=Paper=
{{Paper
|id=None
|storemode=property
|title=Publishing and Discovery of Intentional Services: Goal-driven Approach
|pdfUrl=https://ceur-ws.org/Vol-593/Paper01.pdf
|volume=Vol-593
}}
==Publishing and Discovery of Intentional Services: Goal-driven Approach==
https://ceur-ws.org/Vol-593/Paper01.pdf
Publishing and Discovery of intentional services:
Goal-driven approach
Kadan Aljoumaa
Centre de Recherche en Informatique, Université Paris 1 - Panthéon Sorbonne,
90, rue de Tolbiac
75013 Paris, France
kadan.aljouma@malix.univ-paris1.fr
Supervised by Professor Carine Souveyet and Associate professor Saïd Assar
Abstract. With the increasing growth in popularity of Web services,
discovering relevant Web services becomes a significant challenge. The
introduction of intentional services is necessary 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 research work, we propose publishing and
discovery of services based on intentions they satisfy by extending the actual
registry to build the intentional one. We also focus on the part of discovery of
intentional services concerning the formulation of the user’s requests. Our
contribution consists of proposing a goal meta-model for user’s request using
ontologies, the descriptor to be published in the registry and the matching
algorithms between services’ intentions and users’ goals using similarity
metrics.
Keywords: intentional service, goal, intentional service publishing, intentional
service discovery, Ontology.
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 [14] [15]. A major problem in the use of SOA is the discovery
of appropriate services that meet business needs [9]. 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 the user. As many writers have observed, there
is a "conceptual mismatch" between the service provider side located on operational
level, and the user’s needs whose are expressed in business terms.
2 Kadan Aljoumaa
The work presented in this thesis is built on earlier work in which the model ISM
(Intentional Services Model) has been proposed for modeling and describing services
in business terms [9], [10], [19]. ISM shares with other approaches the need to
describe service to ease their retrieval but departs from their function driven
perspective to propose an intention drive service description. As a consequence, ISM
service descriptions will bring 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 on class objects. We believe that this approach contributes to
resolve the current mismatch of languages between low level services descriptions
such as WSDL statements and business perceived services.
Therefore, this work is part of the platform iSOA and specifies the capacity to
search services in the registry using goal driven approach. It is related to the problem
of publishing, querying and discovering of intentional services based on user goal and
on the service intention.
We use this framework and this methodology to specify and implement the registry
of the iSOA platform. Specifically, it will lead us to choose the most effective
techniques for intentional services discovery and suggest matching algorithms to
select the services that best meet user needs.
This article is organized as follows: first we present the research question
concerning the discovery of services based on the goal they satisfy. Then, we
introduce the proposed solution to this problem. The idea consists of proposing a goal
meta-model used for formulating user query, the ontologies needed in the discovery
and finally, the intentional descriptor required for intentional services publishing will
be defined and implemented in an extended registry.
Before we conclude our work, we present the related work in this domain and how
we compare other approaches to our solution.
2 Research question
The problem addressed in this thesis deals with the publishing and discovery of
intentional services. Users formulate their needs in natural language in which they
express a query with one goal to be achieved (Fig. 1).
The reply of natural language queries raises two major problems:
- Several intentional services candidate can match this query with variable
degrees of similarity. For example, a query such as "gather information" may
correspond to the intentional service "integrate data" with a degree of
similarity 85% and another intentional service "reassemble files" with a degree
of similarity 45%.
- The answer to a query could be an individual intentional service, as it could be
in some cases a group of several intentional services that the user may
compose to meet its needs. For example, "accept delivery of goods" may
correspond to the intentional services "acquire products", "enter the product in
stock" and "enter in stock the delivered goods".
The solution of these problems requires three steps: (i) defining a service descriptor
that allows the intentional publication in a registry, (ii) developing a query language
Publishing and Discovery of intentional services:
Goal-driven approach 3
that helps to discover intentional services published in the registry and (iii) specifying
an approach to perform intentional service discovery based on similarities calculation.
Fig. 1. Intentional services Querying.
The first key issue of this thesis focuses on specifying the intentional descriptor to
be published in the registry and on the publication of aggregated intentional services.
Additionally, it seeks to couple intentional service with software services executable
by market standards. We rely on the concept of intentional atomic service which
enriches the operational web service1 with the concept of intention.
2.1 Meta-model of intentional services
The publishing of intentional services is the first step toward building the intentional
registry. For this reason, we use the intentional model ISM [9] to present the services
in the registry where the concept of goal is originally used in this model. 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.
The model of intentional service of [9, 19], 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 (Fig. 2).
1 Web services are one possible technological solution for implementing intentional service.
But this notion of intentional service is not limited to a specific technology.
4 Kadan Aljoumaa
Intention 0..* 1..* 0..*
1 satisfies Pre-condition
0..* State
Post-condition 0..*
1..* Service 1..*
- Code
- Comment
1
0..*
Initial Situation 1..* Class
0..* 1..* -Attribute
Final Situation
Aggregate Atomic 1 1
0..* 0..*
Operationalized by Relation
Variant Composite
Legend
Software service
Service Interface
Service Behavior
Service Composition
Fig. 2. Intentional Service Model [9, 19].
2.2 User query
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 thesis, 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 components of the user query and the attributes that make up
the targeted intentional services published in the registry. In addition, we could
reformulate user needs in order to enlarge the searching possibilities.
2.3 Discovery of intentional services
The third issue of interest is service discovery in the registry. The methodology
proposed in [9] has no mechanisms for finding services at intentional level in the
registry. A process proposal that aims at locating intentional services can contribute to
enriching the methodology. Finding intentional service consists in establishing the
matching between the goal (what a user of the registry is seeking to achieve) and
intention displayed by the service (what the service guarantees to meet).
In our work, we propose mechanisms for finding intentional services available in
the registry. The finding process can integrate several aspects including:
- The intentional services retrieval, i.e. select services in the registry based on the
characteristics of the descriptor.
- Metrics of similarity: We need to measure how two intentions are semantically
similar even if they are not expressed in the same way.
Publishing and Discovery of intentional services:
Goal-driven approach 5
3 Proposed solution
To address the problems identified in the previous section, our approach focuses on
four elements: first, we introduce the goal meta-model proposed to analyze the
requests made by the user in structured natural language. Second, we propose our
Ontologies needed to assist in resolving user queries. Third, we propose the use of
annotation to specify the descriptor to be published in the registry. Finally, we
propose the use of similarity metrics in our discovery algorithm. The elements of our
proposed solution are discussed in the following paragraphs:
3.1 Goal meta-model
In this thesis, 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 registry.
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 [16, 17]. This approach inspired by the case grammar of
Fillmore [6] and extensions [5] 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 user goal and service intention (fig. 3). 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 needs, and on the other hand, the
intentions that intentional services can meet.
Fig. 3. Goal meta-model for capturing user needs
6 Kadan Aljoumaa
The formalism shows that the ‘target’ is either ‘product’ or ‘result’. Result is non-
tangible object and represents an output of the service. On the other hand, ‘product’
could be found as input and output.
3.2 Ontologies needed
We propose, from the intentional model, the ontologies needed to match the concepts
of user queries with those of intentional services. Sharing the same ontologies allows
establishing mappings at the time of service discovery.
However, 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. For example,
finding a service to specify the requirements for booking a hotel room is reflected by
the query “Book a hotel room”. For that reason, we can write queries using ontologies
and in particular each goal is expressed as a verb, a target and parameters. We
differentiate two types of ontologies:
a) 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 classification of
verbs in [20] to define this ontology.
b) Ontology of products defines a common vocabulary for all objects
manipulated during the intentional services search [8]. This ontology is used
especially to specify the inputs and outputs provided by the services.
The relation between these two ontologies defines the ontology needed for query
resolution. In order to establish this relation, we related each concept in the ontology
of products to a verb in the ontology of verbs.
3.3 Use of annotations
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
registry (for cost reasons of and standards adoption).
The introduction of intentional perspective enriches the description of operational
services. For this reason, we could use a semantic approach to annotate descriptors of
Web services to enrich existing standards with intentional descriptions. We justify
this choice by three simple reasons: (i) industries prefer updating their existing
approaches to complete change, (ii) it is possible to annotate specific intentions using
an ontology, which makes searching easier and (iii) from technical point of view: the
annotations can be stored inside or outside the description. We propose the use of
standard SAWSDL [23] to add intentional annotations then store them in the UDDI.
This proposal is justified by [24] who also cited several reasons to show that
SAWSDL directly supports the functional model (the formal description of the
functionality of services) and data semantics (the formal description of the data
exchanged between services). In this context, they demonstrated how SAWSDL can
be used to achieve reuse, interoperability and agility. Furthermore, SAWSDL is an
Publishing and Discovery of intentional services:
Goal-driven approach 7
independent approach to semantic representation languages thanks to the separation
between the mechanism of semantic annotation and representation of semantic
descriptions, which gives developers the flexibility to choose their semantic
representation language, reuse models semantic domain, and annotate descriptions
with multiple ontologies [2].
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 queryConcept to give references to the query
concepts corresponding in the same order, to the domain concepts listed in the
original SAWSDL "modelReference" attribute. 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 query' concepts. The second type of
ontologies is the verb Ontology; it is described and classified by Urrego [20]. The
third type of ontologies is the product Ontology (Domain Ontology), which contains
the semantics of the service domain products (e.g. travel).
In this way, we can define for each WSDL element two attributes. The first
attribute, called queryConcept, references the corresponding concepts in query terms.
The second attribute, called modelReference, contains a set of URI corresponding to
the first list and which relay the Ontologies of verbs and products. Let’s consider the
example presented in Figure 4. The example presents the annotation of service named
book_hotel. We can identify in the goal of this service the verb, the product and the
destination. The importance of the extended attribute queryConcept is to distinguish
the role of each term in the goal.
1
2
3
4
5
8 booking not made
9 booking made
10
11 …
Fig. 4. Example of intentional service descriptor
3.4 Use of similarity metrics
Many approaches have been proposed in various fields to measure the similarities:
information systems engineering through the reuse of components, software
8 Kadan Aljoumaa
engineering to ensure the traceability of software code in the context of literature to
index and retrieve documents, or even for the analysis of patterns of heterogeneous
databases [25, 26, 27, 28, 29, 30, 31]. These different approaches provide metrics
expressed as formulas more or less adapted to different situations. Most of them
particularly interested in measuring the similarity between two texts, others look for
similarities between the structured models.
Our position is that the mapping must be performed using metrics appropriate to
the situation. Two specific criteria allow us to define such situations: first analysis of
similarity between simple elements (such as verbs, products …), on the other hand,
the analysis of similarity between complex elements (such as models of goals).
Different types and properties of simple and complex elements can be identified, thus
defining a complex type of metrics useful for measuring similarities [32].
A collection of such metric similarities can be exploited by a complex typology of
similarity measures suitable for the analysis of similarities of the texts. Such a
typology of similarity measures can be produced consistently and, as in our approach,
used for mapping between users needs and services intentions.
5 Related work
Our work fits into the family of research approaches of goal-driven services. Most of
these approaches [13, 22, 21, 4], 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
[12, 3], proposes ways to assist end users in the explanation of their intentions (goals).
Moreover, the approach GODO [7] proposes models and tools to capture the goals of
users with the help of an ontology and natural language. SATIS differs from this
approach by proposing a process of incremental refinement of user needs to specify
the characteristics of web services sought, as is the case in [10, 4]. And it differs from
the latter approach in that it relies on models and techniques of semantic web to
enrich the description of user needs and thus to suggest ways of reasoning and
explanations of web services found to implement a business need.
Concerning the discovery of services, many logical approaches for the discovery of
services [8] and hybrid matching algorithms have been proposed [11] using the metric
of similarity. Other algorithms [2] make use of the service elements added to the
interface. All these algorithms primarily exploit the degree of similarity by modifying
the existing metrics. Classification mechanisms have been proposed too [1, 11, 2].
5 Conclusion
This work is in the research context to publish and discover services in a registry said
intentional. We intend to design a comprehensive registry that meets the needs of
business agents and the goal-driven discovery of these services.
The problem addressed in this article concerns querying and finding of intentional
services. A user expresses his needs in natural language in a query with a goal. For
this reason, we proposed a model aims to formulate these queries. This model will
Publishing and Discovery of intentional services:
Goal-driven approach 9
allow the exploitation of ontologies to find matching and similarities between the
concepts of goals made by user requests and intentions of those services.
The result of our work is a goal model and a proposal for new descriptor to be
published in the registry. Finally, our future work will be the proposition of an
algorithm to make the matching between the concepts of user query and those of
intentional services published in the registry.
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