Abstract The paper analyses the application of grammar knowledge representation of Bulgarian inflectional morphology. We present the implementation of inflectional morphology of Bulgarian possessive and reflexive-possessive pronouns using the semantic networks interpretation. It is focused on modelling the inflectional morphology of Bulgarian possessive and reflexive-possessive pronouns using the Universal Networking Language (UNL). The formal analysis and related encodings take into account the specific morphological and syntactic properties of possessive and reflexive-possessive pronouns, and represent their inflectional morphology interpretation with respect to the feature of definiteness. The definitions of presented inflectional rules are given after the detailed analysis of both semantic and grammar features of the related pronouns. The evaluation of generated inflected forms is given by some example words. The analysis of basic problems of rule-based inflectional morphology grammar representation of Bulgarian possessive and reflexive-possessive pronouns is offered, and the semantic network using rule-based knowledge representation and non-monotonic reasoning in UNL framework with related encoding is presented. The particular model is explained in terms of its linguistic motivation.