Patent Publication Number: US-7216126-B2

Title: System and method for RDBMS to protect records in accordance with non-RDBMS access control rules

Description:
This application is a continuation of application Ser. No. 09/598,553, filed Jun. 21, 2000, now U.S. Pat. No. 6,581,060 for an invention entitled SYSTEM AND METHOD FOR RDBMS TO PROTECT RECORDS IN ACCORDANCE WITH NON-RDBMS ACCESS CONTROL RULES, from which priority is claimed. 

   FIELD OF THE INVENTION 
   The present invention relates to methods and systems for allowing applications to directly access a relational database while protecting records in the database. 
   BACKGROUND OF THE INVENTION 
   Information management systems (IMS) typically use a relational database management system (RDBMS) to manage data records in a database. As an example, an IMS might manage document data, with the desire that some documents can be read by all users but only written to by a few. Many other high-level access rules can be enforced by the IMS. In any case, when a user wants to access the records of a document in the RDBMS, the user is routed through the IMS to first check for access control. 
   The documents themselves are broken down into records of various formats by the IMS and the records are stored in tabular form in the RDBMS, which can efficiently manage the records for querying using a language known as SQL. Only the IMS knows the high level access control rules. User applications must access the RDBMS indirectly, through the IMS, to ensure integrity and protection of data. 
   Unfortunately, as recognized herein requiring applications to access data indirectly, i.e., through the IMS, slows down performance. As stated above, however, with the current state of the art, applications cannot be permitted to access the RDBMS directly because this would bypass the access control functions of the IMS. Moreover, the present invention recognizes that RDBMS manage low level access protection for sets of homogeneously structured records, and not for individual entities. The IMS must enforce access protection rules at the entity (document) level. 
   As also recognized herein, some new applications, such as e-commerce applications, require heretofore unusual rules in the database context, namely, distribution rules (as opposed to access rules) that are related to content licensing. These licensing rules can and do change over time, so that a data system&#39;s protection rules advantageously should be extensible. The present invention recognizes that it would be desirable to allow a user to access an RDBMS directly, without first going through an IMS, while maintaining IMS access control and without requiring reengineering of the RDBMS to account for extensions of access control. 
   SUMMARY OF THE INVENTION 
   The invention is a general purpose computer programmed according to the inventive steps herein. The invention can also be embodied as an article of manufacture—a machine component—that is used by a digital processing apparatus and which tangibly embodies a program of instructions that are executable by the digital processing apparatus to undertake the present invention. This invention is realized in a critical machine component that causes a digital processing apparatus to perform the inventive method steps herein. The invention is also a computer-implemented method for undertaking the acts disclosed below. 
   Accordingly, a computer program product includes computer usable code means programmed with logic for enforcing high level access control rules of an information management system (IMS) for an application directly communicating with a relational database management system (RDBMS) associated with the IMS. The program product includes computer readable code means for binding at least one RDBMS table using one or more access control list (ACL) codes representing the high level access control rules. Also, the logic includes computer readable code means for issuing a query from the application against an RDBMS view, and computer readable code means return the result of the query against the view. 
   In another aspect, a data system includes a server computer programmed to undertake method acts for responding to user queries for data from a database controlled by the server computer. The method acts undertaken by the server computer include receiving a query, and receiving an access control output from at least one algorithm. In response to the query and the access control output, the computer populates a view for presentation thereof to the user. Thus, the view encapsulates the access control rules. 
   The system can include a database management system (DBMS), and the application directly communicates with the DBMS. In a particularly preferred embodiment, the method executed by the computer includes defining at least one view on at least one table in the database, and executing a query against the view using at least the access control output. The results of the query against the view are then returned. 
   As set forth in detail below, the access control output preferably is represented by at least one Access Authorization table (AAT), and the view is defined as a join between the AAT and the information table. The tables are joined using a join key, and the join key is at least one access control code binding the information table to the AAT. With this system, multiple rows of the information table can be bound to respective multiple access control rules, or all rows of the information table can be bound to a single set of access control rules. 
   In another aspect, a method is disclosed for enforcing at least one access control rule in a data system including at least one application accessing at least one information management system (IMS) associated with a database management system (DBMS). The method includes receiving a specification for IMS data schema and generating a DBMS view in response to the specification, with the view encapsulating the IMS access control rule. The view is then presented to a user via a direct communication path to the DBMS. 
   In still another aspect, a system includes at least one information management system (IMS), at least one application communicating with the IMS, and at least one relational database management system (RDBMS) communicating with the IMS. The application communicates directly with the RDBMS via at least one direct communication path that does not include the IMS. 
   In yet another aspect, a method is disclosed for enforcing high level access control rules of an information management system (IMS) for an application directly communicating with a relational database management system (RDBMS) that is associated with the IMS. The method includes providing at least one access authorization table (AAT). The AAT contains data: representing high level access control rules. Also, the method includes providing at least one information table in the RDBMS, and in response to a query for data from the application, the AAT is joined with at least one information table to return a result in accordance with at least one of the high level access control rules. 
   In another aspect, a data system includes a server computer programmed to undertake method acts for responding to user queries for data from a database controlled by the server computer. The method acts undertaken by the server computer include storing the database in a second system, such as but not limited to a DBMS and more particularly a RDBMS, and maintaining access control specifications that restrict access to data. The methods acts also include allowing a user to access data directly through the second system, and in response to the direct access by the user, causing the second system to enforce the access control specifications without intervention from the data system. 
   In a preferred implementation of this aspect, the user is an application. In one preferred embodiment the data system supports a data model that is different from a data model supported by the second system, whereby the access control specifications are not directly enforceable by a native access control capability of the second system. 
   As set forth in further detail below, the access control specifications preferably are stored in at least a first table in the RDBMS, and a RDBMS view is generated by joining a data table with the first table. The view can be used by the user for directly accessing data. Preferably, the view includes at least one UDF on the first table, with the UDF implementing the data system&#39;s access control model. The view can be created when the data table is created. Moreover, resolutions of the access control specifications can be computed using the data system&#39;s access control model and stored in an access authorization table (AAT) in the RDBMS. Thus, in a particularly preferred embodiment the RDBMS view is a join between a data table and the AAT, for use of the view by a user for direct access to data. 
   The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of the present system; 
       FIG. 2  is a schematic representation of the data structure of an access control list (ACL); 
       FIG. 3  is a flow chart of the logic for generating a global RDBMS view embodying access control rules; 
       FIG. 4  is a flow chart showing the logic for generating/updating the Access Authorization Table; 
       FIG. 5  is a schematic diagram of an information table being joined with an ACL table; and 
       FIG. 6  is a flow chart of the logic for executing a query using the present system. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring initially to  FIG. 1 , a system is shown, generally designated  10 , that includes at least one user computer  12  having a software-implemented application  14  that generates queries. Input to the user computer  12  is via one or more input devices  16 , and query results can be output on an output device  18 . The input device  16  can be any suitable device, such as a keyboard, keypad, mouse, joystick, trackball, voice-recognition software, and so on. The output device  18  can be a monitor, a speaker, another computer or computer network, a printer, and so on. 
   As shown in  FIG. 1 , the user computer  12  communicates with an information management system (IMS)  20  via an IMS communication path  22  using high-level application programming interfaces (API). The IMS  20  communicates with a relational database system (RDBMS)  24 , such as the present assignee&#39;s DB2, that stores records of documents managed by the IMS  20 , with the IMS  20  enforcing high level access control rules pertaining to the application  14  vis-a-vis the records of the RDBMS  24 . Each IMS document consists of a root record, which is a row in a root table, and optionally some number of dependent records, which are rows in certain dependent tables. The way the system  10  achieves this enforcement, which is the subject of the present invention, enables the application  14  to issue queries and otherwise to communicate, via a direct communication path  26 , directly with the RDBMS  24  using SQL (or other DBMS query language) without the direct communication path  26  going through the IMS  20  while nevertheless maintaining access control. One or both of the IMS  20  and RDBMS  24  can be hosted on a server computer  28 , or each can have its own associated computer. 
   As intended herein, either or both of the user computer  12 /server computer  28  can be a server computer made by International Business Machines Corporation (IBM) of Armonk, N.Y. Other digital processors, however, may be used, such as personal computers, laptop computers, mainframe computers, palmtop computers, personal assistants, or any other suitable processing apparatus can be used. 
   In any case, the processor of the computers access appropriate software to undertake the logic of the present invention, which may be executed by a processor as a series of computer-executable instructions. The instructions may be contained on a data storage device with a computer readable medium, such as a computer diskette having a computer usable medium with a program of instructions stored thereon. Or, the instructions may be stored on random access memory (RAM) of the computer, on a DASD array, or on magnetic tape, conventional hard disk drive, electronic read-only memory, optical storage device, or other appropriate data storage device. In an illustrative embodiment of the invention, the computer-executable instructions may be lines of C or C++ or Java code. 
   Indeed, the flow charts herein illustrate the structure of the logic of the present invention as embodied in computer program software. Those skilled in the art will appreciate that the flow charts illustrate the structures of computer program code elements including logic circuits on an integrated circuit, that function according to this invention. Manifestly, the invention is practiced in its essential embodiment by a machine component that renders the program code elements in a form that instructs a digital processing apparatus (that is, a computer) to perform a sequence of function steps corresponding to those shown. 
     FIG. 2  schematically shows root information entities  30  that include respective access control list (ACL) codes  32  and respective owner fields  34 . The owner field is needed only if each information entity has a distinct owner. Each root record  30  might have further dependent entities which, like the root record, have entity identifications. The owner field  32  can specify one or more owners or it can be null. If owner privilege is enabled, the owner of an entity can perform all legitimate operations on an entity he owns. Alternatively, table-level access control, instead of entity-level, can be established by ignoring the ACL codes  32  in each entity and associating the entire information table with a single ACL code that is recorded in an RDBMS system table. 
   In any case, the user defines which ACL codes pertain to which entities, with the ACL codes  32  being associated with the row (or table) defined by the user. The user can change or delete access control rules, and when this occurs the ACL codes  32  of the information tables are changed accordingly. Thus, as intended by the present invention, when entity-level access control is established the entities  30  are bound by means of the ACL codes  32  to access control rules embodied in an access control table, generally designated  36 . Specifically, the access control table  36  includes plural rows, each having an ACL code field  38  that, along with the ACL code  32  in the entities  30 , is the binding key. Also, each ACL code field  38  has an associated ACL attribute  40  that in one preferred embodiment includes a user attribute  42 , a privileges attribute  44 , and a conditions attribute  46 . If desired, a description field  48  can be provided to describe the ACL rules embodied in the ACL attribute  40 . 
   The user attribute  42  specifies the user to which the privileges attribute  44  and conditions attribute  46  pertain. It can represent a single user by identification, or a group of users by group ID. Moreover, the user attribute  42  can be qualified, i.e., it can be evaluated for users belonging to a specific department, acting in a certain role, possessing a particular certificate, holding a certain content subscription, or performing a predetermined action (e.g., paying a preselected sum of money). It will be appreciated that in evaluating the user attribute  42 , a RDBMS user-defined function (UDF) might access one or more auxiliary tables or even interact with a system external to the system  10 . 
   On the other hand, the privileges attribute  44  specifies the operations that the user associated with the user attribute  42  is allowed to perform. To support licensing rules as might be required in e-commerce, operations that are not supported by the system  10  can be included as well. One preferred way to represent a privilege is by using a bit vector, in which each bit represents whether an operation or a set of operations is allowed or not. 
   In contrast, the conditions attribute  46  represents whether certain optional conditions apply to the privileges represented by the privileges attribute  44 . Examples of conditions include temporal conditions (e.g., the privileges can be exercised only during a predetermined period), environment conditions (e.g., access can be had only from a corporate intranet), and usage conditions, e.g., only five users at a time can access an entity. 
   In accordance with the present invention, the values in the ACL attribute  40  are interpreted, using SQL, by respective user-defined functions (UDFs). Given a user, a user&#39;s state, an operation requested by the user on a target entity  30 , and a system state, an ACL attribute value can be evaluated to either “allow” or “disallow” with respect to the requested operation. Thus, the access protection rules are encapsulated in the ACL attribute  40 . With this in mind, the skilled artisan will recognize that advantageously, both the ACL attribute  40  and the UDFs can be extended without changing the logic of the system  10 . 
   Now referring to  FIG. 3 , the logic embodying portions of the above description can be seen. Commencing at block  50  an information table in the RDBMS  24  is defined to the IMS  20  by a user and the system table updated at block  52 . The information table remains unaccessible to users directly. 
   Moving to block  54 , a relational database view is created by joining the information table created at block  52  with the Access Authorization Table (AAT), described more fully below. The view, having incorporated access control rules from the AAT, thus embodies both information and access control rules. Next, at block  56  the entire user community is authorized to use the view created at block  54 . 
     FIG. 4  shows the logic for defining, updating, and deleting access control rules. At block  58  the definition/update/deletion is received by the IMS  20 , and the below-described corresponding system tables pertaining to the access control rule involved at block  58  are changed accordingly at block  60 . In the preferred embodiment, the logic continues to block  62  to undertake certain precomputing, namely, the generation/modification of the AAT, which is essentially a combination of the various system tables related to access control and modified at block  60 . 
   Accordingly, at block  62  an algorithm that implements the IMS&#39;s high-level access control model is applied to the below-described system tables to render or update the AAT. When the step at block  62  is precomputed, the algorithm can be a UDF associated with the RDBMS, or it can be an algorithm that is resident in and executed by the IMS  20 . In contrast, if precomputing is not used and the step at block  62  is executed at query time, a UDF must be used to evaluate the algorithm to support direct access  26 . 
     FIG. 5  illustrates the above-mentioned system tables that pertain to access control, and the AAT that is derived therefrom. A user table, a user group table, an operation table, a condition table, and an access control list (ACL) table are shown in  FIG. 5 . Depending on the implementation, there may be additional tables. The user table and user group table essentially embody a set of user attributes  42  ( FIG. 2 ), while the operation table contains permissible operations and, thus, essentially embodies (with proper processing) the privileges attributes  44  ( FIG. 2 ). The condition table embodies the conditions attribute  46 , and the ACL table embodies the binding between these and other tables. 
   As described above in relation to block  62  of  FIG. 4 , the access control attributes embodied in the user table, user group table, operations table, condition table, and ACL table are evaluated in accordance with the high-level access control model to render a single Access Authorization table. Accordingly, the Access Authorization table represents access control rules, namely, user, privilege, and condition attributes shown in  FIG. 2 . 
   It may now be further appreciated in light of the above disclosure how the applicable access control rules are folded into the view that is presented by the RDBMS directly to the application at query time. Referring to  FIG. 6 , at block  64  a user such as the application  14  of  FIG. 1  accesses the RDBMS  24  via the direct access path  26  and issues a query against the view created at block  54  of  FIG. 3 . Moving to block  66  of  FIG. 6 , the RDBMS  24  converts the query to a query against the relevant information table(s) and the AAT, which query is evaluated and the AAT table joined to the information table(s) to populate the view at block  68 . The query results are then returned to the user via the direct access path  26 . 
   The above join between the information table(s) and AAT is accomplished using the ACL codes  32 ,  38  ( FIG. 2 ) as a join key as indicated by line “join” in  FIG. 5 , and containing a predicate to select rows from the AAT that are applicable to the user and the intended operation. Thus, the information table implicated in the query is joined with the Access Authorization table as indicated in  FIG. 5  to populate a view tailored for a particular user. Accordingly, when a query is issued at block  68  by a user against the view, which encapsulates the access control rules applicable to the user, the result of the query accounts for the IMS&#39;s access control. 
   Consequently, with the IMS&#39;s access control rules folded adaptively into the view, there is no need for the RDBMS to enforce access control rules explicitly. In other words, in contrast to conventional RDBMS systems, the present logic does not require special SQL statements to control information access. 
   In one preferred embodiment, the view generation syntax when implementing access control on a row by row basis on an information table (a feature not provided in conventional systems) is as follows. 
   
     
       
         
             
           
             
                 
             
           
          
             
               CREATE VIEW R_ABC AS 
             
             
               SELECT * FROM ABC 
             
             
               WHERE OWN (OWNER, USER) = 1 
             
          
         
         
             
             
          
             
                 
               OR 
             
             
                 
               ACL_CODE IN 
             
          
         
         
             
             
          
             
                 
               (SELECT ACL_CODE FROM ACLTABLE 
             
             
                 
               WHERE ALLOW (ACL, USER, “READ”) = 1); 
             
          
         
         
             
          
             
               GRANT SELECT ON R_ABC TO PUBLIC; 
             
             
               where 
             
          
         
         
             
             
          
             
                 
               ABC is a root-record table created by a user, 
             
          
         
         
             
          
             
               containing system attributes OWNER and 
             
             
               ACL_CODE, USER is a DB2 Special Register 
             
             
               that contains the authorization ID for the current 
             
             
               user, ACLTABLE is the access control list table 
             
             
               shown in Figure 2, OWN( ) is a system-provided 
             
             
               UDF on OWNER attribute, which checks whether 
             
             
               a user is an owner, and ALLOW( ) is a system- 
             
             
               provided UDF on ACL attribute, which checks 
             
             
               whether a user has a certain privilege. 
             
             
                 
             
          
         
       
     
   
   Although in this example access privilege on this generated view R_ABC is granted to the public, it can instead be granted to selected users. Such users may further create more restrictive views on this view and authorize other users to use the more restrictive views. 
   The R_ABC view above is generated for use by all users on a root-record table ABC. The “OWN(OWNER,USER)=1” predicate is needed only if the owner privilege is enabled. Checking of the IMS protection rules is undertaken by the UDF ALLOW( ), which essentially encapsulates the ACL attribute of the ACL table shown in  FIG. 2 . With this encapsulation, any protection rules and models can be supported by the system  10 , as well as multiple models so long as the UDF ALLOW( ) is able to determine which model is applicable for the conditions. Furthermore, encapsulation also facilitates subsequent protection extension or the addition of a new protection model to extend the system  10 , because such changes are confined to the ACL attribute (rule representation) and its UDFs (rule interpretation). 
   The sub-query SELECT ACL_CODE FROM ACLTABLE identifies the set of ACL codes that the current user is authorized to read. The view masks/filters the table according to the access control rules as applied to a given user and to each respective record in the information table. 
   In any case, in one preferred embodiment the sub query can be predefined as a separate view ReadAuthorization as follows, so that it can be reused by other view definitions and so that system performance is enhanced. 
   
     
       
         
             
           
             
                 
             
           
          
             
               CREATE VIEW ReadAuthorization AS 
             
             
               SELECT ACL_CODE FROM ACLTABLE 
             
             
               WHERE ALLOW(ACL, USER, “READ”) = 1; 
             
             
               CREATE VIEW R_ABC AS 
             
             
               SELECT * FROM ABC 
             
             
               WHERE OWN (OWNER, USER) = 1 
             
          
         
         
             
             
          
             
                 
               OR 
             
             
                 
               ACL_CODE IN•(SELECT ACL_CODE FROM 
             
             
                 
               ReadAuthorization); 
             
          
         
         
             
          
             
               GRANT SELECT ON R_ABC TO PUBLIC; 
             
             
                 
             
          
         
       
     
   
   As known to the skilled artisan, there are alternate syntax that would create equivalent views. 
   It is to be understood that when the triplets of attributes shown in  FIG. 2  are used, the ALLOW( )=1 predicate set forth above can be replaced by a test for the existence, among the collection of triplets (USERS, PRIVILEGES, CONDITIONS) of a triplet that satisfies USR(USERS, USER)=1 AND READ(PRIVILEGES)=1 AND SATISFY(CONDITIONS)=1, where USR( ), READ( ), and SATISFY( ) are UDFs that respectively check whether the user is authorized, whether the READ privilege is granted, and whether any conditions are satisfied. 
   Although the AAT is preferably precomputed as discussed above, it can be determined at query time from the various system tables that pertain to access control. Moreover, as intended by the present invention the reusable view described above can be materialized using DB2 Summary Table capability or as a dependent table managed by the IMS  20 . It can be materialized or refreshed as user logon, and can be evaluated either directly from the ACL table or indirectly from an intermediate view or Summary Table that contains the ACL_Codes for all users. This intermediate table can be refreshed when new rules are added, altered, or deleted. Because access protection is checked by the UDF and not by the RDBMS, the UDF ALLOW( ) can use the user ID passed as a parameter instead of using the USER variable, such that a “trusted application” (e.g., a http server) can operate under a single RDBMS user ID on behalf of many system users, and can authenticate users and pass their IDs to the RDBMS. This allows a reuse of RDBMS connections for different users as well as exploiting DB2&#39;s static query and statement caching features for improved performance. 
   It was mentioned above that in addition to providing access of root tables in the RDBMS, the system  10  supports access of dependent tables. This can be undertaken as follows, in which “DEF” is a dependent record table of root table ABC in the context of IMS documents, OWN( ) is a UDF, and the sub-query “SELECT A.ENTITY_ID FROM ABC” identifies the set of entity IDs (obtained from the root records) such that the user is either an owner or READ-authorized user for these entities. An Entity-ID identifies a document, and is stored in every record of the document. 
   
     
       
         
             
           
             
                 
             
           
          
             
               CREATE VIEW R_DEF AS 
             
             
               SELECT * FROM DEF 
             
             
               WHERE ENTITY_ID IN 
             
          
         
         
             
             
          
             
                 
               (SELECT A.ENTITY_ID FROM ABC A, ReadAuthorization R 
             
             
                 
               WHERE OWN(A.OWNER, USER) = 1 OR 
             
             
                 
               A.ACL_CODE=R.ACL_CODE); 
             
          
         
         
             
          
             
               GRANT SELECT ON R_DEF TO PUBLIC; 
             
             
                 
             
          
         
       
     
   
   It was also mentioned that in addition to instance-level protection, set-level protection (also referred to herein as table-level protection) can be provided as follows: 
   
     
       
         
             
             
           
             
                 
                 
             
           
          
             
                 
               CREATE VIEW R_XYZ AS 
             
             
                 
               SELECT * FROM XYZ 
             
             
                 
               WHERE 123 IN (SELECT ACL_CODE FROM ReadAuthorization); 
             
             
                 
               GRANT SELECT ON R_XYZ TO PUBLIC; 
             
             
                 
               where 
             
             
                 
               XYZ is a table of information entities, 123 is the ACL_CODE 
             
             
                 
               assigned to protect the table. 
             
             
                 
                 
             
          
         
       
     
   
   For heterogenous sets, set membership must be maintained for each member of the set by, e.g., keeping the containing set entity ID in the root record or by storing it in a separate table. A view is then generated using the principles set forth above for generating set-level views. 
   It is to be understood that in the above examples, a “READ” operation was shown, but UPDATE operations can also be undertaken using a U_ACL view instead of an ReadAuthorization view. 
   While the particular SYSTEM AND METHOD FOR RDBMS TO PROTECT RECORDS IN ACCORDANCE WITH NON-RDBMS ACCESS CONTROL RULES as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. All structural and functional equivalents to the elements of the above-described preferred embodiment that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”.