1. A computer implemented method for structure evaluation of time-dependent acyclic graphs, the method comprising the following steps performed by at least one hardware processor: processing a data model of a stored data repository, wherein at least a subset of data model nodes include at least one recursive node stored in the data model, the at least one recursive node including an identifier of the particular recursive node's parent node; identifying a runtime transient relation between the at least one recursive node and an identified parent node, the parent node identified using a generic graph service and the identified parent node stored in the at least one recursive node, and wherein the transient relation between the at least one recursive node and the identified parent node is generated at runtime; instantiating an acyclic graph structure using the generic graph service, the acyclic graph structure including the runtime transient relation between the at least one recursive node and the identified parent node based on the processed data model, and wherein the generic graph service provides functionality for a software application to retrieve data from the acyclic graph structure without identifying the structure of the acyclic graph structure; determining a validity of at least one node of the acyclic graph structure, with the at least one hardware processor, by comparing an identified validity period to the at least one node of the acyclic graph structure, each of at least a subset of the at least one node associated with a particular time period; identifying at least one invalid node, the at least one invalid node associated with a time period outside the identified validity period; removing the at least one identified invalid node; substituting, for each of the at least one removed invalid nodes, a corresponding skip node, where each skip node corresponds to a single removed invalid node, each skip node including a skip function, each skip function defining a skip relation that defines a relationship for valid nodes adjacent each skip node, the relationship pointing from a last valid node located before the skip node to a next valid node located after the skip node; generating a validity graph for the identified validity period including: at least one of the nodes of the acyclic graph structure that is valid for the identified validity period based on the time period associated with each of the at least one nodes, and at least one skip relation for each skip node, where data in the at least one invalid node is absent from the validity graph; and storing the validity graph in a repository.