**Modeling and Querying Scientific Simulation Mesh Data**

B. Lee, R. Snapp, L. Chen (U. Vermont), and I. Song (Drexel U.)

Abstract Number: **92**

**Introduction**: Scientific simulation is gaining attention as an
inexpensive means of experimentation in scientific computing, and so is
the data generated by simulation. Scientific simulation typically
generates mesh data in a sequence of time steps. (See Figure 1.) The
data and file structure are complex. Understanding them involves the
topology and geometry of grid points, as well as the fields at these
points. Unfortunately, there is no data model, nor query language,
accepted widely for this kind of
data.![](media/image1.png){width="0.9770833333333333in"
height="0.9770833333333333in"}![](media/image2.png){width="0.9625in"
height="0.9625in"}![](media/image3.png){width="0.9305555555555556in"
height="0.9305555555555556in"}

**Methods and Materials**: We developed a compact, generic, abstract
model of simulation mesh data, and validated the model through
implementation. The data model is based on computer graphic object
modeling ^1^, and comprises a minimum number of necessary abstract data
structures and base operators. Structural duplicability was used as the
correctness criterion of our data model. Additional derived operators
were introduced to supplement computational operations as per query. The
implementation was done using a standard query language on an
object-oriented database management system (OODBMS).

**Results**: Constituents of the data model are three simple data
structures (a mesh topology graph, a vertex coordinate set, and a field
vector set) and four base operators (parents, children, coordinates, and
fields). We implemented the model in ODMG Object Definition Language ^2^
and executed a range of reference queries in ODMG Object Query Language
^2^ on lambda-DB OODBMS. The types of queries encompassed the topology,
geometry, and fields of simulation mesh data. We successfully produced
query outputs and, for queries that retrieved zones, displayed the
results on a visualization tool meshTV. (See Figures below for the
results of selected queries on the crushing can
data.)![](media/image6.png){width="0.9770833333333333in"
height="0.9770833333333333in"}![](media/image7.png){width="0.9770833333333333in"
height="0.9770833333333333in"}![](media/image8.png){width="0.9770833333333333in"
height="0.9770833333333333in"}

**Conclusions**: The data model is concise and generic, and yet proved
powerful enough to support sophisticated ad-hoc queries on all three
(i.e., topological, geometrical, and field) aspects of the data. To our
knowledge, this was the first successful attempt of executing ad-hoc
queries on scientific simulation mesh
data.![](media/image9.png){width="0.8243055555555555in"
height="0.8243055555555555in"}![](media/image10.png){width="0.8006944444444445in"
height="0.8006944444444445in"}![](media/image11.png){width="0.8090277777777778in"
height="0.8090277777777778in"}

**Acknowledgments**: We thank Professor Leonidas Fegaras at U. of Texas
at Arlington for lambda-DB, and DataFoundry team at Lawrence Livermore
National Laboratory for meshTV and Silo data files.

**References**: ^1^ J. Foley, A. Dam, S. Feiner, and J. Hughes,
"Computer Graphics: Principles and Practice in C" (2nd edition),
Addison-Wesley, 1996, p. 473-476. ^2^ R. Cattell (ed.), "The Object Data
Standard: ODMG 3.0," Morgan Kaufman, 2000, Chapters 3-4.