Tacit programming - Revision history

en>Leo C Stein: Dubious template added for misuse of category theory

2014-11-29T01:17:01Z

Dubious template added for misuse of category theory

← Older revision		Revision as of 03:17, 29 November 2014
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en>Jarble: Linking

2014-02-25T04:44:44Z

Linking

← Older revision		Revision as of 06:44, 25 February 2014
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	~~The '''HRU''' security model (Harrison, Ruzzo, [[Jeffrey Ullman\|Ullman]] model)~~ is ~~an [[operating system]] level [[computer security model]] which deals with~~ the ~~[[data integrity\|integrity]]~~ of ~~[[access control\|access rights]] in the system~~. ~~It is an extension of the [[Graham-Denning model]], based around the idea of a [[finite set]] of [[algorithm\|procedures]] being available~~ to ~~edit the access rights of a subject <math>s</math> on an object <math>o</math>. It is named after its three authors, Michael A. Harrison, Walter L. Ruzzo~~ and ~~Jeffrey D. Ullman.<ref name=HRU-paper/>~~		She is recognized by the title of Myrtle Shryock. Years ago he moved to North Dakota and his family members enjoys it. For years I've been working as a payroll clerk. One of the things she loves most is to study comics and she'll be starting something else along with it.<br><br>Feel free to surf to my webpage ... at home std testing ([http://www.noonptm.com/fox/upload/index.php?do=/profile-3715/info/ Full File])

	~~Along with presenting the model, Harrison, Ruzzo and Ullman also discussed the possibilities and limitations of proving the safety of systems using an [[algorithm]]~~.~~<ref name=HRU-paper/>~~

	~~== Description of the model ==~~
	~~The HRU model defines a~~ '~~'protection system'' consisting of~~ a ~~set of generic rights ''R'' and a set of commands ''C''~~. ~~An instantaneous description~~ of the ~~system~~ is ~~called a~~ ''configuration'' and is defined as a [[tuple]] <math>(S,O,P)</math> of current subjects <math>S</math>, current objects <math>O</math> and an access matrix <math>P</math>. Since the subjects are required to be part of the objects, the access matrix contains one row for each subject and one column for each subject and object. An entry for subject <math>s</math> and object <math>o</math> is a subset of the generic rights <math>R</math>.

	~~The commands are composed of primitive operations and can additionally have a list of pre-conditions that require certain rights to be present for a pair~~ <~~math~~>~~(s,o)~~<~~/math~~> ~~of subjects and objects.~~

	The primitive requests can modify the access matrix by adding or removing access rights for a pair of subjects and objects and by adding or removing subjects or objects. Creation of a subject or object requires the subject or object not to ~~exist in the current configuration, while deletion of a subject or object requires it~~ to ~~have existed prior to deletion~~. ~~In a complex command, a sequence of operations is executed only as a whole~~. ~~A failing operation in a sequence makes the whole sequence fail, a form of~~ [~~[database transaction]]~~.

	~~== Discussion of safety ==~~
	~~Harrison, Ruzzo and Ullman<ref name=HRU-paper~~/> discussed whether there is an algorithm that takes an arbitrary initial configuration and answers the following question: is there an arbitrary sequence of commands that adds a generic right into a cell of the access matrix where it has not been in the initial configuration?

	They showed that there is no such algorithm, thus the problem is [[undecidable problem\|undecidable]] in the general case. They also showed a limitation of the model to commands with only one primitive operation to render the problem decidable.

	=~~= See also ==~~
	* [[EROS (microkernel)\|EROS - ~~Extremely Reliable Operating System]]~~

	~~== References ==~~
	~~{{reflist\|refs=~~
	<ref name=HRU-paper>{{cite journal \| first1 = Michael A. \| last1 = Harrison \| first2 = Walter L. \| last2 = Ruzzo \| first3 = Jeffrey D. \| last3 = Ullman \| id = {{citeseerx\|10.1.1.106.7226}} \| title = Protection in Operating Systems \| journal = Communications of the ACM \| volume = 19 \| issue = 8 \| pages = 461–471 \| month = August \| year = 1976 }}</~~ref>~~
	}}

	~~[[Category:Capability systems]]~~
	~~[[Category:Computer security models]~~]

82.73.99.231 at 13:52, 21 October 2013

2013-10-21T13:52:32Z

← Older revision		Revision as of 15:52, 21 October 2013
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	~~Nice~~ to ~~satisfy you~~, ~~my title is Araceli Oquendo but I don~~'~~t like when people use my complete name~~. ~~One~~ of ~~his favorite hobbies~~ is ~~taking part in crochet but he hasn~~'~~t produced~~ a ~~dime with it~~. ~~Her spouse~~ and ~~her chose to reside in Alabama~~. ~~Bookkeeping~~ is ~~what I do~~ for a ~~living.~~<br><br>~~Also visit my web blog~~ ... ~~auto warranty~~ - [~~http://Www~~.~~Thelamda~~.~~com/index~~.~~php?mod~~=~~users&action~~=~~view&~~id=~~3598 Suggested Site~~] -		The '''HRU''' security model (Harrison, Ruzzo, [[Jeffrey Ullman\|Ullman]] model) is an [[operating system]] level [[computer security model]] which deals with the [[data integrity\|integrity]] of [[access control\|access rights]] in the system. It is an extension of the [[Graham-Denning model]], based around the idea of a [[finite set]] of [[algorithm\|procedures]] being available to edit the access rights of a subject <math>s</math> on an object <math>o</math>. It is named after its three authors, Michael A. Harrison, Walter L. Ruzzo and Jeffrey D. Ullman.<ref name=HRU-paper/>

			Along with presenting the model, Harrison, Ruzzo and Ullman also discussed the possibilities and limitations of proving the safety of systems using an [[algorithm]].<ref name=HRU-paper/>

			== Description of the model ==
			The HRU model defines a ''protection system'' consisting of a set of generic rights ''R'' and a set of commands ''C''. An instantaneous description of the system is called a ''configuration'' and is defined as a [[tuple]] <math>(S,O,P)</math> of current subjects <math>S</math>, current objects <math>O</math> and an access matrix <math>P</math>. Since the subjects are required to be part of the objects, the access matrix contains one row for each subject and one column for each subject and object. An entry for subject <math>s</math> and object <math>o</math> is a subset of the generic rights <math>R</math>.

			The commands are composed of primitive operations and can additionally have a list of pre-conditions that require certain rights to be present for a pair <math>(s,o)</math> of subjects and objects.

			The primitive requests can modify the access matrix by adding or removing access rights for a pair of subjects and objects and by adding or removing subjects or objects. Creation of a subject or object requires the subject or object not to exist in the current configuration, while deletion of a subject or object requires it to have existed prior to deletion. In a complex command, a sequence of operations is executed only as a whole. A failing operation in a sequence makes the whole sequence fail, a form of [[database transaction]].

			== Discussion of safety ==
			Harrison, Ruzzo and Ullman<ref name=HRU-paper/> discussed whether there is an algorithm that takes an arbitrary initial configuration and answers the following question: is there an arbitrary sequence of commands that adds a generic right into a cell of the access matrix where it has not been in the initial configuration?

			They showed that there is no such algorithm, thus the problem is [[undecidable problem\|undecidable]] in the general case. They also showed a limitation of the model to commands with only one primitive operation to render the problem decidable.

			== See also ==
			* [[EROS (microkernel)\|EROS - Extremely Reliable Operating System]]

			== References ==
			{{reflist\|refs=
			<ref name=HRU-paper>{{cite journal \| first1 = Michael A. \| last1 = Harrison \| first2 = Walter L. \| last2 = Ruzzo \| first3 = Jeffrey D. \| last3 = Ullman \| id = {{citeseerx\|10.1.1.106.7226}} \| title = Protection in Operating Systems \| journal = Communications of the ACM \| volume = 19 \| issue = 8 \| pages = 461–471 \| month = August \| year = 1976 }}</ref>
			}}

			[[Category:Capability systems]]
			[[Category:Computer security models]]

2001:0:53AA:64C:1072:214F:4379:F556: category: remove irrelevant one

2012-06-13T10:07:17Z

category: remove irrelevant one

New page

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