Publishing intentional services using new annotation for WSDL

Kadan Aljoumaa Centre de Recherche en Informatique

Université Paris 1 - Panthéon Sorbonne

90, rue de Tolbiac 75013 Paris, France +33 (0)1 44 07 86 45

kadan.aljouma@univ-paris1.fr

Saïd Assar Institut Telecom

Telecom Business School

9, rue Ch. Fourier

91011 Evry, France

+33 (0)1 60 76 44 88

said.assar@it-sudparis.eu

Carine Souveyet Centre de Recherche en Informatique

Université Paris 1 - Panthéon Sorbonne

90, rue de Tolbiac 75013 Paris, France +33 (0)1 44 07 86 45

carine.souveyet@univ-paris1.fr

ABSTRACT

With the increasing growth in popularity of Web services, discovering relevant Web services becomes a significant challenge. The introduction of intentional services has been proposed to bridge the gap between low level, technical software-service descriptions and high level, strategic expressions of business needs for services. Current Web Services technology based on UDDI and WSDL does not make use of this “intention” and therefore fails to address the problem of matching between capabilities of services and business user needs. In this work, we are interested in extending existing approaches for the description of intentional Services. Our proposed approach is an extension of the W3C recommendation on semantics for Web services (SAWSDL) and uses two types of ontologies: verb ontology representing syntactic and semantic concepts related to verbs, and product ontology, which is a Domain Ontology containing the concepts defining a common vocabulary for all objects manipulated in the business domain. We present how our approach can help publishing intentional services.

Categories and Subject Descriptors

D.2.10 [Software Engineering]: Design– Representation.

General Terms

Design.

Keywords

Intentional Services, SAWSDL, Intentional Service description.

1. INTRODUCTION Within a decade, Web services and SOA became a viable technical solution for the development of information systems. They provide flexibility in maintenance and evolution of systems, and ensure a high degree of interoperability between

heterogeneous systems [13]. A major problem in the use of SOA is the discovery of appropriate services that meet business needs [14]. This difficulty will increase with the number and variety of web services available online. The technological tools currently available (such as WSDL for Web Service Description Language and UDDI for Universal Description Discovery and Integration) are semantically poor and conceptually far from the concerns of users. As many researchers have observed, there is a conceptual

mismatch between the service provider side located on operational level, and the user’s needs expressed in business terms [9, 17].

The work presented in this paper is built on earlier research in which the Intentional Services Model (ISM) has been developed for modeling and describing services in business terms [9, 10, 17, 18]. With ISM, the service description brings out the business intention that the service allows to fulfill with pre and post conditions instead of defining the signatures of operations that can be invoked. The problem that is tackled here is related to intentional web service publication. We propose an approach in which user queries are expressed in structured natural language, and where matching with intentional services is made using domain ontologies for verbs and products. Therefore, we propose to extend SAWSDL to publish the goal of intentional services.

This paper is organized as follows. Section 2 presents a review of research works related to the topic of semantic web description and search; in section 3 we describe briefly the intention and goal meta-models; in section 4, we introduce the verb and product ontology's which are used to describe and annotate the intentional web services. In section 5, the XML intentional service descriptor is introduced and illustrated in an example. The paper ends with concluding remarks in section 6.

2. RELATED WORKS The lack of semantics in WSDL [2] prevents automatic discovery and hence automatic invocation and composition. To deal with these issues several approaches were developed that use semantic models (ontologies...) for description of semantic Web services. We can cite among others, OWL-S, SAWSD and WSMO.

WSMO proposes high-level objectives and approaches similar to those of OWL-S but focuses on goals mediation and choreography. OWL-S focuses on process model. In SAWSDL there is no explicit mention of precondition and effects that one can find in WSMO and OWL-S. In addition SAWSDL is not dedicated to describe Web service behavior, which is essential for

Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. iiWAS2010, 8-10 November, 2010, Paris, France. Copyright 2010 ACM 978-1-4503-0421-4/10/11...$10.00.

Web Services and Ontologies iiWAS2010 Proceedings

881

service invocation and composition. Nevertheless, SAWSDL is an approach independent of the used semantic representation language thanks to the separation of semantic annotation mechanism from the representation of the semantic descriptions. This gives flexibility to the developers’ community to select their favorite semantic representation language, to reuse semantic domain models and annotate descriptions using multiple ontologies. In our work, we are interested in description of intentional services taking into account existing approaches. Our proposed description of intentional services is based on the de-facto standard to describe Web services, namely WSDL. It requires no other changes to existing WSDL or XML Schema [5] documents, or the way in which they had been used previously. Specially, the developed tools for parsing WSDL documents or for service invoking. To meet this target, we propose an extension of SAWSDL.

Our work fits also, into the family of research approaches of goal-driven services. Most of these approaches [3, 11, 20, 21], focus on specifying goals in the context of searching Web services that meet these goals. In these approaches, different models have been proposed to specify goals without focusing on the problem of their capture. SATIS [11], proposes ways to assist end users in the explanation of their needs (goals). Moreover, the approach GODO [7] proposes models and tools to capture the goals of users with the help of ontology and natural language.

3. GOAL/INTENTION META-MODEL In this section, we briefly present the intentional service meta-model and the goal model for expressing queries.

3.1 Intentional Service meta-model The concept of goal is originally used in ISM model [9]. An

intentional service is a service captured at the business level, in business comprehensible terms and described in an intentional perspective, i.e. focusing on the intention it allows to achieve rather than on the functionality it performs. The model defines each intentional service as building brick in the application by associating it with the situational knowledge in the interface. Each intentional service fits a particular situation in order to achieve a particular intention.

Figure 1. Intentional service meta-model

The model of intentional service of [10, 18], takes the form of a composition of services based on graphs, AND/OR tree of goals. The composition of services driven by goals introduces a composition on several levels: for the highest service level, which may be strategic in nature, is broken down itself into sub/intentional services, may require a new de/composition to

achieve the intentional services. There is therefore a recursive composition of services (Figure 1).

3.2 Goal meta-model We assume that the user needs are driven by goals, and are expressed using a language easily understandable by non-expert domain users, which is different from service models definition languages that require technical knowledge of the area.

In this article, we focus on user needs expressed in structured natural language. We propose an ontology based solution for the interpretation of these needs. The implementation of the ontology requires the prior definition of a goal model for expressing queries. This model will allow the exploitation of ontology to find similarities between the elements of the user query and the attributes of the intentional services published in the directory.

The concept of basic goal we present in our work uses a lexical formalism with verb, target and parameters representing semantic functions of the verb. We support, in this context, the formulation of goals of ISM [9] based on a linguistic approach originally developed by [15, 16]. This approach inspired by the case grammar of Fillmore [6] and extensions [4] based on the fact that the semantics of goal is captured by a verb and parameters that correspond to roles associated to the verb. This formalism allows representing the intentions of users and the goals of services (fig. 2). In this approach, a goal is expressed by a verb, a target and one or more parameters so-called 'direction', 'ways', 'time', 'beneficiary', 'quality', 'quantity' and 'location'. The verb and the target are mandatory while the parameters are optional. In general, any sentence can be expressed by Goal formalism. This formalism allows representing user’s needs, and on the other hand, the goal that intentional services can meet.

Figure 2. Goal meta-model

4. QUERY’S ONTOLOGIES We propose, from the intentional model, the ontologies needed to match the concepts of user’s queries with those of intentional services. Sharing the same ontologies allows establishing mappings at the time of service discovery.

Figure 3. Mapping between query and goals

Queries are expressed by the users to find adapted services to solve their business needs. In practice, the needs are expressed as goals to be met (figure 3). For example, finding a service to

iiWAS2010 Proceedings Web Services and Ontologies

882

specify the requirements for booking a hotel room is reflected by the query “Book hotel room”. For that reason, we can write queries using ontologies and in particular each query is expressed as a verb, a target and parameters. We differentiate two types of ontologies:

Ontology of verbs representing syntactic and semantic concepts related to verbs. It gives the different meanings of verbs and characterization of components used by these verbs in sentences of natural language. The specifications of the verb that agrees or refuses to construct sentences are syntactic concepts contained in the ontology. We rely on the work of Urrego [19] to define it.

Ontology of products defines a common vocabulary for all objects manipulated during the intentional services search. This ontology is domain based and used especially to specify the inputs and outputs provided by the services [8].

The relation between these two ontologies defines the ontology needed for query resolution (figure 4). In order to establish this relation, we related each concept in the product ontology to a verb in the verb ontology.

Figure 4. Verb – product relationship in the ontology

In figure 5, we show an image of the ontology of travel where a concept “voyage” of this domain ontology of products is related to another concept “organize” in the ontology of verbs. The concept “organize” represents the verb that goes with the product concept of “voyage”. We can notice that the verb “organize” is member of a class in the ontology of verbs.

Figure 5. Example of links between products ontology and

verb ontology

The relation between these two ontologies defines the ontology needed for query resolution (figure 5). In order to establish this relation, we related each concept in the product ontology to a verb in the verb ontology.

5. INTENTIONAL SERVICE DESCRIPTOR We propose to use an annotation approach to implement the intentional descriptions of services whose interpretation is made at the time of publishing the service in the directory.

The main idea is to extend SAWSDL for enhancing expressiveness of service description. In SAWSDL, for a given WSDL element one can use many references to concepts in domain ontology but there is no specification of the semantic information nature: is it a verb, a target, a destination? etc. That is why we propose, in our description, a new attribute called goalConcept to give references to the goal concepts

corresponding in the same order, to the domain concepts listed in the original SAWSDL "modelReference" attribute [1]. Indeed, our approach for intentional service description is based on the use of three types of ontologies. The first one contains only the concepts defining terms of goal concepts (verb, target, …). The second type of ontologies is the verb Ontology [20]. The third type of ontologies, called Product Ontology, contains the semantics of the product domain concepts (e.g. travel).

In this way, we can define for each WSDL element two attributes. The first attribute, called goalConcept, references the corresponding concepts in goal terms. The second attribute, called modelReference, contains a set of URI corresponding to the first list and which defines the intention of the service in the Ontologies of verbs and products. Let’s consider the example presented in Figure 6. The example presents the annotation of service named BookHotel. We can identify in the goal of this service the verb, the product and the destination. The importance of the extended attribute goalConcept is to distinguish the role of each term in the goal: book and room hotel referenced by modelReference attribute. The goalConcept references two goal concepts: verb and target that correspond to the domain concepts book and room hotel. The order is important here. It associates the first goal concept with the first verb concept, the second goal concept with the second domain product concept and so on.

This new approach provides another advantage: we can extend the Ontologies by new concepts (new description element, more precise concepts ...) and there is no impact on the annotation system. This makes the system of annotation independent of the used goal business domain representation language and ontology and the used intentional service representation language and ontology. This gives flexibility to the developers’ community to select their favorite semantic representation language, to reuse semantic domain models and annotate descriptions using multiple ontologies.

The intentional service for hotel reservation, given below, provides room reservation based on the specification of a hotel request. If the desired room is available, a reservation number will be returned.

1

2

3

4

5

6

7

8

9

<?xml version = "1.0" ?>

<!DOCTYPE Intentional_Service SYSTEM

"Service.dtd">

<Intentional_Service Code ="BookHotel">

<Atomic_Service>

<Interface

goalConcept="&QueryOntology;#verb

&QueryOntology;#product

&QueryOntology; #destination“

modelReference="&VerbsOntology;#book

&TourismOntology;#hotel

&TourismOntology;#France">

<Intial_Situation> booking not made

</Intial_Situation>

<Final_Situation> booking made

</Final_Situation>

</Interface>

…

Web Services and Ontologies iiWAS2010 Proceedings

883

Figure 6. Example of intentional service descriptor

The semantic annotation of the interface called BookHotel (line 3) is ensured by two attributes: goalConcept and modelReference (lines 6 and 7). In the service interface (line 5), its goalConcept attribute (line 6) provides a list of goal concepts to which corresponds, in the same order, a list of model references from the verb ontology and tourism domain ontology provided by the modelReference attribute (line 6) respectively. The goal has as verb associated to the concept of book and has as product the concept of hotel.

6. CONCLUSION In this paper, we have proposed a new annotation for WSDL. It is an extension of the W3C recommendation on semantics for Web services (SAWSDL) and use two ontologies: Verb Ontology and Product Ontology (domain ontology). The Verb Ontology represents syntactic and semantic concepts related to verbs and product ontology contains the concepts defining a common vocabulary for all objects manipulated in the business domain.

This new annotation allows the developer community to specify the correspondence between intentional service concepts and business goal concepts. This explicit correspondence can be used to bridge low level service description languages for Web services and user business goals.

In addition, we have presented how our approach is more expressive than the W3C recommendation and submissions to W3C on semantics of Web Services. Our ongoing work aims at providing means to intentional services based applications for service description and discovery. This annotation is to propose a new description language we are using in the discovery of intentional services.

7. REFERENCES [1] Chabeb, Y., Tata, S. and Ozanne, A. 2010. YASA-M:

Semantic Web Service Matchmaker. International

Conference on Advanced Information Networking and

Applications, Perth, Australia, 20-23.

[2] Chinnici, R., Weerawarana, S., Moreau, J.-J. and Ryman, A. 2007. Web services description language (WSDL) version 2.0 part 1: Core language. W3C recommendation. W3C.

[3] Da Silva Santos, L. O. B., Guizzardi, G., Pires, L. F. and van Sinderen, M. 2009. From User Goals to Discovery and

Composition. Advances in Conceptual Modeling - Challenging Perspectives. Lecture Notes in Computer Science 5833/2009. Springer Verlag, Berlin, pp. 265-274.

[4] Dik, S.C. 1989. The theory of functional grammar. Foris Publications, Dodrecht, Holland.

[5] Fallside, D. C. and Walmsley, P. 2004. XML schema part 0: Primer second edition. W3C recommendation. W3C.

[6] Fillmore, C.J. 1968. The case for case. In Universals in

linguistic theory. Holt, Rinehart and Winston, Inc, E.Bach/R.T.Harms (eds).

[7] Gomez, J., Rico, M., Garcia-Sanchez, F. 2006. GODO: Goal Oriented Discovery for Semantic Web Services. 5th

international Semantic Web Conference.

[8] Guzélian, G. 2007. Conception de systèmes d’information:

une approche orientée service. Doctoral Thesis, University of Paul Cézanne d’Aix-Marseille III.

[9] Kaabi, R.S. 2007. Une Approche Méthodologique pour la

Modélisation Intentionnelle des Services et leur

Opérationnalisation. Doctoral Thesis, University of Paris 1.

[10] Kaabi, R. S. and Souveyet, C. 2007. Capturing Intentional services with Business Process Maps. Research Challenges

in Information Science (RCIS), Ouarzazate, Morocco.

[11] Mirbel, I. and Crescenzo, P. 2009. Des besoins des

utilisateurs à la recherché de services web : une approche

sémantique guidé par les intentions. Rapport de recherche ISRN I3S/RR-2009-12-FR.

[12] Stollberg, M., Norton, B. 2007. A Refined Goal Model for Semantic Web Services. Second International Conference on

Internet and Web Applications and Services. The 2nd Int. Conf. on Internet and Web Applications and Services, ICIW 2007, May 13-19, 2007 - Mauritius.

[13] Papazoglou, M. P and van den Heuvel, W-J. 2007. Service Oriented Architectures: Approaches, Technologies and Research Issues, VLDB Journal, 16(3), pp.389-415.

[14] Papazoglou, M.P., Traverso, P., Dustdar, S. and Leymann, F. 2008. Service-Oriented Computing: a Research Roadmap, Int. J. of Cooperative Inf. Syst., Vol. 17, No. 2, pp. 223–255.

[15] Prat, N. 1997. Goal formalization and classification for requirements engineering. Proceedings of the Third

International Workshop on Requirements Engineering:

Foundations of Software Quality REFSQ’97, Barcelona.

[16] Prat, N. 1999. Réutilisation de la trace par apprentissage

dans un environnement pour l’ingénierie des processus. Doctoral Thesis, University of Paris1.

[17] Rolland, C., Kaabi, R. S. and Kraeim, N. 2007. On ISOA: Intentional Services Oriented Architecture. International

Conference on Advanced information Systems Engineering

(CAISE), Springer-Verlag, Trondheim, Norway.

[18] Rolland, C., Souveyet, C., Kraiem, N. 2008. An Intentional View of Service-Oriented Computing. Revue Ingénierie des

Systèmes d´Information (ISI), RSTI (Revue des Sciences et

Technologies de l'Information). ISI 13[1]: 107-137.

[19] Urrego, G. S. 2005. Approches linguistiques pour

l’ingénierie de besoins fonctionnels et non- fonctionnels. Doctoral Thesis, University of Paris 1 La Sorbonne.

[20] Vukovic, M. and Robinson, P. 2005. GoalMorph : Partial Goal Satisfaction for Flexible Service Composition. Int.

Conference on Next Generation Web Services Practices,

August 22-26, 2005, Seoul, Korea.

[21] Zhang, K., Li, Q. and Sui, Q. A. 2006. Goal-driven Approach of Service Composition for Pervasive Computing. 1st Int. Symposium on Pervasive Computing and Application,

(SPCA06), August 3-5, 2006, Urumchi, Xinjiang, P.R.

China.

iiWAS2010 Proceedings Web Services and Ontologies

884