Web-based Virtual Laboratory is emerging as a promising teaching assistant tool for modern distance education and attracts many attentions from both of academia and industry. In this paper, a novel virtual laboratory platform based on dynamic service composition, which is named as VL-DSC, is presented. In this platform, experimental process can be customized by service virtualization. A domain-oriented service composition description language is designed to describe the relationship between heterogeneous virtual instruments. Furthermore, based on the description language, dynamic message routing is adopted to realize dynamic schedule and replacement of virtual instruments. VL-DSC can significantly improve the customizability and dynamic interoperability of virtual lab, which can be used to develop virtual lab easily and quickly.

A novel indexing structure-the join index hierarchy-is proposed to handle the "gotos on disk" problem in object-oriented query processing. The method constructs a hierarchy of join indices and transforms a sequence of pointer-chasing operations into a simple search in an appropriate join index file, and thus accelerates navigation in object-oriented databases. The method extends the join index structure studied in relational and spatial databases, supports both forward and backward navigation among objects and classes, and localizes update propagations in the hierarchy. Our performance study shows that a partial join index hierarchy outperforms several other indexing mechanisms in object-oriented query processing.

A deductive database system prototype, LogicBase, has been developed, with an emphasis on efficient compilation and query evaluation of application-oriented recursions in deductive databases. The system identifies different classes of recursions and compiles recursions into chain or psuedo-chain forms when appropriate. Queries posed to the compiled recursions are analyzed systematically with efficient evaluation plans generated and executed, mainly based on a chained-based query evaluation method. The system has been tested using sophisticated recursions and queries with satisfactory performance. This paper introduces the general design principles and implementation techniques of the system and discusses its strength and limitations.

Optimizationof object queries containing encapsulated methods is still an open problem.In some previous studies of object query optimization, encapsulated methods are considered w black boxes and therefore, optimal query evaluation plans may be excluded from consideration.In the others, only methods coded in query languages are taken into consideration during optimization process and the application of methods is, therefore, restricted.In this paper, a systematic way of revealing and exploiting useful information from encapsulated methods is applied in object query optimization.Some new strategies of object query optimization are proposed according to the classifications and evaluations of selections and joins containing path expressions or methods.Object query graphs are used to represent object queries and to capture different kinds of selections and joins.They are also used to factorize common sub path expressions among not only path expressions in queries but also maximal common sub argument path expressions in methods and to generate query evaluation plans.

Two scaling theorems are given. Instead of delta functions, polynomial functions are used as input. The advantages are twofold: the smoothness conditions on kernels are not required, so that kernels of the form e/sup -k mod X mod / can be included; the proofs are based on calculus completely and so can be more easily understood.>

Fingerprint theorems, i.e. under what conditions the primal sketch can determine the image uniquely, are discussed. The weakness of A.L. Yuille and T. Poggio's fingerprint theorem (1986) is pointed out and two novel 1-D fingerprint theorems are presented. Then a practical algorithm based on one of these theorems is given for reconstructing the image from its primal sketch. From the given examples, it is shown that the fingerprint theorems are a substantial improvement over Yuille and Poggio's conjecture that Gaussian function is the only filter which can be used as the basis of a fingerprint theorem. The 1-D fingerprint theorems are generalized to 2-D ones.>

The Laplacian of Gaussian operator, Del /sup 2/G, is very important as an edge detector in the theory of computer vision. The bias of zero-crossing and output signal-to-noise-ratio of Del /sup 2/G under the models of four typical kinds of edges corrupted by white noise are given, and these theoretical results are confirmed by experiments. The relations among bias of zero-crossing, output and input signal-to-noise-ratio and parameter sigma of Del /sup 2/G are presented.>