McCarthy ( 2013 ) asks whether there are phonological systems necessitating irreducible parallelism in grammar—systems requiring that multiple changes to the input apply in parallel, in a single derivational step. Such systems would necessitate a framework with lookahead : the ability to see from a given derivational step the results of applying multiple changes to its input. This article makes the following claims: (i) a variety of systems across languages, involving a diverse array of processes, require lookahead; (ii) these systems share the same underlying character, despite superficial differences. Our evidence comes primarily from the distribution of stress, lengthening, and epenthesis in Mohawk; reduplication and hiatus repair in Maragoli; syncope and gemination in Sino-Japanese; and assimilation and epenthesis in Lithuanian. All these systems involve what we call a COMPARISON OF PROCEDURES. To best satisfy constraints, the grammar applies one change followed by another, unless the final result is dispreferred. In such a case, the grammar instead applies a different series of changes. We make the argument for lookahead in grammar by comparing the ability of two frameworks—Parallel Optimality Theory and Harmonic Serialism—to capture these systems. We show that Parallel OT captures them naturally, as it permits lookahead and therefore allows the grammar to compare entire procedures. HS, on the other hand, is challenged by them, as it forbids lookahead and thus does not permit the grammar to compare entire procedures unless the changes involved are specified to apply in a single derivational step. That the problem arises in connection with a diverse array of processes suggests that lookahead is not merely the reflex of a single exceptional phenomenon, but rather is a property of the grammar as a whole.

中文翻译：

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音韵学中不可约的平行性

McCarthy (2013) 询问是否有语音系统需要语法中不可约的并行性——系统需要在单个推导步骤中并行应用对输入的多个更改。这样的系统需要一个具有前瞻性的框架：能够从给定的推导步骤看到对其输入应用多个更改的结果。本文提出以下主张：(i) 跨语言的各种系统，涉及各种进程，需要先行；(ii) 尽管表面上存在差异，但这些系统具有相同的基本特征。我们的证据主要来自莫霍克语中的重音、加长和插词分布；Maragoli 的重复和中断修复；中日晕厥与双生；以及立陶宛语的同化和插入。所有这些系统都涉及我们所说的程序比较。为了最好地满足约束条件，除非最终结果不受欢迎，否则语法会先应用一个更改，然后再应用另一个更改。在这种情况下，语法会应用一系列不同的更改。我们通过比较两个框架——并行最优理论和和谐序列主义——来捕捉这些系统的能力来论证语法中的前瞻。我们展示了 Parallel OT 自然地捕获它们，因为它允许前瞻，因此允许语法比较整个过程。另一方面，HS 受到他们的挑战，因为它禁止前瞻，因此不允许语法比较整个过程，除非将所涉及的更改指定为在单个派生步骤中应用。