the property "foo" means that each instance of a "foo" can have zero or one instance of a "bar". Entries within sdfProperty, sdfAction, and sdfEvent, within sdfObject entries, are declarations. Similarly, entries within an sdfThing describe instances of sdfObject (or nested sdfThing) that form part of instances of the Thing.¶
SDF definition files may contribute to a global namespace, and may reference elements from that global namespace. (An SDF definition file that does not set a defaultNamespace does not contribute to a global namespace.)¶
Global names look exactly like https:// URIs with attached fragment identifiers.¶
There is no intention to require that these URIs can be dereferenced. (However, as future versions of SDF might find a use for dereferencing global names, the URI should be chosen in such a way that this may become possible in the future.)¶
The absolute URI of a global name should be a URI as per Section 3 of
[RFC3986], with a scheme of "https" and a path (hier-part in [RFC3986]).
For the present version of this specification, the query part should
not be used (it might be used in later versions).¶
The fragment identifier is constructed as per Section 6 of [RFC6901].¶
The fragment identifier part of a global name defined in an SDF definition file is constructed from a JSON pointer that selects the element defined for this name in the SDF definition file.¶
The absolute URI part is a copy of the default namespace, i.e., the default namespace is always the target namespace for a name for which a definition is contributed. When emphasizing that name definitions are contributed to the default namespace, we therefore also call it the "target namespace" of the SDF definition file.¶
E.g., in Figure 1, definitions for the following global names are contributed:¶
Note the "#", which separates the base part from the fragment identifier part.¶
A name reference takes the form of the production curie in
[W3C.NOTE-curie-20101216] (note that this excludes the production safe-curie),
but also limiting the IRIs involved in that production to URIs as per [RFC3986]
and the prefixes to ASCII characters [RFC0020].¶
A name that is contributed by the current SDF definition file can be referenced by a Same-Document Reference as per section 4.4 of [RFC3986]. As there is little point in referencing the entire SDF definition file, this will be a "#" followed by a JSON pointer. This is the only kind of name reference that is possible in an SDF definition file that does not set a default namespace.¶
Name references that point outside the current SDF definition file need to contain curie prefixes. These then reference namespace declarations in the namespaces section.¶
For example, if a namespace prefix is defined:¶
"namespace": {
"foo": "https://example.com/#"
}
¶
Then this reference to that namespace:¶
{ "sdfRef": "foo:/sdfData/temperatureData" }
¶
references the global name:¶
"https://example.com/#/sdfData/temperatureData"¶
Note that there is no way to provide a URI scheme name in a curie, so all references outside of the document need to go through the namespace map.¶
Name references occur only in specific elements of the syntax of SDF:¶
In a JSON map establishing a definition, the keyword "sdfRef" is used to copy all of the qualities of the referenced definition, indicated by the included name reference, into the newly formed definition. (This can be compared to the processing of the "$ref" keyword in [I-D.handrews-json-schema-validation].)¶
For example, this reference:¶
"temperatureProperty": {
"sdfRef": "#/sdfData/temperatureData"
}
¶
creates a new definition "temperatureProperty" that contains all of the qualities defined in the definition at /sdfData/temperatureData.¶
The value of "sdfRequired" is an array of name references, each pointing to one declaration the instantiation of which is declared mandatory.¶
The keyword "sdfRequired" is provided to apply a constraint that defines for which declarations corresponding data are mandatory in an instance conforming the current definition.¶
The value of "sdfRequired" is an array of JSON pointers, each indicating one declaration that is mandatory to be represented.¶
The example in Figure 4 shows two required elements in the sdfObject definition for "temperatureWithAlarm", the sdfProperty "temperatureData", and the sdfEvent "overTemperatureEvent". The example also shows the use of JSON pointer with "sdfRef" to use a pre-existing definition in this definition, for the "alarmType" data (sdfOutputData) produced by the sdfEvent "overTemperatureEvent".¶
{
"sdfObject": {
"temperatureWithAlarm": {
"sdfRequired": [
"#/sdfObject/temperatureWithAlarm/sdfData/temperatureData",
"#/sdfObject/temperatureWithAlarm/sdfEvent/overTemperatureEvent"
],
"sdfData":{
"temperatureData": {
"type": "number"
}
},
"sdfEvent": {
"overTemperatureEvent": {
"sdfOutputData": {
"alarmType": {
"sdfRef": "cap:/sdfData/alarmTypes/quantityAlarms",
"const": "OverTemperatureAlarm"
},
"temperature": {
"sdfRef": "#/sdfObject/temperatureWithAlarm/sdfData/temperatureData"
}
}
}
}
}
}
}
Definitions in SDF share a number of qualities that provide metadata for
them. These are listed in Table 3. None of these
qualities are required or have default values that are assumed if the
quality is absent.
If a label is required for an application and no label is given, the
last part (reference-token, Section 3 of [RFC6901]) of the JSON
pointer to the definition can be used.¶
| Quality | Type | Description |
|---|---|---|
| description | text | long text (no constraints) |
| label | text | short text (no constraints) |
| $comment | text | source code comments only, no semantics |
| sdfRef | sdf-pointer | (see Section 4.4) |
| sdfRequired | pointer-list | (see Section 4.5, applies to qualities of properties, of data) |
Data qualities are used in sdfData and sdfProperty definitions.¶
Table 4 lists data qualities borrowed from [I-D.handrews-json-schema-validation]; the intention is that these qualities retain their semantics from the versions of the json-schema.org proposal they were imported from.¶
Table 5 lists data qualities defined specifically for the present specification.¶
The term "allowed types" stands for primitive JSON types as well as homogeneous arrays of numbers, text, or Booleans. (This list might be extended in a future version of SDF.) An "allowed value" is a value allowed for one of these types.¶
| Quality | Type | Description |
|---|---|---|
| type | "number" / "string" / "boolean" / "integer" / "array" | JSON data type |
| enum | array of allowed values | enumeration constraint |
| const | allowed value | specifies a constant value for a data item or property |
| default | allowed value | specifies the default value for initialization |
| minimum | number | lower limit of value |
| maximum | number | upper limit of value |
| exclusiveMinimum | number or boolean (jso draft 7/4) | lower limit of value |
| exclusiveMaximum | number or boolean (jso draft 7/4) | lower limit of value |
| multipleOf | number | resolution of the number [NEEDED?] |
| minLength | integer | shortest length string in octets |
| maxLength | integer | longest length string in octets |
| pattern | string | regular expression to constrain a string pattern |
| format | "date-time" / "date" / "time" / "uri" / "uri-reference" / "uuid" | JSON Schema formats as per [I-D.handrews-json-schema-validation], Section 7.3 |
| minItems | number | Minimum number of items in array |
| maxItems | number | Maximum number of items in array |
| uniqueItems | boolean | if true, requires items to be all different |
| items | (subset of common/data qualities; see Appendix A | constraints on array items |
| Quality | Type | Description | Default |
|---|---|---|---|
| (common) | Section 4.6 | ||
| units | string | SenML unit name as per [IANA.senml], subregistry SenML Units | N/A |
| scaleMinimum | number | lower limit of value in units | N/A |
| scaleMaximum | number | upper limit of value in units | N/A |
| readable | boolean | Reads are allowed | true |
| writable | boolean | Writes are allowed | true |
| observable | boolean | flag to indicate asynchronous notification is available | true |
| nullable | boolean | indicates a null value is available for this type | true |
| contentFormat | string | content type (IANA media type string plus parameters), encoding | N/A |
| subtype | "byte-string" / "unix-time" | subtype enumeration | N/A |
The following SDF keywords are used to create definition groups in the target namespace. All these definitions share some common qualities as discussed in Section 4.6.¶
The sdfObject keyword denotes a group of zero or more Object definitions. Object definitions may contain or include definitions of Properties, Actions, Events declared for the object, as well as data types (sdfData group) to be used in this or other Objects.¶
The qualities of an sdfObject include the common qualities, additional qualities are shown in Table 6. None of these qualities are required or have default values that are assumed if the quality is absent.¶
| Quality | Type | Description |
|---|---|---|
| (common) | Section 4.6 | |
| sdfProperty | property | zero or more named property definitions for this object |
| sdfAction | action | zero or more named action definitions for this object |
| sdfEvent | event | zero or more named event definitions for this object |
| sdfData | data | zero or more named data type definitions that might be used in the above |
The sdfProperty keyword denotes a group of zero or more Property definitions.¶
Properties are used to model elements of state.¶
The qualities of a Property definition include the common qualities and the data qualities, see Section 4.7.¶
The sdfAction keyword denotes a group of zero or more Action definitions.¶
Actions are used to model commands and methods which are invoked. Actions have parameter data that are supplied upon invocation.¶
The qualities of an Action definition include the common qualities, additional qualities are shown in Table 7.¶
| Quality | Type | Description |
|---|---|---|
| (common) | Section 4.6 | |
| sdfInputData | array | Array of JSON Pointers to Data items in the input data for an Action |
| sdfRequiredInputData | array | Array of JSON Pointers to mandatory Data items in the input data for an Action |
| sdfOutputData | array | Array of JSON Pointers to Data items in the Output data for an Action (mandatory items are listed under sdfRequired) |
| sdfData | data | zero or more named data type definitions that might be used in the above |
sdfInputData, as refined by sdfRequiredInputData, define the input data
of the action. sdfOutputData, as refined by sdfRequired, (a quality
defined in Table 3) define the output data of the
action.¶
The sdfEvent keyword denotes zero or more Event definitions.¶
Events are used to model asynchronous occurrences that may be communicated proactively. Events have data elements which are communicated upon the occurrence of the event.¶
The qualities of sdfEvent include the common qualities, additional qualities are shown in Table 8.¶
| Quality | Type | Description |
|---|---|---|
| (common) | Section 4.6 | |
| sdfOutputData | array | Array of JSON Pointers to Data items in the Output data for an Action (mandatory items are listed under sdfRequired) |
| sdfData | data | zero or more named data type definitions that might be used in the above |
sdfOutputData, as refined by sdfRequired (a quality
defined in Table 3), define the output data of the
action.¶
The sdfData keyword denotes a group of zero or more Data type definitions.¶
An sdfData definition provides a semantic identifier for a data item and describes the constraints on the defined data item.¶
sdfData is used for Action parameters, for Event output data, and for reusable constraints in Property definitions.¶
The qualities of sdfData include the common qualities and the data qualities, see Section 4.7.¶
The requirements for high level composition include the following:¶
The model namespace is organized according to terms that are defined in the definition files that are present in the namespace. For example, definitions that originate from an organization or vendor are expected to be in a namespace that is specific to that organization or vendor. There is expected to be an SDF namespace for common SDF definitions used in OneDM.¶
The structure of a path in a namespace is defined by the JSON Pointers to the definitions in the files in that namespace. For example, if there is a file defining an object "Switch" with an action "on", then the reference to the action would be "ns:/sdfObject/Switch/sdfAction/on" where ns is the namespace prefix (short name for the namespace).¶
Modular composition of definitions enables an existing definition (could be in the same file or another file) to become part of a new definition by including a reference to the existing definition within the model namespace.¶
An existing definition may be used as a template for a new definition, that is, a new definition is created in the target namespace which uses the defined qualities of some existing definition. This pattern will use the keyword "sdfRef" as a quality of a new definition with a value consisting of a reference to the existing definition that is to be used as a template. Optionally, new qualities may be added and values of optional qualities and quality values may be defined.¶
ISSUE: Do we want to enable qualities from the source definition to be overridden in future versions? The above only says "added". (Yes, we do want to enable overriding, but need to warn specifiers not to use this in a way that contradicts the referenced semantics.)¶
"sdfData":
"length" : {
"type": "number",
"minimum": 0,
"units": "m"
"description": "There can be no negative lengths."
}
...
"cable-length" : {
"sdfRef": "#/sdfData/length"
"minimum": 0.05,
"description": "Cables must be at least 5 cm."
}
¶
An sdfThing is a set of declarations and qualities that may be part of a more complex model. For example, the object declarations that make up the definition of a single socket of an outlet strip could be encapsulated in an sdfThing, and the socket-thing itself could be used in a declaration in the sdfThing definition for the outlet strip.¶
sdfThing definitions carry semantic meaning, such as a defined refrigerator compartment and a defined freezer compartment, making up a combination refrigerator-freezer product.¶
An sdfThing may be composed of sdfObjects and other sdfThings.¶
The qualities of sdfThing are shown in Table 9.¶
| Quality | Type | Description |
|---|---|---|
| (common) | Section 4.6 | |
| sdfThing | thing | |
| sdfObject | object |
An sdfProduct provides the level of abstraction for representing a unique product or a profile for a standardized type of product, for example a "device type" definition with required minimum functionality.¶
Products may be composed of Objects and Things at the high level, and may include their own definitions of Properties, Actions, and Events that can be used to extend or complete the included Object definitions.¶
Product definitions may set optional defaults and constant values for specific use cases, for example units, range, and scale settings for properties, or available parameters for Actions.¶
The qualities of sdfProduct are the same as for sdfThing and are shown in Table 9.¶
This appendix describes the syntax of SDF using CDDL [RFC8610]. Note
that this appendix was derived from Ari Keranen's "alt-schema" and
Michael Koster's "schema", with a view of covering the syntax that is
currently in use at the One Data Model playground repository.¶
This appendix shows the framework syntax only, i.e., a syntax with liberal extension points.
Since this syntax is nearly useless in finding typos in an SDF
specification, a second syntax, the validation syntax, is defined that
does not include the extension points.
The validation syntax can be generated from the framework syntax by
leaving out all lines containing the string EXTENSION-POINT; as this
is trivial, the result is not shown here.¶
start = sdf-syntax
sdf-syntax = {
info: sdfinfo ; don't *require* this in flexible syntax, though
? namespace: named<text>
? defaultNamespace: text
? sdfThing: named<thingqualities> ; Thing is a composition of objects that work together in some way
? sdfProduct: named<productqualities> ; Product is a composition of things and objects that can model a SKU-level instance of a product
? sdfObject: named<objectqualities> ; Object is a set of Properties, Actions, and Events that together perform a particular function
? sdfProperty: named<propertyqualities> ; Property represents the state of an instance of an object
? sdfAction: named<actionqualities> ; Action is a directive to invoke an application layer verb associated with an object
? sdfEvent: named<eventqualities> ; Event represents an occurence of something associated with an object
? sdfData: named<dataqualities> ; Data represents a piece of information that can be the state of a property or a parameter to an action or a signal in an event
EXTENSION-POINT
}
sdfinfo = {
title: text
version: text
copyright: text
license: text
EXTENSION-POINT
}
; Shortcut for a map that gives names to instances of X (has text keys and values of type X)
named<X> = { * text => X }
EXTENSION-POINT = ( * text => any ) ; only used in framework syntax
sdf-pointer = text ; .regexp curie-regexp -- TO DO!
pointer-list = [* sdf-pointer] ; ISSUE: no point in having an empty list, no? but used for sdfRequired in odmobject-multiple_axis_joystick.sdf.json
commonqualities = (
? description: text ; long text (no constraints)
? label: text ; short text (no constraints); default to key
? $comment: text ; source code comments only, no semantics
? sdfRef: sdf-pointer
? sdfRequired: pointer-list ; applies to qualities of properties, of data
)
; for building hierarchy
thingqualities = {
commonqualities,
? sdfObject: named<objectqualities>
? sdfThing: named<thingqualities>
EXTENSION-POINT
}
productqualities = thingqualities ; ISSUE: get rid of sdfProduct?
; for single objects
objectqualities = {
commonqualities,
? sdfProperty: named<propertyqualities>
? sdfAction: named<actionqualities>
? sdfEvent: named<eventqualities>
? sdfData: named<dataqualities>
EXTENSION-POINT
}
propertyqualities = dataqualities ; the definitions in sdfData are declarations in sdfProperty
actionqualities = {
commonqualities,
? sdfInputData: pointer-list ; sdfRequiredInputData applies here (a bit redundant)
? sdfRequiredInputData: pointer-list
? sdfOutputData: pointer-list ; sdfRequired applies here
? sdfData: named<dataqualities> ; zero or more named data type definitions that might be used in the above
EXTENSION-POINT
}
eventqualities = {
commonqualities
? sdfOutputData: pointer-list ; sdfRequired applies here
? sdfData: named<dataqualities> ; zero or more named data type definitions that might be used in the above
EXTENSION-POINT
}
dataqualities = { ; also propertyqualities
commonqualities,
jsonschema,
? units: text
? scaleMinimum: number
? scaleMaximum: number
? observable: bool
? readable: bool
? writable: bool
? nullable: bool
? subtype: "byte-string" / "unix-time"
/ text ; EXTENSION-POINT
? contentFormat: text
EXTENSION-POINT
}
allowed-types = number / text / bool / null
/ [* number] / [* text] / [* bool]
/ any ; EXTENSION-POINT
jsonschema = (
? type: "number" / "string" / "boolean" / "integer" / "array" ; / "object"
/ text ; EXTENSION-POINT
? enum: [+ allowed-types] ; should validate against type
? const: allowed-types
? default: allowed-types
; number/integer constraints
? minimum: number
? maximum: number
? exclusiveMinimum: bool / number ; jso draft 4/7
? exclusiveMaximum: bool / number ; jso draft 4/7
? multipleOf: number ; ISSUE: Do we need this?
; text string constraints
? minLength: number
? maxLength: number
? pattern: text ; regexp
? format: "date-time" / "date" / "time"
/ "uri" / "uri-reference" / "uuid"
/ text ; EXTENSION-POINT
; expand on demand
; array constraints
? minItems: number
? maxItems: number
? uniqueItems: bool
? items: { ;;; ultimately, this will be mostly recursive, but, for now
;;; let's find out what we actually need
? sdfRef: sdf-pointer ; import limited to the subset that we allow here...
? description: text ; long text (no constraints)
? $comment: text ; source code comments only, no semantics
; commonqualities, ; -- ISSUE: should leave this out for non-complex data types, but need the above three
? type: "number" / "string" / "boolean" / "integer" ; no "array" / "object"
/ text ; EXTENSION-POINT
; jso subset
? minimum: number
? maximum: number
? enum: [+ any]
? format: text
? minLength: number
? maxLength: number
EXTENSION-POINT
}
)
¶
This appendix describes the syntax of SDF defined in Appendix A, but using a version of the description techniques advertised on json-schema.org [I-D.handrews-json-schema-validation].¶
The appendix shows both the validation and the framework syntax.
Since most of the lines are the same between these two files, those lines are shown only once, with a leading space, in the form of a unified diff.
Lines leading with a - are part of the validation syntax, and lines leading with a + are part of the framework syntax.¶
{
- "title": "sdf-validation.cddl",
+ "title": "sdf-framework.cddl",
"$schema": "http://json-schema.org/draft-07/schema#",
"$ref": "#/definitions/sdf-syntax",
"definitions": {
"sdf-syntax": {
"type": "object",
"required": [
"info"
],
"properties": {
"info": {
"$ref": "#/definitions/sdfinfo"
},
"namespace": {
"type": "object",
"additionalProperties": {
"type": "string"
}
},
"defaultNamespace": {
"type": "string"
},
"sdfThing": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/thingqualities"
}
},
"sdfProduct": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/productqualities"
}
},
"sdfObject": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/objectqualities"
}
},
"sdfProperty": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/propertyqualities"
}
},
"sdfAction": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/actionqualities"
}
},
"sdfEvent": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/eventqualities"
}
},
"sdfData": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/dataqualities"
}
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
},
"sdfinfo": {
"type": "object",
"required": [
"title",
"version",
"copyright",
"license"
],
"properties": {
"title": {
"type": "string"
},
"version": {
"type": "string"
},
"copyright": {
"type": "string"
},
"license": {
"type": "string"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
+ },
+ "EXTENSION-POINT": {
+ "type": "object",
+ "additionalProperties": {
+ }
},
"thingqualities": {
"type": "object",
"properties": {
"sdfObject": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/objectqualities"
}
},
"sdfThing": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/thingqualities"
}
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
},
"commonqualities": {
"type": "object",
"properties": {
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
}
},
"additionalProperties": false
},
"sdf-pointer": {
"type": "string"
},
"pointer-list": {
"type": "array",
"items": {
"$ref": "#/definitions/sdf-pointer"
}
},
"objectqualities": {
"type": "object",
"properties": {
"sdfProperty": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/propertyqualities"
}
},
"sdfAction": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/actionqualities"
}
},
"sdfEvent": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/eventqualities"
}
},
"sdfData": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/dataqualities"
}
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
},
"propertyqualities": {
"$ref": "#/definitions/dataqualities"
},
"dataqualities": {
"type": "object",
"properties": {
"units": {
"type": "string"
},
"scaleMinimum": {
"type": "number"
},
"scaleMaximum": {
"type": "number"
},
"observable": {
"type": "boolean"
},
"readable": {
"type": "boolean"
},
"writable": {
"type": "boolean"
},
"nullable": {
"type": "boolean"
},
"subtype": {
- "type": "string",
- "enum": [
- "byte-string",
- "unix-time"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "byte-string"
+ },
+ {
+ "type": "string",
+ "const": "unix-time"
+ },
+ {
+ "type": "string"
+ }
]
},
"contentFormat": {
"type": "string"
},
"type": {
- "type": "string",
- "enum": [
- "number",
- "string",
- "boolean",
- "integer",
- "array"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "number"
+ },
+ {
+ "type": "string",
+ "const": "string"
+ },
+ {
+ "type": "string",
+ "const": "boolean"
+ },
+ {
+ "type": "string",
+ "const": "integer"
+ },
+ {
+ "type": "string",
+ "const": "array"
+ },
+ {
+ "type": "string"
+ }
]
},
"enum": {
"type": "array",
"items": {
"$ref": "#/definitions/allowed-types"
},
"minItems": 1
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"anyOf": [
{
"type": "boolean"
},
{
"type": "number"
}
]
},
"exclusiveMaximum": {
"anyOf": [
{
"type": "boolean"
},
{
"type": "number"
}
]
},
"multipleOf": {
"type": "number"
},
"minLength": {
"type": "number"
},
"maxLength": {
"type": "number"
},
"pattern": {
"type": "string"
},
"format": {
- "type": "string",
- "enum": [
- "date-time",
- "date",
- "time",
- "uri",
- "uri-reference",
- "uuid"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "date-time"
+ },
+ {
+ "type": "string",
+ "const": "date"
+ },
+ {
+ "type": "string",
+ "const": "time"
+ },
+ {
+ "type": "string",
+ "const": "uri"
+ },
+ {
+ "type": "string",
+ "const": "uri-reference"
+ },
+ {
+ "type": "string",
+ "const": "uuid"
+ },
+ {
+ "type": "string"
+ }
]
},
"minItems": {
"type": "number"
},
"maxItems": {
"type": "number"
},
"uniqueItems": {
"type": "boolean"
},
"items": {
"type": "object",
"properties": {
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"description": {
"type": "string"
},
"$comment": {
"type": "string"
},
"type": {
- "type": "string",
- "enum": [
- "number",
- "string",
- "boolean",
- "integer"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "number"
+ },
+ {
+ "type": "string",
+ "const": "string"
+ },
+ {
+ "type": "string",
+ "const": "boolean"
+ },
+ {
+ "type": "string",
+ "const": "integer"
+ },
+ {
+ "type": "string"
+ }
]
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"enum": {
"type": "array",
"minItems": 1
},
"format": {
"type": "string"
},
"minLength": {
"type": "number"
},
"maxLength": {
"type": "number"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
},
"jsonschema": {
"type": "object",
"properties": {
"type": {
- "type": "string",
- "enum": [
- "number",
- "string",
- "boolean",
- "integer",
- "array"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "number"
+ },
+ {
+ "type": "string",
+ "const": "string"
+ },
+ {
+ "type": "string",
+ "const": "boolean"
+ },
+ {
+ "type": "string",
+ "const": "integer"
+ },
+ {
+ "type": "string",
+ "const": "array"
+ },
+ {
+ "type": "string"
+ }
]
},
"enum": {
"type": "array",
"items": {
"$ref": "#/definitions/allowed-types"
},
"minItems": 1
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"anyOf": [
{
"type": "boolean"
},
{
"type": "number"
}
]
},
"exclusiveMaximum": {
"anyOf": [
{
"type": "boolean"
},
{
"type": "number"
}
]
},
"multipleOf": {
"type": "number"
},
"minLength": {
"type": "number"
},
"maxLength": {
"type": "number"
},
"pattern": {
"type": "string"
},
"format": {
- "type": "string",
- "enum": [
- "date-time",
- "date",
- "time",
- "uri",
- "uri-reference",
- "uuid"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "date-time"
+ },
+ {
+ "type": "string",
+ "const": "date"
+ },
+ {
+ "type": "string",
+ "const": "time"
+ },
+ {
+ "type": "string",
+ "const": "uri"
+ },
+ {
+ "type": "string",
+ "const": "uri-reference"
+ },
+ {
+ "type": "string",
+ "const": "uuid"
+ },
+ {
+ "type": "string"
+ }
]
},
"minItems": {
"type": "number"
},
"maxItems": {
"type": "number"
},
"uniqueItems": {
"type": "boolean"
},
"items": {
"type": "object",
"properties": {
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"description": {
"type": "string"
},
"$comment": {
"type": "string"
},
"type": {
- "type": "string",
- "enum": [
- "number",
- "string",
- "boolean",
- "integer"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "number"
+ },
+ {
+ "type": "string",
+ "const": "string"
+ },
+ {
+ "type": "string",
+ "const": "boolean"
+ },
+ {
+ "type": "string",
+ "const": "integer"
+ },
+ {
+ "type": "string"
+ }
]
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"enum": {
"type": "array",
"minItems": 1
},
"format": {
"type": "string"
},
"minLength": {
"type": "number"
},
"maxLength": {
"type": "number"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
}
},
"additionalProperties": false
},
"allowed-types": {
"anyOf": [
{
"type": "number"
},
{
"type": "string"
},
{
"type": "boolean"
},
{
"type": "null"
},
{
"type": "array",
"items": {
"type": "number"
}
},
{
"type": "array",
"items": {
"type": "string"
}
},
{
"type": "array",
"items": {
"type": "boolean"
}
+ },
+ {
}
]
},
"actionqualities": {
"type": "object",
"properties": {
"sdfInputData": {
"$ref": "#/definitions/pointer-list"
},
"sdfRequiredInputData": {
"$ref": "#/definitions/pointer-list"
},
"sdfOutputData": {
"$ref": "#/definitions/pointer-list"
},
"sdfData": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/dataqualities"
}
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
},
"eventqualities": {
"type": "object",
"properties": {
"sdfOutputData": {
"$ref": "#/definitions/pointer-list"
},
"sdfData": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/dataqualities"
}
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
}
},
- "additionalProperties": false
+ "additionalProperties": {
+ }
},
"productqualities": {
"$ref": "#/definitions/thingqualities"
}
}
}
¶
This draft is based on sdf.md and sdf-schema.json in the old
one-data-model language repository, as well as Ari Keranen's
"alt-schema" from the Ericsson Research ipso-odm repository (which
is now under subdirectory sdflint in the one-data model tools
repository).¶