Utente:Dalmax79/Sandbox
The composition of a product can be represented using a directed acyclic graph, called real structure, in which every node is the result of its children aggregation:
- the graph leaves are the components acquired from the suppliers;
- the intermediate nodes are some partial product (assemblies);
- the graph root(s) are the final products
On the graph arcs is indicated the quantity of the child component required to realize a single element of its parent. The use of a graph instead of a tree is usefull beacuse it permits to represent the cases where the same component type is used to build different assemblies.
Considering the production process, it can be defined another type of graph with no cycles, called ideal structure, in which each node represents a process step:
- the leaves of the graph correspond to one step of the production process;
- the intermediate nodes represent a macro phase or a next step;
- the root of the graph is the entire process.
 Y3 = 1*X4 + 1*Y2, Y2 = 1*X3 + 2*Y1, Y1 = 3*X1 + 1*X2 |
 Production steps sequence:: A, B, C |
It is possible to create a single structure that contains both the ideal (production steps), and the real one (components, assemblies), called technological structure: to the nodes of the ideal structure, known as idealnodes, there are links to the nodes of the real structure, called real nodes, used in the production step mapped by the ideal node. If the considered ideal node is a leaf of the ideal structure, it is linked to the entire real sub-graph that expresses the composition of the real node used in its production step; otherwise it binds only the single real node used, while his components are linked to the ideal nodes of the sub-graph which describes the production steps. On the arcs of the graph that connect a real node to an ideal node is indicated the quantity of the real node used in the ideal node mapped production step.
Step A) aggregates 1*X3 + 2*Y1; generates assembly Y2
Step B) aggregates 1*Y2 + 1*X4; generates assembly Y3
Step C) final product Y3
Use of characteristics to configurate the Bill Of Material (BOM) Structure[modifica | modifica wikitesto]
The product variations can be expressed using characteristics (or features): every product variation is defined by a combination of these characteristic values. If the considered product can have several variations, it can be too expensive to define each one of these with a different BOM structure. Using the technological structure and the characteristics, it is possible to define at the same time all the product variations in a single BOM structure: it is sufficient to assign to the link between a real node and an ideal node, a characteristics based boolean function, called application function, which will be true only when the combination of the characteristic values corresponds to a product variation where the real node is effectively used.
Characteristics: a = { 0, 1 }
The real nodes X1, X2, X4,Y1 are common to each final products: Y3, Y5 (Application function always true)
The real nodes X3, Y2 are specific to the final product Y3
The real nodes X5, X6, Y4 are specific to the final product Y5
[modifica | modifica wikitesto]
Given a product variation, represented by a specific characteristics valorization, it is possible to dynamically obtain the BOM structure navigating the technological structure and selecting only the real nodes having a true application function. Furthermore, linking each selected assembly with the real nodes selected in his sub graph it is possible to dynamically build also the real structure.
It is similarly possible to obtain the composition of an assembly related to an ideal node: it is sufficient to visit the sub-graph having as root the ideal node itself, excluding the starting real node siblings, and selecting the real nodes which application function has a not empty intersection with the application function of the starting real node (i.e. it exists a characteristic values combination where the two functions are both true ).
It is moreover possible, given a real node, to obtain all the assemblies it can belong to; if it belongs to a real structure, it navigates the structure in bottom-up direction: all the encountered real nodes are composed by the starting real node. Then, for each encounterd real node linked to an ideal node, it traces the application function f and visit in bottom-up direction the ideal structure: foreach parent ideal node, all the real node related to it and having a not empty application function intersection with f (i.e. it exists a characteristic values combination where the two functions are both true ) are then composed by the starting real node.
