This method involves groups of participants defining the key concepts about an issue and then organizing them into a shared language recognizable to the whole population, from lay person to politician to architect.
Problems and Purpose
This method, while originally designed for architectural planning, has been augmented to the democratic engagement process.
Origins and Development
How it Works
First used by British architect, Christopher Alexander, the general structure of the process is as follows:
"Usually the author of a pattern language or collection chooses a generic structure for all the patterns it contains, breaking each into generic sections like context, problem statement, solution etc.
When design is done by a team, pattern names will form a vocabulary they can share. This makes it necessary for pattern names to be easy to remember and highly descriptive. Some examples from Alexander's works are WINDOW PLACE (helps define where windows should go in a room) and A PLACE TO WAIT (helps define the characteristics of bus stops and hospital waiting rooms, for example)." 
Analysis and Lessons Learned
Participatory Landscape Design "Il Paesaggio Partecipato" (Scansano, Italy)
 Pattern Language. Wikipedia https://en.wikipedia.org/wiki/Pattern_language#Application_domains
Participatory pattern workshops: a methodology for open learning design inquiry
Using Pattern Languages in Participatory Design
Participatory Design in Open Education: A Workshop Model for Developing a Pattern Language
Pattern Languages in Participatory Design