7.3.1 Overview
The semantic modelling environment is based on the ARIS software tools. The follow- ing parts are added to the ARIS software tools to enable support for semantic business process management:
• Semantic descriptions like WSMO goals can be loaded into the ARIS software tools. Therefore, the semantic descriptions must be represented by the ARIS modelling language. This is described in subsection7.3.2.
• Business experts must be able to annotate an EPC business process model with the semantic descriptions. The belonging user interface concept is described in subsection7.3.3.
• Semantic annotations also add ontological input and output instances to the busi- ness process model. Those instances must be combined to define a complete data flow. The belonging tool is described in subsection7.3.4.
• The EPC to BPEL transformation application must be extended to preserve the se- mantic annotations during process transformation. The implemented solution is de- scribed in subsection7.3.5.
7.3.2 Representation of Semantics in ARIS
The semantic web community develops and supports different formalisms like OWL-S [MBH+04] and WSMO [FLP+06] (see also section2.6). Therefore, the semantically ex- tended ARIS software tools must not be bound to a specific semantic formalism, but in- stead be as independent as possible. This means, the way semantic descriptions are represented by the ARIS modelling language must be the same for different semantic formalisms if possible. In an ideal case, this allows exchanging the semantic formalism without having to change the semantically annotated process models. Also, the user in- terface to select or create a semantic description must be identical, because the semantic formalism used does not matter for a business expert. The semantic business process management application developed supports semantic annotations based on WSMO (see
Verify-Formal- Requirements FormalVerification customer::TP_Cust omer formalVerification::F ormalVerification
Figure 7.2: Function annotated with WSMO goal
subsection 2.6.3). Nevertheless, the general modelling principle used in the application can be straightforwardly transferred to other formalisms like OWL-S.
Describing the functionality of (IT) systems is not a completely new approach and is used in IT architecture management since several years. However, the semantic community proposes a much more formal approach, which is harder to understand by people with no background in logic, mathematics or computer science, but which, on the other hand, is expressive enough to use automated reasoning. The ARIS modelling language uses the “capability” object type to describe the functionality of systems. This object is used to represent the semantic descriptions as well.
Figure 7.2 shows a part of an EPC process model with the function “Verify-Formal- Requirements”. In a complete EPC process model, this function would be related to other functions or events (see subsection2.1.4). The semantic description “Formal Verification” is represented by a “capability”, which is connected to the function. The “capability” was created by importing a WSMO goal description as described in the next subsection. As the semantic description is represented by a separate modelling object and not stored as an attribute value of the function, it can be reused to annotate different functions or IT systems. For example, if the semantic description is changed, only this object and its attributes must be updated. All other objects like functions related to it will have the updated semantic description as well. This ensures that semantic descriptions stay consistent and it prevents redundancy, because each semantic description is only stored once in the ARIS software tools. Figure7.2also shows the ontological input/output instances defined by the WSMO goal. They are represented by a separate object and connected the function as well. The following subsection shows the graphical user interface used to add semantic descriptions to business process models.
7.3.3 Selecting a WSMO Goal in ARIS
Functions of an EPC process model can be annotated with semantic descriptions to de- scribe their functionality. In the semantic business process management application, the
Figure 7.3: GUI to select WSMO goal in ARIS software tools
annotation is supported by the graphical user interface shown in figure7.3. The dialog is executed after selecting the function in the EPC, which should be annotated.
First, the user selects a folder on the local hard drive, where WSMO goal descriptions as WSML files are stored. The dialog lists all files found in the selected folder on the left side of the dialog. If the user clicks on an entry in the list, the content of the file is shown on the right side of the dialog. At this stage, the content of the WSML file is shown without any syntax highlighting or other visual support.
The user evaluates the applicability of a WSMO goal based on the WSML code. Finally, the user confirms the selection of a WSMO goal by clicking the “OK” button. A “capability” object type is created and automatically related to the function as shown in figure7.2and discussed before.
Another small support functionality is provided allowing to remove a semantic descrip- tion from a function, too. The dialog to select a WSMO goal and the support functionality to remove a WSMO goal are implemented by the scripting language embedded in the ARIS software tools. The scripts are available to the user and can be changed by them if necessary.
7.3.4 Completing the Data Flow
By selecting a WSMO goal to annotate a function, the WSMO goal and the ontological input/output instances are added to the EPC. The ontological input/output instances must be mapped to define a complete data flow. This is illustrated in figure 7.4. A support functionality is provided by the semantic business process management application to define this mapping between ontological input/output instances. The user first selects an output instance and afterwards the input instance. Now, the support functionality is
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Figure 7.4: Completing data flow in EPC
executed by the user. The functionality creates a new diagram where the mapping is documented. The semantic business process management application also includes a functionality to remove such mappings.
Another small functionality is provided to define condition expressions at process branches. The user selects the belonging operator and calls the functionality. The func- tionality adds a function in front of the operator. This function is used to maintain the condition expression. As it is only a minor functionality, it is not visualised here.
7.3.5 Injecting Semantic Annotations in BPEL
After all functions of the EPC are semantically annotated, the business process model is transformed into an executable one. The EPC to BPEL transformation application de- scribed in chapter5does not preserve those semantic descriptions, because the applica- tion is not aware of this concept. Therefore, the semantic business process management application extends the transformation. Each time a function is semantically annotated, a special call to a proxy web service able to handle the semantic description is generated in the BPEL process. The generated BPEL process is standard conform and can be ex- ecuted on an ordinary BPEL execution engine. The discovery of web services based on the semantic descriptions provided are handled by the proxy service, which is described in detail in the following section.