Christian Fillies & Frauke Weichhardt
Tall Tree Labs
presents some use
We also present a graphical notation for authoring OWL in Visio and discuss which part of Description Logic can be expected to be used frequently.
It provides business
Only a small section of our users create OWL models for its own sake. In
most of the current models ontologies are used to normalize names of items in
models made for a different purpose than authoring OWL. Examples are the
Any existing OWL or RDFS source can be used as a repository or glossary
to ensure consistency. People often use lists of business
The resulting models are published in two ways: For end users graphical representations of the models are published on the intranet as HTML, MS Word or PowerPoint. For other modellers the model itself is available as a reusable component, e.g. a process model to be refined with subprocesses or reused as a process component. This makes all models a distributed web of knowledge.
Modelling of business processes and products in the context of a distributed web of knowledge differs significantly from the way those models have been created before. Before new terms are introduced, the user has to investigate if the term or fact already exists in the community semantic web. If the term already exists, the user model will reference that term by using the same URN and providing an URL to obtain its definition. Existing terms may be extended by subclasses or existing definitions of properties are added. If the concept is identical but the current domain requires a different name, a synonym can be added. For example a customer will be called patient in a medical domain.
The ontology contained, e.g. in a process is available for reuse in different processes in the same domain. The most common use case of ontologies in process modelling is to localize content to multiple languages. This is done by translating objects in the ontology which will automatically generate translated business processes.
Sometimes ontologies created for one specific purpose can be reused for a new modelling problem in the same domain. For example a product catalogue made for the web shop can be reused in a process modelling project.
The specification of business processes is a task executed by end users or consultants who are often specialized on process optimization or ERP systems. Those people are usually not educated in Description Logic and we do not experience a lot of enthusiasm to learn about it in order to make “better” ontologies.
For our purpose, which is ensuring consistency of other models, it is sufficient to build taxonomies, sometimes enriched with properties in order to make them more readable. Users have to learn about process modelling languages and a minimum of object-oriented thinking in order to apply the ontologies to their process models.
We use subclassing, DataProperties and ObjectProperties. For process models we also add the list of valid verbs to the classes.
Figure 1: Class Shapes
UML-style symbols (Figure 1) are used to represent classes and connectors for “Property” and “subClassOf”. There is also a specific connector named “Association” which can display cardinalities on ObjectProperties in a UML like style. DataProperties and methods (verbs) are displayed within the UML class shape. A lot of users are familiar with UML class shapes. The language which is used and supported by the SemTalk internal inference engine is similar to RDFS.
In order to be able to express the complete language set of OWL within Visio we extended the UML shapeset with OWL specific connectors and shapes (see Figure 2).
On classes we have added the constraints “disjointWith” and “equivalentClass”.
Different from standard SemTalk, instances are allowed in class diagrams and are allowed to be instance of multiple classes.
Figure 2: OWL Shapes
Anonymous classes such as unionOf
are being expressed by a mastershape (“OWL
Figure 3: Anon Classes
As an addition to standard SemTalk class diagrams we have special Visio shapes to represent ObjectProperties (“RelationType”) and DataProperties (“AttributeType”) as objects in the diagram which can have graphical links “hasDomain” and “hasRange” to other objects (Figure 4).
Figure 4: Properties in an OWL Diagram
Using these expressions new OWL files can be created and existing OWL files can be presented in a manually or automatically arranged way.
Because predefined Visio shapes can be used to represent classes and objects, OWL models designed with SemTalk are often better understandable for non-technical end users than models created with other tools.
Even if the graphical notation makes authoring OWL simpler than entering the same OWL data with other tools, it does not educate people in Description Logic.
Compared to the amount of users entering knowledge using MS PowerPoint and MS Visio, the number of users specifying knowledge with OWL will be small and limited to technical experts integrating IT-Systems in EAI or Portal scenarios. We do not expect people to annotate their documents manually by modelling the contents of documents in a way inference engines can “understand” the documents.
Resulting from complexity of the DL-modelling paradigm in full OWL even for stand-alone models an inference engine is needed to prove their correctness.
For some of the constraints it also makes sense to enforce consistency in a distributed environment even for taxonomies. This is especially true for disjointness, which can be violated without using any other OWL constructs other than subclassOf.
A major challenge we see for inference engines is to support the distributed modelling of business processes including support for finding homonyms. Homonyms are different words having the same meaning.
In the early nineties business process modelling has started from revolutionary ideas of Michael Hammer, who proposed business process reengineering. Pushed by the success story of ERP systems, 10 years later process modelling made its way from an academic discipline using research prototypes to a commercial component integrated in Microsoft Office used for any serious system integration.
Ontology modelling is still in its early stage. Most ontologies are made by academics using non-commercial tools which have their roots in research often in Artificial Intelligence. The “Semantic Web” in its original sense seems to be far away from reaching the critical mass required for a takeoff. But semantic technology is one of the very few technologies of the last decade which seems to ignore Gartner’s “Hype Cycle” [Eric Miller, STC05]. There has been slow but continuous growth on semantic technology and an end is not foreseeable.
Ontologies offer great value to common modelling problems especially to process modelling. Specification of procedural knowledge in processes is very common. Specification of static knowledge and rules in ontologies can be seen as an extension. Support for maintenance of static and dynamic knowledge will become part of knowledge worker’s workplace. Building end user tools for static knowledge can and will benefit from experiences made with process modelling tools.
We believe in ontology modelling as a great way of enhancing current
possibilities of writing computer programs on one hand and of closing the gap
between users and IT specialists on the other hand. For this we see the need to
enable everybody to develop, document and maintain his or her ontology, be it
in a conscious manner using DL metaphors or be it unconsciously while modelling
[HF03] van Hoof,
[FWW02] Fillies, C., Wood-
[OWL02] OWL We
 The OWL Shapeset was jointly developed with
Network Inference in