Игорь Волков – Hardware and software of the brain (страница 8)

The adverb may modify the adjective. 'very big', 'brightly green'. How is it possible if we defined the adverb as an attribute of the verb? In principle, receptors of the human eye encode both color and brightness so correct expression would be 'bright and green'. 'brightly green' may be shortening from 'a green leaf brightly shines in the sun'.

The action may turn into the item. The verb has even not one form for this. 'To define the concept is the first stage.' 'Defining the concept is the first stage.' Here the infinitive and the gerund are used. This may be easily explained. The action is represented in the brain as a dynamic image, a movie. Take a single picture from this movie and you will have the static item which may represent this action.

The action can also become a property of the noun instead of the adjective. 'Running man'. 'Running' is a participle here and we already see ambiguity with the gerund on the level of word forms which could be easily fixed. Where did creators of the language look? The explanation is in the next paragraph.

The noun may be a property of another noun. 'Animal paw'. This also has a more distinct variant – 'animal's paw' but may be expressed by the basic construct – 'paw of the animal'. There is yet another variant in English. Many words may be nouns and adjectives simultaneously so this feature may be implemented both on lexical and syntax levels.

Auxiliary verbs. 'Be' and 'have' are used in verb tenses and compound predicates, but they retain usual meaning there. In 'Maple is a tree.' 'is a tree' may be interpreted either as a purely formal construct representing a predicate as a whole or as a normal predicate phrase. In the latter case 'tree' will be a direct object. This has deeper semantical issues, but is very convenient programmatically. Nevertheless this also may have problems on the syntax level. 'The lemon is yellow.' The direct object can't consist of the attribute only. A full-scale noun phrase is required. A solution may be that this is ellipsis from 'The lemon is a yellow fruit.'

Different types of actions. In some cases, an action is directed at some object. In others, this object is absent. Accordingly, language distinguishes transitive and intransitive verbs. Reflexive verbs denote a situation when an action performed by some subject is directed at this subject itself. In English, this is encoded by means of the reflexive pronoun (he washed himself) or is not marked at all (he looks nice).

In complex sentences, the simple sentence becomes a clause. It still represents an action, but may play different roles. 'That I have a vacation is convenient now.' The subordinate clause stands in place of the subject. 'I decided that I must take a vacation.' Here, the similar clause is the direct object already. Indeed, the subordinate clause may be any part of the sentence. No problems if the action becomes the item and the item is the attribute.

Compound sentences like 'People stood on the shore, and the ship moved in front of them.' are short lists. A more extended variant is the paragraph of the text.

Affirmative sentences are basic units of a description. They represent knowledge. Questions and orders are related to using this knowledge. The former are queries for information extraction. The latter are used primarily in communication so as to prompt some action rather than transmit data.

Relations

There are 2 main types of relations: cause-consequence and general-particular (or abstract-concrete). The first type links actions. It may be expressed by complex sentences in both directions – with subordinate clauses of cause or goal. Conditional sentences are semantically close. Here the condition is not the reason completely but may be considered as a part of it. Causes and reasons may also be expressed by adverbial modifiers of the simple sentence. As they are made of noun-type words, some transformations are required. To represent the goal, the infinitive may be used. An example is the previous sentence itself. Reasons are often expressed by nouns. This may be interpreted as a reduced form. 'He turned his vehicle because of a man on the road.' 'He turned his vehicle because a man stood on the road.' The first is a simple sentence while the second – the complex sentence with the full subordinate clause of cause.

The concrete-abstract or is-a relation is used to represent conceptual hierarchy. The human neocortex has at least 3 levels of such hierarchy – the photographic image, abstraction in the limits of a given modality (vision, hearing, etc.), and complex multimodal images. Hence this type of semantics may be processed immediately on the hardware level.

Spatial and temporal relations are the next by popularity. They are encoded by various prepositions: on, upon, by, under, before, after, etc. In this case, the prepositional phrase is called the adverbial modifier.

The text

Now that we have determined semantics of the single sentence, let's try to understand how the meaning of a text is composed. In linguistics it is called coherence. This is closely related to the work of human memory and upper levels of perception. What happens when you try to understand the architecture of some building? You will walk around and look at it from different sides. Human memory is able to do interpolations. If you need a picture from some point which you didn't visit, you can easily imagine it. The result of such exploration is a set of images taken from a number of optimal points. The text reproduces this structure, only each image is replaced by a single sentence. The same principle works for processes. In this case, each reference point corresponds to a dot on the time scale so the set should be ordered. An intermediate state of the process may be easily interpolated from 2 neighboring points.

Nowadays, human texts have more complicated structure. Sentences are grouped into a hierarchy of blocks on the principle paragraph – chapter – book – library. Inside each block, elements of lower levels are listed as described above.

In addition, sentences are not just non-related elements of the list. They are interlinked. The mechanism used resembles variables of programming languages, only the implementation is very rudimental. Close analogue of the variable is the pronoun. Their implementation in human language is so poor that binding pronouns to their values became one of the major problems of natural language understanding.

Another method resembles the class-object pair. In programming languages, you should declare a variable of some class, then assign an instance of that class (object) to that variable. Human language doesn't like formalities. You can immediately use the name of a class as a variable with an already bound value. When you read 'apple', this may be either an abstract concept denoting the whole class or a concrete material fruit. Definite vs. indefinite articles may be used so as to distinguish between them. Unfortunately, the number of possible variants is so large that any programmatic implementation should list them explicitly.

The methods to define a concrete object (to create an instance) may vary. You may mention a class in concrete circumstances. 'A cup stands on the table.' Since then, this class turns into the object and you can use this word with the new meaning. Additional details may be added in separate sentences. All of them will be linked to the same object. After that, it is possible to use this object in some action.

Otherwise you may use the relative clause. 'Take the cup that stands on the table.' Here, all is done inside one sentence. There is also a difference in general use. Programming languages use classes mostly to define their methods and properties and to create object instances from them. The program will use that objects afterwards. Human language, in contrast, manipulates classes and concrete objects in equal degree.

Indirect meaning

All these elements represent the direct meaning of a text. There is also an indirect meaning in addition. It is produced by reasoning. For example: "The price of item1 was $10 last month. The price of item1 is $8 now." The conclusion from this short text will be: "The price dropped." Indirect meaning is always pragmatical that is dependent on the situation. For one person one feature of the sentences is important. For the second – another one. Their conclusions may be different. Context-free languages restrict their semantic scope to direct meaning. This is a relatively simple task routinely solved by standard programming languages. What do humans use in addition?

Semantic transformations

Associative memory of neural nets not only stores data but also provides various processing based on similarity immediately on the hardware level. This is widely used during language understanding.

Anaphora

Pronouns are analogous to variables in programming, but their usage is peculiar. In strict languages, you must declare the type of a variable, then assign a value to it; only then you may use this variable in some expression. In natural language, you just use 'it' which refers to some previously mentioned noun. 'A cup stands on the table. It is large and bright.' The reader often guesses which one you keep in mind. Human language has an even more vague but simultaneously more embracing feature. 'it' or 'this' may refer to the whole paragraph describing some phenomenon of any nature possible. It may be a material object, an action, or even a relation.