InkML is an XML-based markup language to describe "ink" data input with an electronic pen or stylus. The specification is maintained by the World Wide Web Consortium (W3C).

It is part of the W3C Multimodal Interaction Activity initiative.

Introduction

As more electronic devices with pen interfaces have and continue to become available for entering and manipulating information, applications need to be more effective at using this method of input. Handwriting is a powerful and versatile input modality that is very familiar for most users since everyone learns to write in school. Hence, users will tend to use this as a mode of input and control when available.

Ink data processing and organization

A pen-based interface is enabled by a device that allows movements of the pen to be captured as digital ink. Digital ink can be passed on to recognition software that will convert the pen input into appropriate computer actions or as textual character that closely matches ink stroke(s). Alternatively, the handwritten input can be organized into ink documents, notes or messages that can be stored for later retrieval or exchanged through telecommunications means. Such ink documents are appealing because they capture information as the user composed it, including text in any mix of languages and drawings such as equations and graphs.

Platform-neutral Ink format

Hardware and software vendors have typically stored and represented digital ink using proprietary or restrictive formats. The lack of a public and comprehensive digital ink format has severely limited the capture, transmission, processing, and presentation of digital ink across heterogeneous devices developed by multiple vendors. In response to this need, the Ink Markup Language (InkML) provides a simple and platform-neutral data format to promote the interchange of digital ink between software applications.

InkML for robust representation of digital ink

InkML supports a complete and accurate representation of digital ink. In addition to the pen position over time, InkML allows recording of information about device characteristics and detailed dynamic behavior to support applications such as handwriting recognition and authentication. For example, there is support to record additional information such as pen tilt and pen tip force (often referred to as "pressure") and information about the recording device such as accuracy and dynamic distortion. InkML also provides features to support rendering of digital ink captured optically to approximate the original appearance. For example, stroke width and color information can be recorded.

Extensible format

InkML provides means for extension. By virtue of being an XML-based language, users may easily add application-specific information to ink files to suit the needs of the application at hand.

Structure

The current InkML specification defines a set of primitive elements sufficient for all basic ink applications. All content of an InkML document is contained within a single <ink> element. The fundamental data element in an InkML file is the <trace> . A trace represents a sequence of contiguous ink points, where each point captures the values of particular quantities such as the X and Y coordinates of the pen's position. A sequence of traces accumulates to meaningful units, such as characters, words or diagrams. In its simplest form, an InkML file with its enclosed traces looks like this: <ink> <trace> 10 0, 9 14, 8 28, 7 42, 6 56, 6 70, 8 84, 8 98, 8 112, 9 126, 10 140, 13 154, 14 168, 17 182, 18 188, 23 174, 30 160, 38 147, 49 135, 58 124, 72 121, 77 135, 80 149, 82 163, 84 177, 87 191, 93 205 </trace> <trace> 130 155, 144 159, 158 160, 170 154, 179 143, 179 129, 166 125, 152 128, 140 136, 131 149, 126 163, 124 177, 128 190, 137 200, 150 208, 163 210, 178 208, 192 201, 205 192, 214 180 </trace> <trace> 227 50, 226 64, 225 78, 227 92, 228 106, 228 120, 229 134, 230 148, 234 162, 235 176, 238 190, 241 204 </trace> <trace> 282 45, 281 59, 284 73, 285 87, 287 101, 288 115, 290 129, 291 143, 294 157, 294 171, 294 185, 296 199, 300 213 </trace> <trace> 366 130, 359 143, 354 157, 349 171, 352 185, 359 197, 371 204, 385 205, 398 202, 408 191, 413 177, 413 163, 405 150, 392 143, 378 141, 365 150 </trace> </ink>

Software

InkML Toolkit (InkMLTk) is targeted at providing a suite of tools for working with InkML documents. The toolkit includes the following libraries and tools,

• InkML processor libraries implementing the W3C InkML specification
• Converters library and tools (to and from other ink and image formats)
• InkML viewers as browser plug-ins, and
• InkML applications such as a graphical editor.

This project is released in SourceForge.net as an open source contribution from HP Labs, India.

See also

• Ink Serialized Format
• Tablet PC

External links

• W3C InkML Home
• InkML Specification
• InkML Toolit - open source contribution from HP Labs, India

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