Safety properties Sample Clauses

Safety properties. The proof of the safety properties of GWTS is analogous to the proof contained in Section 5.1.1. From the properties of reliable broadcast we have the following:
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Safety properties. ‌ Observation 1. Given any correct process pj its SvS contains at most one value for each process in P. The above observation derives from the specification of reliable broadcast, and the fact that in the disclosure phase each participating process broadcasts a single value. We say that a message m containing a set of proposed values is “safe” for a process pi if such set of values is contained in SvS. It is immediate from function at Lines 35-39 that proposers (in state proposing) change their Proposed set only when they receive safe messages. The analogous holds for the Accepted set of acceptors. We say that a value v receives m acks if it is contained in a Proposed set, that is in turn contained in ack messages in the form < ack, , ts > sent by m acceptors. The same meaning is intended when we say that Proposed set receives acks. Algorithm 1 WTS (Wait Till Safe) -Algorithm for Proposer process pi 1: proposed value = proi
Safety properties. ‌ Observation 1. Given any correct process pj its SvS contains at most one value for each process in P. Algorithm 1 WTS (Wait Till Safe) -Alg. for Proposer pi 1: proposed value = proi 2: init counter = ts = 0
Safety properties. To ensure the safe functioning of the Dwarf Signal system we need to impose a number of safety properties. These properties should at all times be preserved by the system. In CML we specify them as a collection of five functions which are enumerated in Table 3. NeverShowAll enforces that it should never be the case that all three lamps are on simultaneously. MaxOneLampChange requires that between any two states only one lamp can change from on to o↵, or o↵ to on. ForbidStopTo- Drive enforces that the signal cannot transition straight from the stop state to the drive state – it must go via the warning state. DarkOnlyToStop and DarkOn- lyFromStop together encode the requirement that a signal may only transition functions NeverShowAll: DwarfType -> bool NeverShowAll(d) == d.currentstate <> {<L1>,<L2>,<L3>} MaxOneLampChange: DwarfType -> bool MaxOneLampChange(d) == card ((d.currentstate \ d.laststate) union (d.laststate \ d.currentstate)) <= 1 ForbidStopToDrive : DwarfType -> bool ForbidStopToDrive(d) == (d.lastproperstate = stop => d.desiredproperstate <> drive) DarkOnlyToStop : DwarfType -> bool DarkOnlyToStop(d) == (d.lastproperstate = dark => d.desiredproperstate in set {dark,stop}) DarkOnlyFromStop: DwarfType -> bool DarkOnlyFromStop(d) == (d.desiredproperstate = dark => d.lastproperstate in set {dark,stop}) from dark to stop, and to dark from stop – a signal in warning or drive should not become stop directly. With our collection of safety properties which can describe the safe version of the Dwarf Signal state: types DwarfSignal = DwarfType inv d == NeverShowAll(d) and MaxOneLampChange(d) and ForbidStopToDrive(d) and DarkOnlyToStop(d) and DarkOnlyFromStop(d) P [|{a,b,c}|] Q Communicate on a then behave like P Input value v over channel a then do P Output value v on channel a then do P Execute action P followed by Q Pick P or Q based on the first communication Execute P and Q in parallel, with synchronisation allowed on a, b and c allow execution of P only if cond holds The Dwarf Signal is a reactive system; it waits for stimuli and behaves accordingly. To specify these sorts of aspects of a system we need to use a suitable formalism. In CML we support the specification of CSP processes. CSP (Communicating Sequential Processes) is a process calculus which specifies behaviour in terms of concurrent processes which communicate on channels. A channel is a two-ended medium with a single listener and a single speaker. A channel can therefore be used to send i...

Related to Safety properties

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  • Existence; Compliance with Laws; Businesses and Properties (a) Do or cause to be done all things necessary to preserve, renew and keep in full force and effect its legal existence, except as otherwise expressly permitted under Section 6.05. (i) Do or cause to be done all things necessary to obtain, preserve, renew, extend and keep in full force and effect the rights, licenses, permits, franchises and authorizations, material to the conduct of its business, except as could not reasonably be expected to have a Material Adverse Effect; (ii) comply in all material respects with all applicable laws, rules, regulations and decrees and orders of any Governmental Authority, whether now in effect or hereafter enacted, except as could not reasonably be expected to have a Material Adverse Effect; and (iii) at all times maintain and preserve all tangible property material to the conduct of such business and keep such property in good repair, working order and condition (subject to ordinary wear and tear, casualty and condemnation) and from time to time make, or cause to be made, all needful and proper repairs, renewals, additions, improvements and replacements thereto necessary in order that the business carried on in connection therewith may be properly conducted at all times, except as could not reasonably be expected to have a Material Adverse Effect.

  • Existence; Businesses and Properties (a) Do or cause to be done all things necessary to preserve, renew and keep in full force and effect its legal existence and (to the extent the concept is applicable in such jurisdiction) good standing under the legal requirements of the jurisdiction of its formation, except as otherwise expressly permitted under Section 6.05, except where failure to do so could not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect. (b) Qualify and remain qualified as a foreign entity in each jurisdiction in which qualification is necessary in view of its business and operations or the ownership of its properties, except where failure to do so could not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect. (c) Do or cause to be done all things necessary to obtain, preserve, renew, extend, maintain and keep in full force and effect the rights, privileges, licenses, permits, franchises, authorizations, patents, copyrights, trademarks and trade names material to the conduct of its business, except where the failure to do so could not reasonably be expected to have a Material Adverse Effect; maintain and operate such business in substantially the manner in which it is presently conducted and operated; comply in all material respects with all applicable laws, rules, regulations, decrees and orders of any Governmental Authority, whether now in effect or hereafter enacted, except where the failure do so could not reasonably be expected to have a Material Adverse Effect; and at all times maintain and preserve all property material to the conduct of such business and keep such property in good repair, working order and condition and from time to time make, or cause to be made, all needful and proper repairs, renewals, additions, improvements and replacements thereto necessary in order that the business carried on in connection therewith may be properly conducted at all times, except where the failure to do so could not reasonably be expected to have a Material Adverse Effect.

  • Access to Properties Subject to the rights of Tenants, Borrower shall permit agents, representatives and employees of Lender to inspect the Properties or any part thereof at reasonable hours upon reasonable advance notice.

  • Business and Properties No business of any Loan Party or any of its Subsidiaries is affected by any fire, explosion, accident, drought, storm, hail, earthquake, embargo, act of God or of the public enemy or other casualty (whether or not covered by insurance) that could reasonably be expected, individually or in the aggregate, to have a Material Adverse Effect.

  • Access to Properties and Records (a) CCE shall, and shall cause TPC to, afford to ETP and ETP’s accountants, counsel and representatives full reasonable access during normal business hours throughout the period prior to the Closing Date (or the earlier termination of this Agreement pursuant to Article VII hereof) to all of the properties, books, contracts, commitments and records (including all environmental studies, reports and other environmental records and all pipeline cost-of-service and rate-related studies, reports and records related to TPC and, during such period, shall furnish to ETP all information concerning the business, properties, Liabilities and personnel related to TPC as ETP may request, provided, however, that no investigation or receipt of information pursuant to this Section 5.2 shall affect any representation or warranty of CCE or the conditions to the obligations of ETP. To the extent not located at the offices or properties of TPC as of the Closing Date, as promptly as practicable thereafter, CCE shall deliver, or cause its appropriate Affiliates to deliver to ETP all of the books of accounts, minute books, record books and other records (including safety, health, environmental, maintenance and engineering records and drawings) pertaining to the business operations of TPC and all financial and accounting records related to TPC. Such delivery shall include all work papers, pleadings, testimony, exhibits, spread sheets, research, drafts, memoranda, correspondence and other documents related to the TPC Rate Case (“TPC Rate Case Work Product”). TPC Rate Case Work Product has been and will be prepared in contemplation of litigation, and the use of TPC Rate Case Work Product has been and will be under the control of TPC’s attorneys. Notwithstanding anything to the contrary contained in this Agreement, CCE shall not be obligated to provide to ETP any documents or records relating to litigation and regulatory matters in which TPC is involved to the extent that CCE reasonably believes such documents or records are subject to the attorney-client or other applicable privilege in circumstances in which TPC is not the sole client unless the parties entitled to such attorney-client or other applicable privilege shall consent thereto and enter into an appropriate joint defense agreement for the purpose of preservation of such attorney-client or other applicable privilege. (b) The information contained herein, in the CCE Disclosure Letter or heretofore or hereafter delivered to ETP or its authorized representatives in connection with the transactions contemplated by this Agreement shall be held in confidence by ETP and its representatives in accordance with the Confidentiality Agreement until the Closing Date with respect to information relating to TPC. Following the Closing Date, CCE shall keep confidential all information related to the business and properties of TPC to the same extent as ETP is obligated to keep such information confidential in accordance with the terms of the Confidentiality Agreement (without regard to the preceding sentence) prior to the Closing Date.

  • Environmental Compliance (a) No Loan Party or Restricted Subsidiary (i) has failed to comply in all material respects with applicable Environmental Law or to obtain, maintain or comply with any Environmental Permit, (ii) has become subject to any Environmental Liability, (iii) has received notice of any claim with respect to any material Environmental Liability or (iv) has a Responsible Officer with knowledge of any basis for any material Environmental Liability, except, in each case, as would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect. (i) None of the properties currently or formerly owned or operated by any Loan Party or Restricted Subsidiary is or was listed or, to the knowledge of any Responsible Officer was proposed for listing on the NPL or on the CERCLIS or any analogous state or local list at any time while such property was owned by such Loan Party or, to the knowledge of any Responsible Officer, at any time prior to or after such property was owned by such Loan Party, and, to the knowledge of any Responsible Officer, no property currently owned or operated by any Loan Party or Restricted Subsidiary is adjacent to any such property, in each case in connection with any matter for which any Loan Party or Restricted Subsidiary would have any material Environmental Liability; (ii) there are no, or, to the knowledge of any Responsible Officer, never have been any underground or above-ground storage tanks or any surface impoundments, septic tanks, pits, sumps or lagoons in which Hazardous Materials are being or have been treated, stored or disposed on any property currently owned or operated by any Loan Party or Restricted Subsidiary in violation of any Environmental Laws or, to the knowledge of any Responsible Officer, on any property formerly owned or operated by any Loan Party or Restricted Subsidiary; (iii) there is no friable asbestos or friable asbestos-containing material on any property currently owned or operated by any Loan Party or Restricted Subsidiary; (iv) Hazardous Materials have not been Released, discharged or disposed of on any property currently or formerly owned or operated by any Loan Party or Restricted Subsidiary in violation of any Environmental Laws; and (v) to the knowledge of any Responsible Officer, there are no pending or threatened Liens under or pursuant to any applicable Environmental Laws on any real property or other assets owned or leased by any Loan Party or Restricted Subsidiary, and to the knowledge of any Responsible Officer, no actions by any Governmental Authority have been taken or are in process which would subject any of such properties or assets to such Liens, except, in the case of clauses (i) through (v) above, as would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect. (c) No Loan Party or Restricted Subsidiary is undertaking, and no Loan Party or Restricted Subsidiary has completed, either individually or together with other potentially responsible parties, any investigation or assessment or remedial or response action relating to any actual or threatened Release, discharge or disposal of Hazardous Materials at any site, location or operation, either voluntarily or pursuant to the order of any Governmental Authority or the requirements of any Environmental Law that has or would reasonably be expected to have a Material Adverse Effect; and all Hazardous Materials generated, used, treated, handled or stored at, or transported to or from, any property currently or formerly owned or operated by any Loan Party or Restricted Subsidiary have been disposed of in a manner not reasonably expected, individually or in the aggregate, to have a Material Adverse Effect.

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  • Existence; Business and Properties (a) Do or cause to be done all things necessary to preserve, renew and keep in full force and effect its legal existence, except, in the case of a Subsidiary of the Borrower, where the failure to do so would not reasonably be expected to have a Material Adverse Effect, and except as otherwise permitted under Section 6.05, and except for the liquidation or dissolution of Subsidiaries if the assets of such Subsidiaries to the extent they exceed estimated liabilities are acquired by the Borrower or a Wholly Owned Subsidiary of the Borrower in such liquidation or dissolution; provided, that Subsidiary Loan Parties may not be liquidated into Subsidiaries that are not Loan Parties and Domestic Subsidiaries may not be liquidated into Foreign Subsidiaries (except in each case as permitted under Section 6.05). (b) Except where the failure to do so would not reasonably be expected to have a Material Adverse Effect, do or cause to be done all things necessary to (i) lawfully obtain, preserve, renew, extend and keep in full force and effect the permits, franchises, authorizations, Intellectual Property, licenses and rights with respect thereto necessary to the normal conduct of its business, and (ii) at all times maintain, protect and preserve all property necessary to the normal conduct of its business and keep such property in good repair, working order and condition (ordinary wear and tear excepted), from time to time make, or cause to be made, all needful and proper repairs, renewals, additions, improvements and replacements thereto necessary in order that the business carried on in connection therewith, if any, may be properly conducted at all times (in each case except as permitted by this Agreement).

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