Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1998-08-04
2002-05-14
Banankhah, Majid (Department: 2151)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C709S217000, C709S218000
Reexamination Certificate
active
06389421
ABSTRACT:
FIELD OF INVENTION
The present invention relates to data processing systems and methods, and in particular to a method and a system for handling processor-intensive operations in a data processing system such as a computer-based data retrieval system. The invention is useful for allocating resources in a data processing system and/or for reducing data access delays.
BACKGROUND OF INVENTION
Data libraries which are accessible from any one of a large number of computer terminals within a distributed network are well known in the art. As the Internet, intranets and the World Wide Web have gained in popularity, and imaging systems have become more widely available, libraries of images and other data objects have been stored on server computers and connected for access by many people via the Internet or intranet. Individuals can, for example, request copies of required objects such as images using a Web Browser installed on a client computer connected to the Internet.
Making data objects such as images accessible to many users can create opportunities for malicious parties to replace the images on the server with forgeries, or to intercept and replace images that have been transmitted to others. In addition, with the development of sophisticated image editing software, tools which allow easy alteration of the content of any digital image are widely available. Thus, the integrity of a digitally stored image may be in question unless safeguards are provided.
Watermarking and digital signature techniques have been developed which allow verification of the source and integrity of an image (i.e. detection of any changes to it), as well as providing a means for checking that the user is authorised to access the image (by only allowing access if the requester knows the digital signature), and enabling subsequent identification of unauthorised copies. Thus, watermarking and digital signature techniques are beneficial to image owners and licensors and can also be beneficial to those requesting image access.
An end user may specify a digital signature of an image when requesting the image file either a) if the data retrieval system requires this before it will deliver the file or b) if the user wishes to check the authenticity and integrity of the image before it is delivered to them. Additionally, a data retrieval server may be adapted to perform dynamic digital signature checking of images even if the user is not required to know the signature.
In addition to digital signature checking, a server computer may be adapted to dynamically execute a watermarking process, either for all stored objects or only for certain categories of object or certain categories of requester, when it receives a request for a copy of an object. This watermarking enables subsequent identification and verification. Since images as stored in a digital image library may not have watermarks, it may be desired to watermark the images prior to distribution of copies in order to embed information such as the identity of either the distributor or the requester.
A problem which arises with systems which perform watermarking dynamically (i.e. when an object is requested from a repository, rather than when the object is stored in the repository or earlier, which is the conventional approach) is the time delay that an end user can experience while waiting for the object to be delivered. Dynamic watermarking is a computer processor-intensive operation leading to the possibility of delays in object retrieval. These delays increase with the number of requests being processed concurrently.
Such delays may be considered particularly undesirable for users who have requested objects for which no signature checking or watermarking is required, since in this case their retrieval and delivery operations involve relatively little processing but can be significantly delayed by digital watermarking of objects for other users.
SUMMARY OF INVENTION
It is a first aspect of the present invention to provide a method and a system for data retrieval, the method including:
responsive to receipt of data retrieval requests by the data retrieval system, identifying requested data retrieval operations requiring a first predetermined task to be performed;
inputting into a first processing queue only the data retrieval operations requiring said first predetermined task to be performed;
handling data retrieval operations which do not require said first predetermined task to be performed without performing said first predetermined task; and
processing the data retrieval operations in the first processing queue including performing said first processing task.
A data retrieval method according to the invention preferably also includes inputting into a second processing queue separate from said first queue data retrieval operations which require a second predetermined task but do not require said first predetermined task, and processing said first and second queues independently.
The first predetermined task is preferably the performance of a watermarking process. By separating simple rretrievals from retrieve-and-watermark operations, which are processor-intensive, it is possible to avoid retrieval operations (and hence users) not requiring watermarking from being overly impacted by the resource demands of users whose requested data objects do require watermarking.
Methods and systems according to one embodiment of the invention determine for each received request both whether watermarking is required and whether a second post-retrieval processing task is required (such as digital signature checking, or conversion from TIFF format to JPEG format). Simple data retrieval operations and retrieval-with-signature-checking operations can then be separated from retrieval-with-format-conversion operations, and all of these are separated from retrieval-with-watermarking operations.
Alternative embodiments of the invention may separate processing operations according to both the size of the requested object and the particular tasks to be performed on it.
Thus, requested data retrieval operations are separated for processing according to the predicted resource requirements of carrying out that processing. This facilitates improved resource allocation and enables a reduction of the delay experienced for operations which are not processor intensive.
The data retrieval operations requiring performance of one or more predetermined tasks are preferably identified by comparing a data-object-identifier obtained from a received request with a table of object types and required processing tasks for each type.
The first and second processing queues are preferably circularly-linked lists to which requested data retrieval operations are added, the operations being indexed according to the ID's of their end user requesters. Each node in the first ring (circularly-linked list) contains a list of all of the operations to be performed for a respective user which require the processor-intensive first post-retrieval task, and each node in the second ring contains a list of all of the operations to be performed for a respective user which require a second post-retrieval task.
The independent processing of each circularly-linked list preferably involves serving each of the plurality of users on a ‘round-robin’ basis, under the control of a scheduler, with a predetermined amount of processing being performed for each user each time that user's tasks in the respective linked-list are given attention. This “predetermined amount of processing” is preferably either an equal amount of processing time (e.g. 2 seconds of CPU time) for each user, or the completion of one or more particular processing tasks for one or more requested objects for each user. Alternatively, predetermined but different amounts of processing may be performed for different categories of user.
It is a second aspect of the present invention to provide a method and a system for allocating data processing resources between users of a data retrieval system, the method including:
inputting data retrieval requests t
Hawkins John Christopher
Ibbotson John Bryan
Nuttall Mark Patrick
Banankhah Majid
Beck Thomas A.
Herzberg Louis P.
International Business Machines - Corporation
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