=Paper=
{{Paper
|id=Vol-160/paper-29
|storemode=property
|title=An MDD annotation methodology for Semantic Enhanced Service Oriented Architectures
|pdfUrl=https://ceur-ws.org/Vol-160/paper27.pdf
|volume=Vol-160
|authors=L. Pondrelli
|dblpUrl=https://dblp.org/rec/conf/caise/Pondrelli05
}}
==An MDD annotation methodology for Semantic Enhanced Service Oriented Architectures==
https://ceur-ws.org/Vol-160/paper27.pdf
An MDD annotation methodology for Semantic
Enhanced Service Oriented Architectures
Lorenzo Pondrelli
Gruppo Formula, Via Mateotti 5, 40050 Villanova di Castenaso (BO), Italy
lorenzo.pondrelli@gruppoformula.it
Abstract. Service Oriented Architectures are increasingly being used to achieve
interoperability among heterogeneous systems. SOAs help developers to inte-
grate different architectures in order to reuse legacy systems and extend soft-
ware boundaries. Semantics could improve SOA features adding a common un-
derstanding of the resources shared among different systems. Model Driven
Development could be useful to produce a scalable and neutral methodology for
guiding developers through software development and integration processes,
employing reusable approaches and platform independency. In this context it is
necessary to understand how we can use the MDD approach to enhance Service
Oriented Architecture with semantics. This paper proposes to use a common
visualization of ontologies and services, based on the industry-standard UML
modelling language and its profiling system, to solve the resources annotation
process in a SOA context. A first analysis of the main UML approaches for
modelling ontologies is followed by the explanation of a general method for de-
scribing service interfaces and the resources exchanged among them.
1 Introduction
Semantic Oriented Architectures simplify the development of complex architectures,
introducing the concepts of black box components and interface programming. Black
boxes are units whose output is a specified function of the input, but for which the
method of converting input to output is not necessarily specified [1], in other words
pieces of software that can be used without knowledge of its inner workings, for
which the user supplies the input assuming the output to be correct. Following this
approach the most important thing in the developing and in the integration process is
the definition of the interfaces of the software components and their description. If we
want to ensure the interoperability among these interfaces we need to add not only a
human understandable explanation but also a computer comprehensible common in-
terpretation of the resources shared among the different systems. To achieve these re-
sults we can use two different approaches: using standards or using ontologies to
share common knowledge.
2 An MDD approach for a semantic SOA
Ontologies could be used to build common knowledge that can be shared among dif-
ferent interfaces in order to exchange information between heterogeneous systems. In
particular Domain Ontologies are formal organization of domain knowledge and in
that way enable knowledge sharing between different knowledge-base applications
[2], thus applicable to SOAs. In a SOA context we can use Domain Ontologies collec-
tions to annotate all resources, both interfaces and content schemas, in order to obtain
shared descriptions of knowledge. There are software applications that allow the an-
notation of resources, in particular most of them permit the annotation of web pages
(Ontomat [3], MnM [4], Cohse [5] and Smore [6]) or text documents (Trellis [7] and
Melita [8]). Service Oriented Architectures are strictly related to the Web services
technology and the associated standards such as SOAP [9], WSDL [10] and UDDI
[11]. It is more difficult to find tools for the annotation of Web services and in general
for the annotation of distributed application interfaces. One example is the METEOR-
S Web Service Annotation Framework (MWFAS) [12] that produces WSDL-S de-
scriptions of service interfaces. However for the purpose of this paper the key point
of is the abstraction from particular technologies, such as WSDL and SOAP, general-
izing from Web services technologies in order to find a more general solution. An
MDD [13] approach should allowing platform independent development. In this con-
text UML seems to be the best solution for proposing a complete developing frame-
work for adding semantics to SOAs, in particular a profile for describing ontologies
and a method for modeling black box interfaces which have been semantically en-
riched.
3 Using UML for modeling ontologies
The semantic languages, used to express ontologies, are not readable by humans be-
cause their representation syntaxes are built for machine understandability. From this
perspective, one of the main open issues in this field is related to the visualization of
ontologies for human readers. Most of the ontologies tools and editors, such as the
most famous Protégé, use a tree arrangement to visualize ontologies following the
structure of classes, slots, properties and instances. There are many proposals regard-
ing the possibility to use UML, the industry-standard of modeling languages, for solv-
ing that issue. Some of the proposals consider the possibility to create a new MOF
metalanguage at the same level of UML [14], [15] but most of them are related to
UML profiles for ontologies [16], [17], [18]. The main difference is that the UML
profiling system is not a first-class extension mechanism so it cannot be used to mod-
ify existing metamodels but only for adapting metamodels with constructs for a par-
ticular domain. It allows the extension of metamodels in order to adapt them for dif-
ferent purposes. The problem is that the ontology languages have many features that
UML does not support. In this perspective could be useful to understand completely
the relationships between the main ontology concepts and UML. Table 1 explains the
most common similarities between them:
Table 1. Mapping between UML and the main ontology languages concepts
UML Ontology concepts
Packages Ontologies
Classes Classes
Attributes, associations and classes Properties
Navigable Domain, range
Note Comment
Multiplicity Cardinality
Data types Data types
Objects Instances
The methods based on UML profiles allow the using of UML, so UML editors too,
for building and managing ontologies. This fact means also that we can represent on-
tologies, abstracting from the different semantic languages, using XMI (now also Pro-
tégé contains a plug-in that includes a storage format compatible to the metadata stan-
dard MOF, obviously based on XMI [19]).
4 Semantic description of interfaces and their content
After the ontology modeling stage, the consequently step is the development of a
methodology to semantically describe interfaces, such as Web services. Each inter-
face needs two different levels of description. The first one regards the meaning of the
interface itself and its operations. The second is related to the content of the objects
exchanged among interfaces, in other words the meaning of the input and output pa-
rameters of each interface.
If we want to use UML as base of our annotation process, we need to profile both
these two different kinds of resources:
• Component Interfaces, such as Web services.
• Business Objects to describe parameters exchanged among interfaces.
In [20], [21], [22], [23] there are proposals about UML profiles for services that can
be used therefore to express Component interfaces. For Business Objects we can sup-
pose to use an UML profile for XML schemas (as in [23]) that allows the description
of semi-structured documents as proposed in [24], [25], [26], [27], [28], [29]. In this
manner we can fully complete the description of all our resources, using UML and
XMI, at a platform independent level.
The last step is the creation of a general technique for linking ontologies designed fol-
lowing a particular profile with other resources. Our proposal regards only the meth-
odology and does not consider the choice of particular profiles. It is based on a double
annotation:
− The first phase annotation is a visual annotation produced using UML dependency
artifacts stereotyped with simples “semRef” labels or more specific stereotypes,
between ontology elements and resource elements, such as service , attributes and
operations. In Figure 1 there is an simple example of this kind of annotation using
the Provost’s service example proposed in [23] and a related ontology built fol-
lowing [16].
Fig. 1. First phase annotation example using “semRef” dependencies between Component In-
terface, Business Objects and ontology on the base of example proposed in [23].
− The second phase annotation produces a more detailed annotation performed using
tagged values related to each resource elements. For instance, it is possible to add
more exhaustive descriptions of the single parameters of the service operations or
particular business information regarding services, such as Business Entities in-
volved in the service lifecycle or Quality of Service information.
− Obviously, we can suppose to add also a method for including more human under-
standable information, using the UML notes system.
In this manner we ensure a complete platform independent description of the re-
sources involved in SOA with the support of ontologies to guarantee interoperability.
5 Conclusions
Using our methodology it is possible to describe interfaces, such as Web services, and
all the resources related, in a platform independent way using UML. The annotation
process allows to add, at the same time, computer and human understandable meta-
data to each element of SOA resources, using common ontologies for sharing the in-
formation among different systems. In this manner we can suppose to use UML tools
as ontology editors and annotators. XMI could become a neutral common language
for describing elements related to ontologies and Service Oriented Architectures in
order to utilize model transformation capabilities to get different Platform Specific
Model for singular technologies.
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