  We introduce ObSynth, an interactive system leveraging the domain knowledge
embedded in large language models (LLMs) to help users design object models
from high level natural language prompts. This is an example of specification
reification, the process of taking a high-level, potentially vague
specification and reifying it into a more concrete form. We evaluate ObSynth
via a user study, leading to three key findings: first, object models designed
using ObSynth are more detailed, showing that it often synthesizes fields users
might have otherwise omitted. Second, a majority of objects, methods, and
fields generated by ObSynth are kept by the user in the final object model,
highlighting the quality of generated components. Third, ObSynth altered the
workflow of participants: they focus on checking that synthesized components
were correct rather than generating them from scratch, though ObSynth did not
reduce the time participants took to generate object models.
