Application Architecture T H E S O C R A T E S G R O U P, I N C.

T H E S O C R A T E S G R O U P Application Architecture (Logical computing view) Middleware Architecture (distributed computing connectivity) Application Architecture Distributed Data Architecture (distributed data access) Technology Architecture (Physical computing view)

T H E S O C R A T E S G R O U P PowerBuilder Smalltalk SQL C++ C COBOL Oracle Sybase VAX 3090 Security? Communications? Location? Tool-Based Architecture  Lots of tools with no clear way of making them work together...

T H E S O C R A T E S G R O U P Application Architecture  Business applications reside & execute within the Application Architecture  Business application developer needs to make fewer choices  Application Architecture provides a clear set of rules to decide what goes where  Business applications can be developed independent of network specifics

T H E S O C R A T E S G R O U P  Put all your eggs in one basket  Watch that basket very closely  Change is the enemy Mainframe Architecture

T H E S O C R A T E S G R O U P Mainframe Desktop Generic ServiceExample TerminalsTerminals CICSCICS IMS, DB/2, VSAM Presentation Services Transaction Services Data Management Services Business Services COBOL Applications Mainframe Application Architecture

T H E S O C R A T E S G R O U P Server Desktop Presentation Services Transaction Services Data Management Services Application Program Network Splitting the Application

T H E S O C R A T E S G R O U P Server Desktop Presentation Services Transaction Services Data Management Services Application Program A More Probable SplitNetwork

T H E S O C R A T E S G R O U P Database Server Business Process Server Application Program Desktop Presentation Services Data Management Services Transaction Services Application Program Network Multi-Tier Split

T H E S O C R A T E S G R O U P User Interface Services Business Process Services Data Access Services Client/Server Application Architecture

T H E S O C R A T E S G R O U P User Interface Services Business Process Services Data Access Services  Graphical or character-based Presumption today is GUI  Visual presentation & navigation  Data input & validation  Initiates requests for remote services  Includes everything that executes on the desktop: Personal productivity tools Data access tools Client applications Development tools User Interface Services

T H E S O C R A T E S G R O U P User Interface Services Business Process Services Data Access Services  Accepts requests for business services  Common business processing logic  Data integrity  Defines transaction boundaries  Makes requests for data access/update Business Process Services

T H E S O C R A T E S G R O U P User Interface Services Business Process Services Data Access Services  Accesses data  Updates data  Data may be: Local to this computer Stored in remote computer(s)  Many forms of data: Databases File systems Remote data feeds Data Access Services

T H E S O C R A T E S G R O U P User User Interface Services Business Process Services Data Management Services Operating Platform Services Enterprise Connectivity Services Data Access Services The Services Model™

T H E S O C R A T E S G R O U P User UI Services Business Process Svcs Data Management Services Operating Platform Services Enterprise Connectivity Services Data Access Services Enterprise Connectivity Services  Primary Service: Inter-Process Communication (i.e. messages)

T H E S O C R A T E S G R O U P Operating Platform Services  Primary Services: Program Execution services Device & File I/O User UI Services Business Process Svcs Data Management Services Operating Platform Services Enterprise Connectivity Services Data Access Services

T H E S O C R A T E S G R O U P Data Management Services  Primary Services: Complex data access & update Data integrity Distributed data synchronization User UI Services Business Process Svcs Data Management Services Operating Platform Services Enterprise Connectivity Services Data Access Services

T H E S O C R A T E S G R O U P Enabling Layers Enabling Layers  The bottom three layers enable the execution of distributed applications User UI Services Business Process Svcs Data Management Services Operating Platform Services Enterprise Connectivity Services Data Access Services

T H E S O C R A T E S G R O U P Solution Layers  The top three layers enable the creation of distributed applications User UI Services Business Process Svcs Data Management Services Operating Platform Services Enterprise Connectivity Services Data Access Services

T H E S O C R A T E S G R O U P Glue Layer UIS BPS DAS NOS LAN DMS The Glue Between The Layers  Distribution models all imply ability to break application processing into multiple distributed processes.  Glue layers allow process distribution.  To work effectively, the glue must be very simple to apply

T H E S O C R A T E S G R O U P NOS LAN NOS LAN NOS LAN DMS NOS LAN DMS DAS BPS UIS Glue Layer Glue Allows Process Distribution

T H E S O C R A T E S G R O U P User User Interface Services Business Process Services Data Management Services Operating Platform Services Enterprise Connectivity Services Data Access Services Glue Layers Glue is called “Middleware”

T H E S O C R A T E S G R O U P Distributed Layers  The enabling layers must be present on all participating systems  The expressive layers may be distributed to two or three tiers  Six models to consider: Stand-Alone Remote Terminal Remote File Remote Data Remote Process Distributed Process UIS BPS DAS Tier 1Tier 2Tier 3 OPS ECS DMS OPS ECS DMS OPS ECS DMS

T H E S O C R A T E S G R O U P Exercise—Model the Models  The next six pages of your notes contain models of various application architectures  Break into small groups and take 1/2 of a sticky wall  Use the sticky wall, the index cards and the marker pens to create each of these models on a sticky wall  Give examples of this model  Discuss & identify the strengths and weaknesses of each of these models  Use the notes page below the model to record the strengths and weaknesses of each model

T H E S O C R A T E S G R O U P DMS UIS SAOS none BPS DAS Stand-Alone Model  No remote processing or access  Stand-Alone OpSys has no remote capabilities

T H E S O C R A T E S G R O U P DMS UIS MUOS Term BPS DAS Remote Terminal Model  Centralized processing managed by multi- user OpSys  All access by remote terminals  No processing done at terminals

T H E S O C R A T E S G R O U P NOS LAN DMS UIS NOS LAN BPS DAS Remote File Model  All application processing performed locally  File I/O performed remotely by Network OpSys

T H E S O C R A T E S G R O U P Optional DAS NOS LAN DMS UIS NOS LAN BPS DAS Remote Data Model  User interface, business process and data access logic performed locally  Some data access may be performed close to database e.g. Database procedures  Data management performed remotely  Also known as “Fat Client” model

T H E S O C R A T E S G R O U P BPS DAS NOS LAN DMS UIS NOS LAN Remote Process Model  BPS and DAS performed on same server as DMS  Implies heavy use of Database Procedures layer  Also known as “Fat Server” model

T H E S O C R A T E S G R O U P NOS LAN DMS DAS NOS LAN DMS BPS DAS NOS LAN DMS UIS NOS LAN Distributed Process Model  Business processes performed on middle tier  Data access can be performed on 2nd or 3rd tier  DMS can be on any server… even one with no BPS

T H E S O C R A T E S G R O U P Discussion Each small group:  Give examples of each model  Describe the strengths & weaknesses of each model  Compare the models  What did you learn from this exercise?

T H E S O C R A T E S G R O U P Data Validation vs. Integrity Checking  What is the difference between: Data input and validation rules Business process & data integrity rules  Why must we distinguish between them?  Why will some rules be implemented twice?

T H E S O C R A T E S G R O U P Fat ClientFat ServerDistributed Process Server Desktop DAS DMS BPS DAS UIS Desktop Server UIS BPS DAS DMS Server Desktop DAS DMS UIS BPS Where does validation logic belong in each of these models? Where Does Validation Belong?

T H E S O C R A T E S G R O U P The Rules!  Code in the UIS layer exists only to enhance user productivity  Rules which must be true about the data reside in the Data Access Services layer(s)  Rules which express decisions made as a part of performing business transactions reside in the Business Process Services layer(s)  DAS rules have precedence over BPS rules  BPS & DAS rules have precedence over UIS rules

T H E S O C R A T E S G R O U P Power- Builder SQL Smalltal k VAX 3090 C++ C COBOL Sybase Oracle Abstract Architecture  An architecture provides the conceptual framework that holds everything together.

T H E S O C R A T E S G R O U P Client Applications Accounting Inventory Employee Sales Reusable, redundant BPS and DAS services located on servers SI: GLSI: APSI: ARSI: Inv SI: Emp EmpSalesAPARInvGL SI: InvSI: SalesSI: ARSI: Emp Enterprise API  The enterprise API is the collection of all SI’s which provide business services  Enterprise API is about the server API

T H E S O C R A T E S G R O U P User Interface Svcs Data Access Services Data Management Services Operating Platform Services Enterprise Connectivity Services Business Process Services Glue Infrastructure Building The Enterprise API  The Enterprise API is: The foundation for user’s applications The repository for business services and data Application Software

T H E S O C R A T E S G R O U P Application Architecture Summary  Having an Application Architecture simplifies client/server development  Determines what code performs which services  Facilitates business process reuse  Simplifies client application development  Assures data integrity  Reduces risk of project failure