  The Large Synoptic Survey Telescope is designed to provide an unprecedented
optical imaging dataset that will support investigations of our Solar System,
Galaxy and Universe, across half the sky and over ten years of repeated
observation. However, exactly how the LSST observations will be taken (the
observing strategy or "cadence") is not yet finalized. In this
dynamically-evolving community white paper, we explore how the detailed
performance of the anticipated science investigations is expected to depend on
small changes to the LSST observing strategy. Using realistic simulations of
the LSST schedule and observation properties, we design and compute diagnostic
metrics and Figures of Merit that provide quantitative evaluations of different
observing strategies, analyzing their impact on a wide range of proposed
science projects. This is work in progress: we are using this white paper to
communicate to each other the relative merits of the observing strategy choices
that could be made, in an effort to maximize the scientific value of the
survey. The investigation of some science cases leads to suggestions for new
strategies that could be simulated and potentially adopted. Notably, we find
motivation for exploring departures from a spatially uniform annual tiling of
the sky: focusing instead on different parts of the survey area in different
years in a "rolling cadence" is likely to have significant benefits for a
number of time domain and moving object astronomy projects. The communal
assembly of a suite of quantified and homogeneously coded metrics is the vital
first step towards an automated, systematic, science-based assessment of any
given cadence simulation, that will enable the scheduling of the LSST to be as
well-informed as possible.
