Summary form only given. We are interested in Workflow Management Systems (WFMS), and particularly, in Resource Management (RM) of WFMS. A WFMS consists of coordinating executions of multiple activities, instructing who (resource) do what (activity) and when. The "when" part is taken care of by the workflow engine which orders the executions of activities based on a process definition. The "who" part is handled by the resource manager that aims at finding suitable resources at the run-time for the accomplishment of an activity as the engine steps through the process definition. Resources of different kinds (human and material, for example) constitute the information system of our interest, their management consists of resource modeling and effective allocation upon users' requests. Since resource allocation needs to follow certain general guidelines (authority, security, for example)-no matter who or what application issues requests: so those general guidelines are better considered as part of the resources' semantics. That is the reason why we are interested in resource policy management in RM. Resource policies are general guidelines every individual resource allocation must observe. They differ from process specific policies which are only applied to a particular process. The policy manager is a module within the resource manager, responsible for efficiently managing a (potentially large) set of policies and enforcing them in resource allocation. We propose to enforce policies by query rewriting.

A trace, defined as a set of points satisfying some constraints, is introduced to specify ranges in which interesting objects are located. The paper shows how the declarativeness of the query language is enhanced by introducing this concept, and how explicitly recognized traces have a significant impact on query optimization. Two typical spatial queries are considered: spatial select and join. For spatial select queries, one needs to collect together distance related conditions concerning the same spatial attribute and to recognize them as a trace; this trace is used against the spatial index (if any) defined on the attribute, for query optimization. The trace concept is then extended to a region (instead of constant objects in the plane). This is necessary for spatial join queries since the spatial objects, in terms of which join conditions are specified, are bound by a relation. Because the whole plane is usually divided into rectangular regions by R -tree indexing, we consider actual traces on the basis of rectangles. A region r of one join relation and a region s of another join relation are 'joinable' (contain potentially joinable tuples) if r (or s) intersects with the trace on the basis of s (or r). By recursively exploring the R -tree indexes on the join attributes from roots to leaves, one may figure out joinable pages before searching for the principal relations.

A logic database has two components. One comprises the base knowledge, represented explicitly, called the extensional base. The other stores more general knowledge in the form of derivation rules, and is called the intensional base. One may calculate derived facts in advance and store (or materialize) them. Thus, the response time can be expected to speed up. In this paper, we study a new evaluation technique for incrementally maintaining derived facts whenever updates occur on base facts. Our method is based on the seminaive evaluation so it is easy to implement; it is set-oriented, multiple updates may be dealt within a single manipulation; and insertion and deletion are treated uniformly. The method is evaluated analytically as well as experimentally. We indicate the potential application of our incremental method to a computational linguistic problem, i.e., parsing incomplete sentences. Related work in both areas of logic databases and computational linguistics are discussed.

To efficiently process recursive queries in a DBMS (database management system), a parallel, direct transitive closure algorithm is proposed. Efficiency is obtained by reorganizing the computation order of Warren's algorithm. The number of transfers among processors depends only on the number of processors and does not depend on the depth of the longest path. The evaluation shows an improvement due to the parallelism and the superiority of the proposed algorithm over recent propositions. The speed of the production of new tuples is very high and the volume of transfers between the sites is reduced.>