1. A computer-implemented method comprising: obtaining data representing a directed graph, wherein one or more nodes of the graph are associated with a respective set of one or more metric instances, wherein each respective set of metric instances for each node in the graph identifies all metric instances associated with the node and all metric instances associated with any node descendant from the node in the graph, wherein each metric instance identifies a location in a source code base, and wherein each metric instance has a respective metric value, and wherein at least one node is reachable by multiple paths in the graph, wherein the graph includes multiple source code location nodes and multiple edges between the source code location nodes, each source code location node representing a portion of the source code base, each edge between source code location nodes representing inclusion of a first portion of the source code base in a second portion of the source code base, wherein the graph includes multiple organizational nodes and multiple edges, each organizational node representing a respective business entity of a business organization, each edge between organizational nodes representing responsibility of a first business entity for a second business entity, wherein each edge between an organizational node and a source code location node represents responsibility of a business entity represented by the organizational node for a portion of the source code base represented by the source code location node; and computing an aggregated attribute value for a first node in the graph, including aggregating respective metric values of each metric instance in a first set of metric instances associated with the first node, wherein the first set of metric instances identifies all metric instances associated with the first node and all metric instances associated with any node descendant from the first node in the graph including the node reachable by multiple paths in the graph.