CA2210982A1

CA2210982A1 - Method and system for accessing data

Info

Publication number: CA2210982A1
Application number: CA002210982A
Authority: CA
Inventors: Hans Verner Thorsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-01-26
Filing date: 1995-11-06
Publication date: 1996-08-01
Also published as: EP0807290A1; NO973432D0; ES2148576T3; AU3858295A; DE69516727D1; EP0807290B1; US6052688A; DE69516727T2; WO1996023267A1; ATE192592T1; US5905984A; NO973432L; JPH11503539A

Abstract

A method and a system for accessing data in a computer-based data processing system. The method comprises the steps of initiating and maintaining data access nodes in a variable access structure. Each access node is provided with references to other access nodes and/or to data items representing an object, each data item carrying only the amount of information which is relevant for its purpose. The data items or the references are provided with a time parameter thus enabling version control and the possibility to handle static or slowly changing data and frequently changed and updated data in a conform manner. The access nodes comprises access control parameters for access control from safety point of view as well as for enabling different views of the access structure and underlying data and objects.

Description

' CA 022l0982 l997-07-2l ~ ~W 096123267 PCT/SE95101315 Me~hod and System ~or Accessing Data Field of the Invention The present invention relates to methods and systems for accessing data and for m~int~ining access structures in a computer-~ased data processing system S Back~round of the Invention In most computer applications there is a need to manage and access data describin;, or repr~sPntin~ properties or conditions of a real or an im~gSin~ry object A database system, which essenti~lly is a computerized record-keepin~
system, is an example in which objects or occurences are described by means of 10 items of information stored in the database. An object could e.g. be a person or an enterprise with a number of characteristics, and typically there is a number of diLr~ellt parties interested in different aspects of that object. Similar examples are databases within corporate networlcs, wherein di~erent departments are interested in different aspects of the activity, such as finance, production, sales and storage.
15In the case of a person being described, the interested parties may e.g. be a hospital, a bank and the tax authorities, each having a separate ~l~t~b~se specialized for their specific needs. Now, the person may be described by such characteristics as name, identification number, blood group, income and debts Some of these p~rticulars are static, e.g. blood group, and others are variable, e.g 20 income and debts. In this example the hospital would be primarily inLele~led in recordin, name, identification number and blood group, while the bank would record name, identification number, income and debts and the tax authorities would record narne, identification number and income.
It is clear that there is an overlap between the dirr;;rtllt databases, and it is ~5 typically uncertain who is the one responsible for the m~int~in~nce of each item of information, with a great risk of inconsistency as a disadvantegeous conseguence. Sometimes the parties need to communicate inforrnation between their databases, whereby data may be exchanged via e.g file systems, which re~uires a common standard regarding operating svstems and communications W 096123267 PCT/SE9~/0131S

means, something which is not so easily achieved. In general, each database is individually designed accordin, to the owner's needs and view of the object and has a unique set of associations within the database. In state of the art databases, e.g. SQL hlte,~reli,.g relational databases, a database model has to be choosen 5 and fixed, and is thereafter in practice statically storing associations and data items in a user specific way. Recent development in the usage of multimedia, where a number of dirrerel1t data presentation techni~ues are used simultaneously, for example sound, images and movement of a simulation device, has shown that state of the art access control is inadequate for this mixture of information.
In this text the term database is used in a broad sense, referring to any computer-based system in which data items or signals are occurring, stored and processed in some way. Firstly, there is the common database concept in the above example, and secondly, any data processing system which handles previously stored data and newly recorded data, such as signals read out or 15 sampled from an apparatus, constitutes a kind of database. An example of the latter is the case in which a periferal device, e.g. a printer, is coupled to a computer network. In order to utilize the printer it is necessary to combine data describing the printer parameters with information about the current condition of the printer. In state of the art data processing systems and methods there is no20 natural way to handle information of d;Lrercllt nature, such as parameters and time dependent signals, in a conform manner.
There are some previously known methods for handling certain time dependent data in a d~t~b~e, for example a method for the storage of multi-versioned data with retrieval based on searched query, which is disclosed in the~5 US patent no. 5,317,729. This method is, however, directed to version control of engineering changes to a product design in a database allowing multiple users towork on the same object. Dirrelel1- data versions are kept track of i.a. by means of change notices and by storing affected data items in certain files. This method allows storage and retrieval of time-oriented and view-oriented versions of 30 engineering change information in which the engineering change information progresses through a set of status conditions, and access to the data by difre ;;nt user ~roups is conditioned upon the status of the information. When an attributeto an object slored in a relational database is changed, a new version of iha~
object is created. A locical key value is used tO ident~f1e data ite ns considered tO
be different instances of attributes to the sarne object. The access level for 5 information associated to an object is based on security aspects for a productproject and can be set by addina to the obJect an attribute dependin~ on the required security level. Direrent user ~roups can then have access to dir rent views of the stored imormation. It is in this method also possible to reLrieve irLrorlna~ion rom di,~erent civen versions ol ~n object. A further object of 'his 10 known method is to provide improved processing efficiency of versioned data stored in a relational data base table.
The US patent no. 5,~3,36~ describes a method for storing, retrieving and indic2ting a plurality of annotations in a dat2 cell. This method a!so employs akind of version control in comparin~ previously stored data with new input data,1~ and in recordinc a time and user indication Ior each data input. This method is, however, primariiy directed to dislribution ol' data to dirIeren; locations, which is suG~ested tO be used in record keeping systern where one piece of inLormla;ion is entered into multiple records.
A data ~cc_ss structure for facilit~tin~ ~rocessinG of statistical inauires on a~ ~ c~ ~ 2~s s~, ~0 stored data is disclosed in the US paleM no. ~,26~,~4~This slructure includes a plurality of data nodes storing whole records of data, and a plurality of accessnodes, each storin~ at leas. one pointer to another access node or to a data node, and or~anized ~o that each access node is linked directly or indirectly tO at leas one data node. Statistical information is associated with a subset o~ the plurality '75 OI access nodes and dala nodes concerning the records stored in the data node or data nodes linked directly or indirectly to the respective access node and/or data node. r 3~ ~
A disadvantaGe with prior ar, access and version handling rnethods is that data to a lar~e extent is fixed in predefmed association st~ctures re~uirin_ 30 dedicated application programs to retrieve da~, and there is a commercial demana Ior an access method that overcomes these and other problems.
AMENDED SHEE~

'- 3a EP-A-O 229 232 discloses a file management system having access nodes where eachaccess node m~int~ins lists of at~ibutes for characterizing the respective nodes.

EP-A-O 398 645 discloses a system for controlling access to objects in an objecto~iented database by means of an access control list. Permission for different operations on the objects of the database are assigned to diLL~ users and listed in the access control list.

AMcl~!DED SHE~

' 4 Obiects of dle InYerllIon It is an obJec; OI che present .nve~ion to provide a me~hod and a system lor contro~l~ng acc_ss tO and associa~ino data in an 2pplication independent f~hion,which enables dara of di~erem n~~nlre tO be handled in a corltorm way. Ano~her object of L~his invention is ~o prov~de a method and a system that enabLes aYoidance of mul~ple databases desc~ibing one and the same object. A further ob~ecl is to provide an ac~ess a.L~cture for controlling access to data and for allowin~ d;~ e~ views of s.ored data o'ojects depending on d;~elc~lt aspec~s o the stored objects or di,~,ererlt ac~ess ri~ls of a user. A still f~rrher object is to 10 caler for fast access ~o shared dâ~ by a se~-erai simultaneously active user applications and ;o achieve ac_ess ~o data stored in dillel~lt d2tabases or datastorage st;uctures It is also an o'oject ol~ this in~-e~lion to provide a method and a system~ for the above purposes thât:
15 - ensures a hiGh de~ee of re~dabllLrY of results and system parameters for a human obserYer, - allows porabiIiry between di~-rent computer ha~dwi~e, operating systems and networ~s, - requires a small amount o,~halu~Le and software resources reCocni7ing the 20 well known fact that small scale ~slems are safer and e~sier L~o kandle than large, - enables a hi_h degree ol traceaDilily of all important events result;n~ from carrying out the method, whereby safety, ef~ c ent m~int~in~nce and error handlin~ is ensured, and that - provides a hi~h de~ree OI modularity in the d~ L steps OI .he method and 25 components of the system, whe.e~y d~Lel~llL combinations are applied to complex applications.
These and other obje~s and adYant~es are accomplished by the present invention by means of a metl~od 2nd a sys~em of the above men~ioned kind, , ~pc~cee~ l which present the fe~lures of tfi~undependent claims ,~ d i?'. Further 30 fe~tures and em~odiments of the inventive concept are indicated in the dependent clalms.
AMEND~D SHEEl W O 96/23267 PCT~SE95~013 Summars~ of the Invention In accordance with one aspect of the invention, data is structured into separate and unassociated atomic data items, each data item carrying only the arnount of information which is relevant for its purpose, or is kept in an existing 5 data structure such as a database table or the like. In such ~istin~ data structures, attributes of an object is typically stored as separate but closely related data items.
A data access node is created for each data item or for a group of data items inwhich access node a reference to said data item or group of data items is stored.
Each access node is incorporated in a variable data access structure, wherein a 10 first access node is linked to a second access node and whereby the nodes preferably are linked independently of whether the data items referred to in thenodes are related to the same object or not. A reference stored in an access node may also point at or refer to a computer program, or a control signal terrninal or a status signal terminal of an apparatus and such instances are in this text comprised 15 in the terrn data item. The access structure may comprise access nodes storing a reference list of one or more referenceses to other access nodes as well as to data items, so that each access node is directly or indirectly linked to each data item.
In this manner, access to data items and objects is controlled through the access structure indepenclently of the data input or output method, data storage format or 20 data storage relations. Thereby, data items being sampled, stored or assorted in different arrangements or databases, m~kin~ up a composite database, can be associated and retrieved by a user without knowledge about the storage and association method used in the respective data storing structure. DiL~.ellL views of a database or a subset of a database is obtainable by rearranging the access 25 structure itself or by retrieving and storing references pointing at data items of a selectable aspect, kind or class.
Each access node in the inventive access structure is provided with an access control means, by means of which the access of a user to the content of an access node and thereby to data items or to other access nodes is controlled. In 30 accordance with the invention, such an access control means has the function of an access filter or a data shell that protects the content of the node. From a user applications point of view, an access node or the access structure is an interface between the environment and an object, a data item or a control means of an apparatus. The access control means may be used for controlling acccess from data security point of view, and is then designed to be responsive to certain 5 pararneters such as access keys, user identity, application group etc, as well as for obtaining different views of the database. Contrary to prior art, data items or objects accessed through the inventive access structure are preferrably associated upon retrieving or when composing a selected view. By means of the access control means and a conkol structure comprising an application dependent 10 specification and an access specification, communication with access nodes isperformed and associations are established by L~dve~ lg the access structure according to presettable rules.
In a ~refelled embodiment of the invention, each data item or reference to the data item is provided with a time parameter indicating the time at which the data 15 item is read, stored sarnpled or any other selectable time. Variable data is updated by replacing an old data value with a new one or, ~rc:fe;lldbly, by creating a new data item in which the last data version is stored and by adding the new data item to a relevant group of data items, whereby data items may be added at any rate enabled by the current data procPs.cin~ system. Updating and adding rate often 20 depends on the type of data, for example illven~oly lists are changed in an uneven, relatively slow pace, while stoclc rates may be changed more often and asampled signal is updated at a high frequency. In accordance with the invention,such different kinds of data items as in the previous example are treated in thesame way by providing a time parameter to each data item and by storing them in 25 a common format, for example the string format.
According to one embodiment, data retrieval or view establishing is carried out by specifying a time value or a time interval for the data to be retrieved or associated, by storing in a result file a data item or a reference to a data item having a time parameter whith the specified time value, or storing in a result file 30 data items or references to data items having time parameters with time values in the specified interval, and then communicating the result file cont~ining said data W<l 96l23267 PCTJSE9~;J01315 item or data items to the retrieving or associating user application. In anotherembodiment of the inventive concept, associa~ion is made by compiling user specific data item information, which describes the data items to which a user has an access right. For each data item, location and access inforrnation is compiled, 5 which describes the loation in the storage structure of the data item and the access parameters and references of the access structure that are necessary to retrieve it.
Upon retrievin;, or possibly in advance, data items to be associated are selected.
Then, by means of said data item information and said location and access inforrnation, the selected data items are associated and retrieved.
Retrieval of information is normally executed in the form of an application procedure calling an access node, whereby an application has a preselectable access right level to certain access nodes or data items A search specification for Lli~V~ ihlg or searching the access structure comprises the identities of a sought after object and the application. Contact with a first access node is established and if the access node contains a reference to the sought after data item, further access to the data item is controlled by means of the access control means of that access node. If, on the other hand, the con~ ted access node does not contain a reference to the sought after data item, the search proceeds dependending on a reference from the first access node to a second access node. The search may proceed via further references until the relevant information is found. In order to ensure an efficient search in the data access structure, which may be distributed geographicaily on di~efel~ hlterconllected computer units, the invention also provides a navigating means which nav~gates among the linked access nodes in accordance with certain navigating rules.
According to a pler~lled embodiment of the invention, each access node is realized by means of an active process also comprising the access control means.Access to and communication with access nodes is controlled by each process, which protects and m~in~inC the references tO che data items and to other nodes of the access structure. When initiating the access structure each access node process is brought into a waiting condition, wherein the access node process is waiting for a user call. If a user application calls the access node, then, by means W 096/23267 PCT/SE95/0131~ , -of said node process, a subprocess, which preferably is a copy of the parent process, is started for controlling access operations on the reference(s) and/or the data item(s) of an access node and a timer is set. The timer is controLling the time during which said subprocess is allowed to exist. The main access node process is 5 again brought into a waiting condition, waiting for further user calls. In this manner, viz. by starting serving subprocesses upon each call access can be provided for an abritrarily large number of simultaneously active user applications.
In accordance with one aspect of the inventive concept, access control may 10 comprise the following steps. Upon a user call, it is by means of the subprocess checlced that the identity and/or the address of the user application or user computer unit is listed in a control file, and if said identity is not listed, then the subprocess is termin~te~ and access is thereby stopped. If the user computer unit is listed, then it is checked that the identity of the user is lis~ed in an access rights 15 catalogue. In one embodiment a personal identity code may be checked and/or an access key may be polled. If the user and/or his personal identity code and/or his access key is/are listed, then the user is allowed or enabled to communicate with the access node subprocess. Access to and communication of data related to objects, such as data and references, int~ ce~ by or encapsulated in the access 20 node is thus controlled by the access conkol means allowin~ or enabling different users to have different views of the access node itself and the rest of the access s ructure and the underlying data items. According to another aspect, the accesscontrol means may be deviced to conkrol access rights more closely connected to the data object, and it is then checked whether or not a user has an access right to 25 an object referred to by an access node rather than an access right to the node itsel~ If an access right exists, a copy of the obJect or a reference to it may be communicated to the user.
When the hlve~lL-~e access structure is used to interface an apparatus, a reference to a data item is stored in an access node and an output signal from said 30 apparatus is ~letecte~ and temporarily stored in said data item, whereby saidoutput signal is made available through said access node, which thereby is WO 96l23267 PCT~SE9S~01315 adapted to represent the condition of said apparatus. In other embodiments, the reference a points directly at the adress of an output terminal of the apparatus or to an input terminal of a computer based data processing system, at which terminal an output signal from the apparatus is available. In a further embodiment 5 of the invention, an apparatus is controlled by creating an apparatus control data item or an apparatus control program, by storing a reference to it in an access node and by transferring the contents of the control data item or an output control item of said apparatus control program to an input termin~1 of said apparatus.
In order to ensure a high degree of portability and readability, data, control 10 files and communication protocols used in the l~lvt;~ti~e method and arrangement are represented in a common, general data format, prefe~ably in the general string format.
A system and an apparatus for ~ocessinp data and controlling access to data according to the inventive method comprises means for performing the steps and 15 the functions of the method. All means may be realized as h~1w~e units and most of them are advantageously implemented as computer programs, executing on hardware parts of the arrangement. In particular, a computer program product,for use with a data proc~ssing and storage system, for carrying out an embodiment the inventive access method and re?.1i~ing an embodiment of the 20 inventive access structure comprises a recording medium and means for performing said method and re~ ing said access structure recorded on the storage medlum.

Brief Description of the Drawin s and Appendices ~5 Fig l shows s~h~m~tically components comprised in a data processing system for the implementation of this invention, Fig 2 illustrates the org~ni7~tion and structuring of a collection of data items;
Fig 3A shows a data table;
Fig 3B illustrates an inventive access structure coupled to a state of the art 30 data base;
Fig 4 illustrates a storage structure in the form of a graph;

CA 022l0982 l997-07-2l Fig 5 illustrates a process hierarchy;
Fig 6 illustrates retrieval and association of data according to one embodiment of the invention;
Fig 7 shows a flowchart for communication with an access nodel and access S control of data according to one embodiment;
Fig 8 shows a flowchart for an embodiment of an object protecting means comprised in an embodiment of the access control means;
Fig 9 shows a flowchart for retrieving information according to one embodiment of the invention;
Fig 10 shows an embodiment of an apparatus for performing the inventive method.

Description of Embodiments 15 1. Data Processin~ Svstem Fig. 1 shows schematically components comprised in an embodiment of an apparatus or a data proces~in~ system for performing the method according to theinvention. As shown in this figure, a data processin~ system comprises a number of real or virtual proc~Qssin~ units 10, linked by means of a network system 20.20 Each processing unit 10 comprises a co.ll~uLel processor 12 or a time shared part of such a processor, a non-volatile storage device 14 and at least one componentof a data control prograrn 16 which operates on the computer processor 12. A
human user or an a~p~Lus may interact with tne data control program 16 through a communications interface 30, which for example may be a standard 25 input and/or output device such as a keyboard, a data screen, an A/D converier or the like. Application data or control data may be transferred to a first processing unit 10 either via a related communications int.or~ce 30 or a second processing unit 10 connected to the network. The, in this text, described steps and mech~ni~m~ of the invention are perforrned by means of this kind of data 30 processinp system, either as especially designed hardware units or in the shape of a computer program ~xecuting on a general purpose computer or data processing WO 96123267 PCT~SE9~i/0131~5 system.

2 Structurin~ Data There are some different cases in the structuring of access to data according to the present invention, which cases are handled in diL'~e~ent embodiments. Forexarnple, new data may be stored in any convenient manner and references or pointers to data items or groups of data items are then established in the hlvt;rlLi~e data access structure and thus creating a new database. In particular, the inventive access method allows data to be stored in simple storage structures that requires short access times since association is made dynamically on the access structurelevel. Already stored and associated data may ~e imported from an existing stateof the art ~l~t~b~ee structure to a more loosely associated data structure coupled to the access structure. However, in many cases it is convenient to keep the data stored in the original database structure but establishing new references from access nodes in an in~rentive access structure to the data items in the P~i~tingdatabase. This is particularly true during transition from s~ate of the art database management to access structures in accordance with the present invention.
In the case of new data, the data describing an object is divided into distinctive and unassociated pieces of data, each carrying inforrnation about a certain aspect of the object. Each piece of data is stored in an atomic data item, whereby the inforrnation content of the item is limited to the smallest possibleamount of information which is relevant for its purpose. For exarnple, if the object is a person and the persons name, identification number and phone number are to be stored, these three pieces of information are clearly separated and each stored in one data item. Each of these three information atoms or data items arethemselves composed of a number of characters such as letters or digits, as the case may be. However, for this purpose only the whole series of characters are relevant and therefore fulfill the atomicity requirement of the inventive method.
3û In the case of importing existing data from a database of a known kind, the above mentioned three pieces of information would typically be clustered and associated in a more or less fixed data structure, e.g. a table or a record.
According to one embodiment of the invention these clusters of information are broken and the information is separated, as in the first case. A data importation means and a data structurin~ means, comprised in an embodiment of the inventive system, extract the information from the existing database and splits it into files adapted to storage according to the inventive method. A control file describes the pieces of clustered data which are to be extracted, the format of the input file and the format of an atomic output file. Thus, data is drained off the old database and said old database can be disposed of.
Fig. 2 shows an example of how data may be imported to the inventive storage structure. A collection of data from e.g. a state of the art database is stored in a text file 22. Data is transferred from the text file to a data structuring means 24, which depending on a control file 26 restructures the data and produces a numberof atomic data items 28. The control file 26 describes the format of the input file 15 and the data atoms to be produced. In some implementations of the invention, depending on the original data storage, a per se known spreadsheet or the like may be used in a further step of the transformation process.
The data file 22 may e.g. contain tables 32 of phone book particulars, as shown in Fig 3, which are transformed to atomic data items 28. The object 20 identities in this example are users id_l and id 2, respectively, and each data item 28 describes an aspect of one of the objects. The data is structured into specific data classes, and each classified piece of data is thus stored in an atomic dataitem. In this particular example, each class represents an aspect of the object and each class col~L~hls one data item. Data that varies over time is updated by addino 25 new data items to the relevant class forming a group of data items.
A third embodiment, where new references to data are established but the data is kept in the old database is especially useful during a transition from a state of the art ~t~b~se to a database according to the invention. This embodiment allows establishing of an illve~Live access structure for ~cce~.~ing data while 30 m~int~inin~ a coexistence of a state of the art database, e.g. an SQL database, and a database managed according to the hlvel,Li~e method. In Fio 3B is shown a state WO 96123267 PCT/SE9~/0131 of the art database 52, storing data in a number of tables 54 and being providedwith specific data associations. Depending on a control file, the data associations are rearranged, references or pointers to each of the selected data items of thetables 54 are arranged and stored in a number of data access nodes 56 A client 5 58, for example an application progJram, communicates with the access nodes 56of the access structure according to the inventive method, and thus a new interface is provided between the old database and the user The same access structure comprising access nodes 56 may simultaneously refer to data in a number of different databases, thereby connecting them and offering a conform 10 access method to all data. In one embodiment an additional interface may be provided between the old database and the inventive access structure, whereby the interface may be arranged as an access node serving the rest of the access nodesor serving a certain application. In such a case, an access node may be communicatably connected to a dedicated database interface means, e.g. an SQL
15 query processor, for accessing data in a ~t~ Ce7 with a common communicationsprotocol for communication between access nodes and the database interface ~ means and a ~t~b~ce specific communications protocol for communication between the database interface means and the ~l~t~b~ce management system.

20 3. Data Access Structure As has been mentioned, a reference to an atomic data item or a group of data items is stored in a data access node, which itself is arranged in a variable data access structure, p~efel~bly in the general form of a graph. The access node in the graph p-~ell~bly comprises a catalogue with a list of references or pointers to 25 other access nodes in the graph or directly to a data item or group of data items.
Generally the content of the catalogue is independent of the data which is referred to in the access node, but each access node is directly or indirectly linked to each data item. One advantage of se~alalh1g the reference listing from the association of data is that the access nodes and the listing may easily and arbitrarily be 30 rearranged. The access nodes may be a~ranged in any configuration, e.g. a tree, a list, a star or any other graph, and is preferably arranged in some k~d of CA 022l0982 l997-07-2l W O 96/23~67 PCT/SE95/0131 hierarchy.
References to data items are thus stored in access nodes in an access structure configured in a general graph. An access nodes may be desi~nated to refer to a certain kind of data. Fi~, 4 shows a part of such a graph 34, comprising a number S of nodes 36. Each node in this exarnple comprises at least one reference to a data item 28 and a node reference catalogue 38 which contains a list of references toother access nodes of the graph 34. As has been mentioned there may also be access nodes referring only to other access nodes. From a user's or user application's point of view a data item 28 can in an abstract sense be said to be 10 stored in an access node. The reference catalogues 38 are used to m~int~in the access structure and to facilitate search navigation in the access structure.
In one embodiment of the invention, an access node is arranged as an interface to an apparatus, whereby a data item or a pointer in said access node refers either directly or indirectly to signal terminals of said apparatus. In general, 15 an access node may thus be used as an interface to data pertaining to any real object. In this text we sometimes, fi~ul~Lively spe~king, refer to this as storing an object in an access node.
In a preferred embodiment of the invention, each access nodel is realized as an active process, which may be execllterl by a multiple of processors (CPU) or 20 by means of one processor and a time sharing system. The control of access todata and to other access nodes is thus managed by the process, which also handles the reference catalogue comprised in said access node. Access nodes may also be implemented in other ways, for example by a common file or any other data structure, but the realization of access nodes by means of processes has 25 shown to be particularly convenient and powerful in order to achieve a dynamic access structure.
The initiation of an access structure in accordance with the invention is carried out by suitable means and comprise the steps of:
-initiating an instance of an access node data structure, which in preferred 30 embodiments includes startin~, a process, by means of an access node ini~i~ting means;

W O 96/23267 PCTJSE9~JO1315 -~si~nin~; each access node a node description and an identitv code;
-establishing references to other access nodes according to a presettable initi~l configuration~ e.g. a hierarchical configuration;
-possibly, establishing a reference to a data item or to a group of data items for 5 example in a table;
-establishing access parameters, for each access node, for controlling access toreferences and possible further information which is ~cce~ed via an access node.The initial access parameters may be deviced to allow a certain view of the initial access structure, for example a fully transparent view, a view completely blocked 10 to other users than a supermanager or any other suitable combination. The initiation may also include establishing communications protocols for communication with and between access nodes.
In one embodiment the means for re~ incr the i~ elll;ve data access structure are implemented in the high level progr~mmin~ l~n~ e C and utilizes system calls to the operating system according to a standard called POSIX 1003.1, whereby the nodes of the access structure uses the protocol TCP/IP to communicate with other nodes or with the environment to the access structure.
Certain nodes may be arranged to communicate with data storage structures or devices by means of particularly dedicated protocols. Any other implementation 20 l~ng~ e and communication protocol may of course be used to realize the inventive method.
Using a client-server architecture abstraction, each access structure user or client in plere~.ed embodiments executes in a separate process during a session.Fig 5 shows a process hie~chy, in which a first access node ~tO is connecting to2~ two clients 42 via access node calls 44. Upon a call, the first access node process 40 initiates a second access node process 46, which i5 a copy of the parent node, i.e. the first access node 40 with all gualities and access parameters ali~ce. The first access node 40 acts as a node server for second access node processes 46, and may serve a large number of such second access nodes 46. The first access 30 node 40 delegates the communication and access control to said second access node processes 46 then acting as session servers, said first access node 40 communicating with said second access nodes 46 by means of session server calls 48. Data is communicated between a session servin~ second access node 46 and a client or user application 42 through process calls and data transfers 50. By means of this delegation me~h~ni.~m, an access node controlling access to certain dataS items or certain views of the data collection may simultaneously serve a large number of users and user applications.
In table I is shown a part of an exarnple of a control file for specific nodes, which describes how these nodes have been listed in the graph. The first fields ".", "..", "finance" and "hospital" are obligatory in this embodiment, and refer to 10 the narne and the position in the graph of the current node. The second field is a type indication. The indication "tcp" means that there is a reference to anothernode and that the reference is implemented in the TCP/IP protocol, whereas the indication "data" means that the node contains a refernence to data. The third field "1Ø0.1", "2Ø0.2" indicates the identity of the computer unit of a networl; in which the node resides. The fourth field "5124", "5126" etc indicates the process number of the access node, and the fifth field represents the identity of the object to which access is controlIed. The sixth field "r-x" indicates access control oraccess filter parameters which represent the relevant access level for that node.
For example, "r" means that readin~, is allowed and that the TCP/IP address to 20 this node may be obtained.

Table I

[OBJECT~]
.=tcp,1Ø0.1,5124,12.ab,r-x ..=tcp,1Ø0.1,5126,12.ac,r-x finance=data,1Ø0.1,5128,12.ad,r-x hospital=data,2Ø0.2,3014,12.ae,r-x 4. Access Control In order to prevent unauthorized access to data, access rights are checked on CA 022l0982 l997-07-2l W O 96t23267 PCTJSE9~/0131 several levels in dirrel~llt embodiments. For example, the adress of the user application or client is first checked, and if the adress is known, the access rights of the client is then checlced. Eve~y object and reference of an access node has an access list which is polled before a client cnmm~ncl is executed. In one embodiment of the invention, a maximum value is set for the time during which a client may communicate with an access node or with a subnode acting as a session server. Unauthorized intruders may thereby be detected on the basis of their communication rate. For example, external intruslons are often carried outthrough a modem with a slower baud rate than users connected to a local area network and setting a short time sufficient for normal communication will delimit the possibilities of data ~xr~h~n~e. A logging system may be comprised, which logs and renders traceability of communication with an access node, readin, and writing operations, client comm~n~ls and accesses as well as the commanding users and/or applications.
In a preferred embodiment of the invention, access control pararneters constituting an access filter are comprised in the access nodes. The access filter is aTranged to let diL~.e~ll interested parties or clients have the}r specific view of the stored object, objects or references of the access node. This access filter is also used together with a navigator, in order to enhance the navigation efficiency.
Fig 7 shows a flow chart of an embodiment of access control according to the invention, wherein the white boxes represent steps of the method, the filled boxes represent control files and the il~le~ P~-t lines show the communication with a user. In step 72 an access node process is started and initi~li7p~l~ and access node parameters concerning other nodes and objects referred to by the node are read 2~ from a control file 74. In step 76 the access node is kept in a waiting condition, waiting for incoming user calls 78. If a user call is received, the access node process starts a subprocess in step 80 and sets a timer depending on the controlfile 82 for the period the subprocess ~s allowed to exist. The purposes of the timer is to protect the access node from intruders having abnormal communication çh~nnnels~ but it is also used to prevellt passive subprocesses from unnecessarily occu~ying system resources. In step 84, the subprocess verif1es the user, W 096123267 PCT/SE9S101315 -, depending on a control file 86 cont~ininp: information about accepted and permitted user identities. The adress and the identity of the user is polled in communication 88. If the user is denied access, the subprocess is termin~te~l instep 100 and a message 102 is sent to the calling user. Thus, both the identity of the user computer and of the user controlling it may be checked. If, on the other hand, the user is permitted and accepted, the user is logged in to the access node in step 104 and 106 and is allowed access to functions of the access node and objects encapsulated in or referred to by the access node. Thereafter, further access to and communication of data and references contained in the access node is controlled by means of an access filter having certain access control parameters and allowing different users dirrelel1t views of the access node, the access structure and the underlying data.
Fig. 8 shows a flow chart of a method for implementing an object access control means or an object filter comprised in an embodiment of the invention.
The object filter is used in conjunction with the previously mentioned access control to protect an object referred to by an access node. In step 124, upon a user command (cmd=dir) all objects are copied to or listed in an object list 128.
Thereafter, in step 132 every object in the object list is checked in respect ofwhether or not the user is permitted access to it. An object access list 134 is thereby used as a check reference. If access right exists for an object, a copy of or a reference to that object is input in a user list, step 136, and is communicated to t~le user in step 138 by call 140.
A further feature comprised in some embodiments is that an access node comprises one access rights list for every object or type of object referred to by ~5 the access node, in order to enable a mech~ni.cm allowing certain users to see references to other access nodes and other users to see only the data or object referred to by the access node.

5. Time Parameter According to ~ fell~d embodiments of the inventive method, all data is provided with a time parameter stored in connection to each data item. This ' CA 02210982 1997-07-21 ~- . WO 96123267 PCrlSE9510131 allows version handling and more important the management of data of diLrele~
nature in a conforrn way. This feature is due to the inventor's recognition of the fact that data in different context mainiy differ in the freqeuncy of changes.
For exarnple, static data has a value with a ch~n~ino frequency of zero changes 5 per time unit, whereas variable data may vary discretely or continuously at any rate. Changes may occur asynchronously at non-anticipatable moments, e.g. stock-exchange rates, or synchronously at predeterrnined moments, e.g. a video signal sampled with a certain sampling frequency In a preferred embodiment, updatings and changes to the ~l~t~b~e may only 10 be made in chronological order, i.e. old data can never be overwritten by a user.
Howe~er, a means is provided which allows a database ~ nistrator to erase data or selected parts of the data. All data may be read by an authorized user or user application, and it may be specified that the last data or any selected data from a certain point of time or data from a selected period is read.
6. Associatin~ Data and Initiatin~ Views Association of data is, according to the h~velllive method, performed dynamically, in the sense that data is associated upon search and retrieving of data, whereby information about the storage of the data is hidden to a user 20 application. As has been mentioned, data is stored in an albiLld~y manner andreferred to by access nodes arranged in a variable access structure, whereby each node has at least one reference to another node. The references are independent of, or losely coupled to the data stored in the nodes. Thereby, association of data is not fixed in the storage structure.
Fig. 6 illustrates one embodiment of how views of data are obtained and data is retrieved and associated via a system of control files when running an application. In an application 60 is composed a table 62 with a specification ofsearched data comprising the name and the type of selected data objects or data items. In an item list 64, a reference to an access list 66 is found depending on each specified data item. In the access list 66, there is information describingwhere the sought after access node 68 is located in the variable access structure CA 022l0982 l997-07-2l W O 96/23267 PCT/SE95/01315 -, 70, said information for example comprising indications of data type, node, portin a network and access parameters.
The initiation of a view of ~he access structure or the underlying data objects comprise the steps of:
5 -~lefinino an application view with a specification of requirements such as type of object, data item, method, control program or Sign~ls7 information sources and functions;
-searching in the access node structure for access nodes havino, references to objects matching an aspect of the specification of requirements;
10 -saving access node identification of m~tchin,o access nodes in for example a view list;
-repeating search until the specification of requirements or other search parameters are satisfied;
-if access nodes are mi~in,o for stored or connected objects, possibly completing 1~ the access node structure by creating new access nodes for said objects.
The references of the variable access structure may be rearranged from time to time, and it may occur that the item list, the access list or the view list do not have up to date information about the location of certain access nodes. For thiscase, an access structure navigator is provided, by means of which the access 20 structure may be searched and the new position of an access node be identified and possibly stored in the access list. The navigator is in general useful for carrying out searches in the access structure according to dynamically specifiedmethods.
Di~fere,~L search parameters may be used, for example every object stored in a 25 data shell has a unique identity, which in some instances is convenient to use as a search parameter. Data may also be searched by first specifying a time value or a time interval for the data item to be found. The data item or data items which has or have a time parameter with the specified time value are read and then communicated to the retrievino, user or user application, alternatively the 30 corresponding access node specifications or references are retrieved and possibiy saved.

WO 96/23267 PCTlSE9~/0131 In Fig. 9 is shown a flowchart of a retrieving method comprised in an embodiment of the invention. If a reading command is received in step 142, then time variables are set in accordance with specifications given in the reading command. First the time variables Be~intime and Endtime are set in step 144 to S the time of a clock in the data processing unit or a server. In step 146 it ischecked if the user has specified a first time value T1, and if so, Be~lntime and F.n~ltime are set to this value T1 in step 148 Then, in step 150, it is checlced if a second time value T2 has been specified, and if so, Fn~time is set to T2 in step152. Thereafter, in steps 154, 158 and 160 a data item 156 in the data shell is 10 read and if it has the specified time value equal to server time or T1 or within the interval T1 to T2, this data item is inserted in a result list or result vector. Then, the result list is sent to the user in step 162 by call 164.
In general, navigation may be conducted interactively or in a more batch oriented m~nner depending on a preset specification of requirements. Common for 15 method is that navigation in accordance with the invention may comprise the steps of:
-setting the navigating means for m~tr~hin2 access node information with a specification of requirements for a certain view of objects;
-calling a first access node giving user identity and view specification, whereupon 20 the access node returns a subview of references to access nodes or objects that are relevant for the specified view;
-calling second access nodes in for exarnple a hierarchical manner, for example until a number of subviews coincide for a set of access nodes or objects, -possibly saving a navigation logging in order to speedy obtain the same view at25 another occasion.
By means of the access control parameters and the navigating means it is possible to preset dirrt~ views for dirre~e~lt users, user groups or h1teresLed parties. One embodiment comprises an updating subscription means, by means of which a user may subscribe on automatically generated messages for every 30 updating of information or event related to an object or object attribute. Such a message may also include updated information or data items per se . The method for achieving this feature comprise the steps of:
-associating or adding to the control file of an access node a sequnce of steps to be performed in response to a detected event related to an object referred to bythe access node;
5 -sending a message possibly including changed data to a su~scribing user application; and/or -activating an al~pal-allls in response to said detected event.

7. Arran ement One embodiment of an arrangement for executing the inventive access structure is shown in Fig 10. A data processing unit 170 comprises a computer processor, astorage device, a data control program being executable by means of the data processing unit 170 and a communications interface. An access node initiation means 172 for initiating and structuring access nodes is communicatably coupled to the data procPssin~ unit 170 and to a time parameter generating means 174 forproviding data item or references to data items with a time parameter, whereby the time pararneter generating means 174 also is communicatably coupled to the data procee.sing unit 170. A data shell generator 176 is communicatably coupled to the data structuring means 172, to the data processing unit 170 and to a datastorage structure generator 178, which also is coupled to a data storage structure carrier 180. Said carrier 180 is also communicatably coupled to the data proces.C;n,cr unit. The communication links between the units may be realized byconductors or by operative hllelco~ ections for data or parameter PYt~h~n~P, i.e.
the units are operatively interconnected.
A computer program product, for use with a data proc~.sin,~ and storage system, for providing an access structure in accordance with the invention, comprises a storage medium and means for initi~ting and m~inL-,1ininV an access structure, means for ~ocescing the access structure and other means for carryingout the steps of the in~entive method. The above described embodiments of the invention are merely non-limiting examples of the invention, and other designs are possible within the scope of the claims.

Claims

1. A computer implemented method, for use in a computer-based data processing and storage system (10,12,14,16,170), for controlling access to data items (28) representing an aspect of an object, comprising the steps of:
-storing a reference to a data item or to a group of data items in a data access node (36,56,68); and -storing a reference to another access node (36,56,68) thus arranging an access structure (34,70) of data access nodes (36,56,68), wherein a first access node is directly or indirectly linked to a second access node or to a data item referred to by the reference of said second access node; characterized in the step of:
- structuring and/or storing data in separate and unassociated data items (28), wherein each data item carries only the amount of information that is relevant for its purpose.

2. The method as recited in claim 1, comprising the further step of providing each data item with a time parameter, wherein the time parameter is associated to or stored in connection with said data item; and wherein said time parameter is the time at which said data item is read, said data item is stored or any other indicated time.

3. The method as recited in claim 1 or 2, comprising the further step of maintaining access control parameters for each access node, the access control parameters defining access conditions to said access node or said references of said access node.

4. The method as recited in any of the preceding claims, comprising the further step of updating variable data by creating a new data item in which the last data version is stored and by adding said new data item to a relevant group of related data items, whereby data items may be added at any rate enabled by the data processing system processing said data.

5. The method as recited in any of the preceding claims, comprising the further step of associating data items upon retrieving, by means of a control structure comprising an application dependent specification and an access specification, by means of which communication with an access node is performed.

6. The method as recited in any of the preceding claims, comprising the further step of controlling read and write operations and access to a data item or to an access node by means of access control parameters provided in the access node.

7. The method as recited in any of the preceding claims, wherein the initiation of an access structure comprises the steps of:
-initiating an instance of an access node data structure;
-assigning said access node a node description and an identity code;
-establishing references to other, already initiated access nodes according to aselectable initial configuration;
-possibly establishing a reference to a data item or to a group of data items, -establishing access parameters, for each access node, for controlling access toinformation that is accessed via said access node; and -possibly repeating the aforementioned steps.

8. The method as recited in any of the preceding claims, wherein an access node is realized by means of an active process, the initiation then including starting a process by means of which all communication with the access node is controlled.

9. The method as recited in any of the preceding claims, comprising the further step of adapting a data item referred to by an access node to represent the condition of an apparatus, whereby an output signal from said apparatus is detected and temporarily stored in said data item, and whereby said output signal is made available via said access node.

10. The method as recited in any of the preceding claims, comprising the further step of controlling access to an apparatus, wherein an access node contains a reference, possibly via a data item, to a signal terminal of said apparatus at which an output signal from the apparatus is available or an input signal is inputtable.

11. The method as recited in any of the preceding claims, comprising the further step of controlling an apparatus by creating apparatus control data, by storing temporarily said control data in a data item referred to by an access node, and by transferring the contents of said control data item to a control signal input terminal of said apparatus.

12. The method as recited in any of the claims 8-12, comprising the further steps of:
- storing a reference list in a first access node;
- bringing the access node process into a waiting condition, wherein said access node process is waiting for a user call;
- if a user calls the access node, then, by means of said access node process, starting a subprocess realizing a copy of the first access node, having characteristics inherited from the first access node process, for controlling access operations on the reference list and/or on a data item referred to by said first access node;
- then again bringing the access node process into a waiting condition, waiting for further user calls.

13. The method as recited in any of the claims 8-12, comprising the further steps of:
by means of said subprocess - checking that the identity and/or the address of the user computer unit is listed in a control file, and if said user computer is not listed then terminating the subprocess; else - checking that the identity of the user is listed in an access rights catalogue, and possibly checking a personal identity code and/or polling an access key, and if said user is not listed then terminating the subprocess; else - allowing said user to communicate with said access node process; and - controlling said access to and communication of data and references contained in the access node by means of access control parameters allowing different users different views of the access node and underlying objects.

14. The method as recited in any of the claims 12-13, comprising the further step of setting a timer controlling the time during which said subprocess is allowed to exist.

15. The method as recited in any of the preceding claims, comprising the further steps of:

-compiling user specific data item information, describing to which data items a user has access rights;
-compiling for each data item, location and access information describing its location in the storage structure and access parameters necessary to retrieve said data item:
- selecting data items to be associated;
- retrieving, by means of said data item information and said location and access information, the selected data items.

16. The method as recited in any of the preceding claims, comprising the further steps of initiating a view of the access structure or underlying objects by:
-defining an application view with a specification of requirements for wanted objects;
-searching in the access structure for access nodes having references to objectsmatching an aspect of the specification of requirements;
-saving access node identification of access nodes for matching objects;
-repeating search until the specifications of requirements or other search parameters are satisfied.

17. The method as recited in any of the preceding claims, comprising the further steps of navigating through the access structure by:
-setting navigation parameters for matching access node information with a specification of requirements for a selected view of objects;
-calling a first access node giving user identity and view specification;
-returning from the access node a subset of references to access nodes and/or objects that are relevant for the specified view;
-calling second access nodes until a number of subsets of references to access nodes and/or objects coincide; and -possibly saving a logging of relevant access nodes.

18. A data processing system (10,12,14,16,170) for maintaining a data access structure (34,70) for controlling access to stored data items, said system being provided with a data processing unit (170) comprising a computer processor (12), a data storage medium (14), a data control program (16) being executable by means of said data processing unit, and a communications interface (30), and comprising means (172) for initiating and maintaining, in the data processing system, a plurality of data access nodes (36,56,68), each storing references to other access nodes and/or to data items stored on the storage medium, characterized in means (172) for structuring and/or storing data in separate and unassociated data items, wherein each data item carries only the amount of information that is relevant for its purpose.

19. The system of claim 18, comprising means for associating each access node with access control parameters for defining access conditions to said access nodes or to said references of said access node.

20. The system of claim 18 or 19. comprising means for providing each data item with a time parameter, wherein said time parameters are stored in connection with or associated to said data items.

21. The system of claim 18, comprising means for generating or initializing a process or a virtual processing unit for each access node.

22. The system of claims 18-21. comprising means for generating or initializing links between each access node or access node processing unit.

23. The system of claims 18-22, comprising means for associating access nodes or data items of said access structure.

24. The system of claim 19-23, comprising means for controlling access to accessnodes depending on said access parameters.

25. The system of claim 18-24, comprising means for traversing, searching or navigating through the data access structure, by means of which search for one or more access nodes or data item constituting a selectable view is performable.

26. A computer program product, for use with a data processing and storage system, for maintaining data access structure for controlling access to stored data items, the computer program product comprising:
-a recording medium;
-means, recorded on the recording medium, for directing the data processing and storage system to initiate and maintain a plurality of data access nodes, each access node storing references to other access nodes and/or to data items stored on a storage medium in the data processing and storage system; and -means, recorded on the recording medium, for directing the data processing and storage system to structure and/or store data in separate and unassociated data items, wherein each data item carries only the amount of information that is relevant for its purpose.

27. The computer program product of claim 26, further comprising means, recorded on the recording medium for directing the data processing and storage system to associate each access node with access control parameters for defining access conditions to said access nodes or to said references of said access nodes.

28. The computer program product of claim 26 or 27, further comprising means recorded on the recording medium for directing the data processing and storage system to provide each data item with a time parameter, wherein said time parameters are stored in connection with or associated to said data items.

29. The computer program product of any of the claims 26-28, further comprisingmeans, recorded on the recording medium, for directing the data processing and storage system to generate or initialize a process or a virtual processing unit for each access node.

30. The computer program product of any of the claims 26-29, further comprisingmeans, recorded on the recording medium, for directing the data processing and storage system to generate or initialize links between each access node or access node processing unit.

31. The computer program product of any of the claims 26-30, further comprising means, recorded on the recording medium, for directing the data processing and storage system to associate access nodes or data items of said access structure.

32. The computer program product of any of the claims 26-31, further comprising means, recorded on the recording medium, for directing the data processing and storage system to control access to access nodes depending on or responsive to said access parameters

33 The computer program product of any of the claims 26-32, further comprising means, recorded on the recording medium, for directing the data processing and storage system to traverse, search or navigate through the data access structure, by means of which search for one ore more access nodes or data items constituting aselectable view is performable.

34. The computer program product, comprising means, recorded on the recording medium, for directing the data processing and storage system to perform the steps as recited in any of claims 1-17.

35. A data access structure (34,70), for controlling access to data items (28) comprising - a plurality of data access nodes (36,56,68) - each data access node comprising a node description, an identity code and a reference to another, already initiated access node according to a selectable initial configuration; characterized in a reference to a data item or to a group of separate and unassociated data items, where each data item (28) carries only the amount of information that is relevant for its purpose.

36. The data access structure of claim 35, wherein each access node comprises anaccess parameter for controlling access to information that is accessed via said access node.

37. The data access structure of claim 35 or 36, wherein an access node is realized by means of an active process, by means of which all communication with the access node is controlled.

38. The data access structure of any of the claims 35-37, wherein a data item referred to by an access node is adapted to represent the condition of an apparatus, whereby an output signal from said apparatus is detected and temporarily stored in said data item, and whereby said output signal is made available via said access node.

39. The data access structure of any of the claims 35-38, wherein the access structure is adapted to control access to an apparatus and wherein an access node contains a reference, possibly via a data item, to a signal terminal of said apparatus at which an output signal from the apparatus is available or an input signal is inputtable.

40. The data access structure of any of the claims 37-39, wherein:
- a reference list is stored in a first access node;
- the access node process is adapted to be brought into a waiting condition, wherein said access node process is waiting for a user call;
- said access node process is adapted to start, upon a user call on the access node, a subprocess realizing a copy of the first access node, having characteristics inherited from the first access node process, for controlling access operations on the reference list and/or on a data item referred to by said first access node; and - the access node process is adapted to be brought into a waiting condition, waiting for further user calls.

41. The data access structure of claims 40, wherein said subprocess is adapted to:
- check that the identity and/or the address of the user computer unit is listed in a control file, and if said user computer is not listed then terminating the subprocess; else - check that the identity of the user is listed in an access rights catalogue, and possibly to check a personal identity code and/or polling, an access key, and if said user is not listed then to terminate the subprocess; else - allow said user to communicate with said access node process; and to - control said access to and communication of data and references contained in the access node by means of access control parameters allowing different users different views of the access node and underlying objects.

42. The data access structure of claim 40 or 41, wherein a timer is set for controlling the time during which said subprocess is allowed to exist.