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<h3>NMR Online Seminar</h3>
<p><br>
<font face="monospace"><font size="4">-- Summary:
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<br>
What? Next talk in the NMR online talk series by
Andreas Herzig<br>
When? Wednesday, 10. December 2025, 16:00 CET (UCT+1)<br>
Where? Online (Zoom): <a
class="moz-txt-link-freetext"
href="https://uct-za.zoom.us/j/92600685092?pwd=ErqWWWKrljbjxLi0CNsgEZr4WR7ZHN.1">https://uct-za.zoom.us/j/92600685092?pwd=ErqWWWKrljbjxLi0CNsgEZr4WR7ZHN.1</a><br>
<br>
<a class="moz-txt-link-freetext"
href="https://nmrseminar.krportal.org/">https://nmrseminar.krportal.org/</a><br>
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We are happy to announce that the NMR online talk series
restarts after the summer break with a talk given by<br>
<b>Andreas Herzig</b> (IRIT)<br>
on <b>Wednesday, 10. December 2025</b>, 16:00 CET:</p>
<p><span><span style="font-weight: bold;">Relevance and
irrelevance in classical and modal revision</span></span></p>
<div class="fs-6 collapse show"
id="divAbstractMartinezOctober2025"> </div>
<p><font size="2"><i>Abstract.</i> Two different notions of
irrelevance have been much debated in the belief revision
literature: irrelevance of syntax and irrelevance of a
piece of information. The former is a basic postulate of
the AGM framework but has been criticised as being too
strong. The latter may be violated by AGM revision
operations, and Parikh (followed by, among others,
Makinson and Peppas) has argued that such a postulate
should be added to the AGM framework. My talk will
re-examine several aspects of irrelevance. First, I will
argue that if one takes the arguments for syntax relevance
seriously then an operation of reformulation of belief
bases should be added to the picture. Second, I will argue
for syntax irrelevance by showing that the most striking
counter-examples can be accommodated if classical material
implication is replaced by strict implication. Third, I
will show that this leads to an account of revision
operations for modal logics. Fourth, I will weaken
Parikh's relevance postulate to an intuitively appealing
postulate of vocabulary preservation that may also be
violated by AGM revision operations. Fifth, I will define
a modal revision operation satisfying AGM, vocabulary
preservation, and relevance.<br>
The talk is based on two papers that were presented at
AAAI 2025: "On the Logic of Theory Base Change:
Reformulation of Belief Bases" (with E.L. Fermé and M.V.
Martinez) and "Minimal Change in Modal Logic S5" (with C.
Aguilera-Ventura and J. Ben-Naim), as well as ongoing
work. </font></p>
<div class="fs-6 collapse show"
id="divAbstractHerzigDecember2025"> </div>
<p>The talk will be given via Zoom.</p>
<p>The plan of this series to have a talk roughly once per
month. If you are interested in learning the next speakers,
please visit the website at<br>
<a class="moz-txt-link-freetext"
href="https://nmrseminar.krportal.org/">https://nmrseminar.krportal.org/</a></p>
<p>We are still looking for speakers for future talks. If
there is something you would like to present in this seminar
series, please do not hesitate to contact us.</p>
Kind regards,<br>
Jonas and Giovanni<br>
<br>
<p></p>
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