There is one kind of intersentential links which requires obligatory realization of predicate actors (predicate place-fillers). A problem area may demand that a certain subset of predicate actors be expressed in a text in one or another form. Thus arithmetic problems dealing with moving objects require obligatory realization of motion attributes - velocity, distance and time. Semantic objects corresponding to the attributes are presented as goals of the hypotheses attached to these words. In the model proposed here the necessity of realization of a particular actor reveals itself in the demand of obligatory merging these indirect referents with semantic objects introduced by other words. One part of these mergers will result from setting syntactic links in the sentence. Hypotheses remaining unrealized hereupon are a model of a linguistic phenomenon known as "textual anticipation". These hypotheses may participate in the analysis of a subsequent text and may be realized there even before setting some internal syntactic and semantic links.
The requirement of necessary realization of indirect referents is also a peculiarity of some words other than predicates, e.g. "оставшийся" ("осталось", "остальной") ("something that remains", "the rest"), "обратный" ("reverse", "opposite"), and others. Here a semantic class of the predicted object is not defined by the word-predictor but is derived from its intermediate syntactic surroundings.
There is a group of words not only demanding obligatory realization of indirect referents but also predicting their syntactic or even morphological features with a certain probability. Consider the following indirect referents of the word "вышла" ("departed") in the sentence "Машина вышла из пункта А" ("A car departed from the point A"): motion, motion termination, the initial point of the route, the final point of the route. Motion termination is realized by verbs with prefixes "при-" or "до-", viz., "пришла", "прибы- ла", "достигла" ("arrived", "came", "reached") whereas a particular semantic and morphological shape of a realization of the final point depends on that of the realization of the initial point ("из пункта А в пункт Б", "из Москвы в Ленинг- рад" ("from A to B" or "from Moscow to Leningrad") but not "из пункта А в Ленинград" ("from A to Leningrad"). Thus not only semantic but also syntactic hypotheses may spread over subsequent text.
One more kind of intersentential links requiring obligatory merging are anaphoric links. Whereas links of previously considered types require obligatory merging for indeirect referents, anaphoric links require obligatory merging of the direct referent of the word-substitute. In this case the value of syntactic features participating in the search for the antecedent is increasing. Consider first the situation with an antecedent represented at the surface level.
If a word-substitute is a 3-d person personal pronoun then the direct referents of the antecedent and the pronoun are to be merged and an anaphoric hypothesis assigned to a word-substitute has a goal which is a syntactic object with a certain number, gender and semantic class of its direct referent. A pronoun may get a semantic class with the syntactic link from a governing predicate word . The idea of inducing semantic features is not a novelty in linguistics, and the model described here proposes quite natural way for doing that due to the possibility of merging association net objects.
If a substitute is represented by a combination of (1) adjective anaphoric element, "этот", "тот", "такой же" ("this", "that", "similar") and (2) a substantive used as a substitute, then the direct referents of the antecedent and the substantive serving as a substitute are merged. Accordingly, the goal of a hypothesis assigned to an adjective anaphoric element is represented by a syntactic object with a lexical unit coinciding with that of the word- substitute, or with a lexical unit designating a subclass or a superclass of the substitute; the third possibility arises when the direct referent of the goal and that of the word-substitute belong to the same semantic class.
There are more complex situations when an antecedent does not exist on the surface level. To handle these situations an anaphoric word must be provided with a semantic hypothesis searching for the direct referent of the word-substitute and which is realized by merging this direct referent with an indirect referent of some other word (in this problem area - with a word denoting motion) as in the example: "Турист прошел 16 км за 4 часа. За какое время он пройдет 20 км, если будет двигаться С ТОЙ ЖЕ СКОРОСТЬЮ?" ("A tourist was walking 4 hours and passed a distance of 16 km. How long will it take him to pass 20 km if he is going to walk WITH THE SAME VELOCITY?")
Thus in the present model setting all kinds of intersentential links is performed by merging semantic objects, but something that varies is the influence syntactic features during the search for a merging candidate.