Transcript Smart Clients

Smart Clients
What, Why, and Where
By: Richard Arthur
Smart Clients Defined
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Best programming benefits of
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Windows applications
Web applications
Benefits are
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Smaller footprint
Richer interaction
More robust code
Easier deployment
Consistent updates
Centralized data stores
Motivation: Web
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Benefits of Web Sites
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Easier deployment
Easier upgrades
Ubiquitous access
Centralized data stores
Drawbacks of Web Sites
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Managing scale
Less-interactive
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HTML – even with JavaScript, it is not great
Stateless
Session management
Limited access to local resources
Motivation: Windows
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Benefits of Windows Applications
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Richer interactions within the application
Faster performance
Better use of local resources
Can be run when disconnected
Drawbacks of Windows Applications
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DLL Hell
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Installation and upgrade headaches
Larger installations
“Heavy Footprint” – consumes more resources
Nifty Graphic
http://msdn.microsoft.com/smartclient/understanding/definition/default.aspx
Groups of Smart Clients
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Windows
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MS Office
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Full-blown stand-alone applications
Applications use Office for data management
Mobile
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Handhelds use Web Services
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store and manipulate data
MS Office?
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Source of confusion
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Developers got a little trigger-happy with “Smart Client” term
Employs many design principles of Smart Clients
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Outlook
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Excel
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works disconnected
Easy to update deployed spreadsheets
Centralize data and reference it
Use Web Services
Word
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Easy to update deployed documents
Centralize the data and reference it
Use Web Services
Existing Applications
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Where are smart clients today?
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AOL/MSN Messenger
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Virus Scanners
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Contact list is centralized
Customizations are stored locally
Seamless application updates
McAfee stores local DB of viruses
Regularly updates itself
MS Passport
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Centralized storage of Credit Card info
Data shared across web sites
Target Environments
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Corporate environments
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Lots of users
Central/shared data stores
Frequent or important updates
Know OS/Environments
Home environments
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Data duplicated/shared across several machines
Frequent or important updates
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Bug fixes
New features
Considerations For Implementing
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Consider Smart Clients when your code
can/may:
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Replicate data across several applications
Data should be centralized for all users
Application needs desktop resources to work
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Needs more power than web apps can provide
Application needs connectivity
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Can do without it for a while
Facilitating Smart Clients
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.NET Framework
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Overcoming DLL Hell
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Overcoming large footprint
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Version conflicts
“XCopy” deployment
“No-Touch” deployment
Many assemblies already exist on client machines
Intermediate code is inherently smaller
Visual Studio .NET 2005
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Overcoming Deployment/Upgrade issues
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ClickOnce technology
XCopy Deployment
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Old DOS tool for copying several files at once
No registry needed
Some drawbacks
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You may need data pre-installed to the registry
You may need data pre-installed outside the install
directory
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User data should go in the UserAppDataPath directory
No transacted installs
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Currently provided by the Windows Installer
No-Touch Deployment
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Post to Web/Shared Server
Runs from the download location
Downloads assemblies on demand
Drawbacks:
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Unreliable offline functionality
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May not have the latest DLLs
DLLs might be cleaned up by IE
Apps can run in “offline” mode only when IE is in
offline mode
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Same DLL problems as mentioned above
More No-Touch Problems
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Runs in “sandbox”-like environment
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No access to
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Global Assembly Cache (GAC)
Unmanaged code
Registry
Windows Shell
Any Files – except for “Isolated Storage”
Databases
Other Applications
Web Sites other than the originating server
Major Design Considerations
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Several areas must be considered
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Data
Network
Security
Deployment & Upgrading
See: http://msdn.microsoft.com/smartclient/default.aspx?pull=/library/enus/dnpag/html/scag.asp for greater details
Data Considerations
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Central Store
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Access from several locations
Share between different users
Local store
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No need to share
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Store locally for the application
Need to be disconnected
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Update regularly: prevent stale data
Update asynchronously: allow interaction while
updating
Networking Considerations
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When connected
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What will you let your users do?
Limit network “chatter”
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When disconnected
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Make it look fast, ensure completion later
Improves performance (real & perceived)
Use a data store to allow continuous operation
Managing updates when reconnected
Handling dependencies (key-based relationships)
When interrupted
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Detecting interruptions to Network service
Recovering from interruptions
Ensuring no data corruption
Security Considerations
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Trust No Data!
On the server:
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Authenticate and Authorize all requests
Always double-check the data
SSL Encryption is good, but still a stop-gap
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On the client:
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Centralize server access
Write consistent code
Write hole-free code
Manage resource permissions properly
Validate all the data
Authenticate and Authorize all incoming data
Read “Writing Secure Code” (ISBN:0735617228)
Deployment Considerations
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Make sure all clients have the .NET Framework
OneClick
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No-Touch
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Easier to maintain and upgrade
Not available with .NET Framework 1.1
Easy to maintain on the server
Harder to maintain on the client
Windows Installation Package
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Easy for developer to maintain
Harder to upgrade the application
May combine with OneClick
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Download and automatically install periodic updates
Thank You
Questions?