The Physical Markup Language (PML) is proposed as a general, standard means for describing physical objects and environments for industrial, commercial and consumer applications. Given the broad scope of this vision, PML is crafted to allow modularity and flexibility.

The objective of PML is a simple, general language for describing physical objects for use in monitoring and control of a physical environment - particularly through the Internet. Applications include inventory tracking, automatic transaction, supply chain management, machine control and object-to-object communication.

Our approach has been to develop a set of standard components that span the breadth of application together with an extension mechanism allowing customization within vertical industries, as illustrated in Figure 1.

Figure 1. PML is comprised of a basis set of components that describes elements common to most industries and a data dictionary system allowing customization within vertical industries.

Since standard PML components are common across industry, they must, by definition, be basic, modular and elemental. These basic description, therefore, must be common to nearly every physical object. For example, objects are composed of matter. They have physical properties - volume and mass. They exist is certain forms (solid, liquid and gas) and have measurable states (temperature, pressure and weight).

Man-made objects exhibit structure. Many have a hierarchical form of system, assembly, subassembly and component. Objects exist in time and place. Their exact movement and location are critical for commerce and industry. Products have attributed values of worth, cost and price - and nearly every object is owned by somebody.

These attributes, we argue, are common to every physical object, independent of particular industry. We should not, therefore, recreate identical definitions within different industries, but rather encourage the adoption of a common standard.

In the PML Specification, we propose standard definitions for these common characteristics. These definitions include time, place, measurement, configuration, geometry, physical properties, classification, presentation and history. We will also introduce a mechanism to allow customization and extension within industry groups.

Together these language elements will allow users to share common data about physical objects within and across industries and applications.