Toward a Unified Scripting Language: Lessons Learned from Developing CML and AML

Abstract

Life-like animated agents present a challenging ongoing agenda for research. Such agent metaphors will only be widely applicable to online applications when there is a standardized way to map underlying engines with the visual presentation of the agents. This chapter delineates functions and specifications of two markup languages for scripting the animation of virtual characters. The first language is Character Markup Language (CML) which is an XML-based, embodied agent, character attribute, definition and animation scripting language designed to aid in the rapid incorporation of life-like agents into online applications or virtual reality worlds. CML is constructed based jointly on motion and multi-modal capabilities of virtual human figures. The other is Avatar Markup Language (AML) which is also an XML-based multi-modal scripting language designed to be easily understandable by human animators as well as easily generated by a software process such as an agent. We illustrate the constructs of the two languages and look at some examples of usage. The experience gained through the development of two such languages with different approaches yet similar aims highlights the need for a degree of unification. This is especially true given that a number of other similar languages exist as illustrated in other parts of this book. We attempt to define metrics for comparison of a set of these languages with the aim of identifying salient constructs for a unified scripting language.