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Ink Model URI Scheme

The Ink Model specification defines a way to use Uniform Resource Identifiers (URI) to reference nodes of the InkModel's primary ink-tree or views by specifying a scheme in accordance with the guidelines in RFC 3986.

URI Scheme

The specification uses the following terms as they are defined in RFC 3986:

  • scheme
  • authority
  • path
  • segment
  • unreserved characters
  • pchar
  • pct-encoded characters
  • fragment

The Ink Model specification provides a specific URI scheme for identification of InkModel nodes and other elements, using the following grammar:

  • URI = "uim:" [ //authority ] [path] [#fragment]
  • authority = skipped
  • path = 1 * ( "/" segment )
  • segment = 1 * ( pchar )
  • fragment = optional


The URI's authority component is skipped. All path definitions in the table below are considered path-rootless according to RFC 3986.

The path component may begin with a segment containing a percent-encoded URI (defined in RFC 3986, Section 2.1: that uniquely identifies an Ink Model. In case the InkModel's identification segment is skipped, the URI is used for local node referencing on Ink Model level and the URI is treated as local URI.

Important note: Implementations must encode URIs of entities, which belong to the serialized model, only in their local form (using local URIs).

Ink Model

Path: <pct-encoded InkModel URI>/node/<node-id>

Fragment: n/a

Description: URI of a node, contained within an Ink Model. The <pct-encoded InkModel URI> segment contains a percent-encoded URI of an InkModel. This segment is optional. The <node-id> segment contains an > > InkNode identifier, encoded as a GUID string value.

Example: Suppose we have an InkNode with GUID 5454710e-608d-4eee-9552-680f3349ab3e, contained within the main ink tree or a view of an InkModel with URI, (provided by the provider

URI of the InkNode in the InkModel's scope (local ID): uim:node/5454710e-608d-4eee-9552-680f3349ab3e

URI of the InkNode (globally unique):

Named entities

Path: <pct-encoded InkModel URI/>ne/<ne-id>

Fragment: n/a

Description: URI of a named entity definition, usually used to group knowledge about a specific InkModel node.

The <pct-encoded InkModel URI> segment contains a percent-encoded URI of an InkModel. This segment is optional. The <ne-id> segment contains an identifier of a named entity definition.

MD5-hash based Unique Identifier Generation Algorithm

The described algorithm allows generation of unique identifiers based on a tag (encoded as string value) and a collection of components.

The supported component types are:

  • Integer number
  • Floating-point number
  • String
  • List of properties defined as key-value pairs; the key and value of a pair are considered to be of type string.

The algorithm is expressed in pseudocode below. The described method takes a tag value and a list of components as arguments and generates a unique MD5 hash as an 8-byte array.

METHOD generateMD5Hash(tag, components): RETURNS byte[8]

SET buffer = new StringBuffer()


FOREACH component OF components
IF (component is defined)

RETURN MD5_HASH(buffer.toString())

The convertToString() method used in the pseudocode snippet above should be implemented as follows per each component type:

  • Integer number - convertToString() returns the string representation of the integer number

  • Floating-point number - convertToString() returns the string representation of the floating-point number using fixed-point number representation with 4 digits after the decimal point

  • String - convertToString() returns the string value

  • List of properties - convertToString() pseudocode implementation:

METHOD convertToString(properties): RETURNS string

SET buffer = new StringBuffer()

properties = SORT(properties) // sort the properties list by ascending alphabetical name order

FOREACH pair OF properties

RETURN buffer.toString()


Sensor Channel Types

The table below describes a list of common sensor channel types, defined as URIs, which are used to distinguish between different sensor characteristics.

will://input/3.0/channel/XSensor channel storing the x-coordinates on a surface or within 3D space.
will://input/3.0/channel/YSensor channel storing the y-coordinates on a surface or within 3D space.
will://input/3.0/channel/ZSensor channel storing the y-coordinates within 3D space.
will://input/3.0/channel/TimestampSensor channel storing the time difference to the previous sample.
will://input/3.0/channel/PressureSensor channel storing the pressure applied on the pen tip.
will://input/3.0/channel/RadiusXSensor channel storing the x-radius of a touch event.
will://input/3.0/channel/RadiusYSensor channel storing the y-radius of a touch event.
will://input/3.0/channel/AzimuthSensor channel storing the azimuth angle of a pen device.
will://input/3.0/channel/AltitudeSensor channel storing the altitude angle of a pen device.
will://input/3.0/channel/RotationSensor channel storing the barrel rotation of the pen device.

Core Elements

The table below describes a list of WILL Core element types, defined as URIs.

will://core/3.0/core/PathInk stroke
will://core/3.0/core/SensordataSensor data

Common InkModel Views

The table below describes a list of known InkModel views.

will://views/3.0/HWRCurrently provided by the Semantic Ink Services.
will://views/3.0/NERCurrently provided by the Semantic Ink Services.

Remark This section is still in experimental state and the listed definitions may change.


The table below describes a list of types and entities, used to store ontological knowledge definitions into the ink model's knowledge graph.

will://semantic/3.0/hasNamedEntityDefinitionPredicate the defines a dedicated entity storing named entity recognition (NER) results.
will://semantic/3.0/hasSourcePredicate for the source of the knowledge graph.
will://semantic/3.0/hasUriPredicate for the URI within the knowledge graph.
will://semantic/3.0/hasAbstractPredicate for a short abstract to describe the entity.
will://semantic/3.0/hasImagePredicate for the image describing the semantic entity.
will://semantic/3.0/hasThumbPredicate for a thumbnail to the concept type.
will://semantic/3.0/hasArticlePredicate for a URL pointing to article about a semantic entity.
will://semantic/3.0/hasTypePredicate for describing the type of the concept.
will://semantic/3.0/hasCategoryPredicate for the category of the semantic entity.
will://semantic/3.0/hasLabelPredicate for label of the semantic entity.
will://semantic/3.0/isPredicate for best math from handwriting recogntion.
will://semantic/3.0/hasAltPredicate for alternative recognition results.
will://semantic/3.0/hasBBoxPredicate for bounding box of the recognized word.
will://semantic/3.0/hasRelevantConceptPredicate for relevant concept type if there are multiple types found by NER.

Remark This section is still in experimental state and the listed definitions may change.

Content Segmentation

The table below describes a list of types and entities used to describe an ink model's structure in terms of content segmentation.

will://segmentation/3.0/TextRegionDefining a larger region with text.
will://segmentation/3.0/ParagraphGroups text lines in a paragraph.
will://segmentation/3.0/TextLineGroups words in a text line.
will://segmentation/3.0/WordGroups ink strokes in a word.
will://segmentation/3.0/PhraseGroups words in a logical in a unit.
will://segmentation/3.0/LineBreakDefining a linebreak.
will://segmentation/3.0/MathBlockGrouping ink strokes to a math formula.
will://segmentation/3.0/ShapeGrouping ink strokes to a shape.

Remark This section is still in experimental state and the listed definitions may change.


The table below describes a list of types and entities in terms of shape recognition and definition.

will://shapes/3.0/RectangleGroups ink strokes as a rectangle.
will://shapes/3.0/CircleGroups ink strokes as a circle.
will://shapes/3.0/EllipseGroups ink strokes as a ellispe.
will://shapes/3.0/TriangleGroups ink strokes as a triangle.
will://shapes/3.0/DoodleGroups ink strokes as a doodle.
will://shapes/3.0/ArcGroups ink strokes as an arc.
will://shapes/3.0/LineGroups ink strokes as a line.
will://shapes/3.0/PolygonGroups ink strokes as a polygon.
will://shapes/3.0/ParallelogramGroups ink strokes as a parallelogram.
will://shapes/3.0/RhombusGroups ink strokes as a rhombus.
will://shapes/3.0/attr/pointsAttribute describing a list of points.
will://shapes/3.0/attr/ptAttribute describing a single point.
will://shapes/3.0/attr/pt1Attribute descibing the first point.
will://shapes/3.0/attr/pt2Attribute descibing the second point.
will://shapes/3.0/attr/pt3Attribute descibing the third point.
will://shapes/3.0/attr/radiusAttribute describing the radius.
will://shapes/3.0/attr/radiusXAttribute describing the radius x.
will://shapes/3.0/attr/radiusYAttribute describing the radius y.
will://shapes/3.0/attr/rectAttribute describing a rectangle.
will://shapes/3.0/attr/centerPointAttribute describing the center point.
will://shapes/3.0/attr/angleAttribute describing an angle.
will://shapes/3.0/attr/phiAngleAttribute describing a phi angle.
will://shapes/3.0/attr/startAngleAttribute describing a start angle.
will://shapes/3.0/attr/sweepAngleAttribute describing a sweep angle.

Remark This section is still in experimental state and the listed definitions may change.