Model Driven Engineering approaches deal with the provision of models, transformations between them and code generators to address software development. One of the main advantages of this approach is the definition of a conceptual structure where the models used by business managers and analysts can be traced towards more detailed models used by software developers. In this paper we focus on this kind of model transformations, that is, model transformations that allow us obtain behavioural models of the service-oriented information system (Platform Independent Models) from high level business models (Computational Independent Models). From our point of view, the main drawback regarding CIM to PIM transformations lies in the alignment between what we model at CIM and PIM levels, the business view in the former and the information system view in the later. All this given, in this work we analyze, by mean of a case study, how it is possible to integrate both views and therefore, how we can help software developers to take the most of the business knowledge represented in high level business models.
This paper focuses on the model driven development of service-oriented information
system. Service-oriented development is currently one of the main research topics in
the field of software development and has brought about an evolution in Information
system (IS) themselves, as well as in how they can be developed. The roadmap for
research in service-oriented computing outlined by Papazoglou, Traverso, Dustdar
and Leymann [roadmap] stresses the importance of defining methodologies that can
facilitate the identification of meaningful services and business process specifications
according to a business scenario, which are very important elements for the
development of service-oriented applications [
According to the authors [
Model Driven Engineering (MDE) is an evolving and promising approach to
software development [
In MDA, the high-level business view is represented by means of Computational
Independent Models (CIM) while the information system view is represented using
Platform Independent Models (PIM) and Platform Specific Models (PSM). So,
attending to the alignment problem described before, in this paper we will focus on the
mappings between CIM and PIM models in the framework of SOD-M [
To the best of our knowledge, the most of the authors working in MDE approaches
do not address the already described problem of views alignment. Some of them just
do not consider the CIM level of the MDA proposal, while others, the most of them,
do not model the business view at CIM level. In fact, they model only the
requirements of the information system, which lie into the information system view.
Moreover, most of them propose using for example UML use case models [
In this paper, according to the MDA proposal, we claim that the CIM shouldn‟t be
used to represent the details of the system itself, but rather those of the business
domain. In that way, they serve as a bridge between the business experts and the
developers of the system. The business model proposed by SOD-M, the value model
[
In this work we analyze, by means of a case study, how we can tackle the problem of the alignment between the business view (at CIM level) and the information system view (at PIM level) following an MDE approach, taking the most of the business knowledge represented in high level business models for the information system modelling. To do so, we describe how we are actually dealing with the coding of mappings rules between both levels and we identify the main learned lessons of our work.
The rest of this paper is structured as follows. In Section 2, we briefly present the SOD-M method, which is the framework of this work. Section 3 describes the partial implementation of the case study, while section 4 presents the learned lessons obtained from it. Finally, in Section 5, we conclude by summarizing the main contributions and outlining future work.
SOD-M (the Service-Oriented Development Method) is a method for the serviceoriented development of IS. It main features are:
It defines a service-oriented approach for the development of IS: it provides
with guidelines for building IS based exclusively on services and use them as
first-class objects for the whole process of the IS development. This approach
facilitates the development of service-oriented applications as well as their
implementation using current technologies, such as Web services [
It is an MDA-based approach: it proposes a set of models, extending from the CIM level, the highest level of abstraction of the MDA, to the PIM and PSM levels. Thus, by means of mapping rules between the models, SOD-M provides the benefits of the alignment of high-level business processes with the technologies currently to deploy the Service-Oriented paradigm.
It defines a set of Domain Specific Languages for the service-oriented
development of IS. This set of newly DSLs includes all the modelling elements
needed at the PIM and PSM levels for the modelling of IS from a service-oriented
perspective at different abstraction levels. Moreover, they are based on a
previously defined UML profile, thus we will be able to move from models
conforming to a well-defined metamodel to extended UML models [
SOD-M focuses on the development of the behavioural aspect of IS and defines guidelines for building the behavioural models from high-level business modelling.
The following sub-sections present a brief description of the concepts proposed by SOD-M. Those concepts are organized according to the Business and the Information System points of view, which are integrated in order to achieve the alignment between high level business processes and information system. In this section we also present the modelling process proposed by SOD-M.
SOD-M proposes a new service-oriented approach for the development of IS. It considers two points of view that need to be analysed in order to develop an IS: Business View: it focuses on the features and the requirements of the business in which the IS will be built.
Information System View: it focuses on the functionalities and processes that need to be implemented on the IS in order to satisfy the business requirements. SOD-M defines a new set of concepts needed for the modelling of both views. Some of them are already known, while others are new and are proposed as part of this work. By means of a class diagram, Figure 1 shows the different concepts on which SOD-M is based, as well as their relationships.
is a result of
Business Process involves 1..* 1..* 1..*
Use Case Business Service needs
End Consumer 1 1..*
1..* has associated
Service Process
involves 1 1
All of the concepts shown in Fig. 1 have a representation in some of the different models proposed by SOD-M. Firstly, those concepts corresponding to the business view describe the elements inherent to the business, and they will be represented on the CIM models proposed by SOD-M: the value model and the business process model. Secondly, those concepts corresponding to the information system view are elements used to describe the functionalities of the system, and they will be represented on the PIM and PSM models proposed by SOD-M: use case model, extended use case model, service process model, service composition model, Web service interface model and Web service composition model. Finally, those concepts corresponding to both views describe elements that can be analysed from both points of view, and, as we shall see later, they support the alignment between high-level business models and IS ones.
For the sake of space, we will use just the case study to describe some of these
concepts. The reader is referred to [
The modelling process of SOD-M (see Figure 2) includes models that are in
correspondence with: a) the three different abstraction levels considered by MDA
[
As Figure 2 shows, the process begins by building the value model and the business process model, and it enables specific models for a Web service platform to be obtained as a result, thereby making it possible to make the transformation to the most typical technology related to the SOC paradigm, the Web service technology. (Business
Collaborators) (Use Cases and End Consumers)
(Business Collaabcotriaotnosr)s and
Business View Information System View Value Model (End Consumers and Business Service)
Business Process
Model Business
Services List (exchange of Value Objects) (Basic Use Cases and their relationships)
Use Case Model Extended Use Case
Model Service Process Model
(Web Service) Web Service Interface
Model
Extended Service Composition Model (Service Activity)
Modelo de ServiceMCoodmelpoodseition
Model Computation Independent
Model
Platform Independent
Model
Platform
Specific Model
The SOD-M process consists of several steps, each one related to the generation of a different model. From here on, we will focus on the transformation from the value model of the business view to the use case model of the information system view. We will describe how to do this transformation using the Travel Agency case study.
The case study presented in this paper is a travel agency providing a set of services to its customers, these services are: accommodation, transportation and tourist packages, which include both, transportation and accommodation.
First, the customer provides a description of the required trip to the travel agency, including personal constraint and preferences. Next, the travel agency selects the Broker Agent that could serve such a trip according to the customer needs. Each Broker Agent may work with several Transportation Companies, asking them to provide with an offer for the requested service. Then, the travel agency offers the customer a set of options, according to the Customer preferences. Once the Customer selects one of the trips, he provides the credit card details to the travel agency, which processes the payment through the corresponding Financial Company. After checking that the payment is correct, the travel agency asks the corresponding Broker Agent to confirm the booking(s) and it notifies the customer.
Finally, once a month the travel agency pays each external Broker Agent for the services it has provided on the previous month.
In the next section we will describe the value model (3.1), the use case model (3.2), and the transformation between them (3.3) for this case study.
CIM models are used to describe the environment in which the system will be used,
with no direct reference to how the system will be implemented [
This model serves to depict a business case as a set of value exchanges and value activities performed by business actors. It allows us to understand the business environment in which the IS will be used and to identify some of the concepts showed in Fig. 1: the end-consumer of the business, the business services that will be offered by the system to satisfy the needs of the consumers and the business collaborators, those entities that collaborate in providing the business services.
The value model is obtained by applying the e3value business modelling method
[
Using the e3value method, we have explored the business model of the Travel Agency, representing actors who wish to exchange value objects with another actor. Fig. 3 shows the value model obtained, where the travel agency is shown as an elementary actor. Customers, Financial Companies and Broker Agents are identified as market segments. The services offered by the travel agency (Accommodation, Transportation and Tourist Package) are value activities, which it expects to be profitable. The value objects are the money, the accommodation, the transportation and the tourist package, as well as the credit card verification and the fee of this service.
The value model allows the representation of dependency paths. Dependency paths enhance the understanding of a business idea by showing all value exchanges triggered by the occurrence of an end-consumer need. A dependency path has a direction and consists of dependency nodes. A dependency node is a start stimulus (represented by a bullet), an AND-fork or AND-join (short line), an OR-fork or ORjoin (triangle), or an end node (bull‟s eye). A stimulus represents a trigger for the exchange of economic value objects while an end node represents a model boundary. Fig. 3 shows the dependency paths for the Travel Agency case study.
The dependency paths identified in Fig. 3 with the tag (a), (b), and (c) are initiated with the needs of the customers that are represented by start stimuli. The (a) dependency path denote a start stimulus causes by the customer when he/she requires accommodation to the travel agency in return of a payment. This payment must be checked with the financial company that gives credit card verification in return of a fee. And the travel agency gets those services from the broker agent paying an amount of money for them. Similar to (a), dependency path (c) and (b) can be described from the start stimulus to the end stimulus by means of navigating the value exchange between the actors and services.
The first thing to do when we aim to handle e3value models in a MDE context is to
define the value metamodel. To do so, we start from the e3value ontology [
This way, in order to automate and trace the transformation between models we
define a complete value metamodel, combining both the concepts from the e3value
ontology and the dependency path technique, using the eclipse modelling framework
(EMF) [
Actor +Name
AInMS 0..*
MSConsistsOfA
0..* CompositeActor 0..*
VIInCA
CAConsistsOfVI ElementaryActor
Once the metamodel is specified we use EMF to generate the editor for representing models based on the e3value methodology. Fig. 5 shows part of the value model for the case study in the generated editor. With this simple editor we are able to model different case studies, to refine those models and even more important, it is very useful when testing model transformations in order to avoid having to code XMI files by hand. However, in order to ease the task of handling value models, we are developing a graphical editor using the Graphical Modelling Framework (GMF) that will allow us to depict graphically value models in a UML-like way.
PIM models are used to model the functionality and structure of the information
system, but without considering the technological details of the platform upon which it
will be implemented [
Fig. 6 shows the use case model for the Travel Agency System (TAS), where the customer is represented as an actor who is the end consumer of the business services. The model represents as use cases the different business services that will be offered by the TAS to the customers: “obtain accommodation”, “obtain transportation” and Travel Agency System
Obtain Accommodation
Obtain Transportation Obtain Tourist
Package 0..*
UseCases
UseCase -Name
BusinessService -Name useCase actor 0..* 0..*
Actor -Name “obtain tourist package”. Such business services must be identified by taking into account the end-consumer needs identified in the value model.
In the same way that the value metamodel was specified, we represent the use case metamodel using EMF. A simplified view of the resultant metamodel is shown in Fig. 7.
Customer
Classifier -Name
Subject 0..* ownedUseCase
To handle use case models in the context of SOD-M we have already developed a graphical editor using GMF. Fig. 8 shows a screen-capture of the editor. It presents the use case model for the case study. It is obtained by applying the ATL model transformation summarized in section 3.3, taking as input the value model showed in Fig. 3.
After introducing both the value and the use case model of SOD-M, we focus on the automation of the model transformation between them.
Model Transformation: Value Model to Use Case Model According to the MDA proposal, a model driven development process comprises models at different abstraction level as well as transformation between them.
Typically, MDA/MDE proposals define transformation rules between PIM and PSM models but just traceability relations between the business requirements of the CIM models and the elements of the PIM and PSM models that fulfil those requirements. This distinction comes from the nature of what each model represents: while CIM models aim to represent the business view, PIM models aim to represent those parts of the business that would be implemented in (or by) the information system.
Moving from CIM to PIM: value to use case model mapping rules
SOD-M defines guides to map requirements at the CIM level into model elements at
the PIM level. These guidelines are summarized in the following table.
In order to automate the transformation we specify the transformation rules using ATL
[
As Fig. 9 shows, once we have identified the transformations rules to map value models into use case models, we code them using ATL. The resulting ATL program (ValueModel2UseCaseModel) is used to generate a use case model of the Travel Agency System from the corresponding value model. Notice that Ecore is the metamodel, not only for the source and target metamodels, but also for ATL itself.
conformsTo
The result of the transformation is the Travel Agency use case model showed in Fig. 8. Next step would be to apply this same transformation to other case studies in order to refine them. 4
As we have claimed previously in this paper, the problem of the alignment between high-level business models (corresponding to the business view) and information technologies (corresponding to the information system view) is becoming one of the crucial aspects in the area of service-oriented development.
In this paper we show how to address this problem using an MDE approach. Thus, we have defined a pair of metamodels according to the different MDA abstraction levels (business view in correspondence with the CIM level and the information system view in correspondence with the PIM level) and we have implemented the transformation between them.
After the development of this work, we can identify a set of lessons learned: some of them are related to the study of previous MDE proposals that considers CIM models, while other are related to the implementation of CIM to PIM transformations.
Regarding previous proposals we remark that the most of them don‟t really deal with the alignment between business and information system views. Especially since they assume that CIM models represent the requirements of the information system and not the requirements of the business in which the information system will be involved. This is a very important characteristic of the CIM models which is crucial for the development of the rest of the information system models, since they are supposed to model the details of an information system which needs to satisfy the business requirements. The CIM models included in SOD-M possess this characteristic and the main challenges for us lie in the ability to take the most of the knowledge represented in these models to (semi-)automatically generate the PIM and PSM models of the information system.
Related to the implementation of CIM to PIM model transformations we can
describe the following conclusions:
a) It is necessary to identify some kind of traceability relation between the
concepts represented at the business view, that model the business requirements
and those represented at the information system view that fulfils those
requirements. This traceability relation is indentified in SOD-M by means of the
concepts of business services, end consumers and business collaborators (see
figure 2) which can be analysed from both points of view, allowing the
alignment between high-level business models and information system ones.
b) It is necessary to establish and handle these correspondences between the
elements of business and information system views, each one defined by means
of a model. These correspondences may be informal, incomplete, and
preliminary. In many cases they may not be used directly to drive an executable
operation. However, those correspondences can be used to drive the execution
of the model transformation if we collect them using weaving models [
The definition of methodologies that support the specification and design of the behaviour of IS, allowing software engineers to go from the earlier stages of business analysis to the final step of implementation is actually one of the main challenges to face in the context of service-oriented development. MDE approaches deal with the provision of models, transformations between them and code generators to address software development. In that way, this kind of approaches offers a conceptual structure for facilitating the alignment between high-level business models, represented at CIM level, and information system, modelled at PIM level.
In this work we have dealt with this alignment problem following an MDE approach. We have focused on the mapping between the CIM and PIM models of SOD-M, a method for the service-oriented development of IS. We have described, by means of a case study, how we are actually dealing with the implementation of the mapping rules between both abstraction levels. More specifically, we have coded the model transformation to move from a value model at CIM level to a use case model at PIM level. We have described the mapping rules needed to obtain the later from the former and we have identified the main learned lessons from this work.
At the present time we are working in the implementation of the rest of mapping rules defined in the framework of SOD-M, and more specifically those that allows us to obtain (in a way as much automatic as possible) information system details from real computational independent models. Moreover, since SOD-M follows a MDE approach for the service-oriented development of information systems, we are currently working in the code generation from SOD-M models to different Web Services platforms. All this given, we will be able to complete the alignment process between high level business models and the IT implementation.
This research is partially granted by the GOLD project financed by the Ministry of Science and Technology of Spain (Ref. TIN2005-00010) and the M-DOS (URJCCM-2007-CET-1607) project co-financed by the University Rey Juan Carlos and the Regional Government of Madrid.