One of the core concepts of the tectogrammatical layer – valency theory – has been developing since 1970s; a substantial summary is provided in Panevová (1974-5), Panevová (1980) and Panevová (1994). Valency is the ability of a word (prototypically a verb) to open a certain number of positions for other, dependent language units. These valency positions are occupied by valency complementations, which are distinguished into inner participants and free (adverbial) modifications on the basis of their syntactic behavior.
The set of valency positions characteristic of a word in one of its senses is called a valency frame of the given word in the given sense.
Further, obligatory (in deep representation) and optional complementations are distinguished. For the determination of obligatoriness of a valency position, a dialogue test is formulated (Panevová, 1974-75); the test can be illustrated by the following dialogue:
The unacceptability of the answer “I don’t know” in the dialogue above indicates the obligatoriness of the free modification of direction where? for the verb přijít [to come].
There are other valency positions governed by a verb that are optional – they may be present in the meaning representation of a sentence; however, their omission does not result in semantically or grammatically incorrect sentences, e.g., Petr se pevně držel (zábradlí) (Eng. Peter held on firmly (to the railing)), Eva se najedla (ovoce) (Eng. Eve has eaten (some fruit)), and Dívka píše (mamince) dopis (Eng. A girl is writing a letter (to her mum)).
In the surface realization of a sentence, participants usually occur in a certain morphemic form which is given by the requirements of the governing verb. Thus the Actor in an active sentence is prototypically expressed by the nominative while the Patient is usually realized as the accusative, e.g. PetrACT-nom ztratil botuPAT-acc (Eng. PeterACT lost his shoePAT). Other verbs require the Actor in the dative, e.g., PetroviACT-dat se ve škole líbilo (Eng. PeterACT likes the school), other verbs require the Patient to be in the dative, e.g., RodičeACT-nom bránili jejich štěstí.PAT-dat (Eng. ParentsACT obstructed their happinessPAT), or in the form of a prepositional group, e.g., Doufali ve vítězstvíPAT-v+acc (Eng. They hoped for victoryPAT). On the other hand, the morphemic expression of free modifications are usually implied by their meaning, e.g., Děti přišly domů / do školy / na hřištěDIR3 (Eng. Children came home/to the school/to the playgroundDIR3), not by the grammatical properties of the governing verb.
The valency theory developed within FGD is applied in several valency lexicons of Czech, esp. VALLEX (Lopatková et al, 2008) and PDT-Vallex (Urešová, 2011), and of English, EngVallex (Cinková, 2006).