Offline-Enabled Data Services And Desktop Applications

1. TL08 Offline-Enabled Data Services And Desktop Applications  Pablo Castro Software Architect Microsoft Corporation

2. Agenda • Why • The problem space • What • The developer experience • How • A look at the details • When • Standard roadmap drill

3. Why: Motivation • Why “offline” • Access to a service may not be always available • Bandwidth may not be enough/too expensive • etc. • Why “data services” • We have sync technology for databases, but… • Lots of data now sits behind a service boundary • We can layer more data capabilities on services with a uniform interface

4. Application Scenarios • Offline-capable applications • Microsoft Outlook-style applications • Service is typically domain specific, includes business logic • Application speed-up/bandwidth usage • Cache service data locally for fast processing • Could be a general purpose data service • Closed-system versus external services • Service side may be a 3rd party service

5. What: Taking Services Offline • Project Codename “Astoria Offline” • End-to-end solution • Visual Studio integrated experience • Sync APIs, algorithms, formats, protocols • Modeled at the level of conceptual “entities” • Client and service environment setup • Sync-enable database schemas • Generate sync-enabled clients • Maintains an open interface

6. Application Model Online clients can consume service Sync-enabled service Sync in the background 1-tier client application Local schema follows service

7. Sync-Enabling a Service • “Piece of cake” scenario • Relational database through Entity Framework • Augment the database with sync information • Add sync-related elements to metadata files • Enable synchronization in the service itself • You can also do everything manually

8. Creating Sync-Enabled Clients • Client-side “piece of cake” flow • “Add service reference” will prompt if the server is sync-enabled • Download service metadata • Create local Compact database • Setup Entity Framework data-access layer • Add sync support to both database and Entity Framework • Can also use the building blocks independently

9. Building On Existing Technology Data Services Framework: RESTful data services Regular Desktop/Server application Sync Framework Sync Framework Entity Framework: local data access Entity Framework: Model & Data Access Data source extensibility Local store: SQL Server Compact Database:SQL Server

10. Typical Requirements • Business logic • Server: Query and change interceptors • Client: Usual UI interaction, plus sync events • Conflict detection and resolution • We’ll precisely detect conflicts • You provide resolution handlers • Incremental synchronization • Batching & dependency management • Choosing which data to sync • Scopes

11. Security Aspects • Authentication • ASP.NET authentication model applies • Built-in Windows, Forms auth • Modules for Basic and custom schemes • Authorization • Query/change interceptors on the server • Use ASP.NET roles or custom code

12. How: The Details • Synchronization Strategy • Interaction model • Database schema requirements

13. Synchronization Strategy • Follow the Microsoft Sync Framework way • Multi-master replication • Peers make changes independently • Sync makes peers aware of all changes • Reliable, precise conflict detection • Minimize over-enumeration

14. Basic Concepts • “Scope” • All things you want to synchronize • “Version” • A change is tagged with “who” and “when” • “Knowledge” • Concise description of the set of changes that a peer is aware of • Can be understood by any peer • Main operations on knowledge • Test if a given knowledge covers a given change • Add one piece of knowledge to another to produce combined knowledge

15. 1. Request changes 3. Send changes 2. Enumerate Changes 4. Apply Changes Interaction Model • Request changes based on A’s knowledge • Enumerate changes in B: Is B’s version covered by A’s knowledge? If not, send • Send changes: Version of change, B’s knowledge • Apply Changes: Is A’s version covered by B’s knowledge? If not, there is a conflict A B

16. Data Store Requirements • Per-scope • A place to put knowledge in (1 row) • Per-entity • Creation version (node, tick count) • Modification version (node, tick count) • Globally unique Sync ID • Deletion markers

17. Sync Metadata In Entity Framework • Default strategy used by Visual Studio • Side tables for sync version information • Columns in user tables (timestamp x 2, syncid) • Delete trigger for deletion markers • Gets better with Compact and SQL Server 2008 • Can be completely replaced • We define an “API” in terms of entry points • Encapsulated in Entity Framework metadata files

18. When: Roadmap To "Astoria Offline" • Alpha preview release before end of year • We’ll ship CTPs as we make progress • What we want to take on • v1: core protocol/service support in place, great tooling • Later: first-class devices support, more application services, scenarios for synchronization other than offline

19. We'd Love To Hear From You • We are following our “transparent design” process • Design notes posted in the Astoria Team blog • http://blogs.msdn.com/astoriateam • Feedback is welcome, the earlier the more likely we can incorporate it • You get to see team members in an awkward setting trying to explain features in videos

20. Summary • “Astoria Offline” enables applications to take data from services offline • Work while disconnected • Speed and bandwidth optimizations • End-to-end solution • Tools, runtime, database support • Starts easy, incrementally customizable • Builds on existing technology for data, services and synchronization

21. Resources • Blogs • Astoria team http://blogs.msdn.com/astoriateam • Minehttp://blogs.msdn.com/pablo • @ MSDN • Data: http://msdn.microsoft.com/data • Sync: http://msdn.microsoft.com/en-us/sync/default.aspx • @ PDC • TL30 Microsoft Sync Framework Advances • TL07 Developing Applications Using Data Services • TL20 Entity Framework Futures

22. Q&A Please use the microphones provided

23. Evals & Recordings Please fill out your evaluation for this session at: This session will be available as a recording at: www.microsoftpdc.com

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