Virtual Directories

I’ve talked to a couple of companies now that sell virtual directory products.  Most recently, I talked to Identyx, a company recently bought by Red Hat to enhance their directory product offerings. A virtual directory is software that looks like a directory (typically, an LDAP one) but doesn’t actually store any data. Whenever a request comes in, the virtual directory retrieves the requested data from one of several configured data sources. A virtual directory can “front” an existing LDAP directory but it can also make data in relational databases, flat files or other sources appear to exist in an LDAP directory.

I think this is a pretty cool concept. Implementing a single, comprehensive, directory is at best difficult and, at worst, impossible. Companies frequently have data in multiple repositories. A virtual directory allows this data to appear to be in a comprehensive directory while actually remaining in their native stores. A virtual directory can also simply synchronization of data across repositories. Adding an object to a virtual directory can implicitly require the addition of data to the constituent repositories. Modifications to a datum might actually result in modifications to multiple repositories that contain the duplicated datum.

The biggest challenge with virtual directories is trying to retrofit them to applications that are currently directly wired to the constituent data sources. In the case of an application that reads database information by using JDBC/ODBC, it might be impossible to change it to using LDAP for its data access. Note that some virtual directories, however, can provide multiple access interfaces, for example, both LDAP and SQL. Even in the case of applications that currently use LDAP, it can be a challenge for a virtual directory to completely mimic a constituent LDAP repository. If the application analyzes the directory schema for example (something that’s possible with Microsoft Active Directory), the virtual directory either has to synthesize a comprehensive schema including data from other sources or it has to “lie” and only deliver the schema elements in the constituent repository. The former approach can confuse applications that expect a specific schema (for example, “Microsoft schema revision 31”) while the latter approach can confuse applications that use schema information to drive their operation. 

LDAP security can also be difficult to emulate/synthesize. If an Active Directory-aware program controls security by manipulating AD access control lists (ACLs), the virtual directory might need to synthesize objectSecurity attributes for objects that lie in repositories that don’t normally support ACLs and then reflect any changes back into the constituent stores. This might be difficult. Placing record-level ACLs on database rows, for example, might not be something that is supported by a constituent data store. In this case, the virtual directory might need to store its own parallel information.

Virtual directories can also be slow. The whole point of LDAP is to be fast (unlike the original X.500 directories that no one actually uses). If, however, data is actually coming from a slower store, fulfilling an LDAP request will be slow, too. For this reason, virtual directories need to perform intelligent caching.

Once virtual directories start storing their caches, they become a hybrid of sorts. They’re virtual directories but they can also behave like meta directories, too. I’ll write about those in some other post.

47 Responses to “Virtual Directories”

  1. I could not resist commenting. Perfectly written!

  2. Homepage says:

    … [Trackback]

    […] Read More: […]

  3. 210048 442792really good post, i truly enjoy this internet web site, maintain on it 221921

  4. some really select blog posts on this site, saved to fav.

  5. An fascinating discussion is value comment. I believe that it is best to write extra on this matter, it may not be a taboo topic however typically persons are not enough to speak on such topics. To the next. Cheers

  6. David Kothe says:

    you’ve got an awesome weblog right here! would you wish to make some invite posts on my blog?

  7. Today, I went to the beach with my kids. I found a sea shell and gave it to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She placed the shell to her ear and screamed. There was a hermit crab inside and it pinched her ear. She never wants to go back! LoL I know this is totally off topic but I had to tell someone!

  8. I’m usually to running a blog and i really admire your content. The article has actually peaks my interest. I am going to bookmark your web site and hold checking for new information.

  9. Hosea Aalund says:

    I really like it when people come together and share views. Great site, stick with it!

  10. as soon as I observed this site I went on reddit to share some of the love with them.

  11. Buy Fast Proxies

    I found a great…

  12. 353529 347608I just now discovered your blog post and now Im remember to start with followers. 956115

  13. Private proxies and also best money saving deals: 50 low cost, no charge proxies and additionally special deals – mainly at

  14. Hello just wanted to give you a quick heads up. The text in your post seem to be running off the screen in Ie. I’m not sure if this is a formatting issue or something to do with internet browser compatibility but I thought I’d post to let you know. The design and style look great though! Hope you get the problem fixed soon. Kudos

  15. 893206 312600I respect your piece of work, appreciate it for all the intriguing content material . 500880

  16. 415151 701163some truly interesting info , nicely written and broadly speaking user genial . 328489

  17. 747066 78621Remarkable! This blog looks just like my old 1! It is on a completely different subject but it has pretty considerably exactly the same layout and design. Great choice of colors! 888981

  18. 609366 852979you make blogging glance 91807

  19. 535617 339807Hello Guru, what entice you to post an article. This write-up was extremely fascinating, specifically since I was looking for thoughts on this topic last Thursday. 266797

  20. 494011 482823Spot on with this write-up, I should say i believe this superb web site needs considerably much more consideration. Ill probably be once once more to learn an excellent deal more, many thanks that data. 950055

  21. 549693 235598Excellent post, I conceive blog owners really should acquire a lot from this web blog its real user pleasant. 131499

  22. 393755 21834Hey! Do you know if they make any plugins to help with SEO? Im trying to get my blog to rank for some targeted keywords but Im not seeing very good outcomes. If you know of any please share. Thanks! 926677

  23. 750013 605326I was recommended this internet site by my cousin. Im not confident whether this post is written by him as nobody else know such detailed about my trouble. You are incredible! Thanks! 438588

  24. 536311 743984Hi there for your individual broad critique, then again particularly passionate the recent Zune, and in addition intend this specific, not to mention the beneficial feedbacks other sorts of everyone has posted, will determine if is it doesnt answer youre searching for. 583457

  25. 454945 385544Id must verify with you here. Which isnt something I often do! I take pleasure in reading a post that could make individuals think. In addition, thanks for permitting me to comment! 273105

  26. 472295 417238This really is some wonderful details. I expect additional facts like this was distributed across the internet today. 624425

  27. 319476 213237hey, your internet website is superb. We do appreciate your work 104539

  28. 479266 115689You completed several nice points there. I did a search on the problem and located almost all people will have the same opinion together with your weblog. 446331

  29. 422022 374228Ill do this if need to as a lot as I hope that is not too far off the track. 101450

  30. 281775 130694This internet site is really a walk-through it genuinely is the info you desired relating to this and didnt know who ought to. Glimpse here, and you will undoubtedly discover it. 801604

  31. 773627 996074Come across back yard garden unusual periods of ones Are typically Weight reduction and every one 1 may be critical. 1 way state could possibly be substantial squandering by means of the diet. shed weight 11268

  32. 298209 320519I dont feel Ive seen all the angles of this topic the way youve pointed them out. Youre a true star, a rock star man. Youve got so much to say and know so significantly about the subject that I think you must just teach a class about it 652921

  33. 746820 124034Wow, great weblog layout! How long have you been blogging for? you make blogging appear effortless. The overall appear of your internet web site is amazing, let alone the content! 145963

  34. 26599 731035How can I attract much more hits to my composing weblog? 650802

  35. hondaqq says:

    787926 509212Significant other, this outstanding website is fabolous, i merely adore it 476686

  36. 760241 979936Often the Are usually Weight reduction plan is unquestionably an low-priced and flexible weight-reduction program product modeled on individuals seeking out shed some pounds combined with at some point maintain a far healthier your life. la weight loss 199420

  37. 832148 483028I feel this web website has got really fantastic indited written content articles . 119884

  38. theweedtube says:

    437412 427765Really excellent written write-up. It will likely be useful to anybody who usess it, including myself. Maintain up the excellent function – canr wait to read a lot more posts. 146558

  39. 540394 509250Directories such given that the Yellow Websites require not list them, so unlisted numbers strength sometimes be alive more harm than financial assistance. 929779

  40. 710874 211555cleaning supplies should have earth friendly organic ingredients so that they do not harm the environment 994118

  41. 164443 322637I recognize there exists lots of spam on this blog. Do you want support cleansing them up? I might help amongst courses! 805946

  42. 735514 886014Cool text dude, maintain up the very good work, just shared this with the mates 67623

  43. 188756 388469I saw a great deal of internet site but I think this 1 contains something unique in it in it 619735

  44. 665291 452903I just put the link of your weblog on my Facebook Wall. really good blog indeed.,-, 119870

  45. 83221 687744just couldnt leave your web website before suggesting that I really loved the standard information a person provide for your visitors? Is gonna be again ceaselessly to check up on new posts 761565

  46. 244693 748574I havent checked in here for some time because I thought it was finding boring, but the last couple of posts are really great quality so I guess Ill add you back to my day-to-day bloglist. You deserve it my friend. insurance guides 91514

Leave a Reply