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107
Partial Constraint Satisfaction
, 1992
"... . A constraint satisfaction problem involves finding values for variables subject to constraints on which combinations of values are allowed. In some cases it may be impossible or impractical to solve these problems completely. We may seek to partially solve the problem, in particular by satisfying ..."
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Cited by 427 (23 self)
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. A constraint satisfaction problem involves finding values for variables subject to constraints on which combinations of values are allowed. In some cases it may be impossible or impractical to solve these problems completely. We may seek to partially solve the problem, in particular by satisfying a maximal number of constraints. Standard backtracking and local consistency techniques for solving constraint satisfaction problems can be adapted to cope with, and take advantage of, the differences between partial and complete constraint satisfaction. Extensive experimentation on maximal satisfaction problems illuminates the relative and absolute effectiveness of these methods. A general model of partial constraint satisfaction is proposed. 1 Introduction Constraint satisfaction involves finding values for problem variables subject to constraints on acceptable combinations of values. Constraint satisfaction has wide application in artificial intelligence, in areas ranging from temporal r...
Quantifying the Causes of Path Inflation
 IN ACM SIGCOMM
, 2003
"... Researchers have shown that the Internet exhibits path inflation  endtoend paths can be significantly longer than necessary. We present a tracedriven study of 65 ISPs that characterizes the root causes of path inflation, namely topology and routing policy choices within an ISP, between pairs of ..."
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Cited by 117 (25 self)
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Researchers have shown that the Internet exhibits path inflation  endtoend paths can be significantly longer than necessary. We present a tracedriven study of 65 ISPs that characterizes the root causes of path inflation, namely topology and routing policy choices within an ISP, between pairs of ISPs, and across the global Internet. To do so, we develop and validate novel techniques to infer intradomain and peering policies from endtoend measurements. We provide the first measured characterization of ISP peering policies. In addition to "earlyexit," we observe a significant degree of helpful nonearlyexit, loadbalancing, and other policies in use between peers. We find that traffic engineering (the explicit addition of policy constraints on top of topology constraints) is widespread in both intra and interdomain routing. However, intradomain traffic engineering has minimal impact on path inflation, while peering policies and interdomain routing lead to significant inflation. We argue that the underlying cause of interdomain path inflation is the lack of BGP policy controls to provide convenient engineering of good paths across ISPs.
Inferring Link Weights using EndtoEnd Measurements
 In ACM SIGCOMM Internet Measurement Workshop
, 2002
"... We describe a novel constraintbased approach to approximate ISP link weights using only endtoend measurements. Common routing protocols such as OSPF and ISIS choose leastcost paths using link weights, so inferred weights provide a simple, concise, and useful model of intradomain routing. Our ap ..."
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Cited by 108 (18 self)
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We describe a novel constraintbased approach to approximate ISP link weights using only endtoend measurements. Common routing protocols such as OSPF and ISIS choose leastcost paths using link weights, so inferred weights provide a simple, concise, and useful model of intradomain routing. Our approach extends routerlevel ISP maps, which include only connectivity, with link weights that are consistent with routing. Our inferred weights agree well with observed routing: while our inferred weights fully characterize the set of shortest paths between 8499% of the routerpairs, alternative models based on hop count and latency do so for only 4781% of the pairs.
The Cassowary Linear Arithmetic Constraint Solving Algorithm: Interface and Implementation
 ACM TRANSACTIONS ON COMPUTER HUMAN INTERACTION
, 1998
"... Linear equality and inequality constraints arise naturally in specifying many aspects of user interfaces, such as requiring that one window be to the left of another, requiring that a pane occupy the leftmost 1/3 of a window, or preferring that an object be contained within a rectangle if possibl ..."
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Cited by 84 (9 self)
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Linear equality and inequality constraints arise naturally in specifying many aspects of user interfaces, such as requiring that one window be to the left of another, requiring that a pane occupy the leftmost 1/3 of a window, or preferring that an object be contained within a rectangle if possible. Current constraint solvers designed for UI applications cannot e#ciently handle simultaneous linear equations and inequalities. This is a major limitation. We describe Cassowaryan incremental algorithm based on the dual simplex method that can solve such systems of constraints e#ciently. This informal technical report describes the latest version of the Cassowary algorithm. It is derived from the paper "Solving Linear Arithmetic Constraints for User Interface Applications" by Alan Borning, Kim Marriott, Peter Stuckey, and Yi Xiao [7], published in the UIST'97 Proceedings. The UIST paper also contains a description of QOCA, a closely related solver that finds leastsquares solut...
Multiway versus Oneway Constraints in User Interfaces: Experience with the DeltaBlue Algorithm
, 1993
"... this paper we argue that many user interface construction problems are handled more naturally and elegantly by multiway constraints than by oneway constraints. We present pseudocode for an incremental multiway constraint satisfaction algorithm, DeltaBlue, and describe experience in using the algo ..."
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Cited by 83 (17 self)
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this paper we argue that many user interface construction problems are handled more naturally and elegantly by multiway constraints than by oneway constraints. We present pseudocode for an incremental multiway constraint satisfaction algorithm, DeltaBlue, and describe experience in using the algorithm in two user interface toolkits. Finally, we provide performance figures demonstrating that multiway constraint solvers can be entirely competitive in performance with oneway constraint solvers
Hierarchical Constraint Logic Programming
, 1993
"... A constraint describes a relation to be maintained ..."
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Cited by 67 (3 self)
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A constraint describes a relation to be maintained
Constraint Hierarchies and Logic Programming
, 1989
"... Constraint Logic Programming (CLP) is a general scheme for extending logic programming to include constraints. It is parameterized by D, the domain of the constraints. However, CLP(D) languages, as well as most other constraint systems, only allow the programmer to specify constraints that must hold ..."
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Cited by 67 (5 self)
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Constraint Logic Programming (CLP) is a general scheme for extending logic programming to include constraints. It is parameterized by D, the domain of the constraints. However, CLP(D) languages, as well as most other constraint systems, only allow the programmer to specify constraints that must hold. In many applications, such as interactive graphics, page layout, and decision support, one needs to express preferences as well as strict requirements. If we wish to make full use of the constraint paradigm, we need ways to represent these defaults and preferences declaratively, as constraints, rather than encoding them in the procedural parts of the language. We describe a scheme for extending CLP(D) to include both required and preferential constraints, with an arbitrary number of strengths of preference. We present some of the theory of such languages, and an algorithm for executing them. To test our ideas, we have implemented an interpreter for an instance of this language scheme with D equal to the reals. We describe our interpreter, and outline some examples of using this language.
Solving linear arithmetic constraints for user interface applications: Algorithm details
, 1997
"... Linear equality and inequality constraints arise naturally in specifying many aspects of user interfaces, such as requiring that one window be to the left of another, requiring that a pane occupy the leftmost 1/3 of a window, or preferring that an object be contained within a rectangle if possible. ..."
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Cited by 65 (17 self)
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Linear equality and inequality constraints arise naturally in specifying many aspects of user interfaces, such as requiring that one window be to the left of another, requiring that a pane occupy the leftmost 1/3 of a window, or preferring that an object be contained within a rectangle if possible. Current constraint solvers designed for UI applications cannot efficiently handle simultaneous linear equations and inequalities. This is a major limitation. We describe incremental algorithms based on the dual simplex and active set methods that can solve such systems of constraints efficiently.
Distributed partial constraint satisfaction problem
 Principles and Practice of Constraint Programming
, 1997
"... Abstract. Many problems in multiagent systems can be described as distributed Constraint Satisfaction Problems (distributed CSPs), where the goal is to nd a set of assignments to variables that satis es all constraints among agents. However, when real problems are formalized as distributed CSPs, th ..."
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Cited by 62 (13 self)
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Abstract. Many problems in multiagent systems can be described as distributed Constraint Satisfaction Problems (distributed CSPs), where the goal is to nd a set of assignments to variables that satis es all constraints among agents. However, when real problems are formalized as distributed CSPs, they are often overconstrained and have no solution that satis es all constraints. This paper provides the Distributed Partial Constraint Satisfaction Problem (DPCSP) as a new framework for dealing with overconstrained situations. We also present new algorithms for solving Distributed Maximal Constraint Satisfaction Problems (DMCSPs), which belong to an important class of DPCSP. The algorithms are called the Synchronous Branch and Bound (SBB) and the Iterative Distributed Breakout (IDB). Both algorithms were tested on hard classes of overconstrained random binary distributed CSPs. The results can be summarized as SBB is preferable when we are mainly concerned with the optimality ofasolution, while IDB is preferable when we want to get a nearly optimal solution quickly. 1
SmartClients: Constraint satisfaction as a Paradigm for Scaleable Intelligent Information Systems
, 2002
"... Many information systems are used in a problem solving context. Examples are travel planning systems, catalogs in electronic commerce, or agenda planning systems. They can be made more useful by integrating problemsolving capabilities into the information systems. This poses the challenge of scalea ..."
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Cited by 54 (18 self)
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Many information systems are used in a problem solving context. Examples are travel planning systems, catalogs in electronic commerce, or agenda planning systems. They can be made more useful by integrating problemsolving capabilities into the information systems. This poses the challenge of scaleability: when hundreds of users access a server at the same time, it is important to avoid excessive computational load.