Towards a Semantic and Contextual Approach for ...

Towards a Semantic and Contextual Approach for Integrating Inter-Organizational Workflow Models Ali Abbassene1,2 and Zaia Alimazighi2 1

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SIA team, Centre de Développement des Technologies Avancées (CDTA) ISI team, Université des Sciences et de la Technologie Houari-Boumédien (USTHB)

[email protected], [email protected] and [email protected]

Abstract. Currently, in an extremely competitive and aggressive market, companies are struggling to acquire new business opportunities. One of the solutions is to collaborate with business partners, by seamlessly connecting their Enterprise Information Systems (EIS) into one Inter-Organizational Information System (IOIS). So they will be aiming to integrate their workflows for a better collaboration, leading to Inter-Organizational Workflows (IOWF). In our approach, we intend to help IOWF designers to detect and correct semantic and contextual incompatibilities occurring between those composed workflow models. We assume that an extension of the W3C standard Open Annotation will be suitable for semantic and contextual annotation of connected workflow models and will enable the process of mediator discovery that are used to correct detected incompatibilities into the considered IOWF model. Keywords: Inter-organizational workflow models; W3C Open Annotation; Semantic annotation; Contextual annotation; Semantic mediation;

1

Introduction

Nowadays, organizations and enterprises are constantly willing to collaborate with business partners to conquer new markets. This collaboration leads to the necessity of interconnecting their EISs and integrating their business processes into one IOWF to fulfill that necessary agility required by the market. There are different interoperability obstacles facing business partners (organizational compatibility, behavioral compatibility, structural compatibility, technical compatibility, semantic compatibility, contextual compatibility, etc.) [6]. Semantic and contextual compatibility issues [1] are mandatory for achieving an adequate level of interoperability between business workflows. And in this context, we are proposing a semantic and contextual based approach to support workflow designers in the process of IOWF model design. This approach will permit the identification and the semi-automated correction of semantic (contextual) inconsistencies occurring in the IOWF model, taking advantage of the semantic discovery of adequate mediators that can tackle these inconsistencies.

So the rest of the present article is organized as described below: Section 2: Describes some of the relevant research results from the literature; Section 3: Presents our proposed IOWF model integration approach; And in Section 4, some concluding remarks and future works will be described.

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Related Works

In the literature, one of the first attempts to conceptualize inter-organizational collaboration problems was the MISE European project [10] [13] which introduce the concept of Utility Computing as a paradigm to address interoperability issues in IOIS. In this project, Rajsirij [10] and Touzi [13] developed a model-driven design approach for collaborative information systems, but they do not address mediation issues. Agarwal [2] and Lin [7] have both addressed issues related to collaborative and distributed workflows. But they focused on using semantic technologies to describe and reuse workflow models, without addressing interoperability issues. Hepp [5] proposed an ontological framework for workflow models semantic description, in order to ensure conceptual compatibility of workflow models and facilitate their sharing and reuse, without considering integration problems. M'Bareck [8] used W3C SAWSDL1 annotation framework to address semantic description of collaborative workflow models, but he focused only on semantic compatibility verification without proposing a correction approach. Zdravkovic [14] has developed an ontological framework, based on the SCOR2 reference model [12], to describe SCM (Supply Chain Management) workflows. He developed a semantic vocabulary based on SCOR [12], in order to unify semantic description of SCM workflow models, but does not address IOWF integration issues. Mrissa [9] has developed a contextual and semantic description model, based on SA-WSDL, for Web services. He intended to detect mismatches in composite Web services, but does not address IOWF integration issues. Also, Amarouche [3] has proposed a semantic mediation and context-driven approach, using mediation Web services, but his proposal was restricted to correcting compositions of data provider Web services.

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Proposed Approach

Our approach is based on the extension of the W3C standard annotation framework, namely Open Annotation (OA) [11], to semantically and contextually describe workflow models. So, detection and correction of semantic and contextual incompatibilities could be done in design time. Correction will be achieved by discovery and insertion of appropriate mediation services into the IOWF.

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W3C Semantic Annotations for WSDL and XML Schema (w3.org/TR/sawsdl/) Supply Chain Operations Reference Model (apics.org/sites/apics-supply-chain-council/frameworks/scor)

3.1

Proposed IOWF model integration steps

To design an integrated IOWF model, we propose the following steps: Step 1 Workflow Design : Workflow designers develop the workflow models (using BPMN3/XPDL4 as languages currently supported by our approach). Step 2 Workflow Annotation : Domain experts have to semantically annotate inputs and outputs of all activities involved in sending/receiving message-flows to/from partner workflow models in the IOWF model. This is done by inserting references to semantic concepts (e.g. PRICE ). After that, each semantic annotation is annotated using appropriate contextual attributes (for PRICE , we could use CURRENCY as a contextual attribute having the value DZD ). Step 3 IOWF Design : Workflow designers will design the IOWF model. Step 4 Semantic Mismatch Detection : Semantic annotations will be compared to detect semantic incompatibilities that cannot be corrected (e.g. if the output is annotated with PRICE and the input is annotated with TEMPERATURE ). Step 5 Contextual Mismatch Detection : Contextual annotations of semantically compatible inputs/outputs will be compared, to detect contextual incompatibilities. Step 6 Mediator Discovery : Detected contextual incompatibilities will be used to discover adequate mediation components. Step 7 Mismatch Correction : Restore semantic and contextual compatibility in the IOWF model, via mediator insertion (e.g. conversion from USD to DZD ). 3.2

Semantic and Contextual Annotation

Workflow model semantic and contextual description is done via an appropriate annotation method, which associates semantic descriptions to syntactic workflow model elements (activities, messages, etc.). Semantic concepts are taken from domain ontologies related to the business field of partner companies [9]. And contextual description is used to explicit the differences in formats, units of measurement, standards and other contextual specificities [9] for each partner (see Fig. 1 for the context of the PRICE concept in Algeria).

Fig. 1. Contextual

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OMG Business Process Model and Notation for workflow models (omg.org/bpmn/index.htm) WfMC XML Process Definition Language : executable format for workflow serialization compliant with OMG BPMN (wfmc.org/standards/xpdl)

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In this work, we propose to extend an annotation framework, developed by the W3C, namely Open Annotation Data Model (OA) [11] [1] that considers the annotations as first order entities having their own attributes and properties [11]. OA describes a simple annotation method focusing on 3 basic concepts [11 element to annotate, the annotation resour which explicates the relation between the two former elements (see Fig. 2 [11]).

Fig. 2. Excerpt

11]

In our proposal, we will expand the annotation method OA to support semantic and contextual annotation of IOWF models [1]: Where in a semantically motivated annotation: Body is a semantic concept (from domain ontology), used to disambiguate syntactic elements of the workflow model. Target refers to the annotated object, which is a syntactic element of the workflow model (activity, message, etc.). Annotation connects the Body to the Target and describes the details of the semantic annotation. And, where in a contextually motivated annotation: Body is a contextual concept (from contextual ontology), which provides the interpretation context for the former basic semantic annotation. Target refers to the targeted former semantically motivated Annotation . Annotation resource connects the Body to the Target and describes the details of the contextual annotation. To annotate a particular syntactic element of the workflow model, it is necessary to precisely target this element. To do that, OA provides an extension mechanism called Fragment Selector (Fig. 2 [11]), which defines the exact scope of an annotation. Fragment Selector is related to the data format specification of the annotated resource type. In our case, it depends on the workflow modeling language (BPMN, XPDL, BPEL5, etc.). For XML-based workflow languages, the Fragment Selector 5

OASIS Business Process Execution Language (docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.html)

must conform to the XML data format specifications (IETF RFC 3023)6, and must describe an identification mechanism for XML fragments, using the W3C XPointer 7. XPointer can be used to select a specific element in any XML document, using its identifier (ID), or any other discriminative value. XPointer provides a selection mechanism that returns the first occurrence which satisfies the condition in the XML document. perty, which explains the reasons that motivate the annotation. 3.3

Incompatibility Detection

Semantic and contextual incompatibilities can be detected by comparing the annotations that are attached to interconnected inputs and outputs of partner activities in the IOWF model. Semantic compatibility is mandatory in order to accept the link of an output and an input between partner workflow models in an IOWF model. In order to guarantee semantic compatibility, semantic concepts used in Body part of annotations for paired syntactic elements in the IOWF model (i.e. input/output activities linked by a message flow) must satisfy one of the following OWL relations: Semantic equivalence Semantic subsumption

A A

B ( A B ( A

owl:equivalentClass B ) owl:subClassOf B )

is the Body of the semantic annotation for the output of the sender and for the input of the receiver. If both conditions are not satisfied, then the semantic compatibility is not guaranteed, and there is no possibility to restore compatibility through semantic mediation. In this case the link (message flow) must be redesigned, because of wrong connection. Concerning contextual compatibility, and after satisfying semantic compatibility, we must examine the equivalence of each contextual attribute. If there is a difference in one or more contextual attribute (described by contextual annotations), we must restore the contextual compatibility by inserting an adequate semantic mediator. 3.4

Semantic Mediation

Contextual incompatibilities can be corrected by inserting appropriate mediation components (mediation Web services), provided in a . In order to identify the correct mediator we take advantage of an equivalent annotation method. Where each input and output port of each operation in the mediation Web service is, accordingly, semantically and contextually annotated. Also, we use an equivalent selection scheme to target the input and output elements to be annotated, where we use XPointer in order to select corresponding elements (operations and ports) of the WSDL8 description file for the Web service. 6

IETF RFC about XML Media Types (ietf.org/rfc/rfc3023.txt) XML Pointer Language for XML fragment identification (w3.org/TR/xptr) 8 W3C Web Services Description Language (w3.org/TR/wsdl) 7

XPointer is used as a selection mechanism for the Target parts of annotations related to WSDL description files, simply because WSDL has XML syntax. So, when we try to solve a particular contextual incompatibility in the IOWF model (e.g. po:USD po:DZD), we have to identify the corresponding mediation Web service, which has corresponding semantic and contextual annotations for input and output ports of one of its operations. In case, there is no satisfactory atomic mediator in the catalog, an appropriate discovery and semantic composition mechanism should be provided to solve the mediation issue. 3.5

Explanatory Example

This workflow delivery schedule IOWF involving two business partners. Enterprise A, request a delivery date for an ordered product from Enterprise B, which responds by scheduling a delivery date (see Fig. 3). We have used the semantic concept fbo:Date from the ontology fake_business_ontology (fbo) to explicit the concept of the message, and we Calendar fdo:Hijri and fdo:Gregorian, from the contextual ontology fake_date_ontology (fdo), to explicit the interpretation context of the exchanges dates. In Fig. 3, we demonstrate the detection of a contextual incompatibility between the confirm delivery date register delivery date used calendars are different (Gregorian and Hijri respectively). We corrected this incompatibility through the insertion of a date convertor Gregorian2Hijri which converts dates from Gregorian calendar to Hijri calendar.

Fig. 3. Sample

IOWF model corrected by Gregorian2Hijri date mediator

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Conclusion and Future Works

The proposed IOWF model integration approach permits semantic and contextual description of IOWF models, to detect and correct their incompatibilities by inserting appropriate semantic mediation services. Next step in our future works will be to develop and implement a semantic and contextual composition mechanism for generating appropriate composite mediators. And also to validate the proposed approach in the context of SMEs supply chains.

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