513,688 research outputs found
Interaction between Path and Type Constraints
This paper investigates that interaction. In particular it studies constraint implication problems, which are important both in understanding the semantics of type/constraint systems and in query optimization. It shows that path constraints interact with types in a highly intricate way. For that purpose a number of results on path constraint implication are established in the presence and absence of type systems. These results demonstrate that adding a type system may in some cases simplify reasoning about path constraints and in other cases make it harder. For example, it is shown that there is a path constraint implication problem that is decidable in PTIME in the untyped context, but that becomes undecidable when a type system is added. On the other hand, there is an implication problem that is undecidable in the untyped context, but becomes not only decidable in cubic time but also finitely axiomatizable when a type system is impose
Constraints for Semistructured Data and XML
Integrity constraints play a fundamental role in database design. We review initial work on the expression of integrity constraints for semistructured data and XML
A Symbolic Execution Algorithm for Constraint-Based Testing of Database Programs
In so-called constraint-based testing, symbolic execution is a common
technique used as a part of the process to generate test data for imperative
programs. Databases are ubiquitous in software and testing of programs
manipulating databases is thus essential to enhance the reliability of
software. This work proposes and evaluates experimentally a symbolic ex-
ecution algorithm for constraint-based testing of database programs. First, we
describe SimpleDB, a formal language which offers a minimal and well-defined
syntax and seman- tics, to model common interaction scenarios between pro-
grams and databases. Secondly, we detail the proposed al- gorithm for symbolic
execution of SimpleDB models. This algorithm considers a SimpleDB program as a
sequence of operations over a set of relational variables, modeling both the
database tables and the program variables. By inte- grating this relational
model of the program with classical static symbolic execution, the algorithm
can generate a set of path constraints for any finite path to test in the
control- flow graph of the program. Solutions of these constraints are test
inputs for the program, including an initial content for the database. When the
program is executed with respect to these inputs, it is guaranteed to follow
the path with re- spect to which the constraints were generated. Finally, the
algorithm is evaluated experimentally using representative SimpleDB models.Comment: 12 pages - preliminary wor
Haptic-GeoZui3D: Exploring the Use of Haptics in AUV Path Planning
We have developed a desktop virtual reality system that we call Haptic-GeoZui3D, which brings together 3D user interaction and visualization to provide a compelling environment for AUV path planning. A key component in our system is the PHANTOM haptic device (SensAble Technologies, Inc.), which affords a sense of touch and force feedback – haptics – to provide cues and constraints to guide the user’s interaction. This paper describes our system, and how we use haptics to significantly augment our ability to lay out a vehicle path. We show how our system works well for quickly defining simple waypoint-towaypoint (e.g. transit) path segments, and illustrate how it could be used in specifying more complex, highly segmented (e.g. lawnmower survey) paths
A Design Path for Hierarchical Self-Assembly of Patchy Colloids
Patchy colloids are promising candidates for building blocks in directed
self-assembly. To be successful the surface patterns need to both be simple
enough to be synthesized, while feature-rich enough to cause the colloids to
self-assemble into desired structures. Achieving this is a challenge for
traditional synthesis methods. Recently it has been suggested that the surface
pattern themselves can be made to self-assemble. In this paper we show that a
wide range of functional structures can be made to self-assemble using this
approach. More generally we present a design path for hierarchical targeted
self-assembly of patchy colloids. At the level of the surface structure, we use
a predictive method utilizing universality of patterns of stripes and spots,
coupled with stoichiometric constraints, to cause highly specific and
functional patterns to self-assemble on spherical surfaces. We use a
minimalistic model of an alkanethiol on gold as a model system and demonstrate
that, even with limited control over the interaction between surface
constituents, we can obtain patterns that causes the colloids themselves to
self-assemble into various complex geometric structures. We demonstrate how
variations of the same design path cause in-silico self-assembly of strings,
membranes, cubic and spherical aggregates, as well as various crystalline
patterns.Comment: 8 pages, 5 figure
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