Tcl/Tk 2002

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Tcl/Tk 2002
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Ten Years of Rapid Development

• Mark Roseman
• University of Calgary
• TeamWave Software Ltd.
• Sonexis Inc.

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Welcome to AOL Digital City
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Yeah ok, maybe not.
Them
Us (not to scale)
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Benefit from the Pain of Others

• Tcl experience papers
• Range of systems
• Growing systems
• Development practices
• Soft issues

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In a nutshell

• Tcl/Tk good.

• Even for bigger systems.

• You can convince others of that.

• But it really helps if you know what youre
  doing!

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Todays Talk

• Development phases
• Prototyping (GroupKit)
• Desktop apps (TeamRooms/TeamWave Workplace)
• Web apps (various)
• Growing pains / solutions
• Tcl in the Hot Seat
• Integration, Configurability, Reliability, Scale
• Strengths, Misconceptions, Roadblocks

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Collaborative Systems

• Groupware
• Conferencing
• Highly interactive
• Networking
• Usability
• People issues

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When did you discover Tcl/Tk?

• 1992 _at_ U Calgary
• Prototypes - TK / BYO
• oops, better finish that damn thesis!
• Tcl-DP

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GroupKit

• Prototyping shared applications
• Internal/external use
• Lots of experimentation

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Tcl/Tk Benefits

• Learning curve
• Higher level programming faster
• Rich widget set
• Cross-platform

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Typical Prototyping Usage

• Prototypes, small apps
• Small number of developers, even novices
• Limited time
• Problems solvable more quickly and easily by
  individuals small groups.

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TeamRooms

• Real app
• Rooms
• Tools
• Client-server
• Cross-platform

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TeamWave Workplace

• Spin-off company
• 2-3 developers
• Rapid changes
• lt 50k loc

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So far so good

• Ad hoc development practices
• Coding style
• Modularity
• Testing
• Some bleeding-edge gotchas
• Some performance issues

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Onwards!
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Starting to Grow

• Modest financing
• 5-10 developers
• Moving to the web
• Users in education, virtual communities
• Download a deterrent

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Rewrite in Java?

• Keep code base (time to market)
• Client-side Java risky
• Still a small team, tight schedules
• Rapid change

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Proxy Tk
Users Workstation
Server
Tcl Application Code
Tcl Application Code
Tk API
Tk API
Tk Library
Proxy Tk Java Applet
Proxy Tk Library
OS Windowing System
AWT
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Get all that?

• Application code moves to server
• Still uses Tk API
• Tk implementation replaced by Proxy Tk
• Messages sent to Java applet on client
• Events sent from Java back to server

Tcl Application Code
Tk API
Proxy Tk Java Applet
Proxy Tk Library
AWT
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Web Site Management

• Application Service Provider model
• Manage accounts, rooms, scheduling
• Originally cgi.tcl
• Later AOLserver
• Centralized Metakit datastore

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Growing Pains

• Growing code base
• 90k loc Tcl, 35k loc C, 10k loc Java
• Ramping up new developers
• Tcl learning curve still okay
• Finding integration points
• Coding styles
• Breakage
• Not exactly a shock

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Software Engineering with Tcl?
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Development PracticesCoding Style

• Lots of advantages to using one
• Pick anything
• Tcl Engineering Manual / Style Guide
• Tcl code base as example

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Development PracticesModularity

• Namespaces, objects,
• Follow commands like file, string
• Toplevel parsing routine (entry point)
• Dispatch to other internal procedures
• Naming, variable access, etc.

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Development PracticesAutomated Testing

• Tcl excels here
• Benefits
• Tcltest
• Single language
• Other automation

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Development PracticesSummary

• Traditional approaches work well in Tcl
• This will slow you down (a bit)
• Better than the alternative!

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Tcl in the Hot Seat!
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Obvious Strengths

• Higher level programming
• Cross platform
• Easy licensing

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Common Misconceptions

• Tcl is unstructured
• Tcl is hard to hire for
• Tcl is unsupported

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Larger Systems Issues

• Integration
• Configurability
• Reliability
• Performance and Scalability

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Integration

• Glue
• Extensions
• COM
• Web services

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Configurability

• Adjust for different customers
• Feature sets
• Extensions
• Appearance changes
• Branding

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Reliability

• AOLserver ?
• Two language solution
• Application features in Tcl
• Core engine in C
• Multiple process model
• Easy in Tcl
• Fault tolerant

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Performance and Scalability
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Performance and Scalability

• AOLserver ? ? ? ? ? ?
• Monitoring performance
• Add telemetry
• Scalability test harness
• Migration to C
• Multiple processes (vs. threads)

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Scalability Results

• Approximately 1000 users
• 2500 Tcl interpreters!

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Many legal bills later
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Bottom Line

• Tcl worked for us
• From prototypes to robust/scalable commercial
  apps
• With Tcl, could take this work much further on
  fewer resources than if using conventional
  development tools.

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Pitfalls

• Interactive web applications
• Web site development
• Tcl best practices?
• Image problem?

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Still Great to be a Tcl Developer

• Core Tcl/Tk
• Tcllib
• Activestate
• Tclhttpd
• Metakit
• Tclkit/Starkit
• Wiki

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Shameless Plug

• CourseForum
• Wiki discussion for education
• Multiple areas, users, versions, tracking
• Ease of use
• Easy deployment
• Uses a little bitof Tcl

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Grab a Beta Version _at_ www.courseforum.com
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Summary
Tcl/Tk good.

• Even for bigger systems.

• You can convince others of that.

• But it really helps if you know what youre
  doing!

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Questions? Comments?Entertaining War
Stories?www.markroseman.com