1. Based on slides by David Schuff

2. Review: N-Tier Architectures  A “tier” is a software layer that serves as a component of a larger solution  Here’s an example of a three-tier architecture: source: http://en.wikipedia.org/wiki/Multitier_architecture

3. Servers as tiers  Commonly, you’ll see  A client tier  Multiple (n-1) server tiers  So a four-tier solution would have 3 server tiers and a client tier  What is a client?  What is a server? How many physical machines are in a four- tier solution?

4. Multi-tier architecture Client tier: Displays the user interface Handles client-side validation Web server tier: Generates HTML pages for the client Requests information from the application server Application server tier: Processes data sent from the web server Delivers processed data to the web server Queries the database server Database server tier: Processes queries received from the application server Returns query results to the application server

5. Multi-tier architecture: Making an online purchase Client tier: User selects products and enters purchasing information in Firefox Web server tier: IIS generated the product information pages and the order entry forms Submits data to the order entry application Application server tier:.NET Runtime executes a C# application Checks and updates inventory Processes payment Arranges packaging Arranges delivery Database server tier: Oracle database stores customer, order, and inventory information

6. N-Tier as a Strategic Choice  What are the technical advantages of an N-Tier architecture?  What are the business advantages of an N-Tier architecture?  What are the drawbacks? …when compared to a “monolithic” (1- tier) solution

7. Service-Oriented Archtecture  Software packaged as reusable components instead of separate applications  These components become “business objects” that perform parts of a business process

8. Example: Package Tracking  USPS.gov  Amazon.com USPS.gov web site USPS tracking application Amazon.com web site USPS tracking application

9. The “S” in SOA  USPS.gov  Amazon.com USPS.gov web site USPS tracking application Amazon.com web site USPS tracking application What is the service? How would making this a service instead of a stand-alone application change its design?

10. SOA and/versus Web Services  Slightly different from “web services”  Web services are one example of how SOA can be implemented  A multi-tiered architecture could be considered a SOA  but it doesn’t have to be web-services

11. Rationale for Web Services  Standards  HTTP – Transportation of data  XML – Structure of messages  SOAP – Format of messages  What are the advantages of using web standards?  What if the USPS tracking application was a service but was proprietary?

12. SOA and Organizational Design  SOA can be a design philosophy for organizations  Example: Travel and expenses reporting  That re-thinking of organizational design informs the development of its software