Chapter 4 Enterprise Architectures ServiceOriented Computing Semantics Processes

Chapter 4: Enterprise Architectures Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005

Highlights of this Chapter n n n Chapter 4 Enterprise Integration J 2 EE. NET Model Driven Architecture Legacy Systems Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 2

J 2 EE Technology Chapter 4 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 3

. NET Technology Chapter 4 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 4

. NET Web Services n COBOL Web service for multiplication <%@ webservice language=''COBOL'' %> CLASS-ID. MULTIPLICATIONSERVICE. FACTORY. PROCEDURE DIVISION. METHOD-ID. MULTIPLY. DATA DIVISION. LINKAGE SECTION. 01 VAL-1 PIC S 9(9) COMP-5. 02 VAL-2 PIC S 9(9) COMP-5. 01 PRODUCT PIC S 9(9) COMP-5. PROCEDURE DIVISION USING BY VALUE VAL-1 VAL-2 RETURNING PRODUCT. COMPUTE PRODUCT = VAL-1 * VAL-2. END METHOD MULTIPLY. END FACTORY. END CLASS MULTIPLICATIONSERVICE. Chapter 4 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 5

Legacy Systems n A pejorative term for computing systems that n n n Notice that “legacy systems” is not synonymous with “mainframe” n Chapter 4 Run on obsolete hardware and nonstandard networks Run poorly documented, difficult-to-maintain software Consist of poorly modeled databases Support rigid user interfaces Mainframes have had a resurgence in the last decade: no longer obsolete hardware; often support modern OSs (Linux); not necessarily poorly modeled or rigid (though some elements are obsolete or arcane) Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 6

How Legacy Systems Arise n Proprietary software n n Meaning embedded procedurally in the code Ad hoc changes to software in response to n n Chapter 4 Not supporting industry standards Sold by vendors who hope to lock in the market through incompatibility Changing requirements (laws, regulations, competition, or other business needs) Bugs Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 7

Legacy Systems: Pros and Cons n Fulfill crucial business functions n n n Run the world’s airline reservation systems Run most air traffic control programs Have loyal users, reluctant to migrate Represent huge investments in time and money Complicate reuse and sharing of data Cause redundancy, wasted effort, and integrity violations Chapter 4 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 8

Migration n Updating technology is n n n All at once? n n n Essential A continual process Expensive Risky Brittle Frustrating for users Gradual change: dismantle legacy and build desired system hand-in-hand n Chapter 4 Install and test piecemeal Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 9

Applying Services New Service Application Services Refactored from Legacy Backend Legacy Interface Chapter 4 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 10

Chapter 4 Summary n n n Services must fit into existing architectures J 2 EE and. NET are architecturally quite similar Legacy systems provide the basis for many modern services n n n Chapter 4 They host key data and processes Interoperating with them is nontrivial Challenge: refactoring legacy capabilities to derive best value from resulting services Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 11