12681881
Synthesis of Constraint Algorithms
7140389
Overcoming Ontology Mismatches in Transactions with Self-Describing Service Agents
One vision of the "Semantic Web" of the future is that software agents will interact with each other using formal metadata that reveal their interfaces. We examine one plausible paradigm, where agents provide service descriptions that tell how they can be used to accomplish other agents' goals. From the point of view of these other agents, the problem of deciphering a service description is quite similar to the standard AI planning problem, with some interesting twists. Two such twists are the possibility of having to reconcile contradictory ontologies -- or conceptual frameworks -- used by the agent, and having to rearrange the data structures of a message-sending agent so they match the expectations of the recipient. We argue that the former problem requires human intervention and maintenance, but that the latter can be fully automated.
17878068
Guarded Transitions in Evolving Specifications
We represent state machines in the category of specifications, where assignment statements correspond exactly to interpretations between theories [7, 8]. However, the guards on an assignment require a special construction. In this paper we raise guards to the same level as assignments by treating each as a distinct category over a shared set of objects. A guarded assignment is represented as a pair of arrows, a guard arrow and an assignment arrow. We give a general construction for combining arrows over a factorization system, and show its specialization to the category of specifications. This construction allows us to define the fine structure of state machine morphisms with respect to guards. Guards define the flow of control in a computation, and how they may be translated under refinement is central to the formal treatment of safety, liveness, concurrency, and determinism.
44957593
Toward a Classification Approach to Design
This paper addresses the problem of how to construct refinements of specifications formally and incrementally. The key idea is to use a taxonomy of abstract design concepts, each represented by a design theory An abstract design concept is applied by constructing a specification morphism from its design theory to a requirement specification. Procedures for propagating constraints, computing colimits, and constructing specification morphisms provide computational support for this approach. Although we conjecture that classification generally applies to the incremental application of knowledge represented in a taxonomy of design theories, this paper mainly focuses on algorithm design theories and presents several examples of design by classification.
26840234
Software Development by Refinement
This paper presents an overview of the technical foundations and current directions of Kestrel’s approach to mechanizing software development. The approach emphasizes machine-supported refinement of property-oriented specifications to code, based on a category of higher-order specifications. A key idea is representing knowledge about programming concepts, such as algorithm design, and datatype refinement by means of taxonomies of abstract design theories and refinements. Concrete refinements are generated by composing library refinements with a specification.
7947888
Constructing Specification Morphisms
Specification morphisms underlie the refinement of algebraic specifications and provide the logical foundations for algorithm and data structure design. We present four techniques for formally, even mechanically, constructing specification morphisms. The first two techniques, verifying a manually constructed signature morphism and composition of specification morphisms are well-known. The remaining two techniques exploit the axioms of the source specification to help infer the translation of sort and function symbols from the source specification. The third, unskolemization, finds the translation of a function symbol by replacing occurrences of it in an axiom by an existentially quantified variable. A constructive proof of the translated axiom yields a witness to the existential that serves as the desired translation of the function symbol. The fourth technique, connections between specifications, allows the transfer of structure from one specification morphism to another. The unskolemization and connection techniques arose as abstractions from the algorithm design tactics implemented in the KIDS program transformation system (Smith (1990)). They suggest a more general approach to providing mechanized support for applying design knowledge expressed axiomatically.
11953962
Detecting events with date and place information in unstructured text
Digital libraries of historical documents provide a wealth of information about past events, often in unstructured form. Once dates and place names are identified and disambiguated, using methods that can differ by genre, we examine collocations to detect events. Collocations can be ranked by several measures, which vary in effectiveness according to type of events, but the log-likelihood measure (-2 log λ) offers a reasonable balance between frequently and infrequently mentioned events and between larger and smaller spatial and temporal ranges. Significant date-place collocations can be displayed on timelines and maps as an interface to digital libraries. More detailed displays can highlight key names and phrases associated with a given event.
16933924
Using architecture evaluation to prepare a large Web based system for evolution
This paper describes an ongoing effort to develop architecture documentation and to evaluate the architecture using the Architecture Tradeoff Analysis Method/sup SM/ (ATAM/sup SM/). The system is a large Web based application using J2EE, portal and Web services technology that is replacing a large number of legacy applications. It has very detailed documentation at the design level, but is lacking overall architecture documentation. We describe how the architecture is being documented in an iterative manner, and how sample scenarios are being developed as input for an ATAM. The package of the documentation, scenarios and ATAM will fill in important gaps in existing knowledge, and it will provide an important baseline for the system's evolution.
12947717
The evolving mSpace platform: leveraging the semantic web on the trail of the memex
Vannevar Bush proposed the memex as a means to support building knowledge in the way he says the human brain works: by association. Achieving this vision has been a core motivation for hypertext research. In this paper, we suggest first that Bush's memex reflects an interaction paradigm rather than system design. Second, we propose that Semantic Web promises to provide the mechanisms to enable these interaction requirements. Third, we propose the mSpace framework and architecture as a platform to deploy lightweight Semantic Web applications which foreground associative interaction. We propose this lightweight approach as a means to evaluate both interaction needs and the cost/benefits of using Semantic Web technologies to support them.
18928754
An improved algorithm to determine lower bounds for the fixed spectrum frequency assignment problem
Frequencies have to be assigned to transmitters whenever a radio network is established or modified. This is ideally done is a way which minimises interference in the network. Lower bounds are necessary to establish the effectiveness of the heuristic algorithms used for this task and to assess the quality of the assignments obtained. 
 
In the fixed spectrum frequency assignment problem the available frequencies are known in advance. The constraints are often binary constraints, specifying the necessary frequency separation between given pairs of transmitters. There may be penalties (or weights) associated with the violation of each constraint; it is then either necessary to minimise the number of constraints violated or, increasingly often, to minimise the sum of the weights associated with violated constraints. 
 
A technique for generating lower bounds for these quantities is presented. This is an evolution of a technique which has recently appeared in the literature. It produces better quality bounds, is in general significantly faster and allows larger problems to be handled.
30879884
Generation of lower bounds for minimum span frequency assignment
Minimum span frequency assignment problems require lower bounds for the span in order to assess the quality of individual assignments, and to effectively compare different meta-heuristic algorithms. The generation of good lower bounds requires the identification of critical subproblems. These subproblems are subgraphs of a constraint graph. Sometimes clique subgraphs lead to good lower bounds. However for some problems the clique must be modified in order to obtain the best possible bound. This can be time consuming, requires manual intervention and is dependent on the initial clique obtained and the specific problem. For practical use, a simple bounding technique is needed that can be universally applied to all problems without modification. Two algorithms based on meta-heuristics are presented that aim to find a subproblem that gives the best possible lower bound. This avoids the need for clique detection routines and manual intervention, and gives a robust and automatic method for generating lower bounds for all minimum span problems. These algorithms use mathematical programming formulations of the frequency assignment problem. Extensive testing on a wide range of problems shows that bounds from the new algorithms match those using previous techniques, and in some cases are significantly better.