Morphological parsing, in
natural language processing
Natural language processing (NLP) is an interdisciplinary subfield of linguistics, computer science, and artificial intelligence concerned with the interactions between computers and human language, in particular how to program computers to pro ...
, is the process of determining the
morphemes from which a given word is constructed. It must be able to distinguish between orthographic rules and morphological rules. For example, the word 'foxes' can be decomposed into 'fox' (the stem), and 'es' (a suffix indicating plurality).
The generally accepted approach to morphological parsing is through the use of a
finite state transducer (FST), which inputs words and outputs their stem and modifiers. The FST is initially created through algorithmic parsing of some word source, such as a dictionary, complete with modifier markups.
Another approach is through the use of an indexed lookup method, which uses a constructed
radix tree. This is not an often-taken route because it breaks down for morphologically complex languages.
With the advancement of
neural networks
A neural network is a network or circuit of biological neurons, or, in a modern sense, an artificial neural network, composed of artificial neurons or nodes. Thus, a neural network is either a biological neural network, made up of biological ...
in natural language processing, it became less common to use FST for morphological analysis, especially for languages for which there is a lot of available
training data. For such languages, it is possible to build character-level
language models without explicit use of a morphological parser.
[Piotr Bojanowski, Edouard Grave, Armand Joulin, and Tomas Mikolov]
"Enriching Word Vectors with Subword Information"
/ref>
Orthographic
Orthographic rules are general rules used when breaking a word into its stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other structure
* Stipe (mycology), the stem of a mushro ...
and modifiers. An example would be: singular English words ending with -y, when pluralized, end with -ies. Contrast this to morphological rules which contain corner cases to these general rules. Both of these types of rules are used to construct systems that can do morphological parsing.
Morphological
Morphological rules are exceptions to the orthographic rules used when breaking a word into its stem and modifiers. An example would be while one normally pluralizes a word in English by adding 's' as a suffix, the word 'fish' does not change when pluralized. Contrast this to orthographic rules which contain general rules. Both of these types of rules are used to construct systems that can do morphological parsing.
Various models of natural morphological processing have been proposed. Some experimental studies suggest that monolingual speakers process words as wholes upon listening to them, while their late bilinguals peers break words down into their corresponding morphemes, because their lexical representations are not as specific, and because lexical processing in the second language may be less frequent than processing the mother tongue.
References
Grammar
parsing
Natural language parsing
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