1. © 2008 IBM Corporation Presenting Data Resources Last updated Nov. 14, 2008

2. © 2008 IBM Corporation 2 Note: This is complete rework of proposal entitled Presentation URLs from Resource URLs (Sep. 22, 2008)

3. © 2008 IBM Corporation 3 The Problem Most data resource will have XML-based representations These representations are not directly presentable to users Interaction with data resources requires client agent that understands data resource format and can present it in proper context What are mechanisms that permit data resources to be presented to users? What are mechanisms that permit user to navigate hyperdata links between data resources?

4. © 2008 IBM Corporation 4 Complicating factors Open-ended set of types of data resources –Unlimited –Even if all XML-based, lots of different schemas Custom data resource types –Resource types and their presentations need not be universal –E.g., customer-defined data resource types Hyperdata links could reference data resources anywhere on web –On same JTS –Off-world On different JTS On non-JTS server Modular clients –Client agents written with knowledge of only certain types of data resources Open-ended set of styles of presentations –Desktop applications –Web UIs –Composable widgets –…

5. © 2008 IBM Corporation 5 Complicating factors Hyperdata links from R to S –From representation of data resource R –To URL of data resource S Client agent authorized to access R might not be authorized to access S –S might live on different server from R Client agent that understands R might not be able to understand S representation –S might have data type arbitrarily different from R Client agent that presents R might not be able to present S –S might require different client agent to present than R

6. © 2008 IBM Corporation 6 Desideratum Desideratum: Client agent presenting data resource R containing hyperdata link to data resource S should be able to determine client agent for S without retrieving S Avoids key issues –Security issues with accessing S –Source client agent not able to understand schema for S representation Familiar examples of systems with this characteristic –Desktop apps – file type registry –How web browser handle media types

7. © 2008 IBM Corporation 7 System How desktop apps do it (for Open As… cases) X presenting R representation 1.X consults System for registry info 2.X chooses client agent Y based on type S – with possible user input 3.X hands over control to Y passing S 4.Y retrieves S Y presents S representation Meets desideratum – client agent X does it without retrieving S Source client agent X Target client agent Y RS 1 2 4 Registry 3 System = desktop OS Client agent = desktop app

8. © 2008 IBM Corporation 8 How web browsers do it X presenting R representation 1.X hands over control to System passing S 2.System retrieves S to discover its type 3.System consults registry and chooses client agent Y based on type S 4.System hands over control to Y passing S representation Y presents S representation Meets desideratum – client agent X does it without retrieving S Source client agent X Target client agent Y System RS Registry 1 2 3 4 System = browser Client agent = browser plug-in

9. © 2008 IBM Corporation 9 Approaches In our world client agent could be –Desktop application; e.g., DOORS client, RTC client, RRC client, … –Webtop application; e.g., RQM web UI, RTC web UI, … –Wigdet/viewlet; e.g., as in Telelogic Webtop, Jazz Web Dashboards –Web browser plug-in; e.g., Acrobat Reader, QuickTime –… (e.g., synopsis/hover help) Key design question: Does client agent X knows which client agent Y to use to present S? YES – Direct approach –Client agent X knows to use client agent Y to present S NO – Discovery-based approach –Client agent X must discover client agent Y to use to present S

10. © 2008 IBM Corporation 10 Preliminaries 2 handy techniques that proposal will use 1.URLs for launching webtop and desktop presentations 2.Embellishing references with information about referent

11. © 2008 IBM Corporation 11 Technique: URLs for launching webtop and desktop presentations URLs provide uniform mechanism for launching desktop and webtop apps –Used extensively in Telelogic CIA Use standard HTTP scheme for webtop app presentations Example URLs for webtop app presentations of http://eg.com/r1 –http://eg.com/present-requirement-r1.html –http://eg.com/show-requirement?url=http://eg.com/r1 –http://webui.eg.com/requirements/eg.com/r1 –http://webui.eg.com/u1656727243 Use non-standard schemes for desktop app presentations –A la “mailto” –Register URL handler with desktop OS when tool installed Example URLs for desktop app presentations of http://eg.com/r1 –doors:eg.com/r1 –rrc:?url=//eg.com/r1 Alternative to non-standard schemes –Run local server on desktop who’s job is to launch desktop apps –http://localhost:1555/applaunch?tool=doors,url=http://eg.com/r1

12. © 2008 IBM Corporation 12 Technique: Embellishing references with information about referent Example: Atom links “title” attribute (optional) – displayable string – for presenting link to user “type” attribute (optional) – advisory media type – hint about target resource Slight de-normalization of data –A bit of info about target resource is duplicated at each site of reference –Tradeoff Up front hint available on the cheap Onus on party creating link to supply duplicate info Duplicated info could become stale –Common in web world where deferencing a URL entails real work

13. © 2008 IBM Corporation 13

14. © 2008 IBM Corporation 14 Approaches 1.Direct approach 2.Discovery-based approach

15. © 2008 IBM Corporation 15 Direct approach Inspired by how blogs and Atom feeds work –Summary of investigation on separate slide deck [TBD – add hyperlink] Embellish hyperdata links with presentation URL “present” attribute (optional) – advisory client agent/home presentation URL –For opening home presentation in appropriate client agent Allows source client agent to DIRECTLY launch appropriate target client agent on target resource

16. © 2008 IBM Corporation 16 Direct approach X presenting R representation – user requests navigation to S 1.X hands over control to client agent Y (link “present” attr) passing S 2.Y dereferences S Y presents S representation Meets desideratum – client agent X does it without retrieving S Source client agent X Target client agent Y RS 2 1 Client agent = {desktop app, webtop app}

17. © 2008 IBM Corporation 17 Discovery-based approach Inspired by desktop OS file type registry JTS-based registry associating media types and client agents Embellish hyperdata links with advisory media type “type” attribute (optional) – advisory media type –For pre-selecting client agent/presentation based on expected media type Allows source client agent to DISCOVER and launch appropriate target client agent on target resource using information in registry

18. © 2008 IBM Corporation 18 System Discovery-based approach X presenting R representation – user requests navigation to S 1.X asks System for registry 2.X uses registry to - determine available client agents based on media type of S (link “type” attr) – with possible user input - choose chooses target client agent Y – possibly with user input - compute presentation URL for S and Y 3.X hands over control to Y passing S 4.Y dereferences S Y presents S representation Meets desideratum – client agent X does it without retrieving S Source client agent X Target client agent Y R S 1 2 4 Registry 3 System = Jazz Team Server Client agent = {desktop app, webtop app}

19. © 2008 IBM Corporation 19 Rule base Rule base is a set of selection rules Presentation type Provider label Provider ID Media type patternURL transformation function (input pattern -> output template) webJFS Web Client 1263application/oslcuser+xml http://{host}/{path} -> http://jf1/webui/user/{host}/{path} desktopRTC Client 7483application/oslcworkitem+xml;tool=rtc http://{host}/{path} -> rtc:{host}/{path} desktopRTC Client 7483application/oslcbuild+xml;tool=rtc http://{host}/{path} -> rtc:{host}/{path} webRTC Web Client 2662application/oslcworkitem+xml;tool=rtc http://{host}/{path} -> http://{host}/webui/workitems/{path} webBuildForg e Web Client 5242application/oslcbuild+xml http://{host}/{path} -> http://b1/show-build?//{host}/path} webRQM Web Client 9177application/oslctest+xml {url} ->http://rqm1.example.com/test&url={PercentEncode(url)} desktopDOORS Client 6321application/oslcrequirement+xml;tool=doors http://{host}/{path}-> doors:{host}/{path} desktopRRC Client 2233application/oslcrequirement+xml;tool=rrc http://{host}/{path} -> rrc:{host}/{path} desktopRRC Client 2233application/oslcrequirement+xml http://{host}/{path} -> rrc:{host}/{path}

20. © 2008 IBM Corporation 20 Selection rules Selection rule is declarative conditional expression Fields –Presentation type: desktop –Provider label: DOORS Client –Provider ID: 6321 –Media type pattern: application/oslcrequirement+xml;tool=doors –URL transformation: http://{host}/{path} -> doors:{host}/{path} –Roughly “The DOORS Client is a desktop application for presenting data resources with media type application/oslcrequirement+xml;tool=doors The data resource URL maps to a corresponding presentation URL by …”

21. © 2008 IBM Corporation 21 Client agent uses rule base to discover presentations Client agent uses a rule base to discover available presentations for given data resource Inputs –Data resource URL –Expected media type of data resource –List of presentation types of interest (e.g., just web presentations, desktop and web, widget, …) –Rule base Client agent determines applicable selection rules by matching entry type and media type pattern –More specific media type pattern trumps less specific Provider labels allow choices to be presented to user Provider IDs facilitate recording user’s selection for future use Client agent applies URL transformation function to map data resource URL to presentation URL

22. © 2008 IBM Corporation 22 Design Assumption Tool-specific tagging of media type –Assuming that tools will tag their resources’ media type with tool ID –E.g., necessary to ensure a requirement created in DOORS repository will be shown with DOORS client agent

23. © 2008 IBM Corporation 23 URL transformation functions URL-to-string transformations are described by input pattern and output tempate –E.g., function http://{host}/{path} -> http://jf1/webui/user/{host}/{path} input http://example.com/users/zoe output http://jf1/webui/user/example.com/users/zoe Simplest possible things that could possibly work –Simple –Flexible –Declarative – describing novel transform does not require adding code to server Note: Interesting information in data resource URL gets encoded in presentation URL –Should be reversible –Presentation provider should be able to reconstruct data resource URL from presentation URL

24. © 2008 IBM Corporation 24 Where does rule base come from? Jazz Team Server provides global Provider Registry Provider Registry is exposed though system-defined resource –Discoverable through other JFS discovery services Provider Registry representation is rule base in XML –Subelements for selection rules Selection rules –Largely contributed by JTS extensions at their install time –Tweakable by system administrator Requires high administrative permissions to update Requires low permissions to retrieve Provider Registry changes slowly Client agent can retrieve once and cache

25. © 2008 IBM Corporation 25 Limitations of proposed discovery approach Limitation of media type pattern matching –Inability to select based on info buried inside representation of resource –Cannot choose a provider based on requirements resource containing elements in a particular XML namespace –Puts premium on making good use of media types (true of web generally) Limitation of global rule base –Inability to select presentation based on project/process –Cannot choose a provider only for resources in a particular project/process –Potential challenge if we want to allow customer to dictate preferred presentations within a particular project/process Inherent JTS-centricity –Having to ask a JTS means it does not work without a JTS –Potential challenge for world envisioned by OSLC initiative

26. © 2008 IBM Corporation 26 Also considered HTTP content negotiation (Accept headers) –Only covers alternative representations of data resource –Cannot handle case where client must launch desktop app

27. © 2008 IBM Corporation 27 Direct vs discovery-based approach Both approaches have their strengths and weaknesses Direct approach + Custom data types +/- No opportunity for user input/influence - Single presentation style Discovery-based approach - Custom data types on another server + User input can influence choice + Multiple and third-party presentations + Multiple presentation styles – widgets, etc. Neither is better than other for everything

28. © 2008 IBM Corporation 28 Combining both approaches Source client agents should provide user affordances for “Open” and “Open As…” navigations for hyperdata links Direct approach for normal “Open” navigation –“present” attribute gives presentation URL –If none, use data resource URL as presentation URL (backstop presentation) –Bonus: Normal web URLs (i.e., ones that are not data resource URLs) work properly Discovery-based approach for “Open As…” navigation –“type” attribute gives advisory media type –If none, disable “Open As…”

29. © 2008 IBM Corporation 29 Additional capabilities Add-on capabilities to further enhance story 1.Web-based presentation chooser 2.Presentation selection service 3.Backstop presentations 4.Home presentation links

30. © 2008 IBM Corporation 30 Add-on: Web-based presentation chooser Web-based presentation chooser –Web page that lets user choose desired client agent for given data resource, media type, … –Hosted on a JTS - uses JTS’s Provider Registry –E.g., GET http://jf1.eg.com/chooser?url=http://eg.com/r1 –Typical response would be HTML page offering choices

31. © 2008 IBM Corporation 31 Add-on: Presentation selection service Presentation selection service –Additional web service that asks server to choose client agent for given data resource, media type, … –Encapsulates presentation selection algorithm on the server (a la earlier straw man proposal) –Hosted on a JTS - uses JTS’s Provider Registry –E.g., GET http://jf1.eg.com/present?url=http://eg.com/r1,type=app/oslcreq+xml –Typical response would be 3xx redirect to appropriate presentation URL http://eg.com/present-requirement-r1.html doors:eg.com/r1 http://eg.com/r1 http://jf1.eg.com/chooser?url=http://eg.com/r1

32. © 2008 IBM Corporation 32 Add-on: Backstop presentations Backstop presentations –XML-based representations of data resources –Should use type-specific XSLT stylesheet to provide backstop webtop presentation –Shows when data resource URL is entered in web browser address bar Example explained on http://moths.ca/jazz/http://moths.ca/jazz/

33. © 2008 IBM Corporation 33 Add-on: Home presentation links Home presentation links –XML-based representations of data resources –Should carry link to home presentation (when there is such a thing) –Gives backstop presentation (and others) easy way to hyperlink to home presentation Example explained on http://moths.ca/jazz/http://moths.ca/jazz/

34. © 2008 IBM Corporation 34 Summary of proposal Client agents should use direct approach for normal “Open” navigation Facilitated by –Hyperdata links embellished with presentation URL for target data resource Client agents should use discovery-based approach for “Open As…” navigation Facilitated by –JTS-based global provider registry with selection rules matching on media type –Hyperdata links embellished with media type for target data resource Further enhanced by –Web-based presentation chooser –Presentation selection service –Backstop presentations –Home presentation links