CAN CSA-Z243 181A-1999 Information processing systems - Open Systems Interconnection - File Transfer Access and Management - Part 2 Virtual Filestore Definition AMENDMENT 1 Files.pdf

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1、Amendment 1:1999 to National Standard of Canada CAN/CSA-2243.181-89 Amendment 1:1992 to International Standard IS0 8571-2:1988 has been adopted without modification as Amendment 1:1999 to CAN/CSA-Z243.181-89. This Amendment was reviewed by the CSA Technical Committee on Information Technology (TCIT)

2、 under the jurisdiction of the Strategic Steering Committee on Information Technology and deemed acceptable for use in Canada. July 1999 Information processing systems - Open Systems Interconnection - File Transfer, Access and Management - Part 2 : Virtual Filestore Definition AMENDMENT 1 : Filestor

3、e Management (Reaffirmed 20 Technologies de Iin formation - lnterconnexion de systemes ouverts (OSI) - Transfert, acces et gestion de fichiers - Partie 2: Definition du systeme de fichiers virtuel AMENDEMENT 1 : Gestion du systeme de fichiers Reference number IS0 8571 -2:1988/Arnd.l: 1992 (E) IS0 85

4、71-2:1988/Amd.l:1992 (E) Foreword IS0 (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of IS0 or IEC participate in the development of International

5、 Standards through technical committees established by the respective organization to deal with particular fields of technical activity. IS0 and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non- governmental, in liaison with I

6、S0 and IEC, also take part in the work. In the field of information technology, IS0 and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an Internationa

7、l Standard requires approval by at least 75 % of the national bodies casting a vote. Amendment 1 to International Standard IS0 8571-21988 was prepared by Joint Technical Committee ISO/IEC JTC 1, lnformation technology. IS0 8571-2 consists of the following parts, under the general title lnformation p

8、rocessing systems - Open Systems interconnection - File Transfer, Access and Management - Part I : General introduction - Part 2 : Virtual Filestore Definition - Part 3 : File Service Definition - Part 4 : File Protocol Specification - Part 5 : Protocol Implementation Conformance Statement Proforma

9、0 ISOilEC 1992 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. iSO/lEC Copyright Office Case postaie 56 CH-I211 Geneve 20 Swit

10、zerland IS0 8571-2:1988/Amd.l:1992 (E) Information processing systems - Open Systems Interconnection - File Transfer, Access and Management - Part 2 : Virtual Fi Iestore Definition AMENDMENT 1 : Filestore Management NOTE -This amendment has additional subclauses and tables to IS0 8571 which are indi

11、cated by the use of lower case Roman letters beginning with “a“ and imply ordering alphabetically, following the clause with the same numerical value in IS0 8571. These and all subsequent subclauses, tables, and cross references will be renumbered in subsequent editions. I nt roductio n (amend 3rd p

12、aragraph, page 7) IS0 8571 defines services for file transfer, access and management. It also specifies a protocol available within the application layer of the Reference Model. The service defined is of the category Application Service Element (ASE). It is concerned with identifiable bodies of info

13、rmation which can be treated as files, stored and managed within open systems, or passed between application processes. (amend 4th paragraph, page 7) IS0 8571 defines a basic file sewice. It provides sufficient facilities to support file transfer, file access, and management of files stored on open

14、systems. IS0 8571 does not specify the interfaces to a file transfer, access or management facility within the local system. 1 Scope and field of application (amend 7st paragraph) This part of IS0 8571 defines an abstract model of the virtual filestore for describing files and filestores (see sectio

15、n one); defines the set of actions available to manipulate the elements of the model (see section two); defines the properties of individual objects and associations in teAs of attributes (see section three). defines the form of representations of files with hierarchical structures (see clause 7 in

16、section one). 1 IS0 8571 -2:1988/Amd.l: 1992 (E) Section one: 5 Basic concepts (amend 3rd paragraph (afier note), page 2) A filestore may contain an arbitrary number (greater than or equal to one) of objects (see figure 1). (amend 4th paragraph, page 2) The properties of each object are defined by t

17、he values of a set of object attributes. These attributes are global; at any one time, a single attribute value is available to all initiators. Different object types may have distinct types of attributes, as well as types of attributes in common. (add following paragraph 5, page 2) Each file-direct

18、ory maintains a parenthood relationship with zero or more subordinate objects. Some of the file-directory attributes may identify access control information to subordinate objects. Each reference maintains a link to exactly one other object. The referent is either a file or a file-directory. The ide

19、ntity of the referent is available as an attribute of the reference, in the form of a (possibly incomplete) primary pathname. This attribute can not be changed. Other reference attributes may identify the object type and access control information to the linked object. If the identity of the referen

20、t changes, the corresponding reference ceases to exist. (amend 7th paragraph, page 3) The first are in one to one correspondence with the object attributes, and indicate the active value of those attributes as perceived by the initiator. (amend 9th paragraph, pages 3 and 41 An arbitrary number (grea

21、ter than or equal to zero) of initiators may have initialized FTAM regimes at any one time. Exchanges between the initiator and the responder lead to the selection of at most one object in the responders virtual filestore to be bound to a particular FTAM regime at any one time. Note that multiple fi

22、le objects may be identified for later selection via the generalized selection service. However only one object may be selected at a time. Further, no guarantees are placed on the availability of any file object in this group if it is eventually selected. (add after clause 5, page 4) The filestore m

23、odel 5a The virtual filestore model 5a.l Filestore Objects A virtual filestore is comprised of one or more of three kinds of objects: a) files; b) file-directories; c) references. 5a.l.l Files File objects contain data, and provide structuring information to access the data within them (see clause 5

24、a.l.2 File-directories File-directory objects maintain a set of relationships to zero or more other objects within the filestore, whether those objects are files, references, or other file- directories. This relationship is parenthood. A file- directory is said to be the parent of an object if it ma

25、intains the relationship of parenthood for that object. Similarly, an object is said to be the child of a specified directory if that directory is the objects parent. In this way, file-directories provide a means of grouping objects within the virtual filestore. These groups can then be used to prov

26、ide a structural order (the filestore tree) to the data files within the filestore. An object is in a file-directory if either 7). a) that file-directory is the parent of the object b) there is a reference whos parent is the file- directory, linking to the object. An object is under a file-directory

27、 if either a) the object is in the file-directory b) the object is in another file-directory that is under the file-directory. (Note this is a recursive definition.) 5a.l.3 References Reference objects maintain exactly one relationship to exactly one other object within the filestore. That relations

28、hip is linkage. The object linked by the reference must be either a file or a file-directory. The structure defined by the parent and linkage relations is called the filestore structure. 2 IS0 857 1-2: 1988/Amd.l :I 992 (E) 5a.2 Filestore structure Every virtual filestore has a root object. The root

29、 is the only object in the filestore that has no parent. This root is either a file or a file-directory. It cannot be a reference. In the case where it is a file, that file will be the only object within that filestore. The relationship of parenthood results in a hierarchical model of the filestore,

30、 where the root node is represented by the filestore root object, intermediate nodes are represented by file-directories maintaining at least one parenthood relationship, and leaf nodes are represented by files, references, and file- directories maintaining no parenthood relationships. References ma

31、y be used for convenience of access in special situations, or for special security needs. References provide a simple means of allowing an object to appear in more than one place in the filestore hierarchy without having to duplicate the object, or worry about maintaining consistency between duplica

32、te objects. In normal use a user will not observe any difference in behavior whether an object is accessed via parenthood or reference. 5a.3 Name resolution An object is identified within the virtual filestore by a pathname. A pathname is comprised of a series of object names. Each object name in th

33、e series identifies the next child object in the virtual filestore. The last object name in the series identifies the target object. The root object in a filestore is identified by a pathname comprised of zero object names. The exact algorithm is described in 5a.3.2. 5a.3.1 The current name prefix W

34、hen the pathname of an object begins its series of object names at the root of the filestore, it is called a complete pathname. Otherwise, to uniquely identify an object within the virtual filestore, the incomplete pathname must be resolved to a complete pathname. This is done with the current name

35、prefix activity attribute. The current name prefix is assigned to the association by the responder. The current name prefix is a complete pathname of a file-directory object. The actual mechanisms for this assignment are outside the scope of FTAM, but possible uses could be for providing default fil

36、e-directories to users, protecting filestore users from potential filestore organizational changes, or for enhanced security control. An incomplete pathname is resolved to a complete pathname by prepending the series of object names within the current name prefix to the incomplete pathname. Objects

37、within a virtual filestore may be referenced by complete pathname, or by an incomplete pathname. In the latter case, the responder resolves the incomplete pathname to a complete pathname using the current name prefix. The file protocol is designed such that the responder need not reveal the current

38、name prefix to the initiator, should it be desirable to conceal the filestore structure above this file-directory for security or other reasons. 5a.3.2 Resolving a pathname A complete pathname is resolved to an object by a series of steps using the object names of the pathname to locate the intermed

39、iate objects along the path in turn. Initially, the root node is located. For each step, while object names of the pathname remain to be resolved: if the object located is a reference, and the filestore user has passthrough access to this reference, then the object which it references is located (if

40、 the user does not have passthrough access to this reference, or if the referenced object is not found, an error is reported); if the object located is a file-directory, and the filestore user has passthrough access to this file-directory, then the child object named by the next object name of the p

41、athname is located (if the user does not have passthrough access to this directory, or the next object name does not correspond to any child of this directory, an error is reported); if the object located is a file, then an error is reported. If the object located when all object names of the pathna

42、me have been exhausted is a reference, then the final action taken depends on the operation being performed: d) if the operation is specific to reference objects, then the operation is performed on the reference object located; e) if the operation is not specific to reference objects, then the objec

43、t to which the reference refers is located, and the operation is performed on the referenced object. 5a.4 Object type checklng If the object located when a pathname is resolved is not of the type required for the operation to be performed then an error is reported. 3 IS0 8571-2:1988/Amd.l:1992 (E) 0

44、 0 0 - file - directory - reference - parenthood - linkage Figure la - An example tree structure of a VFS 5a.5 Example c) G,J,K,D Figure la shows an example of a filestore containing references. The file F has primary pathname E,F. However, it may also be accessed by the following names involving re

45、ferences: a) AD b) G,H,F Thus for file selection, the filestore in this example appears as if duplications of data took place as in figure 1 b. NOTES 1) In normal use, except when explicit manipulation of the reference object is carried out, a user will not observe any difference in behaviour whethe

46、r an object is accessed via parenthood or reference. Flgure 1 b - An example of the apparent structure of a VFS 4 IS0 857 I -2:1988/Amd.l:1992 (E) 2) References may be used for convenience of access in special situations. References may have, in conjunction with the path access control attribute, ap

47、plications to security and secure views of the filestore structure. (amend title of clause 6, page 4) 6 Object selection (amend 7st paragraph, page 4) From outside the filestore, selection of an object is always made using the pathname of the object. Even in the case of generalized selection service

48、s, the actual selection of a single object from within the group of file objects maintained in the generalized selection group activity attribute is made by implicit (Le., internal to the responder controlling the filestore) reference to the pathname of the object. The reference to an object is with

49、in the context of a particular filestore identified by the application entity title. The application entity title refers to the location of file storage, and is known to the file service users, but lies outside the scope of FTAM. The pathname of an object is defined in clause 13.1 9. (insert after 7st paragraph, page 4) 6.1 Methods of object selectlon Two methods of objectselection are provided. 6.1.1 Simple object selection (amend 2nd paragraph of clause 6, page 4) Simple object selection takes place in two stages. First, an FTAM regime is initialized with the application entity hand