INF 123 SW ARCH, DIST SYS & INTEROP LECTURE 2 Prof. Crista Lopes

Objectives  Present the course – take 2  Introduction Recap of Architecture

INF 123 in Context  Formerly ICS 123, same title and purpose  Taught it 3 years in a row, ICS students  Focus on applied architectures and protocols  Renumbered INF 123 for Informatics program  Prof. Taylor took over, Software Architecture book  Course materials largely drawn from book  Focus on general concepts  Now  Back to me  ???

INF 123, S10: The Final Deal  Focus on applied architectures and protocols  Link to general concepts that you already know  Projects: OpenSimulator framework  3D application server, MMO Virtual Worlds  C# (.NET or mono)  ~500,000 LOC  1,000s of users    “Diva”  Watery Break: World BuilderWorld Builder

Recap on Architecture

Definition: Architecture  “Set of principal design decisions”  “Design decision” implies design options  Not all design decisions are architectural in nature “principal” depends on Goals Perspectives  Design decisions may change over time  Architecture may change over time  Two fundamental points  Every system has an architecture  Every system has at least one architect

Definition: Component  “Architectural element that (1) encapsulates a subset of the system’s functionality and/or data; (2) restricts access to that subset via an interface, and (3) has explicitly defined dependencies on its operational context.”  E.g. database, Web server, jar/dll files with specific functionality, …

Definition: Connector  “Architectural element tasked with effecting and regulating interactions among components.”  Most common: DB connectors  Perhaps the less understood and most powerful concept for engineering extensible systems, especially when coupled with the concept of plugin

Definition: Configuration  “Set of concrete associations between components and connectors”

Definition: Architectural Style  “Named collection of [architectural] design decisions”  i.e. Architecture with a name

Definition: Architectural Model  “An artifact that represents most or all of the architecture.”  Notation: “Language or means of capturing that representation”  E.g. UML, PowerPoint bullets, sketches, etc.

Where is “Software”?  Read the definitions again. Is it there?  These are general concepts in artifact creation, too general to draw meaning between creative activities  Buildings (architecture)  Cars (design)  Furniture (design)  Medical instruments (engineering)  Music (composition)  Computers (engineering)  Institutions (design)  …  Software (design/architecture/engineering) Software Architecture ≠ Buildings Architecture ≠ Car Design …

“Architecture” in software systems  Software architecture  System architecture  Deployment architecture  Testing architecture  Usability architecture  …  These are all different aspects of the same system  All creative activities, all different  Must qualify the word “architecture”

Web Usability Architecture

Web Deployment Architecture

Web System Architecture

Apache HTTPD Software Architecture

“Architecture” in software systems  Software architecture: set of principal design decisions regarding the software itself  System architecture: set of principal design decisions regarding the system’s concepts and operation  Deployment architecture: set of principal design decisions regarding the mapping between software and hardware  Testing architecture: set of principal design decisions regarding the testing procedures and tools  Usability architecture: set of principal design decisions regarding the user experience

Overview: OpenSimulator

Usability Architecture: The VW operators perspective Simulator (OpenSim.exe) Simulator (OpenSim.exe) Configuration (OpenSim.ini) Configuration (OpenSim.ini) ROBUST Services (OpenSim.Server.exe) ROBUST Services (OpenSim.Server.exe) Configuration (OpenSim.Server.ini) Configuration (OpenSim.Server.ini) Client (Hippo, etc.) Client (Hippo, etc.) Client (Hippo, etc.) Client (Hippo, etc.) … DB …

Deployment Architecture(s) Simulator DB Standalone Simulator DB ROBUST Services ROBUST Services Grid Simulator DB Serverless Grid Simulator

System Architecture Asset Service Asset Service Authentication Service Authentication Service Avatar Service Avatar Service Voice Service Voice Service Gatekeeper Service Gatekeeper Service Grid Service Grid Service Grid User Service Grid User Service Inventory Service Inventory Service Login Service Login Service Presence Service Presence Service User Accounts Service User Accounts Service User Agents Service User Agents Service Physics Engine Script Engine Scene Management Client Protocol Stack Client Protocol Stack Client Protocol Stacks Client Protocol Stacks Module Loader Module Loader HTTP Handlers HTTP Handlers …… Service Infrastructure Simulator C# HTTP Server C# HTTP Server LibOMV ODE log4net Mono Addins Mono Addins MySql SQLite Open JPEG Open JPEG … External Dependencies DB Service Connectors

System Architecture  Previous picture is incomplete  Important parts missing:  Protocol descriptions Login protocol Teleport protocol Instant Messaging Protocol …  Security Permissions Authorization …  Extensibility features

Software Architecture Framework Framework. Servers Framework. Servers. HttpServer Framework. Servers. HttpServer Region. Framework Region. Framework Region. Framework. Scenes Region. Framework. Scenes Region.Framework.Interfaces Region. CoreModules Region. CoreModules Region. Physics. Manager Region. Physics. Manager Region. Physics. ODE Region. Physics. ODE … Services.Interfaces S S S S S S …

Main Points  Many architectures, not just one!  Main focus of this course:  Well-known software system architectures  Secondary focus:  “Good” software architectures

“Design” and “Implementation” and “Documentation”  The objective is to create machine-executable source code and an explanation for it  Where do you start? Option a) Think hard and long, document, then write the code Option b) Write the code, make it work, code is documentation Option c) Think, write, think, write, think, write, … Option d) Write, think, write, think, write, think, …  In all cases, there will be architectures

Where is “Software”?  Read the definitions again. Is it there?  These are general concepts in artifact creation, too general to draw meaning between creative activities  Buildings (architects)  Cars (designers)  Furniture (designers)  Medical instruments (engineers)  Music (composers)  Computers (engineers)  Institutions (leaders)  …  Software (lead architects/designers/engineers)

Software Lead Architects/Designers/Engineers  “jack of all trades”  Maintainer of system’s conceptual integrity  Part of team  Set of people with complementary skills  Committed to common Purpose Performance goals Approach  Hold each other accountable  Life is long series of locally suboptimal decisions made partly in the dark  Sometimes painful

Skill Set  Long software development expertise  Domain expertise  Communicator  Strategist  Leader  Technologist  Cost estimator  Cheerleader  Politician  Salesperson

Skill Set (from the book)  What architects are usually not in a project  Developers – though they may prototype their ideas (they are developers! – very experienced ones)  World-class software programmers (they need to be the best around)  Managers – except in small organization