ParaMor’s Final Scheme Clusters as Viable Models of Paradigms

4.5ParaMor’s Final Scheme Clusters as Viable Models of Paradigms

Now, take a return look at Error: Reference source not found, which contains a sampling of clusters ParaMor constructs from the initially selected schemes before any filtering. As noted when Error: Reference source not found was first introduced in Section 4.3, the cluster on the top row of Error: Reference source not found models the most prevalent inflection class of Number on Spanish nouns and adjectives, containing the scheme Ø.s. This 1^st cluster is correctly retained after all filtering steps. The 2^nd scheme cluster in Error: Reference source not found incorrectly places a morpheme boundary after the epenthetic vowel a which leads off most suffixes in the ar inflection class. ParaMor’s left-looking morpheme boundary filter correctly and successfully removes this 2^nd cluster. ParaMor correctly retains the scheme clusters on the 3^rd, 4^th, 7^th, and 8^th rows of Error: Reference source not found. These clusters have respectively the 3^rd, 4^th, 11^th, and 17^th most licensing types. The 3^rd scheme cluster covers the scheme, a.as.o.os, which models the cross-product of gender and number on Spanish adjectives, and which was the 2^nd selected scheme during ParaMor’s initial search. The other candidate suffixes in this cluster include a version of the adverbial suffix (a)mente, and a number of derivational suffixes that convert adjectives to nouns. The 4^th, 11^th, and 17^th scheme clusters in Error: Reference source not found are correct collections of, respectively, verbal ar, er, and ir inflectional and derivational suffixes.

The 5^th scheme cluster in Error: Reference source not found segments a Spanish nominalization internally. But ParaMor’s morpheme boundary filters are unsuccessful at removing this scheme cluster because this Spanish nominalization suffix has four allomorphs: sion, cion, sión, and ción. The 5^th scheme cluster places a morpheme boundary immediately before the i in these allomorphs. The left-looking morpheme boundary filter is unable to remove the cluster because some c stems end in s while others end in c, increasing the leftward link entropy. But the right-looking morpheme boundary filter is also unable to remove the cluster, because, from a majority of the schemes of this cluster, after following a link through the initial i of these c suffixes, ParaMor’s right-looking filter reaches a scheme with two rightward trie-style paths, one following the character o and one following the character ó. In fact, the largest class of errors in the remaining 42 scheme clusters consists of clusters which somewhere involve a morphophonological change in the c suffixes or c stems. Thirteen clusters fall into this morphophonological error category. In Error: Reference source not found, in addition to the 5^th cluster, the cluster on the 9^th row, with the 21^st most licensing types, is also led astray by morphophonology. Both the 5^th cluster and the 21^st cluster are marked in the Phon. column of Error: Reference source not found. The 21^st cluster subsumes a scheme very similar to the 1000^th selected scheme of Error: Reference source not found, which hypothesizes a morpheme boundary to the left of the true stem boundary. Although the cluster with the 21^st most licensing types includes the final characters of verb stems within c suffixes, the 21^st cluster is modeling a regular morphophonologic and orthographic change: stem final c becomes zc in some Spanish verbs. The only way ParaMor can model morphophonology is by expanding the c suffixes of a scheme or cluster to include the variable portion of a verb stem.

Nearing the end of Error: Reference source not found, the scheme cluster on the 6^th row of Error: Reference source not found, with the 10^th most licensing types, and the scheme cluster on the 10^th row, with the 100^th most licensing types, hypothesize morpheme boundaries in adjectives too far to the left, internal to the stem. Both are correctly removed by ParaMor’s right-looking morpheme boundary filter. Correctly, neither morpheme boundary filter removes the scheme cluster on the 11^th row, with the 122^nd most licensing types, which models plural number on nouns. Finally, as mentioned in Section 4.4.1, the last six scheme clusters in Error: Reference source not found were previously removed by the filter that looks at the number of licensing types in a cluster.

And so the scheme clusters that ParaMor produces as models of paradigms are generally quite reasonable. Still, there are three reasons that scheme clusters are not full descriptions of the paradigms of a language. First, ParaMor does not associate morphosyntactic features with the c suffixes in each cluster. ParaMor might know that the c suffix ar attaches to c stems like apoy, but ParaMor does not know either of the facts that the string apoy is a verb in Spanish or that the ar suffix forms the infinitive. Second, ParaMor’s scheme clusters contain incorrect generalizations. As noted in Section Error: Reference source not found, most of ParaMor’s clusters contain c suffixes, which model idiosyncratic derivational suffixes, that do not form valid word forms with all the c stems in the cluster. Third, although clustering introduces some model generalization, the scheme clusters ParaMor produces remain highly specific. By associating a set of c suffixes with a particular set of c stems, ParaMor constrains its analyses only to the word types covered by a c stem - c suffix pair in the scheme cluster. Despite these three deficiencies in ParaMor’s discovered paradigms, Chapters 5 and 6 successfully apply scheme clusters to morphologically segment word forms.