Electrical computers and digital processing systems: multicomput – Computer conferencing
Reexamination Certificate
1998-09-11
2002-06-04
Maung, Zarni (Department: 2152)
Electrical computers and digital processing systems: multicomput
Computer conferencing
C709S224000
Reexamination Certificate
active
06401111
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to interaction monitoring systems used in electronic commerce. More particularly, this invention relates to automatically creating and maintaining, with an interaction monitor, interaction history data for a long running application wherein the interaction history data can be accessed by the application.
BACKGROUND OF THE INVENTION
With the substantial increase in use of the Internet and, particularly, the World Wide Web (“Web”), electronic commerce is emerging as an important tool for service providers. Such applications may be long running, perhaps spanning over many hours and days, where not only a single interaction may be asynchronous, i.e., a long time may pass before a response to a request is returned, but related interactions may be dispersed in time. Consequently, a need has developed for a system of providing long running service applications whose interaction history is maintained for application access so that compensation of an earlier service request is a capability.
Monitors are software systems that support simple creation and execution of application programs with complex requirements. They manage underlying resources (both physical computing resources as well as logical resources, such as data files) which the applications require and monitor the access to these resources in an orderly fashion. There are many types of monitors (e.g., transaction processing and security monitors) creating different application execution environments and ensuring different properties for these applications.
FIG. 1
illustrates a conventional transaction processing (TP) monitor system for supporting transactional applications. Transactional applications access various data and logical resources such that access to these resources needs to be controlled to enforce certain properties, namely atomicity, consistency, isolation and durability (ACED). A TP monitor provides an execution environment for automatically ensuring these properties. The transactional applications T
1
130
and Tn
135
are registered with the TP monitor
120
. There can be many such transactional applications. Upon receiving a request
110
for execution of one such registered application (e.g., Tn
135
), the TP monitor
120
allocates necessary physical resources to the system and instantiates an instance, Tnj
152
, of the application Tn
135
. The TP monitor
120
passes the input parameters received with the request to the application instance
152
over path
116
. Each application instance is referred to as a transaction. Thus, transactions T
11
150
and T
1
12
151
are instances of the registered application T
1
130
. Once a transaction is completed, the results
153
are returned by the monitor
120
to the client application. In a different type of monitor environment, the application instance may be started and stopped locally under administration control.
Transactions access logical resources (e.g., databases) maintained by the resource managers
140
and
141
. The monitor
120
intercepts all access to these resources by the transactions and maintains a history of access to these resources in their log
160
. The monitor
120
also detects any application failure either due to a failure of the underlying computer system or due to software errors. As indicated hereinabove, the TP monitor system supports execution of transactions ensuring ACID properties. Atomicity refers to the property where all updates by a transaction to the monitored resources are made permanent only if the entire application succeeds. Incomplete execution of the application, due to any failure, will result in the restoration of the state of the resources to that state which existed prior to any access by the transaction. The TP monitor and/or resource managers maintain a history of accesses by all transactions to achieve this restoration of state. However, this history creation/maintenance is performed automatically by the monitor
120
without any knowledge of or assistance from the applications. Ensuring the other three properties (i.e., Consistency, Isolation and Durability) also requires monitoring any accesses to the controlled resources and making use of the history. Thus, the TP monitor provides reliability and execution support to applications by providing a system guarantee that all persistent effects are removed on failure.
Many other types of access monitors exist for ensuring a subset of these or other access properties (e.g., security, access control). In all cases, the underlying monitor intercepts access to the monitored resources by the supported applications and exercises certain access monitoring logic based on the present access state. However, in all cases, the applications are unaware of the details of the underlying operations of the monitor, other than the semantics of these properties guaranteed by the monitor. Therefore, in the TP monitor and the other similar access monitors of the prior art, the applications do not have direct access to the interaction history maintained by the monitor.
This conventional monitoring is implemented in many different ways. The monitoring logic may be distributed across many computer systems. Additionally, the applications may execute in a system different from the monitor systems.
FIG. 2
illustrates the working of a transactional application executing outside the monitor systems. T
1
230
, T
2
235
and T
3
240
represent three instances (transactions) of transactional applications. These transactions access the logical resources monitored by the servers
210
and
215
. All accesses to these resources by these transactions
230
,
235
and
240
are referred to as transactional remote procedure calls (TRPCs)
250
through
255
, since the access to the monitored resources follows the ACID properties. The monitoring software in the servers
210
and
215
coordinates the monitoring logic to achieve these properties. As in
FIG. 1
, the servers
210
and
215
maintain transaction logs
220
and
225
, respectively to maintain various properties.
In contrast to typical ACID transactional applications, workflow applications are long running and may be created as multi-step applications consisting of independent application steps. Such applications are reliably executed under a workflow monitor. Workflow systems, e.g., IBM's Flowmark product, maintain a persistent record of process and process instance state for the purpose of controlling (starting and stopping) the activities in the process flows. The state management functions of a conventional workflow system are illustrated in FIG.
3
. Workflow systems must store both the process flow form (for managed processes) and the state of each process instance. In FIG.
3
(
a
), elements
301
through
316
show information which would be stored defining a process flow. In FIG.
3
(
b
), elements
317
through
328
describe state information which would be recorded for each process instance.
In FIG.
3
(
a
), the process flow PF includes activities or processing action blocks
301
through
306
which the workflow system is responsible for controlling. The arrows
307
through
315
represent data and control flows so that arrows
307
and
315
represent the start and the end of the process flow, respectively. The other data/control flow arrows,
308
through
314
, show how the output data produced by the completion of one activity will be made available as input to other activities. The workflow system is responsible for scheduling activities as soon as all necessary inputs are available for them and managing the distribution of data to activities following the data/control flow arrows in the process flow graph. Element
316
is a pool of resources such as skilled agents. The work flow system, when starting an activity, may also be required to select an available and appropriately skilled resource to perform the activity. To carry out the above functions, workflow systems store a persistent record of the information illustrated above for process flow PF.
In addi
Dan Asit
Goyal Ambuj
Parr Francis Nicholas
Cardone Jason D.
F. Chau & Associates LLP
Maung Zarni
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