Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932482
Satyaki Das, D. Dill
Recently, we have improved the efficiency of the predicate abstraction scheme presented by Das, Dill and Park (1999). As a result, the number of validity checks needed to prove the necessary verification condition has been reduced. The key idea is to refine an approximate abstract transition relation based on the counter-example generated. The system starts with an approximate abstract transition relation on which the verification condition (in our case, this is a safety property) is model-checked. If the property holds then the proof is done; otherwise the model checker returns an abstract counter-example trace. This trace is used to refine the abstract transition relation if possible and start anew. At the end of the process, the system either proves the verification condition or comes up with an abstract counter-example trace which holds in the most accurate abstract transition relation possible (with the user-provided predicates as a basis). If the verification condition fails in the abstract system, then either the concrete system does not satisfy it or the abstraction predicates chosen are not strong enough. This algorithm has been used on a concurrent garbage collection algorithm and a secure contract-signing protocol. This method improved the performance on the first problem significantly, and allowed us to tackle the second problem, which the previous method could not handle.
{"title":"Successive approximation of abstract transition relations","authors":"Satyaki Das, D. Dill","doi":"10.1109/LICS.2001.932482","DOIUrl":"https://doi.org/10.1109/LICS.2001.932482","url":null,"abstract":"Recently, we have improved the efficiency of the predicate abstraction scheme presented by Das, Dill and Park (1999). As a result, the number of validity checks needed to prove the necessary verification condition has been reduced. The key idea is to refine an approximate abstract transition relation based on the counter-example generated. The system starts with an approximate abstract transition relation on which the verification condition (in our case, this is a safety property) is model-checked. If the property holds then the proof is done; otherwise the model checker returns an abstract counter-example trace. This trace is used to refine the abstract transition relation if possible and start anew. At the end of the process, the system either proves the verification condition or comes up with an abstract counter-example trace which holds in the most accurate abstract transition relation possible (with the user-provided predicates as a basis). If the verification condition fails in the abstract system, then either the concrete system does not satisfy it or the abstraction predicates chosen are not strong enough. This algorithm has been used on a concurrent garbage collection algorithm and a secure contract-signing protocol. This method improved the performance on the first problem significantly, and allowed us to tackle the second problem, which the previous method could not handle.","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131274014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932513
S. Abiteboul
Semi-structured data is data that presents some regularity (i.e. it is not an image or plain text), but perhaps not as much as some relational data or some ODMG data (the standard for object databases). Such data is becoming increasingly important and, with XML, should become the standard for publishing data on the World Wide Web. With XML, the Web is turning into a worldwide heterogeneous distributed database. In this paper, we briefly discuss typing and languages for semi-structured data and some new issues arising from the context of data management on the Web.
{"title":"Semistructured data: from practice to theory","authors":"S. Abiteboul","doi":"10.1109/LICS.2001.932513","DOIUrl":"https://doi.org/10.1109/LICS.2001.932513","url":null,"abstract":"Semi-structured data is data that presents some regularity (i.e. it is not an image or plain text), but perhaps not as much as some relational data or some ODMG data (the standard for object databases). Such data is becoming increasingly important and, with XML, should become the standard for publishing data on the World Wide Web. With XML, the Web is turning into a worldwide heterogeneous distributed database. In this paper, we briefly discuss typing and languages for semi-structured data and some new issues arising from the context of data management on the Web.","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129288944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932507
N. Yoshida, Martin Berger, Kohei Honda
Introduces a typed /spl pi/-calculus where strong normalisation is ensured by typability. Strong normalisation is a useful property in many computational contexts, including distributed systems. In spite of its simplicity, our type discipline captures a wide class of converging name-passing interactive behaviours. The proof of strong normalisability combines methods from typed /spl lambda/-calculi and linear logic with process-theoretic reasoning. It is adaptable to systems involving state and other extensions. Strong normalisation is shown to have significant consequences, including finite axiomatisation of weak bisimilarity, a fully abstract embedding of the simply-typed /spl lambda/-calculus with products and sums and basic liveness in interaction. Strong normalisability has been extensively studied as a fundamental property in functional calculi, term rewriting and logical systems. This work is one of the first steps to extend theories and proof methods for strong normalisability to the context of name-passing processes.
{"title":"Strong normalisation in the /spl pi/-calculus","authors":"N. Yoshida, Martin Berger, Kohei Honda","doi":"10.1109/LICS.2001.932507","DOIUrl":"https://doi.org/10.1109/LICS.2001.932507","url":null,"abstract":"Introduces a typed /spl pi/-calculus where strong normalisation is ensured by typability. Strong normalisation is a useful property in many computational contexts, including distributed systems. In spite of its simplicity, our type discipline captures a wide class of converging name-passing interactive behaviours. The proof of strong normalisability combines methods from typed /spl lambda/-calculi and linear logic with process-theoretic reasoning. It is adaptable to systems involving state and other extensions. Strong normalisation is shown to have significant consequences, including finite axiomatisation of weak bisimilarity, a fully abstract embedding of the simply-typed /spl lambda/-calculus with products and sums and basic liveness in interaction. Strong normalisability has been extensively studied as a fundamental property in functional calculi, term rewriting and logical systems. This work is one of the first steps to extend theories and proof methods for strong normalisability to the context of name-passing processes.","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130146152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932479
H. Ruess, N. Shankar
Decision procedures for equality in a combination of theories are at the core of a number of verification systems. R.E. Shostak's (J. of the ACM, vol. 31, no. 1, pp. 1-12, 1984) decision procedure for equality in the combination of solvable and canonizable theories has been around for nearly two decades. Variations of this decision procedure have been implemented in a number of specification and verification systems, including STP, EHDM, PVS, STeP and SVC. The algorithm is quite subtle and a correctness argument for it has remained elusive. Shostak's algorithm and all previously published variants of it yield incomplete decision procedures. We describe a variant of Shostak's algorithm, along with proofs of termination, soundness and completeness.
结合各种理论的平等决策程序是若干核查系统的核心。R.E.肖斯塔克的《美国计算机学会学报》，第31卷，第31期。(1, pp. 1-12, 1984)在可解理论和可规范理论的结合中，相等的决定程序已经存在了近二十年。该决策程序的变体已在许多规范和验证系统中实现，包括STP, EHDM, PVS, STeP和SVC。该算法相当微妙，其正确性的论证仍然难以捉摸。肖斯塔克的算法和所有以前发表的它的变体产生不完整的决策过程。我们描述了Shostak算法的一个变体，以及终止、健全和完备性的证明。
{"title":"Deconstructing Shostak","authors":"H. Ruess, N. Shankar","doi":"10.1109/LICS.2001.932479","DOIUrl":"https://doi.org/10.1109/LICS.2001.932479","url":null,"abstract":"Decision procedures for equality in a combination of theories are at the core of a number of verification systems. R.E. Shostak's (J. of the ACM, vol. 31, no. 1, pp. 1-12, 1984) decision procedure for equality in the combination of solvable and canonizable theories has been around for nearly two decades. Variations of this decision procedure have been implemented in a number of specification and verification systems, including STP, EHDM, PVS, STeP and SVC. The algorithm is quite subtle and a correctness argument for it has remained elusive. Shostak's algorithm and all previously published variants of it yield incomplete decision procedures. We describe a variant of Shostak's algorithm, along with proofs of termination, soundness and completeness.","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124173633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932481
Guillem Godoy, R. Nieuwenhuis
It is crucial for the performance of ordered resolution or paramodulation-based deduction systems that they incorporate specialized techniques to work efficiently with standard algebraic theories E. Essential ingredients for this purpose are term orderings that are E-compatible, for the given E, and algorithms deciding constraint satisfiability for such orderings. In this paper, we introduce a uniform technique providing the first such algorithms for some orderings for Abelian semigroups, Abelian monoids and Abelian groups, which we believe will lead to reasonably efficient techniques for practice. The algorithms are optimal since we show that, for any well-founded E-compatible ordering for these E, the constraint satisfiability problem is NP-hard, even for conjunctions of inequations, and that our algorithms are in NP.
{"title":"On ordering constraints for deduction with built-in Abelian semigroups, monoids and groups","authors":"Guillem Godoy, R. Nieuwenhuis","doi":"10.1109/LICS.2001.932481","DOIUrl":"https://doi.org/10.1109/LICS.2001.932481","url":null,"abstract":"It is crucial for the performance of ordered resolution or paramodulation-based deduction systems that they incorporate specialized techniques to work efficiently with standard algebraic theories E. Essential ingredients for this purpose are term orderings that are E-compatible, for the given E, and algorithms deciding constraint satisfiability for such orderings. In this paper, we introduce a uniform technique providing the first such algorithms for some orderings for Abelian semigroups, Abelian monoids and Abelian groups, which we believe will lead to reasonably efficient techniques for practice. The algorithms are optimal since we show that, for any well-founded E-compatible ordering for these E, the constraint satisfiability problem is NP-hard, even for conjunctions of inequations, and that our algorithms are in NP.","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130470745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932497
M. Adler, N. Immerman
We introduce a new Ehrenfeucht-Fraisse game for proving lower bounds on the size of first-order formulas. Up until now such games have only been used to prove bounds on the operator depth of formulas, not their size. We use this game to prove that the CTL/sup +/ formula Occur/sub n//spl equiv/E[Fp/sub 1//spl and/Fp/sub 2//spl and//spl middot//spl middot//spl middot//spl and/F/sub n/] which says that there is a path along which the predicates p/sub 1/ through p/sub n/ occur in some order; requires size n! to express in CTL. Our lower bound is optimal. It follows that the succinctness of CTL+ with respect to CTL is exactly /spl Theta/(n). Wilke (1999) had shown that the succinctness was at least exponential. We also use our games to prove all optimal /spl Theta/(n) lower bound on the number of boolean variables needed for a weak reachability logic (/spl Rscr//spl Lscr//sup w/) to polynomially embed the language LTL. The number of booleans needed for full reachability logic RC and the transitive closure logic FO/sup 2/(TC) remain open (Immerman and Vardi, 1997; Alechina and Immerman, 2000).
{"title":"\"An n! lower bound on formula size\"","authors":"M. Adler, N. Immerman","doi":"10.1109/LICS.2001.932497","DOIUrl":"https://doi.org/10.1109/LICS.2001.932497","url":null,"abstract":"We introduce a new Ehrenfeucht-Fraisse game for proving lower bounds on the size of first-order formulas. Up until now such games have only been used to prove bounds on the operator depth of formulas, not their size. We use this game to prove that the CTL/sup +/ formula Occur/sub n//spl equiv/E[Fp/sub 1//spl and/Fp/sub 2//spl and//spl middot//spl middot//spl middot//spl and/F/sub n/] which says that there is a path along which the predicates p/sub 1/ through p/sub n/ occur in some order; requires size n! to express in CTL. Our lower bound is optimal. It follows that the succinctness of CTL+ with respect to CTL is exactly /spl Theta/(n). Wilke (1999) had shown that the succinctness was at least exponential. We also use our games to prove all optimal /spl Theta/(n) lower bound on the number of boolean variables needed for a weak reachability logic (/spl Rscr//spl Lscr//sup w/) to polynomially embed the language LTL. The number of booleans needed for full reachability logic RC and the transitive closure logic FO/sup 2/(TC) remain open (Immerman and Vardi, 1997; Alechina and Immerman, 2000).","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130940518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932486
M. Fiore, D. Turi
Provides a semantic framework for (first-order) message-passing process calculi by combining categorical theories of abstract syntax with binding and operational semantics. In particular, we obtain abstract rule formats for name and value passing with both late and early interpretations. These formats induce an initial-algebra/final-coalgebra semantics that is compositional, respects substitution and is fully abstract for late and early congruence. We exemplify the theory with the /spl pi/-calculus and value-passing CCS (calculus of communicating systems).
{"title":"Semantics of name and value passing","authors":"M. Fiore, D. Turi","doi":"10.1109/LICS.2001.932486","DOIUrl":"https://doi.org/10.1109/LICS.2001.932486","url":null,"abstract":"Provides a semantic framework for (first-order) message-passing process calculi by combining categorical theories of abstract syntax with binding and operational semantics. In particular, we obtain abstract rule formats for name and value passing with both late and early interpretations. These formats induce an initial-algebra/final-coalgebra semantics that is compositional, respects substitution and is fully abstract for late and early congruence. We exemplify the theory with the /spl pi/-calculus and value-passing CCS (calculus of communicating systems).","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134427115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932504
L. D. Alfaro, T. Henzinger, R. Majumdar
Dynamic programs, or fixpoint iteration schemes, are useful for solving many problems on state spaces. For Kripke structures, a rich fixpoint theory is available in the form of the /spl mu/-calculus, yet few connections have been made between different interpretations of fixpoint algorithms. We study the question of when a particular fixpoint iteration scheme /spl phi/ for verifying an /spl omega/-regular property /spl Psi/ on a Kripke structure can be used also for solving a two-player game on a game graph with winning objective /spl Psi/. We provide a sufficient and necessary criterion for the answer to be affirmative in the form of an extremal-model theorem for games: under a game interpretation, the dynamic program /spl phi/ solves the game with objective /spl Psi/ iff both (1) under an existential interpretation on Kripke structures, /spl phi/ is equivalent to /spl exist//spl Psi/, and (2) under a universal interpretation on Kripke structures, /spl phi/ is equivalent to /spl forall//spl Psi/. In other words, /spl phi/ is correct on all two-player game graphs iff it is correct on all extremal game graphs, where one or the other player has no choice of moves. The theorem generalizes to quantitative interpretations, where it connects two-player games with costs to weighted graphs. While the standard translations from /spl omega/-regular properties to the /spl mu/-calculus violate (1) or (2), we give a translation that satisfies both conditions. Our construction, therefore, yields fixpoint iteration schemes that can be uniformly applied on Kripke structures, weighted graphs, game graphs, and game graphs with costs, in order to meet or optimize a given /spl omega/-regular objective.
{"title":"From verification to control: dynamic programs for omega-regular objectives","authors":"L. D. Alfaro, T. Henzinger, R. Majumdar","doi":"10.1109/LICS.2001.932504","DOIUrl":"https://doi.org/10.1109/LICS.2001.932504","url":null,"abstract":"Dynamic programs, or fixpoint iteration schemes, are useful for solving many problems on state spaces. For Kripke structures, a rich fixpoint theory is available in the form of the /spl mu/-calculus, yet few connections have been made between different interpretations of fixpoint algorithms. We study the question of when a particular fixpoint iteration scheme /spl phi/ for verifying an /spl omega/-regular property /spl Psi/ on a Kripke structure can be used also for solving a two-player game on a game graph with winning objective /spl Psi/. We provide a sufficient and necessary criterion for the answer to be affirmative in the form of an extremal-model theorem for games: under a game interpretation, the dynamic program /spl phi/ solves the game with objective /spl Psi/ iff both (1) under an existential interpretation on Kripke structures, /spl phi/ is equivalent to /spl exist//spl Psi/, and (2) under a universal interpretation on Kripke structures, /spl phi/ is equivalent to /spl forall//spl Psi/. In other words, /spl phi/ is correct on all two-player game graphs iff it is correct on all extremal game graphs, where one or the other player has no choice of moves. The theorem generalizes to quantitative interpretations, where it connects two-player games with costs to weighted graphs. While the standard translations from /spl omega/-regular properties to the /spl mu/-calculus violate (1) or (2), we give a translation that satisfies both conditions. Our construction, therefore, yields fixpoint iteration schemes that can be uniformly applied on Kripke structures, weighted graphs, game graphs, and game graphs with costs, in order to meet or optimize a given /spl omega/-regular objective.","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129599195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-16DOI: 10.1109/LICS.2001.932491
W. Szwast, Lidia Tendera
The guarded fragment with transitive guards, [GF+TG], is an extension of GF in which certain relations are required to be transitive, transitive predicate letters appear only in guards of the quantifiers and the equality symbol may appear everywhere. We prove that the decision problem for [GF+TG] is decidable. This answers the question posed in (Ganzinger et al., 1999). Moreover, we show that the problem is 2EXPTIME-complete. This result is optimal since the satisfiability problem for GF is 2EXPTIME-complete (Gradel, 1999). We also show that the satisfiability problem for two-variable [GF+TG] is NEXPTIME-hard in contrast to GF with bounded number of variables for which the satisfiability problem is EXPTIME-complete.
带传递保护的被保护片段[GF+TG]是GF的扩展，其中某些关系必须是传递的，传递谓词字母只出现在量词的保护中，等式符号可以出现在任何地方。证明了[GF+TG]的决策问题是可决定的。这回答了(Ganzinger et al.， 1999)中提出的问题。此外，我们还证明了这个问题是2EXPTIME-complete的。这个结果是最优的，因为GF的可满足性问题是2EXPTIME-complete (Gradel, 1999)。我们还证明了两变量[GF+TG]的可满足性问题是expptime -hard的，而具有有限变量数的GF的可满足性问题是EXPTIME-complete的。
{"title":"On the decision problem for the guarded fragment with transitivity","authors":"W. Szwast, Lidia Tendera","doi":"10.1109/LICS.2001.932491","DOIUrl":"https://doi.org/10.1109/LICS.2001.932491","url":null,"abstract":"The guarded fragment with transitive guards, [GF+TG], is an extension of GF in which certain relations are required to be transitive, transitive predicate letters appear only in guards of the quantifiers and the equality symbol may appear everywhere. We prove that the decision problem for [GF+TG] is decidable. This answers the question posed in (Ganzinger et al., 1999). Moreover, we show that the problem is 2EXPTIME-complete. This result is optimal since the satisfiability problem for GF is 2EXPTIME-complete (Gradel, 1999). We also show that the satisfiability problem for two-variable [GF+TG] is NEXPTIME-hard in contrast to GF with bounded number of variables for which the satisfiability problem is EXPTIME-complete.","PeriodicalId":366313,"journal":{"name":"Proceedings 16th Annual IEEE Symposium on Logic in Computer Science","volume":"269 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115313788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：