Using MDA for designing and implementing Web-based applications

Using MDA® for designing and implementing Web-based applications Nathalie Moreno and Antonio Vallecillo Universidad de Málaga Dept. Lenguajes y Ciencias de la Computación {vergara, av}@lcc. uma. es http: //www. lcc. uma. es/~av/ Munich, 27 July 2004 MDA 4 Web. Apps http: //www. lcc. uma. es/~av/mis. Confs/ICWE 2004/ -- Tutorial @ ICWE 2004

Agenda 1. Introduction – Models and Metamodels 2. MDA primer 3. Web-based Applications 4. Applying MDA to Web-based Applications 5. What is left, and what is next 6. Conclusions Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 2

Agenda 1. Introduction – Models and Metamodels 2. MDA primer 3. Web-based Applications 4. Applying MDA to Web-based Applications 5. What is left, and what is next 6. Conclusions Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 3

Models and meta-models Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 4

What is a Model? • A description of (part of) a system written in a well-defined language. (Equivalent to specification. ) [Kleppe, 2003] • A representation of a part of the function, structure and/or behaviour of a system [MDA, 2001] • A description or specification of the system and its environment for some certain purpose. A model is often presented as a combination of drawings and text. [MDA Guide, 2003] • A set of statements about the system. [Seidewitz, 2003] (Statement: expression about the system that can be considered true or false. ) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 5

Examples of models • Newtonian models of objects movements in space • City models – Underground and bus maps, commuting models, . . . • Building/house maps – floor plans, electric wiring, water conductions, central heating pipes, etc. • Software system models – – – Requirements (use cases) Structure (class diagrams) Behavioural models Choreography models Load balancing and Deployment models, . . . Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 6

Characteristics of models [Selic, 2003] • Abstract – Emphasize important aspects, hide irrelevant ones • Understandable – Expressed in a form readily understood by users • Accurate – Faithfully represents the modelled system • Predictive – Can be used to derive correct conclusions about the system • Inexpensive – Cheaper to construct and study than the system Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 7

Usefulness of models • Specify the system – Structure, behaviour, . . . – Separate concepts at different conceptual levels – Communicate with stakeholders • Understand the system – If existing (legacy applications) • Validate the model – Detect errors and omissions in design ASAP • Mistakes are cheaper at this stage – Prototype the system (execution of the model) – Formal analysis of system properties • Drive implementation – Code skeleton and templates, complete programs (? ) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 8

Current limitations of (SE) models • Models are used only as documentation • “Gap” between the model and the implementation of the system – Semantic gap between the respective languages – Changes in the model do not reflect in the code – Changes in the code do not reflect in the model (the model is thrown away after the first implementation, and never updated or used again) • No “merge” of models – Unrelated views of a system (horizontal) – Unrelated towers of models (vertical) • No model “transformations” – Few defined transformation languages – No tools • We are still far behind more mature engineering industries, such as aerospace, automotive and electrical engineering. . . . Even hardware design is ahead of software design! Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 9

What is a Metamodel? • A model of a well-defined language [Kleppe, 2003] • A model of models [MDA, 2001] • A model that defines the language for expressing a model [MOF, 2000] – A meta-metamodel is a model that defines the language for expressing a metamodel. The relationship between a meta-metamodel and a metamodel is analogous to the relationship between a metamodel and a model. • A model of a modelling language [Seidewitz, 2003] – That is, a metamodel makes statements about what can be expressed in the valid models of a certain modelling language. Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 10

OMG’s Four-layer metamodel architecture • As with Magritte’s picture of the pipe, we need to separate – the “thing” – from the “model” of the thing (I cannot smoke a picture) – from the “language(s)” in which the model is written (“Ceci” is not a pipe) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 11

Four-layers metamodel hierarchy Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 12

Four-layers metamodel hierarchy (example) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 13

MOF Metamodel (simplified) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 14

CORBA IDL for the MOF interface Class : Classifier. Class { readonly attribute Class. UList all_of_class; Class create_class ( /* from Model. Element */ in : : Model: : Name. Type name, /* from Model. Element */ in : : Model: : Annotation. Type annotation, /* from Generalizable. Element */ in boolean is_root, /* from Generalizable. Element */ in boolean is_leaf, /* from Generalizable. Element */ in boolean is_abstract, /* from Generalizable. Element */ in : : Model: : Visibility. Kind visibility, /* from Class */ in boolean is_singleton ) raises (Reflective: : Mof. Error); }; // end of interface Class : Class, Classifier { boolean is_singleton () raises (Reflective: : Mof. Error); void set_is_singleton (in boolean new_value) raises (Reflective: : Mof. Error); }; Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 15

UML 2. 0 Infrastructure UML extension mechanism s Boolean, Integer, . . . Namespace, Classifier, Relationship, Generalization. . . Basic definition of Class. . . Extended notion of Class, Association, . . . Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 16

New (improved) alignments in 2. 0 Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 17

Language definition mechanisms Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 18

UML 2. 0 Profiles • Profiles specialize UML for specific domains – When there is no need to change UML 2. 0 metamodel and semantics, just to extend or customize them • Metamodel concept – Defined on metamodel – Used on model • Excellent mechanism for defining MDA “Platforms” • Examples: – OMG standards: • • EAI: Enterprise Application Integration EDOC: Enterprise Distributed Object Computing CORBA, CCM Schedulability, Performance and Time – Proprietary: • UML-RT: UML for Real Time Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 19

UML 2. 0 Profile Example Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 20

UML 2. 0 Profile Example: EJB Platform Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 21

MOF/ QVT (Query-View-Transformations) • Query: Expression evaluated over a model – Results in one or more instances of types (either defined in the source model, or in the query language) • Example 1: List all packages that do not contain child packages • Example 2: Does attribute A of source model have public visibility? • View: A model completely derived from other model – Views are usually read-only – Views are generated by transformations – A query is a restricted kind of view • Transformation: Generates a target model from a source • model Relations and Mappings – Relations specify transformations – Mappings implement transformations – A relation can be refined by one or more mappings Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 22

QVT Transformation Requirements • • • Configurable Parametrizable Traceable Incrementally consistent Bidirectional Source-driven, Target-driven, Arbitrary One-2 -One, One-2 -Many, Many-2 -One, Many-2 -Many Declarative, Imperative, or Hybrid definition Simple Scalable Tool supported (fully or partially) Munich, 27 July 2004 [OMG, 2003] MDA 4 Web. Apps -- Tutorial @ ICWE 2004 23

Agenda 1. Introduction – Models and Metamodels 2. MDA primer 3. Web-based Applications 4. Applying MDA to Web-based Applications 5. What is left, and what is next 6. Conclusions Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 24

Beyond technology. . . • Too many platforms and technologies – Distributed Objects, Components, Web services, . . . – Not really interoperable! – Which technology is the best (today)? • Too fast evolution – – Technologies evolve. . . and get obsolete very soon Which technology will be out tomorrow? And how long will it last? How to protect my investment in business logic? • I want my business logic (processes, rules) to be as independent as possible from the supporting technologies – So they can separately evolve. . . . Without having to start from scratch each time. . And protecting the investment in each one Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 25

MDA: a New Kid in Town • New orientation for OMG activities – New step beyond the OMA – A framework for a set of standards in support of MDD • Models are centric! – Target middleware is not important! • Focus on Platform Independent Models (PIM) – Without middleware details • Abstract Platform Specific Models (PSM) – Including all middleware details • Define PIM to PSM transformations Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 26

MDA principles • Inspired by: – The widespread public acceptance of UML – OMG moving beyond middleware (CORBA) – The availability of mature MDD technologies • Purpose: – Enable inter-working between complementary tools – Foster specialization of tools and methods – Provide guidance for MDD • MDA overview papers and resources: – http: //www. omg. org/mda Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 27

MDA (expected) benefits • Protects software investment from technological changes and evolutions – preserves PIMs when new middleware appears! • Allows to handle larger and more complex systems – Through separation of conceptual levels/concerns • Allows the integration of separate aspects from the start, and in a uniform way – security, reliability, performance, . . . • Allows legacy systems to be integrated into the MDA chain • Allows simulation and automatic implementation of models Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 28

MDA Concepts (1/2) • Architecture – “The architecture of a system is a specification of the parts and connectors of the system and the rules for the interactions of the parts using the connectors” • Viewpoint – “A viewpoint on a system is a technique for abstraction using a selected set of architectural concepts and structuring rules, in order to focus on particular concerns within that system” • View – “A viewpoint model or view of a system is a representation of that system from the perspective of a chosen viewpoint” • Implementation – “An implementation is a specification, which provides all the information needed to construct a system and to put it into operation” Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 29

MDA Concepts (2/2) • Platform – “A set of subsystems/technologies that provide a coherent set of functionality through interfaces and specified usage patterns that any subsystem that depends on the platform can use without concern for the details of how the functionality provided by the platform is implemented. ” • Platform Independent Model (PIM) – “A model of a subsystem that contains no information specific to the platform, or the technology that is used to realize it. ” • Platform Specific Model (PSM) – “A model of a subsystem that includes information about the specific technology that is used in the realization of it on a specific platform, and hence possibly contains elements that are specific to the platform. ” Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 30

MDA models (1/2) • Computation Independent Model (CIM) – A view from a system from the Computational Independent Viewpoint. – A CIM Focuses on the system and its environment; the details of the structure of the system are hidden or as yet undetermined. – A CIM is sometimes called a domain model or a business model, and is specified using a vocabulary that is familiar to the practitioners of the domain in question – It may hide much or all information about the use of automated data processing systems. • Platform Independent Model (PIM) – A platform independent model is a view of a system from the platform independent viewpoint. A PIM exhibits platform independence and is suitable for use with a number of different platforms of similar type. Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 31

MDA models (2/2) • Platform Specific Model (PSM) – A platform specific model is a view of a system from the platform specific viewpoint. – A PSM combines the specifications in the PIM with the details that specify how that system uses a particular type of platform. • Platform Model (PM) – A platform model provides a set of technical concepts, representing the different kinds of parts that make up a platform and the services provided by that platform. – It also provides, for use in a platform specific model, concepts representing the different kinds of elements to be used in specifying the use of the platform by an application. Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 32

Examples of MDA models • CIM – “Priority must be given to shipping the oldest deliverables” • PIM – “The Deliverables are ordered according to date for shipment” • PSM/OOD – “Deliverables are sorted for shipment() in increasing order, using their attribute date” • PSM/OOP – “Use quicksort() to sort Deliverables, using Deliverable. date as sorting key, before passing them to shipment()” Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 33

Model transformations: MDA Pattern • Model transformation is the process of converting one model to another model of the same system • The MDA pattern includes (at least): – – a PIM, a Platform Model, a Transformation, and a PSM Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 34

Examples of MDA transformations UML Model (PIM) XMI Document (PSM) F IDL, Java… (PSM) interface Auto {Class Auto }; {public String color; public int Door; public int Engine; } Munich, 27 July 2004 I O M M X XMI <Auto> <Color> Red </Color> <Door> 4 </Door> <Engine> 2 </Engine> </Auto> XMI DTD, Schema (PSM) <!Element Auto (Color*, Door*, Engine*)> MDA 4 Web. Apps -- Tutorial @ ICWE 2004 35

Applying the MDA pattern: 1) Marking UML Profiles can be used to define the marks and for marking PIMs MOF QVT languages will define the mappings Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 36

Model mappings and marks • Mappings – An MDA mapping provides specifications for transformation of a PIM into a PSM for a particular platform. The platform model will determine the nature of the mapping • Marks – Model instance mappings define marks – A mark represents a concept in the PSM, which can applied to an element of the PIM to indicate how that element is to be transformed • Templates – A mapping may also include templates, which are parameterised models that specify particular kinds of transformations – These templates are like design patterns, but may include much more specifications to guide the transformation Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 37

Example of the result of a mapping interface My. Class { int get. Attribute. One(); void set. Attribute. One(int v); int one. Operation(); } Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 38

Result of a transformation template using a Security Profile (example) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 39

Marks • Marks distinguish multiple possible targets Local Invocation <<is. Local>> PIM <<is. Remote>> • Kinds of marks – Discriminators and enumerators PSM Remote Invocation [ is. Remote | is. Boolean ] – Quantities ( if ( num. Instances < Q and frequency < F) Linked. List | Hash. Table ) – Inputs ( append “db_” to all operation names ) –. . . Munich, 27 July 2004 [Mellor, 2003] MDA 4 Web. Apps -- Tutorial @ ICWE 2004 40

Applying the MDA pattern: 2) Metamodel transformation MOF QVT languages define the transformations Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 41

MDA Transformations — detailed [Bezivin, 2004] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 42

Example of transformation XML UML Attribute name: String type: String Munich, 27 July 2004 Element Ato. X Attribute name: String value: String MDA 4 Web. Apps -- Tutorial @ ICWE 2004 43

The relation and the mapping relation Ato. X { domain { (UML. Attribute) [name = n, type = t] } domain { (XML. Element) [ name = "Attribute", attrs = { (XML. Attribute) [name = "name", value = n], (XML. Attribute) [name = "type", value = t] } } mapping MAto. X refines Ato. X { domain { (UML. Attribute) [name = n, type = t] } body { (XML. Element) [ name = "Attribute", attrs = { (XML. Attribute) [name = "name", value = n], (XML. Attribute) [name = "type", value = t] } } Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 44

A transformation rule (1/2) Transformation Class. To. Class (UML, UML) { source c 1: UML: : Class; target c 2: UML: : Class; source condition -- none target condition -- none mapping try Public. To. Private. Attribute on c 1. features <~> c 2. features; -- everything else remains the same } Transformation Public. To. Private. Attribute (UML, UML) { source. Attribute : UML: : Attribute; target. Attribute : UML: : Attribute; getter : UML: : Operation; source condition source. Attribute. visibility = Visibility. Kind: : public; Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 45

Transformation rule (2/2) target condition target. Attribute. visibility = Visibility. Kind: : private and -- define the set operation setter. name = 'set'. concat(target. Attribute. name) and setter. parameters->exists( p | p. name = 'new'. concat(target. Attribute. name) and p. type = target. Attribute. type ) and setter. type = Ocl. Void and -- define the get operation getter. name = 'get'. concat(target. Attribute. name) and getter. parameters->is. Empty() and getter. returntype = target. Attribute. type; mapping try String. To. String on source. Attribute. name <~> target. Attribute. name; try Classifier. To. Classifier on source. Attribute. type <~> target. Attribute. type; } [Kleppe, 2003] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 46

Applying a transformation “template” Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 47

Applying the MDA pattern: 3) Model merging Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 48

Applying the MDA pattern: 4) Additional information – Example. A particular architectural style may be specified: information may be added to connectors to specify quality of service. Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 49

Applying the MDA Pattern several times • The MDA pattern can be [has to be usually] applied several times in succession – What is a PSM resulting from one application of the pattern, will be a PIM in the next application Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 50

Example: A Multimedia Application’s PIM [Fuentes et al. , 2003] UML Profile for CAM Transf. 1 PIM Application’s CAM model UML Profile for DAOP Transf. 3 DAOP model Application’s DAOP model UML Profile for EDOC Application’s EDOC model UML Profile for CORBA Transf. 2 EDOC model Transf. 4 Transf. 5 CORBA Implementation Munich, 27 July 2004 CORBA model MDA 4 Web. Apps -- Tutorial @ ICWE 2004 51

Multi-platform systems • Many systems are [can be] built on more than one platform Platform. Independent Model • An MDA transformation can use marks from several Platform Models to transform a PIM into a PSM with parts of the system on several different Platforms Munich, 27 July 2004 CORBA Model Java/EJB Model XML/SOAP Model Other Model Map PSM to application interfaces, code, GUI descriptors, SQL queries, etc. CORBA Java/EJB MDA 4 Web. Apps -- Tutorial @ ICWE 2004 XML/SOAP Other 52

Alternative implementations Application’s PIM UML Profile for CAM Application’s DAOP model UML Profile for EJB UML Profile for EDOC Application’s CAM UML Profile for DAOP EJB Implementation Application’s EDOC model Application’s DAOP model UML Profile for CORBA UML Profile for EDOC CORBA Implementation Application’s EDOC model UML Profile for CORBA [Fuentes et al. , 2003] CORBA Implementation Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 53

Advantages • Each model is independent from the rest – Separately defined – Each model defines its own “entities”, and resides at a welldefined level of abstraction • Software development becomes model transformation – Each step transforms (one or more) PIM at one level into (one or more) PSM at the next level –. . . Until a final system implementation (PSM) is reached • Transformations can be automated • We gain modularity, flexibility, and facilitate evolution • Application models capturing business logic and IP become corporate assets, independent from the final implementation technologies Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 54

The MDA Process: Summary (1/2) • A CIM of a system is prepared showing the system in the environment in which it will operate – That model will help understand exactly what the system is to do, independently of how the system is implemented • A PIM is built – It describes the system, but does not show details of its implementation in any platform • The architect will then choose a Platform (or several) – They enable implementation of the system with the desired architectural qualities • Then, a) In model instance mapping, the PIM is marked: the architect marks elements of the PIM to indicate the mappings to be used to transform that PIM into a PSM; or b) In Metamodel transformations, a transformation engine is used Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 55

The MDA Process: Summary (2/2) • Transform the (marked) PIM into a PSM – This can be done manually, with computer assistance, or automatically – The input to the transformation is the marked PIM, and the mapping – The result is the PSM, and the record of transformation • A PSM may provide more or less detail, depending on its purpose – A PSM will be an implementation, if it provides all the information needed to construct a system and to put it into operation – A PSM can be the PIM of the next iteration of the MDA process, until a suitable implementation is reached Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 56

MDA “components” Transfor. Mations Editors Model Editors Transform. Tools Code Text Generators Code Files MDA bus: Model Interchange (XMI, IDL o JMI) Transform. Repository Munich, 27 July 2004 Model Validators Models Repository Model Weavers MDA 4 Web. Apps -- Tutorial @ ICWE 2004 IDE 57

Current MDA technologies – – – – Meta Object Facility (MOF) Unified Modelling Language (UML) XML Model Interchange (XMI) Common Warehouse Meta-model (CWM) Software Process Engineering Meta-model (SPEM) Action Semantics Language (ASL) Query-View-Transformation (QVT) Various UML profiles • EDOC (ECA, CCA), • UML-RT, • EJB, • CCM, . . . EDOC Munich, 27 July 2004 . NET BPML XML WSDL XLANG SOAP XML-Schema MDA 4 Web. Apps -- Tutorial @ ICWE 2004 58

MDA Tools • • • ATLAS Transformation Language is language for general transformation within the MDA framework MIA Model-in-Action is a tool that implements the concepts of MDA. Optimal. J is a MDA tool for J 2 EE. Arc. Styler is a MDA tool for J 2 EE and. NET. UMT UML Model Transformation is a tool for model transformation and code generation of UML/XMI models MTL Model transformation at Inria Model. Ware Mod. Fact is an Open Source project for the MDA at LIP 6 Andro. MDA is an open source code generation framework that follows the MDA paradigm Middlegen is a free general-purpose database-driven code generation engine based on JDBC , Velocity , Ant and XDoclet • Open. Model is a java-based framework for generating executable applications from UML models and it • • • MCC is a MDA tool supporting J 2 EE and. NET(in the works). Codagen Architect is MDA tool for J 2 EE and. NET. UMLX is an experimental graphical transformation language. MDA Transf is a MDA transformation engine GMT (Generative Model Transformer) is a project to build MDA tools such as UMLX JAMDA (Java Model Driven Architecture) is an open-source framework for building applications • • complements Argo. UML generators which create Java code from a model of the business domain Path. MATE Model Automation & Transformation Environment is an industry's MDA environment providing tools for analysis, and model transformation engine GRe. AT is a metamodel based graph transformation language useful for the specification and implementation of model-to-model transformation Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 59

Agenda 1. Introduction – Models and Metamodels 2. MDA primer 3. Web-based Applications 4. Applying MDA to Web-based Applications 5. What is left, and what is next 6. Conclusions Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 60

Web Engineering and Applications • Web Engineering – “The systematic, disciplined, quantifiable approach to the development, operation and maintenance of Web applications. ” • Web Application – “An Information System which uses Web-based technologies and platforms, and which supports interaction through Web-based interfaces. ” Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 61

Web-based Applications • Web-based Applications Architectural Patterns – Thin Web Client • Minimal client-side functionalities (web browser) • Business logic resides in the server side – Thick Web Client • Client-side scripting and custom objects (controls, applets, . . . ) • A significant amount of business logic resides in the client – “Web Delivery” • Clients participate in a distributed object systems [Conallen, 2000] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 62

Web-based Enterprise Layers Supply Chain EAI Applications & B 2 B E-Commerce Web Browser Client Applications Enterprise Components XML Corba EJB DCOM MQ SQL DBMS, Client/Server & Legacy Applications Web Server Applications HTTP User interface and application logic go here Munich, 27 July 2004 Standard Middleware Connects: applications to components, and components to Business and data components rules go here MDA 4 Web. Apps -- Tutorial @ ICWE 2004 The data goes here 63

Web-based Enterprise Architecture PDAs Browsers Applets, Applications Client Apps Web Services clients Client Tier servlets JSPs Server Tier External Web Services EJBs DB J 2 EE Container Middleware Back-end Systems Munich, 27 July 2004 CORBA ORB/CORBA Services DB DB Application servers MDA 4 Web. Apps -- Tutorial @ ICWE 2004 External Web Services 64

From three to a six layer architecture Three layers model User interface Six layers model (Refined) Presentation / Navitation GUI Device-independent Presentation / Navigation Business Logic Process control (Functionality) Business Objects Data access Data Physical data Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 65

Example: A Travel Agent [Bezivin, 2004] + many others Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 66

“Conceptual model” Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 67

Web-Apps Development proposals • Currently, Web applications can be generated from models – They are good code generators (i. e. , ad-hoc “model compilers”) • Web-Apps Modelling (pre-Web Engineering) – Example: Jim Conallen’s proposal J Model Web entities (web pages, servers, forms, etc) • MDD Web Engineering (pre-MDA) – Examples: UWE (Argo. UWE), OO-H (Visual. WADE), OOHDM, OOWS, WSDM, Web. ML J Model the presentation and navigation aspects J Their conceptual models capture and successfully handle the application’s structure Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 68

Jim Conallen’s Model (excerpt) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 69

OO-H (Object-Oriented Hypermedia) Object-Oriented Hypermedia Method Functional View. Point Conceptual View Process View Munich, 27 July 2004 Presentation View Navigational View MDA 4 Web. Apps -- Tutorial @ ICWE 2004 70

OO-H Domain (Conceptual) Model Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 71

OO-H Navigation Model Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 72

OO-H Presentation Model Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 73

OO-H: Final result Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 74

UWE (UML-based Web Engineering) [Koch et al. , 2001] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 75

UWE Metamodel (1/2) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 76

UWE Metamodel (2/2) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 77

UWE: Conceptual model Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 78

UWE Navigational Model Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 79

UWE Presentation model: Structural view Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 80

UWE Presentation model: User Interface Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 81

Web-Apps Development proposals: Summary • Web-Apps Modelling (pre-Web Engineering) – Example: Jim Conallen’s proposal J Model Web entities (web pages, servers, forms, etc) L Too low level (basically, useful to model the PSM only) • MDD Web Engineering (pre-MDA) – Examples: UWE (Argo. UWE), OO-H (Visual. WADE) , OOHDM, OOWS, WSDM J Model the presentation and navigation aspects J Their conceptual models capture and successfully handle the application’s structure L Do not address (properly) other aspects: business processes, choreography, distribution, etc. L Ad-hoc code generation (i. e. , model compilation) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 82

Agenda 1. Introduction – Models and Metamodels 2. MDA primer 3. Web-based Applications 4. Applying MDA to Web-based Applications 5. What is left, and what is next 6. Conclusions Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 83

MDA for Web Applications • “MDA is suitable for developing distributed systems that are made up of components running on different platforms/tiers. For example, there may be web tier implemented on ASP. Net, but which talks to a middle-tier using EJBs, with a back-end being a Sybase RDBMS. MDA can generate the software for the tiers, plus the code to glue it all together. ” [Haywood, 2004] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 84

Is MDA a right option for you? • Are models important for you? – i. e. , does your business care about models? • Are your platforms that unstable? • Could your development process cope? – Including your development team. . . New skills are required! • Would your business buy it? • Isn’t having two different flavours (Schools) of MDA somewhat worrying? – Elaborationalists (e. g. Optimal/J, Arc. Styler) 70% executable annotated PIMs – Translationists (e. g. Executable UML) 100% executable PIMs • Down at the coal-face, do you – honestly – believe it would work? – Will be able to generate code from models, even when we do not yet agree on how to represent behaviour? [Dan Haywood, 2004] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 85

The two current MDA approaches • Models do not contain all the • Models are a complete, executable • • • information (e. g. behaviour) Missing information is added as refinement in the PSM or code Round-trip engineering is sometimes possible Munich, 27 July 2004 • • statement of a solution Model compilers translate these models into a running system ASL are used to model behaviour No manual intervention required MDA 4 Web. Apps -- Tutorial @ ICWE 2004 86

The MDA way • Define the system PIMs (structure, behaviour, • navigation, presentation, components, distribution, . . . ) Select the target platform(s) – Web pages (navigation), Java (Travel Agency), WSDL and JWSDP (external services: banks, airlines, . . . ), . . . • Define the transformations – Either using transformation rules between the PIM metamodels (the PIM languages) and the target platforms metamodels – Or by marking the PIM elements using the marks defined by the mappings • Apply the mappings to the PIM elements – Using a transformation engine, or manually – This will produce a set of elements of different PSM • Bridges (e. g. , calls) between elements in heterogeneous target PSMs should be defined! Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 87

The Travel Agent Example [Bezivin, 2004] + many others Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 88

PIM of the system (structure) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 89

PIM of the system (Processes – excerpt) (EDOC) [Bezivin, 2004] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 90

Transforming the PIM (structure) • Metamodel transformations – An alternative approach to using marks (taken from the UML Profile that defines the Platform) • More powerful • More general – The basis of the QVT proposals – Currently, the preferred option • Let us see how to transform the PIM of the system structure to Java, WSDL, and JWSDP implementations – Transformations between the different metamodels should be defined: • UML<~>Java, UML<~>WSDL, UML<~>JWSDP, Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 91

UML Metamodel (over-simplified) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 92

Java Metamodel (simplified) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 93

UML to Java transformation (ATL) P 2 P G 2 s Ae 2 F C 2 C I 2 I A 2 F OM 2 M Pr 2 Pr Dt 2 Pt Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 [Bezivin, 2004] 94

WSDL Metamodel Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 95

UML to WSDL transformation (ATL) Dt 2 T P 2 D C 2 T P 2 Part I 2 Pt O 2 O Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 [Bézivin, 2004] 96

JWSDP Metamodel Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 97

PSM using Java, WS, and JWSDP Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 98

Transforming the PIM (behaviour) • Metamodel transformations seem to be appropriate for behaviour as well • No agreed notation for describing behaviour – State-based approaches (state machines, ASL, SDL) – Declarative approaches (pre-post, contracts) – Protocol-based approaches (sequence and interaction diagrams) • They do not share a common behavioural model • Either vanilla UML or some UML dialects and Profiles are commonly used (UML Profile for EDOC, UML-RT, . . . ) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 99

PIM of the system (Processes – excerpt) (EDOC) [Bezivin, 2004] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 100

EDOC Process Components to Java Dt 2 T A 2 F Cd 2 C F 2 P O 2 M P 2 I Pc 2 C [Bezivin, 2004] Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 101

MDA-based proposals: Summary • MDA-based (model transformations): ATLAS’s, Optimal/J, Arc. Styler J Structured model compilation, according to MDA approach and disciplines J Very good treatment of the business structure (Conceptual Model): modularity, platform independence, separation of concerns, . . L Very simplistic treatment of navigation and presentation L Lack of consensus to model behaviour and choreography L Optimal/J and Arc. Styler are very much focused on particular technologies (J 2 EE, . NET) Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 102

And now? • Define all system PIMs • Analyse each proposal’s coverage • Play with current tools, see how far it can go, and how • • • much you can integrate it within you development processes Try to use each proposal and tool wherever it shows its strength and benefits Identify gaps not covered by any of the current proposals Research and development activities: – Adapt current proposals to make them conformant to MDA (and thus make them interoperable, with modular design, etc. ) – Develop new proposals that fill the gaps – Work on more tools Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 103

Models (PIMs) of a Web Application Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 104

Models covered by Conallen Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 105

Models covered by UWE Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 106

Models covered by OO-H Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 107

Models covered by Optimal/J Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 108

Models covered by ATLAS works Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 109

Let’s try to do it right! ü Define all system PIMs • Use/adapt each proposal to model the aspects it is more suitable, e. g. ü OO-H or UWE can model navigation and presentation 1 But adapt them so they do not generate code in an ad-hoc manner, but according to the MDA principles ü ATL can be used for metamodel transformations (between the models generated by each proposal) ü Optimal/J and Arc. Styler can generate the EJB or. NET code 1 But adapt them so they can generate other platforms’ code more naturally ü Conallen’s proposal can model the PSM • . . . And the gaps? Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 110

Agenda 1. Introduction – Models and Metamodels 2. MDA primer 3. Web-based Applications 4. Applying MDA to Web-based Applications 5. What is left, and what is next 6. Conclusions Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 111

Next steps MDA is still in its infancy. . . • Define and implement “MDA components” – – Model Editors and Builders Model Compilers Model Transformers and Weavers Transformation Languages and Engines (QVT) • Sort out the Behaviour, Choreography, Distribution, Transactions, . . . – Agree on a set of behavioural notations with well-defined semantics – Agree on notations for expressing choreography – Be able to deal with the aspects at different conceptual levels (CIM, PSM) • Deal with COTS and legacy applications – MDA seems to imply a top-down development process. What do we do with re-use? • Extra functional requirements? . . • Architecture and Architectural styles? . . . Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 112

Agenda 1. Introduction – Models and Metamodels 2. MDA primer 3. Web-based Applications 4. Applying MDA to Web-based Applications 5. What is left, and what is next 6. Conclusions Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 113

Conclusions • MDA seems to be the right way to go – Conceptually clean and well defined – Protect investment and IP by separating the business model from the supporting technologies – Model centric! • But there is still a long way ahead – (see previous slides) • and MDA is not the panacea – Many sceptical positions and critiques – “No manual coding” is not 100% achievable in general – We need to identify the domains in which MDA can be effectively used, and develop tools for it (e. g. , Web-based systems) • Research is required! Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 114

Bottom line – Ideas to take home with you • Capture each system “concern” (subject matter) in an independent model – Presentation, navegation, business processes, business rules, functionality, . . . – Each models deals with an independent subject matter, each one is platform independent – Decomposition should aim at modular separation of concerns (changes in one subject matter do not need to imply changes in models of other concerns) • Use mappings between the models representing each concern – Refinements, abstractions, representations, migrations, . . . • Models and Mappings become your CORPORATE ASSETS • Use tools to automate the mappings Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 115

Basic References – Models and MDA • • • • • J. Bézivin. “In Search of a Basic Principle for Model Driven Engineering. ” Upgrade 5(2): 21 -24, 2004. D. Frankel. “Model Driven Architecture: Applying MDA to Enterprise Computing. ” J. W. & Sons, 2003. L. Fuentes, A. Vallecillo. “An Introduction to UML Profiles. ” Upgrade 5(2): 6 -13, 2004. L. Fuentes, M. Pinto, A. Vallecillo. “"How MDA Can Help Designing Component- and Aspectbased Applications". In Proc. of EDOC 2003, Brisbane, Australia, Sept. 2003. T. Gardner et al. “A review of OMG MOF 2. 0 Query/Views/Transformations Submissions and Recommendations towards the Final Standard”. July 2003. www. omg. org/docs/ad/03 -08 -02. pdf D. Haywood. “MDA in a nutshell. ” May 2004. http: //theserverside. com/articles/ A. Kleppe, J. Warmer, W. Bast. “MDA Explained: The Model Driven Architecture, Practice and Promise. ” Addison-Wesley, 2003. A. Mc. Neile. “MDA: The Vision with the Hole? ”, 2003. http: //www. metamaxim. com/download/documents/MDAv 1. pdf A. Mc. Neile, N. Simmons. “Methods of behaviour modelling”, 2004. www. metamaxim. com S. Mellor, M. Balcer. “Executable UML: A Foundation for Model Driven Architecture. ” Addison. Wesley, 2002. S. Mellor, “MDA Distilled. ” www. projtech. com OMG. “MDA Guide. ” OMG doc. ab/2003 -05 -01. OMG. “Model Driven Architecture. ” OMG doc. ormsc/2001 -07 -01. Ed Seidewitz. “What Models Mean. ” IEEE Software 20(5): 26 -32, Sep/Oct 2003. B. Selic. “The Pragmatics of Model-Driven Development. ” IEEE Software 20(5): 19 -25, Sep/Oct 2003. D. Thomas. “MDA: Revenge of the Modellers or UML Utopia? ” IEEE Software 21(4): 15 -17, May 2004. J. Warmer, A. Kleppe. “The Object Constraint Language: Getting Your Models Ready for MDA, ” Second Edition, Addison-Wesley, 2003. Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 116

Basic References – Models & Web Eng. • L. Baresi, F. Garzotto, P. Paolini. “Extending UML for Modelling Web Applications. ” In Proc. of • • • 34 th HICSS, 2001. J. Bézivin et al. “An Experiment in Mapping Web Services to Implementation Platforms. ” Research Report#04. 01, Univ. Nantes, March 2004. S. Ceri, P. Fraternali, A. Bongio. “Web Modelling Language (Web. ML): A modelling language for designing Web sites. ” In Proc. of the 9 th WWW Conference, May 2000. J. Conallen. “Building Web Applications with UML. ” Addison-Wesley, 2000. J. Gomez, C. Cachero, O. Pastor. “On Conceptual Modelling of Device-independent Web Applications: Towards a Web Engineering Approach. ” IEEE Multimedia 8(2)20 -32, 2001. N. Koch, A. Kraus, R. Hennicker. “The Authoring Process of the UML-based Web Engineering Approach”. In Proc. of IWWOST 2001, Valencia, Spain, 2001. N. Koch, A. Kraus. “Towards a Common Metamodel for the Development of Web Applications”. In Proc. of ICWE 2003, LNCS 2722, pp. 497 -506, 2003. N. Koch et al. “Modelling Web Business Processes in Web Application Models”. In Journal of Web Engineering 3(1): 22 -49, 2004. P-A. Muller, P. Studer, J. Bézivin. “Platform Independent Web Application Modelling. ” In Proc. of UML 2003, LNCS 2863, pp. 220 -233, 2003. D. Schwabe, L. Esmeraldo, G. Rossi, F. Lyardet. “Engineering Web Applications for Reuse. ” IEEE Multimedia, Special issue on Web Engineering, 1(3): 20 -31, 2001. D. Schwabe, G. Rossi. “Designing Hypermedia Applications using OOHDM. ” In Proc. of Workshop on Hypermedia Development Processes, Methods and Models (Hypertext’ 98), 1998. D. Schwabe, O. Pastor (eds. ). Proc. of IWWOST 2001. http: //www. dsic. upv. es/~west/iwwost 01 O. de Troyer, S. Casteleyn. “WSDM: A user-centred design method for Web sites. ” In Proc. of the 7 th WWW Conference, May 1998. Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004 117

End of Presentation llo eci l Val io ton a. es n m A 4 cc. u @l 79 2 av 13 952 +34 http: //www. lcc. uma. es/~av/mis. Confs/ICWE 2004/ Munich, 27 July 2004 MDA 4 Web. Apps -- Tutorial @ ICWE 2004