Life is a process which can be abstracted away from any particular medium
- John von Neumann
Artificial Life either refers to the field of study of life and its origin through artificial models (Ranging from abstract models to biochemical simulations); or generalizations of the process of life; or to the simulated models which, according to the Strong Alife Hypothesis, are forms of life on par with biological entities.
Strong Alife Hypothesis
This position is exemplified by Tierra's creator, Thomas Ray Tom Ray, who has claimed that "The intent of this work [Tierra] is to synthesize rather than simulate life" 
Artificial Life Models in Software by Maciej Komosinski (Editor), Andrew Adamatzky, 2009
"The advent of powerful processing technologies and the advances in software development tools have drastically changed the approach and implementation of computational research in fundamental properties of living systems through simulating and synthesizing biological entities and processes in artificial media. Nowadays realistic physical and physiological simulation of natural and would-be creatures, worlds and societies becomes a low-cost task for ordinary home computers. The progress in technology has dramatically reshaped the structure of the software, the execution of a code, and visualization fundamentals. This has led to the emergence of novel breeds of artificial life software models, including three-dimensional programmable simulation environment, distributed discrete events platforms and multi-agent systems. This second edition reflects the technological and research advancements, and presents the best examples of artificial life software models developed in the World and available for users."
Artificial Life Models in Hardware by Edited by Andrew Adamatzky and Maciej Komosinski, 2009
"Hopping, climbing and swimming robots, nano-size neural networks, motorless walkers, slime mould and chemical brains --- this book offers unique designs and prototypes of life-like creatures in conventional hardware and hybrid bio-silicon systems. Ideas and implementations of living phenomena in non-living substrates cast a colourful picture of state-of-the-art advances in hardware models of artificial life.
Focusing on topics and areas based on non-traditional thinking, and new and emerging paradigms in bio-inspired robotics, this book has a unifying theme: the design and real-world implementation of artificial life robotic devices."
- ↑ Evolution, Ecology and Optimization of Digital Organisms, Thomas S. Ray, School of Life & Health Sciences, University of Delaware, link, p.3