March 2009 - glue-wg - lists.ogf.org

1st Draft of the GLUE 2.0 LDAP Implementation
by David Horat 12 May '09

12 May '09

Hello all, I just commited my first draft, which does not include any foreign keys. You can check it at our SVN: http://forge.ogf.org/svn/repos/glue/LDAP2/ Do not forget to read the README file first: http://forge.ogf.org/svn/repos/glue/LDAP2/README I am willing to have any kind of feedback. :) Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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Question about ssociation end and inherited association end
by David Horat 17 Apr '09

17 Apr '09

In the GLUE Specification v. 2.0, page 9, there is the Location class, which has: Association.End: Service.ID Domain.ID Inherited association end: Extension.Key ComputingService.ID StorageService.ID AdminDomain.ID UserDomain.ID This seems to try to represent the fact that making a relationship with a class, you are also making it with all its subclasses. From the theoretical point of view, you can not imply that pointing to a class you have access to its subclasses, but just to its superclasses because of the definition of inheritance in the object oriente programming. Moreover, this is misleading because it depends on the implementation language whether you can cast a subclass of the current class without knowing exactly the current class. So I would propose two solutions here depending on what you wanted to describe: 1) Add ComputingService, StorageService, AdminDomain and UserDomain to the Association End list if you really want to access attributes exclusively from those in the Location class, which will add more Foreign Key attributes. 2) Just taking them out from the Inherited Association End list if in the Location class you just want to have access to the attributes of the Service and Domain classes. Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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Finalizing the LDAP implementation of GLUE 2.0
by David Horat 17 Apr '09

17 Apr '09

Hello to everyone! I am trying finalizing the initial draft of the LDAP implementation and have a few questions that need to be resolved before I can finish. Question 1: In the Entity class on page 8 of the GLUE Specification, the Association.End has just one field, Extension.Key, but in the Extension class its unique identifier is LocalId. The Extension.Key should probably not be used as its description is "This identifier is not required to be unique; several instances of this class MAY hold the same value of this attribute". So in the Entity class, should Extension.LocalId be specified instead of Extension.Key? Question 2: The relations in the association end list are always specified with the attribute they have to link with. (E.g. Service.ID). There are several reasons why this may not be a good idea. a) In the Entity-Relationship models, relationships between entities/classes/objects are generally specified without any knowledge of each of the attributes in them. b) To know which attribute you wish to link to from a related object, you will need to to take a look at its definition to get the key field. c) There could be more than one key field and sometimes the key of an entity could be a combination of several fields, which would not work with the current approach As a solution I would suggest just taking out every attribute in all the Association End lists. Question 3: >From the theoretical definition of inheritance, just by pointing to a class we cannot be sure to have access to its subclasses, only to its superclasses. As a solution I would propose to choice one of the following depending on what we are trying to describe: a) Add ComputingService, StorageService, AdminDomain and UserDomain to the Association End list if we really would like to access attributes exclusively from those in the Location class, which results in more Foreign Key attributes. b) Remove them from the Inherited Association End list if we just want to have access to the attributes of the Service and Domain classes in the Location class. c) Just take out the Inherited Association End list and put in the Association End list all the concrete classes we want to point out. I would personally prefer this last option. In addition to the questions above, I have three proposals on how to implement the relationships and would appreciate some feedback on each of them and which one is prefered. 1) Use an 'EntityFK' attribute (same as GlueForeignKey used in GLUE 1.3) in every entity that has a relationship 2) Differentiate each final object in the relationship from its superclass point of view. E.g. LocationFKService 3) Differentiate each final object in the relationship to the very concrete classes we would like. E.g. LocationFKComputingService. I would personally prefer this last option. Also should we use 'FK' or 'ForeignKey'?. Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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Foreign Key implementation on GLUE 2.0 LDAP implementation
by David Horat 16 Apr '09

16 Apr '09

Hello all, After having a talk with Maarten, a few emails with Laurence, seen the GLUE 1.3 LDAP implementation on lcg-bdii.cern.ch and though about it thoroughly, I have come to the next idea for implementing Foreign Keys on LDAP: Having an object ObjectA related to object ObjectB and being the relationship ObjectA 0..* - 0..* ObjectB, - ObjectA will contain the attribute ObjectAObjectBFK pointing to ObjectB's DN - ObjectB will contain the attribute ObjectBObjectAFK pointing to ObjectA's DN - In case the multiplicity was 1..X, with X between 1 and *, ObjectYObjectZFK will be mandatory - In case the multiplicity was 1 or 0..1, ObjectYObjectZFK will be SINGLE-VALUE - In case the relationship was Object A 0..* - 1 Object B, ObjectA will be the only one holding the ForeignKey Since LDAP is not relational, there are a few pitfalls with LDAP: - ObjectYObjectZFK is not checked to be the correct - The duality ObjectAObjectBFK and ObjectBObjectAFK is not checked to have the relation stated in both directions - Moving between relations is done in the client and not the server, which is not optimal These should be checked in an external client at appropriate invertals to ensure the integrity of the LDAP server plus all the specifcations done in GLUE 2.0 that can not be covered in LDAP (types, maximum range, etc.). I would like to have an approval of 1 or 2 people before starting with it. So, do you like it this way? :) Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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LDAP Rendering
by Laurence Field 16 Apr '09

16 Apr '09

David Horat from CERN will start looking at the LDAP schema rendering. Does anyone have any comment/suggestions before he gets started? Laurence

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Question about Entity and its relationship with Extension
by David Horat 16 Apr '09

16 Apr '09

In the GLUE Specification v. 2.0, page 8, it is specified the Entity class. In its "Association.End" there is just one field: "Extension.Key", but in the Extension class, its unique identifier is "LocalId". So in the Entity class, it should be specified "Extension.LocalId" instead of "Extension.Key". "Extension.Key" shouldn´t be used because of its description, which I quote here: "This identifier is not required to be unique; several instances of this class MAY hold the same value of this attribute". So this could be another erratum, isn´t it? Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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Question about LocalId_t
by David Horat 30 Mar '09

30 Mar '09

Hello guys, The LocalId attribute of the Extension class specified in page 8 of the GLUE 2.0 Specifications is of type LocalId_t. The LocalId_t is specified in page 72, which basically says that is must be a string that starts with a-zA-Z and the following characters can be into a-zA-Z_0-9. I am just curious to know why did you apply this restriction. I am sure there is a good reason behind it. Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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Tighten defn of Country property?
by Paul Millar 30 Mar '09

30 Mar '09

Hi all, Current defn of Location.Country is simply "Name of country." However, this can lead to confusion. Is the United States of America "US", "USA", "United States", "United States of America"? Is the United Kingdom represented by "GB", "GBR", "UK", "U.K." etc. Perhaps we should clarify this. I would change the definition to: Name of country. The value SHOULD be the country's ISO 3166-1 Alpha-3 code. (we could use any code, but ISO 3166-1 Alpha-3 seems appropriate). Cheers, Paul.

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Question about the way of specifying relationships
by David Horat 27 Mar '09

27 Mar '09

In the GLUE Specification v. 2.0, in the association end list, relations are always specified with the attribute they have to link with. (E.g. Service.ID) This is not correct because of several reasons: - In the Entity-Relationship models, you just specify relationship between entities/classes/objects, without any knowledge of each of the attributes in them. - To know which attribute you want to link with from the related object, you should have to take a look of its definition to get the key fields. - The key fields could be more than one. Sometimes the key of an entity is a combination of several fields, so the current way of visualizing relations will be broken. I suggest just taking out every attribute in all the Association End list to comply on how to use this kind of diagrams, to avoid problems in the future with multiple key fields. Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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Admin needed: Lack of permissions commiting to GLUE SVN
by David Horat 25 Mar '09

25 Mar '09

Hello all, I just tried to commit for the first time to the GLUE SVN and this is what it happens: horat@horat-hpnc6220:~/gridsrc/glue$ svn commit --username horat svn: Commit failed (details follow): svn: Server sent unexpected return value (403 Forbidden) in response to MKACTIVITY request for '/svn/repos/glue/!svn/act/1e158427-8963-49f4-8251-ec5b4fb8bb27' It seems that the *authentication* succeeded, but the *authorization* was unsuccessful, thus it may be due to a lack of permissions. Can any admin give me permissions to commit to the GLUE repository? My username is "horat". Regards, David -- David Horat Software Engineer specialized in Grid and Web technologies IT Department – Grid Deployment Group CERN – European Organization for Nuclear Research » Where the web was born Phone +41 22 76 77996 http://davidhorat.com/ http://cern.ch/horat http://www.linkedin.com/in/davidhorat

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