Model-Driven Architecture TM Reality and Implementation

Transcription

1 Model-Driven Architecture TM Reality and Implementation David S. Frankel Chief Consulting Architect IONA Technologies, Inc. OMG Architecture Board Member

2 The Sisyphus Syndrome There is no question that if Web services are to take off as smoothly as vendors hope, a significant chunk of the more than 20 million programmers in the world will have to write to UDDI, WSDL, XML and SOAP. Web Services InfoWorld, vol. 23, issue 11, March 12, 2001, page 39

3 This Won t Scale Technologies for Web services are in flux Several different ways of stacking them XML evolved to XML Schema: What s next? SOAP and WSDL are new and evolving Will port 80 be what it was intended to be when it is multiplexing myriad Web service messages? These technologies are bound to change Having Web service developers program directly to them invites rapid obsolescence And is too labor intensive

4 The Forest for the Trees The information, and the services that use and create the information, are central Exposing them over the Internet is the breakthrough concept XML, SOAP, WSDL, UDDI, etc., are important, but must be kept in perspective The process of producing individual Web services must be as independent of these technologies as possible

5 Maximizing Reuse Over Different Technology Stacks Business Service Designs WSDL SOAP WAP Java Interactive SOAP Binding HTTP Binding MIME Binding

6 Raising the Level of Abstraction Part of general trend Already well-established for front and back ends WYSIWYG GUI modeling and data modeling Hand coding no longer predominates But tuning allowed Early Web applications wired Web front end directly to back end Some companies avoided building intermediate tiers Web services and B2B require intermediate tiers to expose coarse grained business services Abstraction to allow reuse of the coarse grained business services via various technologies

7 Unified Modeling Language TM (UML TM ) Standard, managed by the OMG Suitable for expressing information and services Widely accepted Has some notable flaws UML 2.0 work in progress

8 Informal UML Models Informal modeling Used to sketch out basic concepts Advantage over typical box and line diagrams because shapes and line types have specific meanings Important way to use UML, but can t drive code generators and dynamic execution engines Analogously, informal text can t be compiled and executed like 3GL text

9 Precise Formal UML Models Precision and detail are not the same! Computationally complete Missing properties and unresolved references not acceptable 3GL analogy an incomplete expression such as a + does not compile An undeclared identifier does not compile

10 Business Information Model Imprecise and Incomplete Account id : String balance : Float 1..n SavingsAccount interestrate : Float CheckingAccount minbalance : Float Customer socialsecuritynum : String name : String address : String PreferredChecking

11 Business Information Model Precise and Complete context Account inv: --The first character of the id must be the same as the first character of the customer name id->substring(1,1) = customer.name -> substring(1,1) {disjoint} SavingsAccount interestrate : Float Account id : String balance : Float 1..n +account CheckingAccount minbalance : Float 1 +customer Customer socialsecuritynum : String name : String address : String PreferredChecking context PreferredChecking inv: --Cannot go below the minbalance balance >= minbalance

12 Business Information Model Precise and Complete Disjoint means no instance can be an instance of both subclasses. context Account inv: --The first character of the id must be the same as the first character of the customer name id->substring(1,1) = customer.name -> substring(1,1) {disjoint} SavingsAccount interestrate : Float Account id : String balance : Float 1..n +account CheckingAccount minbalance : Float 1 +customer Customer socialsecuritynum : String name : String address : String Multiplicity could be 1 or 0..1, must be specified Invariant rules expressed in UML s Object Constraint Language (OCL) PreferredChecking context PreferredChecking inv: --Cannot go below the minbalance balance >= minbalance = composition (a.k.a. strong aggregation) Composition of Account by Customer formally captures an important business rule: An account cannot be transferred from one customer to another.

13 Business Service Model Design by Contract TM <<BusinessService>> FundsXFer XFerFromChecking(in fromacct : CheckingAccount, in toacct : SavingsAccount, amount : Float, out fromacctbal : Float, out toacctbal : Float) context FundsXFer (XFerFromChecking) --Pre and post conditions pre: {fromacct.balance >= amount} {fromaccount.customer = toaccount.customer} post: {fromacct.balance = fromacct.balance@pre - amount} {toacct.balance = toacct.balance@pre + amount} {fromacctbal = fromacct.balance} {toacctbal = toacct.balance}

14 Mapping the Business Information Model to XML Platform- Independent Model XMI s UML-XML Mapping Rules Produce XML DTD (or (or Schema) Customer SocialSecurityNum : String name : String Address : String <!ELEMENT Bank.Customer.SocialSecurityNum (#PCDATA XMI.reference)*> <!ELEMENT Bank.Customer.name (#PCDATA XMI.reference)* > <!ELEMENT Bank.Customer.Address (#PCDATA XMI.reference)* >

15 Mapping the Business Service Model to WSDL <<BusinessService>> FundsXFer XFerFromChecking(in fromacct : CheckingAccount, in toacct : SavingsAccount, in amount : Float, out fromacctbal : Float, out toacctbal : Float) PortType 0..n 1 +operation +porttype {ordered} Operation input Message output The message payload format is based on a UML-XML mapping applied to the business information model.

16 Fine Tuning XML Generation Using XMI Parameters context Account inv: --The id must begin with "A" and be seven characters long id->substring(1,1) = "A" and id->size( ) = 7 SavingsAccount interestrate : Float Account id : String balance : Float {disjoint} 1..n CheckingAccount minbalance : Float +account {href = true} {enforcemaximummultiplicity = true} 1 +customer Customer socialsecuritynum : String name : String address : String PrefferedChecking context PreferredChecking inv: --Cannot go below the minbalance balance >= minbalance

17 UML Profiles In order to define a profile Select a subset of UML Use UML s built in extension mechanisms to extend the subset Stereotypes, e.g. Tagged Values, e.g. {href = true} Two uses of profiles To model a particular domain, e.g. business information, business services, business collaborations, realtime systems, telecomm, etc. To parameterize mappings to specific technologies

18 from ebxml Information model to... Adapted from Klaus-Dieter Naujok s ebxml and Web Services webcast...xml representation

19 The Frontier Automating Business Processes and Choreographies Here again, there is a mix of technologies ebxml Business Process Specification Schema (BPSS) RosettaNet PIP WSFL, WSEL (IBM) XLANG (Microsoft) Here again, the business processes and choreographies are central UML Activity and Interaction Models can provide the necessary abstractions With mappings to the various technologies

20 Informal UML Activity Model Obtain Acceptable Payment Offer from Buyer for Providing Goods or Services [ significant currency exposure ] [ insignificant currency exposure ] Obtain Option Price [ option worth purchasing ] [ option too expensive or unavailable ] Purchase Option [ unacceptable currency exposure ] [ acceptable currency exposure ] [ option out-of-the-money ] Obtain Payment from Buyer [ option in-the-money ] Decline Payment Offer for Goods and Services Accept Payment Offer for Goods and Services Exercise Option

21 Formal UML Activity Model START <<BusinessTransactionActivity>> Query Available Time Slots [ TimeSlotReservationConfirmation.acknowledgement = false ] [ TimeSlotOfferResponse.timeslot->isEmpty ] [ AvailableTimeSlotsResponse.timeSlots->isEmpty ] <<BusinessTransactionActivity>> Offer Available Time Slots NO TIME SLOTS [ exception.type = CONTROL ] [ exception.type = CONTROL ] [ exception.type = CONTROL ] <<BusinessTransactionActivity>> Request Time Slot Reservation <<NotificationActivity>> > Notify of Failure FAILED END Reused with permission from Jim Clark

22 UML Interaction Model BuyerService/: SellerService/: Request(PurchaseOrderRequest) Signal(ReceiptAcknowledge) Signal(AcceptanceAcknowledgement) Response(PurchaseOrderResponse) Signal(ReceiptAcknowledge) From UN/CEFACT Modeling Methodology (UMM)

23 MDA: The Big Picture Raising the level of abstraction on a broader scale Efforts underway to define UML profiles for Realtime Component Composition and Assembly Meta Object Facility (MOF TM ) Subset of UML Dual purpose Model-driven metadata management Defining languages where UML profiling s limitations are an issue Mappings to XML (XMI), Java (JMI), and CORBA MDA can be overhyped Transition will unfold gradually But will be profound

24 MDA vs. CASE CASE limitations Mappings to implementation technologies were proprietary Risk to CASE customers too great Very limited or no capability to extend the specification language MDA overcomes these limitations via Standardized mappings Not one UML-Java mapping, but different ones for different domains UML profiles and MOF

25 Platform Independent A Relative Term 2000s MDA 1990s Middleware 1970s & 80s 3GLs Each raising of the abstraction level improved Productivity Longevity Quality 1960s Processors

26 More on relativity Abstract Components (EDOC-CCA) Abstract Distributed Components (DCP) Abstract Message- Oriented Components (UML4EAI) Web Services (UMM) EJB CCM MQSeries MSMQ WSDL WAP COM+

27 Generating APIs and Formats vs. Generating Impelementations Much easier to generate IDL, Java APIs, XML DTDs than generating implementations of the above This is one reason why it is logical for standards bodies to be the early adopters Standards needed for the mappings that produce APIs and formats Not for producing implementations

28 MOF Model of Metadata CheckConstraint deferrability : DeferrabilityType * /constrant ColumnSet /constraint * 0..1 /feature /owner * {ordered} /constrainedelement Column {ordered} precision : Integer scale : Integer isnullable : NullableType length : Integer collationname : String charactersetname : String / optionscopecolumnset : NamedColumnSet / referencedtabletype : SQLStructuredType * * /structuralfeature /type 1 SQLDataType typenumber : Integer NamedColumnSet / optionscopecolumn : Column / type : SQLStructuredType / usingtrigger : Trigger QueryColumnSet query : QueryExpression SQLDistinctType length : Integer precision : Integer scale : Integer / sqlsimpletype : SQLSimpleType * /constrainedelement {ordered} Table istemporary : Boolean temporaryscope : String / trigger : Trigger View isreadonly : Boolean checkoption : Boolean queryexpression : QueryExpression sqldistincttype * SQLSimpleType charactermaximumlength : Integer characteroctetlength : Integer numericprecision : Integer numericprecisionradix : Integer numericscale : Integer datetimeprecision : Integer issystem : Boolean 1 sqlsimpletype

29 MOF Overview = MOF CORBA Interfaces = MOF Java Interfaces (JMI) MOF Repository = MOF XML (XMI) Import / Export Work in progress: MOF-WSDL mapping UML Models Data Models Process Models CCM CORBA Interfaces B2B Choreography Descriptions

30 IONA MDA Projects Model-Driven Metadata Management UBS, Zurich Warborg Dillon Reed ArcStyler Cartridge Extends ArcStyler standard J2EE cartridge Targeted to IONA s J2EE application server Developed by IONA personnel in cooperation with Interactive Objects

31 MDA Summary Using Modeling Languages as programming languages to Improve productivity Improve quality Improve longevity

32 To Learn More UML MOF XMI JMI Public Review Release /jsr040/index.html UML Profile for Schedulability, Performance, and Time (a.k.a. UML Profile for Realtime)

33 Trademarks Design by Contract is a trademark of Interactive Software Engineering CORBA, Model-Driven Architecture, MDA, Unified Modeling Language, UML, XMI, and MOF are trademarks of the Object Management Group (OMG) Java, EJB, and J2EE are trademarks of Sun Microsystems. MQSeries is a registered trademark of International Business Machines