Workflow is a collection of tasks organized to accomplish some business process. It also
defines the order of task invocation or conditions under which task must be invoked,
task synchronization, and information flow. Before the execution of the workflow, a
correct execution schema, in other words, the schedule of the workflow, must be determined.
Workflow scheduling is finding an execution sequence of tasks that obeys the
business logic of workflow. Research on specification and scheduling of workflows has
concentrated on temporal and causality constraints, which specify existence and order
dependencies among tasks. However, another set of constraints that specify resource allocation
is also equally important. The resources in a workflow environment are agents
such as person, machine, software, etc. that execute the task. Execution of a task has a cost and this may vary depending on the resources allocated in order to execute that
task. Resource allocation constraints define restrictions on how to allocate resources,
and scheduling under resource allocation constraints provide proper resource allocation
to tasks. In this thesis, we present two approaches to specify and schedule workflows
under resource allocation constraints as well as temporal and causality constraints. In
the first approach, we present an architecture whose core and novel parts are a specifi-
cation language with the ability to express resources and resource allocation constraints
and a scheduler module that contains a constraint solver in order to find correct resource
assignments. In the second approach, we developed a new logical formalism,
called Concurrent Constraint Transaction Logic (CCTR) which integrates constraint
logic programming (CLP) and Concurrent Transaction Logic, and a logic-based work-
flow scheduler that is based on this new formalism. CCTR has the constructs to specify
resource allocation constraints as well as workflows and it provides semantics for these specifications so that validity of a schedule can be checked.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/739193/index.pdf |
| Date | 01 January 2003 |
| Creators | Senkul Karagoz, Pinar |
| Contributors | Toroslu, Ismail Hakki |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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