Anywhere Access to Data

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Anywhere Access to Data

• Markus Egger
• President, EPS Software Corp.
• Publisher, CoDe Magazine

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About Me

• Markus Egger
• President and Chief Software ArchitectEPS
  Software Corp.
• Publisher CoDe and CoDe Focus Magazines
• International Author and Speaker
• Microsoft MVP C
• Tablet PC Influential

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Todays Agenda

• Accessing File-Based Data
• Synchronization Manager for Offline Data
• Data Access Scenarios
• Data Access Architecture for Anywhere Access
• Accessing Data in Databases
• Client-Side Caching
• Service Oriented Architecture
• SQL Server and SQL CE
• ADO.NET

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• Accessing File-Based Data
• Markus EggerEPS Software Corp.CoDe Magazine
• markus_at_eps-software.com

5
File-Based Data Scenarios

• File-based almost always means accessing files
  either on a local drive or on a local network
  share.
• Note Technologies for distributed file access
  are available (and can be implemented manually),
  but we are not concerned with these technologies
  in this talk.
• For distributed scenarios, files generally have
  to be synchronized for offline consumption.
• Microsoft provides everything needed for offline
  file caching and synchronization on computers as
  well as mobile devices.

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Synchronization Manager

• Centralized, standard technology for
  synchronizing files for offline use.
• Files are synchronized independently of the
  protocol.
• Intended for applications that run primarily on
  mobile computers.
• This technology is not just for files!
• More about that later

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Mobile Computing Configurations

• Synchronization Manager is useful for computers
  configured as follows
• Mobile computer in docking station but
  occasionally used over a dial-in connection.
• Mobile computer used mostly over a dial-in
  connection.
• Desktop computer used strictly over a dial-in
  connection, such as a computer used by a
  telecommuter.
• Desktop computer used strictly over a high
  bandwidth network.

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Application Scenarios for Synch Manager

• Microsoft Office applications that need to
  prepare files for offline use.
• Client-side caching that lets you cache files
  locally.
• Browsers that can cache HTML pages locally.
• Mail programs that can cache e-mail messages
  locally.
• Databases that can store information locally.

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Synchronization Manager Architecture

• End user can
• Schedule applications for synchronization.
• Set up automatic synchronization to occur in
  conjunction with specified system events.
• Programming interface can
• Enable applications to register for
  synchronization features.
• Process errors.
• Receive progress information and notifications
  during the synchronization process.

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Programmable Interface

• To use the Synchronization Manager
  programmatically, you must implement COM
  interfaces
• Your object must implement
• ISyncMgrSynchronize
• ISyncMgrEnumItems
• SyncMgr implements
• ISyncMgrSynchronizeCallback
• ISyncMgrSynchronizeInvoke

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Longhorn Application Sync

• Centralized and consistent sync experience for
  applications, services, and devices.
• Users are in control.
• Clear what is being synchronized to and from the
  computer.
• Consistent experience for status, errors, and
  conflicts.
• Frequent synchronization tasks at most two clicks
  away.
• Synchronization is not obtrusive.

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Longhorn Synchronization Manager
XP Sync Man
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• Database Scenarios
• Markus EggerEPS Software Corp.CoDe Magazine
• markus_at_eps-software.com

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Data Access Scenarios

• Applications must work well in LAN scenarios.
• Basically, all types of applications support
  basic networking.
• Applications must work in distributed scenarios.
• ASP.NET Web applications are an obvious choice
  here.
• Smart Client applications now also work well over
  protocols such as HTTP.
• Applications must work in disconnected or
  partially connected scenarios.
• Smart Client applications (running on various
  devices or operating systems) are the only choice
  here.

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Data Access Goals

• Top priority Create an application that can be
  used anywhere and any time.
• Create an architecture that can be used in many
  scenarios and over an extensive period of time.
• The architecture needs to be OS-independent and
  device-independent.
• The architecture should carry us well into new
  operating systems and device generations.
• Applications should also support flexible
  deployment scenarios.

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Therefore Smart Clients Rule!

• Smart Client applications cover all the different
  scenarios and goals.
• Smart Client applications are great for known
  permanent users.
• These are users that are known to us and use our
  application extensively.
• We may supplement Smart Clients with HTML-based
  Web applications.
• These are great for occasional users and
  public users.
• We need to make sure our data access strategy
  works well in this scenario too.

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Architectural Overview
Database(SQL Server) Business Logic(The
App) User Interf. ServiceInterface
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Core Application Architecture
Deployment Boundary
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Data Access Architectural Goals

• Disconnected from database
• Flexible access to different back ends
• Automatic failover when needed
• Simple usage approach (for developers)
• Easy to extend

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Data Access Architecture

• Note A production implementation will probably
  feature a lot more methods.

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Implementing the Data Service
Markus EggerEPS Software Corp.CoDe
Magazine markus_at_eps-software.com
23
Data Service Recap

• Abstracted object that takes care of the details
  of talking to a database
• Instantiated by a Factory object
• Can be extended through fundamental interface
  (IDataService)

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Business Object Architectural Goals

• Scalability
• Database Independence
• Simple to Use
• Simple to Program
• Stateless
• Reusable

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Business Object Architecture
Business Object
GetList( )
IBusinessObject
Verify( )
Save( )
GetList( )
GetSingleRecordByPK( )
Verify( )
GetInstance( )
Save( )
GetSingleRecordByPK( )
CustomerBO
OrderBO
XyzBO
GetCustomersByCompanyName( )
GetOrdersByCustomerID( )
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Implementing the Business Object
Markus EggerEPS Software Corp.CoDe
Magazine markus_at_eps-software.com
27
Business Object Recap

• A fundamental business object (BO) implementation
  provides default functionality.
• New BOs can be easily created by subclassing the
  base implementation.
• A generic interface provides great flexibility.
• Static GetInstance() helper provides great
  deployment flexibility.
• Abstract away all access to the data layer!

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Related Topics

• Security refresher
• SQL Injection!
• Use Stored Procedures and Parameters!
• Execution rights and CAS
• Make sure your distributed access is secure
• Replay attacks, data interception, command
  interception, data tampering,

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Related Topic DataSets

• Topic of heated discussion -)
• DataSets provide lots of functionality, but
• They are not always efficient.
• Think, for example, of serialization.
• Who knows? They might change in the future.
• Strongly typed DataSets provide type-safety and
  compile-time verification.

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DataSets (continued)

• Custom data objects can be strongly typed and
  more efficient, but they are more work.
• Custom data objects provide full control (for the
  developer) and independence from potential .NET
  Framework changes
• My recommendation combine the two approaches!
• Create a custom wrapper for DataSets.
• Wrappers provides strong typing and other
  functionality.
• Since the DataSet is not exposed, you can always
  change these implementation details.

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• Implementation Details
• Markus EggerEPS Software Corp.CoDe Magazine
• markus_at_eps-software.com

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Different Data Services

• LAN data services simply access local database
  instances and servers.
• Distributed data services perform the same basic
  task, but have to use in between technologies
• Web Services
• Remoting
• Isnt that outdated?
• No, not really, but it needs to be handled as a
  replaceable technology.
• Microsoft Code Name Indigo

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Different Data Services (cont.)

• Offline Data
• Needs to store data in a local database such as
  MSDE or SQL CE.
• XML can be used as a poor mans database.
• Offline copies of data can be created
  automatically when data is accessed.
• The Synchronization Manager can be used to
  trigger and handle synchronization.

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Offline Update Scenarios

• Upload scenarios can get tricky!
• Database applications tend to be more
  interconnected than applications such as Outlook.
• Example Updating one item (address) can change
  other data (shipping fee on an unprocessed
  invoice).

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Offline Update Scenarios (cont.)

• Often, local data needs to duplicate almost all
  server-side structures and referential integrity
  as well as business rules (checks and
  processing).
• Sometimes additional consideration needs to be
  given to business scenarios that are unique to
  the offline-cache situation.
• Applications may need to handle a special
  unprocessed state for items that may still have
  to change or may not yet have triggered other
  actions.

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• Case Study Outlook 2003
• Markus EggerEPS Software Corp.CoDe Magazine
• markus_at_eps-software.com

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Outlook 2003

• Major re-write of the application
• Builds on
• Cached Exchange
• Improved Synchronization
• Conflict Resolution
• RPC over HTTP
• PST/OST Enhancements

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Cached Mode Shields Users From Network
Conditions

• Outlook runs against a local copy of the users
  mailbox (OST).
• Uses the Offline Address Book (OAB) for basic
  addressing functions .
• The OST and OAB are automatically kept in sync
  with server.
• Classic Online features are available
  (Calendaring, Public Folders, Delegate Access).

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Cached Mode Uses Improved Synchronization

• Fewer bytes over the wire and less roundtrips
• Bi-directional data compression
• Increased buffer sizes
• Partial item upload
• These changes plus others yielded 50 reduction
  in BoW
• More robust synchronization
• Check-pointing
• Skip bad item
• Deliver most important data first
• Synchronizations initiated on user navigation
• Most recent items first (LIFO) within a folder

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Cached Mode Handles Connectivity Changes

• Outlook just keeps working when the network goes
  away.
• Few annoying error messages
• Users data is available
• User can create new items and modify existing
  items
• Outlook automatically re-connects to the Exchange
  server.

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Cached Mode Bandwidth Aware

• On fast networks
• Downloads full items on all folders and address
  book updates.
• On slow networks ( lt 128 Kb)
• Synchronizes only headers on all folders.
• Headers small but contain sufficient information
  to render views.
• Users can triage their mail download important
  messages and delete junk mail.

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Questions?

• Feel free to send me email!
• Markus Egger
• EPS Software Corp.
• CoDe Magazine
• markus_at_eps-software.com

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MEDC Mobile PC Talks

• CLI204 - Tablet PC Development Overview
• Speaker - Dave Hale
• Time Tuesday 5/10 1130 AM
• CLI208 Anywhere Access to Data
• Speaker Markus Egger
• Time Tuesday 5/10 300 PM
• CLI324 - Advanced Tablet PC Development Topics
• Speaker Todd Landstad
• Time Wednesday 5/11 800 AM
• CLI325 - In Depth - Ink Data Management
• Speaker Stefan Wick
• Time Wednesday 5/11 930 AM
• CLI329 - Network Awareness
• Speaker Dr. Neil Roodyn
• Time Thursday 5/12 800 AM

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Mobile Hands On Labs at MEDC

• Building Network-Aware Mobile PC Applications
• Build a network-aware application using the
  Windows Network Location Awareness (NLA) API.
• Building Power-Aware Mobile PC Applications
• Learn how to tune your applications to save
  power, extend battery life, and enhance the
  user's mobile PC experience.
• Building Managed Applications with Microsoft
  Windows XP Tablet PC SDK
• Create a cool Tablet application using the
  Windows XP Tablet PC Edition SDK 1.7.

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The Tablet and Mobile PC Developer
Center http//msdn.microsoft.com/mobilepc
46
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