Abstract
In a distributed context where data is dispersed over many computing nodes, monotone queries can be evaluated in an eventually consistent and coordination-free manner through a simple but naive broadcasting strategy which makes all data available on every computing node. In this paper, we investigate more economical broadcasting strategies for full conjunctive queries without self-joins that only transmit a part of the local data necessary to evaluate the query at hand. We consider oblivious broadcasting strategies which determine which local facts to broadcast independent of the data at other computing nodes. We introduce the notion of broadcast dependency set (BDS) as a sound and complete formalism to represent locally optimal oblivious broadcasting functions. We provide algorithms to construct a BDS for a given conjunctive query and study the complexity of various decision problems related to these algorithms.
Highlights
We assume the setting introduced in the context of declarative networking [6, 14], where queries are specified on a logical level over a global schema and are evaluated by multiple computing nodes over which the input database is distributed
We make the following contributions: (i) We provide a semantical characterization of when an oblivious broadcasting function (OBF) correctly evaluates a given conjunctive query
Neven (ii) We introduce the notion of a broadcast dependency set (BDS) as a formalism to specify OBFs
Summary
We assume the setting introduced in the context of declarative networking [6, 14], where queries are specified on a logical level over a global schema and are evaluated by multiple computing nodes over which the input database is distributed. A B-fact B(i, j) is broadcast only when A(j, i) does not occur in the local database Executing this strategy for every computing node in our example results in c broadcasting the set {B(2, 1)} while c broadcasts {B(4, 4), C(1, 3)}. We make the following contributions: (i) We provide a semantical characterization of when an oblivious broadcasting function (OBF) correctly evaluates a given conjunctive query. We turn to a slightly weaker notion of optimality, called local optimal, which requires that an OBF is optimal w.r.t. the local instance at every computing node This means that no broadcast fact can be made static without sacrificing correctness.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
