=Paper=
{{Paper
|id=None
|storemode=property
|title=Process Monitoring Using Sensors in YAWL
|pdfUrl=https://ceur-ws.org/Vol-982/YAWL2013-Paper07.pdf
|volume=Vol-982
|dblpUrl=https://dblp.org/rec/conf/yawl/ConfortiRF13
}}
==Process Monitoring Using Sensors in YAWL==
https://ceur-ws.org/Vol-982/YAWL2013-Paper07.pdf
Process Monitoring Using Sensors in YAWL
Raffaele Conforti1 , Marcello La Rosa1,2 , and Giancarlo Fortino3
1
Queensland University of Technology, Australia
{raffaele.conforti,m.larosa}@qut.edu.au
2
NICTA Queensland Lab, Australia
3
Università della Calabria, Italy
g.fortino@unical.it
Abstract. This article describes the architecture of a monitoring com-
ponent for the YAWL system. The architecture proposed is based on
sensors and it is realized as a YAWL service to have perfect integration
with the YAWL systems. The architecture proposed is generic and ap-
plicable in different contextes of business process monitoring. Finally, it
was tested and evaluated in the context of risk monitoring for business
processes.
1 Introduction
The growing number of cases in which workflow management systems are utilized
to execute business processes, created the need for companies to monitor the
execution of their process instances [4]. Being able to monitor a process instance
is a basic requirements for companies that want to prevent the eventuation of
risks, be aware of the processing cost of process instances, or simply verify if a
process instance is being delayed.
Several commercial workflow management systems already provide monitor-
ing functionality for their systems, e.g. WebSphere4 , Oracle BAM5 , Sybase6 .
This type of functionality is not yet available in open-source workflow manage-
ment systems, such as the YAWL workflow management system.7
In this article we will illustrate how to realize a multi-purpose monitoring
component for the YAWL system. The component will be realized as a service
for the YAWL system, to guarantee a perfect integration with the system.
This article is structured as follows. Section 2 provides a briefly description of
the YAWL systems. Section 3 shows how to realize the monitoring component,
which is evaluated in Section 4. Section 5 discusses related work and finally
Section 6 concludes the article.
4
http://www-142.ibm.com/software/products/au/en/subcategory/SW920
5
http://www.oracle.com/technetwork/middleware/bam/overview/index.html
6
http://www.sybase.com.au/products/financialservicessolutions/complex-event-
processing
7
http://www.yawlfoundation.org/
49
2 Requirements and Preliminaries
In order to monitor a business process, being able to have a complete overview
of process instances is a requirements. The status of a process instance is fully
provided by information about instances of tasks (work items) and subprocesses
(nets) belonging to such a process instance.
When we consider a work item, to properly describe its status is essential to
know: i) if the work item was performed or not (status in the life-cycle of a work
item); ii) who (resource) performed the work item; iii) when the work item was
performed (time stamp); and iv) how it was performed (data). A similar set of
information is required for an instance of a net, except for the resource.
YAWL Engine
Interface A Interface B Interface E Interface X
Resource Service Web Service Worklet Service Generic
Invoker YAWL Service
Fig. 1. YAWL Architecture [8]
A clear understanding of the YAWL environment [8] is required if we want
to be able to access the status of work items and nets. The YAWL system is
a service-oriented architecture built using Java. Figure 1 provides a simplified
overview of the architecture of the YAWL system. The core element of this
architecture is the YAWL engine, it is in charge of managing the instantiation of
process instances and work items. The engine provides four interfaces to allow
services to interact with the engine, for example allowing the resource service,
which manages resources, to perform a work item instantiated.
These four interfaces are: i) interface A, which provides connection capa-
bilities and allows process models to be uploaded and unloaded, and external
services to be registered and unregistered; ii) interface B, which allows process
instances to be lunched, work items to be checked-out for their execution, and
process information to be retrieved; iii) interface E, which allows process logs to
be retrieved; and iv) interface X, which provides a terminal for detecting and
handling exceptions.
50
3 Monitoring Component
We can now describe how to create a monitoring component for the YAWL
system, as the one realized for [1]. The best way to realize a new component for
the YAWL system is to realize it as a YAWL service. Our service will use the
interfaces provided by the system, described in section 2, to receive notifications
from the engine about the initialization of the system and the starting of new
instances.
Two are the interfaces that will provide information that may be relevant for
us, they are interface B and interface X. The first interface will notify us with
events related with the life-cycle of a process instance and the initialization of
the YAWL system. Interface X will notify us when a process instance is canceled,
and a case is enabled or completed.
Fig. 2. Monitor Component: Class Diagram
In order to receive the notifications sent by these two interfaces, our monitor-
ing component must extend the java class InterfaceBWebsideController and im-
plements the java interface InterfaceX Service. We are only interested in a subset
of all notifications that interface B and X will send, for this reason we only need
to implements these four methods: i) handleCancelledWorkItemEvent; ii) han-
dleCaseCancellationEvent; iii) handleEngineInitialisationCompletedEvent; and
iv) handleCheckCaseConstraintEvent. Figure 2 shows the UML [5] class dia-
gram of how our monitoring component is built. In the diagram are only shown
the classes required for the realization of the monitoring component and the
methods that are relevant for us.
51
Our monitoring component works through the use of sensors (YSensor ). Each
sensor monitors a specific condition, composed of variables that are the result of
functions and actions, and is managed by the sensor manager (YSensorManager-
ImplLayer ). The sensor manager manages the creation of sensors and notifies
them when changes occur in a process instance. The sensor manager creates new
sensors each time a new process instances is started. Information about the ini-
tialization of the system and the starting, completion and cancellation of process
instances are retrieved by the sensor manager using the YAWL EngineInterface.
Fig. 3. DatabaseInteface Package Class Diagram
Changes in the process instance are discovered using the classes provided by
the package databaseInterface (see Figure 3). This package provides an abstrac-
tion layer on top of the database which allows queries to be executed through
the invocation of java methods. Executing queries gives to the system the pos-
sibility of retrieving information from different cases, and then have monitoring
conditions defined across cases. In order to know which changes are relevant for
a sensor, the sensors manager retrieves from it the list of LogVariables. Each
of this logVariable is associated with an action that using the ActionIdentifier
and the ActionExecutor is identified and executed, retrieving from the log the
information of interest. Each action captures a specific aspect of a work item or
a net, the list of all possible actions is shown in figure 4.
Changes in a process instance are then notified to a sensor using messages
(YSensorMessageUpdate). Every time a sensor receives a message, it checks its
monitoring condition using the updated information. The condition is checked
using a specific interpreter (ForInterpreter ) which interprets the languages de-
fined in [1] and verifies if the condition is violated or not. In case the condition
52
is violated the sensor will notify the administrator by sending a notification
through the YAWL MonitorInterface. The condition that a sensor can monitor
is a boolean expression which may contain nested loops, if-then-else constructs,
and algebraic operators.
Fig. 4. Actions Package Class Diagram
4 Evaluation and Possible Uses
The architecture here proposed was evaluated in [1]. In the experiment we mea-
sured the time required to retrieve the result of the execution of an action. In
table 1 we show the result grouped for type of action, e.g. NetStartTime and
NetCompleteTime are grouped under the name NetXTime.
The results show that in general a result is produced in few milliseconds
(ca. 20ms). Retrieving a net or an activity variable and retrieving information
about the distribution set and the initiator of an activity require more time, this
because they require the parsing of XML strings since the data are not directly
stored in the database.
53
time
Actions Description
[ms]
functions checking if a net status
NetIsX 18.9
has been reached
NetXTime functions returning the time when
18.8
NetXTimeInMillis a net status has been reached
NetVariable returns the value of a net variable 432.6
number of times a task has been
ActivityCount 19.8
completed
functions that return the resources
XResource 20.9
associated with a task
functions checking if a task status
ActivityIsX 30.5
has been reached
ActivityXTime functions returning the time when
22.3
ActivityXTimeInMillis a task status has been reached
ActivityVariable returns the value of a task variable 96.7
functions returning the resources
XDistribution 243
associated with a task by default
functions returning the allocation
XInitiator 249.6
strategy for a resource association
Table 1. Performance of basic functions.
Risk monitoring is not the only context in which our component can be
used. It is a multi-purpose monitoring component that provides the possibility
of adding new actions in order to make it usable in other context such as for
example cost monitoring, resource monitoring, or time monitoring.
5 Related Work
The idea of monitoring business processes is not new in the area of business pro-
cess management. Academics explored the possibility of monitoring business pro-
cesses using Complex Event Processing (CEP) systems [2, 3]. Commercial work-
flow management systems in general provide integrated monitoring features, e.g.
Oracle Business Activity Monitoring (BAM) [6], webMethods Business Events8 ,
and SAP Sybase [7].
The monitoring component here discussed was used in the approach proposed
in [1] for risk monitoring. In this approach business processes are integrated with
aspects of risk management, specifically risk monitoring. Risk conditions are
composed of two elements, a risk likelihood which monitors the likelihood of a
risk to occur and a risk threshold which defined level of risk which the company
is willing to accept before detecting the eventuation of a risk.
Gay et al. [2] propose the use of complex event processing for workflow moni-
toring on Petri nets. They identify six events that can represent the basic activi-
ties that a workflow can perform (i.e. Transition activation, Resource allocation,
Resource liberation, Advance token, Start workflow, and End workflow). Using
these simple events they have created six complex events that represent un-
wanted situations: i) Lack of resource; ii) Activity delay; iii) Lack of resource
delay; iv) Transition delay; v) Workflow delay; vi) Interruption warning. This
8
http://www.softwareag.com/au/products/wm/events/overview
54
approach, compare to our approach, does not take in consideration the data
prospective. This limitation produces as consequence the possibility of defining
conditions that are mainly related to the performance of a process instance.
Finally, Hermosillo et al. [3] propose a framework for dynamic business pro-
cess adaptation in the context of BPEL processes. In this approach they use the
monitoring functionality obtained using a CEP engine to detect conditions that
will then trigger an adaptation, i.e. the add or change of a service.
6 Conclusion
In this article we showed how to realize a monitoring component for the YAWL
system using the interfaces provided by the system itself. The monitoring is done
using sensors, which monitor conditions that can be defined using information
across cases.
The main contribution of this work is the identification and documentation
of a minimal set of classes required for the realization of a monitoring component
for the YAWL system.
The component is realized as a custom YAWL service, in order to guarantee
a perfect integration with the YAWL system. The structure of the component
also results to be independent from a specific monitoring purpose, consenting its
application in different contexts could they be risk monitoring, or cost monitor-
ing.
Finally, the architecture was implemented and tested. The results of the test
show that the retrieving of information can be computed efficiently and without
requiring additional work engine side.
References
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55