Chapter 7. BDI Tracer

The BDI Tracer is accessible from the Jadex Control Center tool bar. It is a tool inspired by the Ph.D. work of Dung N. Lam working on agent software comprehension with abductive reasoning. The tracer provides basically an interface and means to log the internal state of a BDI agent, and to analyze and visualize the logged information. It is made of two components. The first one is the TracerAdapter placed in front of an agent as a tool adapter. It is responsible for filtering messages concerning the tracing process away from the message queue of an agent and it collects the information about agent's internal state changes and other occurrences in the system. The information is then sent to the Tracer Agent, if an instance is present on the platform. The latter has the duty to analyze the traces, store them, and to present them to the user in a graphical form.

7.1. Main Window

The main window of the tracer agent may be seen in Figure 7.1, “Tracer Main Window”.

Tracer Main Window

Figure 7.1. Tracer Main Window

The traces presented above are from the Blocksworld example. In order to indicate a type of traces, they are marked with icons and their different meaning is explained in Table 7.1, “Information logged by the tracer”:

Table 7.1. Information logged by the tracer

Actions describe internal processes (i.e. internal agenda meta actions) of an agent and are by default ignored by the tracer.

Beliefs are meta traces that collect all traces concerning the use of beliefs and their change. Belief read and write access indicate that an agent or one of its plans have accessed a belief and possibly changed it.

The icons stand for message reception or send events respectively.

Goals are traced when they are adopted by the agent. The icons on the left side represent different goals: achieve goal, perform goal, query goal, maintain goal, meta goal.

Plans are shown, when created in response to a goal or event.

Internal events are traced whenever they are dispatched within the agent.

The tracer perspective is split into four views including a tree view of agents and traces, a tabular view of traces, tracing settings and a 2D trace space exploring panel.

7.1.1. Trace Tree

At the left there is a tree view showing all agents known to the tracer. The meaning of a particular icon depicting an agent is shown in Table 7.2, “State of an agent”. Descending from the BDI agents, all traces are linked beneath nodes identified to be their cause.

Table 7.2. State of an agent

The agent is ignored by the tracer.

The agent sends its traces to the tracer.

The agent has died.

The functionality provided by the tree popup menu is similar to the functionality from the Agent menu (Section 7.2.1, “Agent Menu”) and concerns the currently selected trace or agent. In the case of an agent the user may choose to observe it and to adjust the trace filter and history limit (Filter). The other options allow to show or hide traces in the graph or table. With the last menu item the trace or the agent may be removed from the tracer perspective.

Tree Popup Menu

Figure 7.2. Tree Popup Menu

7.1.2. Trace Table

On the right side there are three views. The upper one in the middle shows a tabular view of the traces, as can be seen in Figure 7.3, “Trace Table”:

Trace Table

Figure 7.3. Trace Table

The traces are ordered in the sequence they arrive. The table shows information like a unique trace id, the agent name, the event name, The event name and the content are closely related and explain which kind of event occurrence has happened. The cause describes the reason for the event occurrence and the time shows when the event has happened.

The user may select traces in the table based on different criteria, remove them from the table, show them in the graph panel or delete from the tracer perspective. All the fuctionality is accessible under the Table Menu (Section 7.2.2, “Table Menu and Tracing Settings”) and a corresponding popup menu.

The view on the upper right side, offers some tracing settings, as can be seen in Figure 7.4, “Tracing Settings”:

Tracing Settings

Figure 7.4. Tracing Settings

Check boxes let the user specify what to trace and above the number of traces to show can be chosen from a pull down menu. The changes can be applied by the button “apply” and the other button labled with “clear” clears the trace table.

7.1.3. Trace Exploration Graph

The lower one of the three right views is the graph panel allowing to explore the space of traces. It also provides multiple presentation options e.g. for selection of and correletion and between the traces. All this functionality may be accessed from the "Graph" and the graph popup menu. (see Section 7.2.3, “Graph Menu”).