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Successful Middleware Integration Using a Common Domain Model

Successful Middleware Integration Using a Common Domain Model. October, 2000 Gregor Hohpe. Middleware Enables Data Exchange Between Applications. Application A stores customer information (name, address, …) Application B stores customer information (name, address, …)

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Successful Middleware Integration Using a Common Domain Model

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  1. Successful Middleware IntegrationUsing a Common Domain Model October, 2000 Gregor Hohpe

  2. Middleware Enables Data Exchange Between Applications • Application A stores customer information (name, address, …) • Application B stores customer information (name, address, …) • Changes to the data in Application A are propagated to Application B Application B Application A Customer Customer

  3. Generally, a Translation Between the Application Specific Data Formats Is Required • Application A stores customer information in a specific format • Application B stores customer information in a different format • The middleware needs to translate between the formats (the adapters don’t perform this task!) • Simple field mapping or structural mapping may be required • Middleware packages provide GUI tools to perform field mapping: TIBCO Integration Manager, Vitria Connection Modeler Application B Application A Mapping Customer Customer

  4. Adding Another Application Requires Additional Mapping • One mapping unit has to be created between each pair of applications Application B Application A Mapping Customer Customer Application C Mapping Customer

  5. What Happens If More Than One Application Is Allowed to Update the Information? • One mapping unit has to be created between each pair of applications • If B is allowed to update customer information, we need to build 4 mapping units • With a larger number of applications, this can lead to an effort that is proportional to the square of the number of applications Application B Application A Mapping Customer Customer Mapping Application C Mapping Customer

  6. This Approach Introduces a Large Number of Tightly Coupled Point-to-point Connections • n / 2 * (n – 1) connections between n systems • Each mapping depends on two specific packages Customer Customer Customer Customer Customer Customer

  7. Define a Common Domain Model to Replace an Unmanageable Number of Point-to-Point Mappings • Define a common model for all entities and their relationships • When publishing a message, translate each application’s private model into the common model and broadcast the message • Manage the Common Domain Model for all entities in a central repository • Provided by the Middleware package or • Through XML and a set of DTDs (or XML Schemas) Application B Application A Mapping Mapping Customer Customer Application C Mapping Customer Common Domain Model

  8. A Common Domain Model Addresses a Variety of Issues Related to Middleware Integration • Applications communicate with each other through a common model rather than through point-to-point translations • Linear effort of integrating an additional application • Loose coupling between application data format • The common model is abstract not specific to any application • The model represents the client’s business domain, not a specific package implementation • Improved ability to replace applications (e.g., legacy to best-of-breed app) • Ability to receive data from more than one source • The Common Domain Model for all entities can be managed in the Middleware Repository • Single point of reference (and maintenance)

  9. A Common Domain Model Is the Platform for Future Extensions • The business logic in the middleware (e.g., Automator, Integration Manager) operates on a common, package independent format • More meaningful reporting • The common model can be (selectively) exposed to external partners for B2B exchanges, Web Services Reporting /Data Warehousing Application B Application A Mapping Mapping Customer Customer Application C BusinessLogic Mapping Customer Common Domain Model B2BIntegration ExternalPartners

  10. The Common Domain Model Is Described in UML Notation • Unified Modeling Language is a standard notation defined by OMG • UML Class Diagram defines entities and their relationships • Even though we use the same notation, the design process differs from OO design (e.g. a Java program) Entity Customer Contact Aggregation(Customer has Sites) 0..N Association Location Primary Contact Specialization(Billing Location is a type of Location) BillingLocation ServiceLocation More info on UML: Book “UML Distilled, 2nd ed.” by M. Fowlerhttp://www.omg.orgUML Brownbag (wrsc/sf/portal)

  11. The Common Domain Model Is Different From the Middleware Message Specification • The Domain Model defines entities and their associations • Message specifications define actions on the entities • TIBCO Repository Classes or Vitria Event IDL define Message Specifications, not the Domain Model! • Message specifications are derived from the Domain Model • Messages act on entity attributes  Message fields • Message need to respect the association between entities  Key management Customer Contact 0..N Location Primary Contact Message Specification Domain Model

  12. Using a Common Domain Model Successfully Requires Special Skill and Experience • Developing a Common Domain Model is a substantial task • Needs to be integrated into the task plan as a parallel activity • Needs to be part of the development methodology, not an afterthought • Simple integration points require 2 translations instead of 1 • Performance considerations • Initial development effort may be higher • Dependency on application packages • Should be independent from the applications, but needs to be similar enough to enable mapping • Avoid lowest common denominator • Additional expertise and skill sets required • Object modeling • UML or other notation • Tool skill like Rational Rose

  13. How to Get Started? • Get familiar with UML Class Diagrams • Look at the whole UML spec; it supports a great use-cases driven development cycle • Read the book, not the OMG spec (unless you suffer from insomnia) • Get a tool like Rational Rose or Visio Professional • Dedicate a resource to be the owner of the Domain Model • More in the upcoming presentation: “Middleware Integration Methodology“

  14. Resources, Questions, Comments • Contact Info: Gregor Hohpe, 415-783-5255, ghohpe@dc.com • Internal Web Site: http://wrsc/vitria • Internal Web Site: http://eTI • Book: “UML Distilled, 2nd Edition” by Martin Fowler, Addison-Wesley ?

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