A computer-implemented method for decreasing a required storage and processing in a Product Data Management system for massive-model visualization, comprising: - storing a hierarchical product data structure (Fig. 2) by a product data management system - in the following denoted by PDM system, the hierarchical product data structure including a plurality of occurrence nodes and component nodes, wherein a single component of the product can be instantiated many different times in the product structure and wherein each instantiation represents a different usage of a same identically defined component and is referred to as an occurrence of that component, wherein two occurrences are "equivalent" if they connect a same parent component and a same child component and if transform matrices of said two occurrences that represent their spatial locations are close to each other as measured by a specified distance threshold δ, wherein the product assembly is represented by a three-dimensional model subdivided into three-dimensional "cells" that are each assigned an index value, wherein the component nodes (210, 220) are associated with one or more cell index values (Fig. 3A) that identify the corresponding product component's spatial location according to the defined cells of the three-dimensional model of the product assembly; - creating an occurrence equivalency table, by the PDM system and from the hierarchical product data structure, that identifies at least one anchor occurrence node, and identifies at least one equivalent occurrence node that connects a same parent component node and a same child component node as the anchor occurrence node, the product component corresponding to the equivalent occurrence node being spatially located within a specified distance threshold (δ) of product component corresponding to the anchor occurrence node; and - creating an anchor occurrence table, by the PDM system and corresponding to the hierarchical product data structure, that lists a plurality of unique occurrence chains represented by the hierarchical product data structure, and that associates each listed unique occurrence chain with an associated cell index value, wherein an occurrence chain is a chain of occurrences that includes a single or multiple occurrences linked in the hierarchical data structure by component nodes, and wherein unique occurrence chains are identified by replacing each equivalent occurrence node by its corresponding anchor occurrence node in the occurrence chains represented by the hierarchical product data structure; and - storing the occurrence equivalency table and anchor occurrence table in the PDM system. - storing a hierarchical product data structure (Fig. 2) by a product data management system - in the following denoted by PDM system, the hierarchical product data structure including a plurality of occurrence nodes and component nodes, wherein a single component of the product can be instantiated many different times in the product structure and wherein each instantiation represents a different usage of a same identically defined component and is referred to as an occurrence of that component, wherein two occurrences are "equivalent" if they connect a same parent component and a same child component and if transform matrices of said two occurrences that represent their spatial locations are close to each other as measured by a specified distance threshold δ, wherein the product assembly is represented by a three-dimensional model subdivided into three-dimensional "cells" that are each assigned an index value, wherein the component nodes (210, 220) are associated with one or more cell index values (Fig. 3A) that identify the corresponding product component's spatial location according to the defined cells of the three-dimensional model of the product assembly; - creating an occurrence equivalency table, by the PDM system and from the hierarchical product data structure, that identifies at least one anchor occurrence node, and identifies at least one equivalent occurrence node that connects a same parent component node and a same child component node as the anchor occurrence node, the product component corresponding to the equivalent occurrence node being spatially located within a specified distance threshold (δ) of product component corresponding to the anchor occurrence node; and - creating an anchor occurrence table, by the PDM system and corresponding to the hierarchical product data structure, that lists a plurality of unique occurrence chains represented by the hierarchical product data structure, and that associates each listed unique occurrence chain with an associated cell index value, wherein an occurrence chain is a chain of occurrences that includes a single or multiple occurrences linked in the hierarchical data structure by component nodes, and wherein unique occurrence chains are identified by replacing each equivalent occurrence node by its corresponding anchor occurrence node in the occurrence chains represented by the hierarchical product data structure; and - storing the occurrence equivalency table and anchor occurrence table in the PDM system.