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A scheme for paction-less extensible delta with JAR archive

IP.com Disclosure Number: IPCOM000029017D
Original Publication Date: 2004-Jun-11
Included in the Prior Art Database: 2004-Jun-11
Document File: 4 page(s) / 33K

Publishing Venue

IBM

Abstract

Disclosed is a scheme for generating a delta between two archives. The scheme has two features; tiny delta size with use-limitation and extensibility with including reproduct algorithm and feature of JAR.

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A scheme for paction-less extensible delta with JAR archive

Backgrounds and Related Arts

The "delta technology" is, as well known, a method to reduce the size of information to transmit. In some years ago (when the network-bandwidth was so expensive), the technology was often used for application updating.

Sender transmits a Delta to Receiver which is a differential information (much smaller than Target) between Original and Target, generated by Extractor. On the other hand, Receiver makes Reproduced data with Compensator from Original and Delta. The Reproduced is the exclusively copy of Target.

Sender Receiver

Figure1: Delta technology

From another standpoint, the delta technology is a contract; it achieves an requirement (effective data transmission) in exchange for some limitations.

<Requirement>

Generating small delta

Original

Target

Original

Reproduced

Extractor Compensator

Delta


1.

1

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2.

<Limitation>

Sender and Receiver have complete bit-level-clone of Original

The two algorithm of Extractor and Compensator must be

corresponded

The requirements and limitations above result in problems below.

<Problems>

Requires strong consensus between Sender and Receiver By reason of Limitation-2, in general, Sender and Receiver must have a same product pair of Extractor and Compensator in same version. For instance, Receiver cannot reproduce if Sender makes a delta with his personal extracting algorithm (unless Sender transmits the algorithm to Receiver).

To avoid this problem, there is a technology named self-compensating delta; because sender implants the reproducing algorithm into Delta, Nothing but only Delta is required for Receiver. However, only the fixed and static-linked algorithm can be implanted.

wsp (http://www.vector.co.jp/soft/dos/util/se000818.html)

Large delta from two compressed archives The size of delta between two compressed archives inclines large unduly; even if the difference is only few content files of archives, the binary-image of archives are so different. A scheme looks good on surface; first, decompress Original and Target, and next, make Delta with different content files. However, with the scheme, the Reproduced may be different image of Target and breach of Requirement-2 because of difference of re-compress parameters, environments, and so on.

Limitation for adaptive encoding Assuming that the problem about Requirement-2 resoluted, the size of Delta can be reduced with adaptive encoding; select and use best algorithm for each contents file of archive. For example, a system supports pluggable extracting/compensating algorithm and switches its for each file type. But by the reason of Limitation-2, it is required for Sender and Receiver to collude what plugins will be used. Hence, the self-compensating delta scheme, featuring its paction-lessness, will require the new paction if with adaptive encoding.

Reproduce data which is complete bit-level-...