Integral Logistics Management — Operations Management and Supply Chain Management Within and Across Companies

4.1.2 Order Management and Graphical Representation of Logistics Processes

Intended learning outcomes: Describe MEDILS (Method for Description of Integrated Logistics Systems), its symbols and connections of the symbols.


The order is the main instrument of logistics, and its processing is the control flow of logistics, both within and among companies. The form of the contract is unimportant: it may be a detailed written contract, or a simple card in a pull system (a Kanban).

Order processing can be compared to a freight train. The cars are coupled together, and the train moves along a certain route. As it goes, goods or information are added to the train. Stopping at certain stations, it signals to other trains to start out and supply goods or informa­tion. Before finally ending its journey, our freight train also delivers goods and information to trains traveling farther on. An observer could sit in the locomotive of the order train and observe the happenings. MEDILS (Method for Description of Integrated Logistics Systems) was designed from this observation point. MEDILS goes beyond the classical flowchart, which was introduced to better understand processes, showing flows, tasks, waiting states, storages, and so on. Figure 4.1.2.1 introduces the symbols used in MEDILS.

Fig. 4.1.2.1        MEDILS symbols.

  • A double arrow represents the flow of goods. In the industrial sector, goods are usually tangible, but they can be information that go with the product from the start, such as drawings or specifications. In the service sector, goods are often intangible. In banks or insurance firms, for example, goods are often composed of information.
  • A single arrow denotes the flow of data for planning & control. This is the flow of information required for administrative and planning purposes. Data describe the characteristics of goods in an appropriate way. Every goods flow is a self-description and thus is also data flow, although it is not drawn separately as such.
  • A broken arrow represents the control flow. This is made up of information that deals with control of the flow of goods and data. Every goods flow and every data flow are also control flow, although they are not drawn separately as such.
  • A hexagon stands for a goods store. Depending on the kind of goods, this may be a warehouse, information store, and so on. An object in this store stands for certain goods and thus represents a waiting state in the flow of goods. In principle, it may stay in this state for an indefinite length of time in the store.
  • A rectangle with a double line on the left represents a data store. An object in this store stands for a certain quantity of data (for example, an order), and it is a waiting state in the flow of data. It may remain in store in this state for an indefinite period of time. The object can be described in more detail by the symbol.
  • A circle stands for a process store, a kind of intermediate store in the logistics process. We can think of a process store in the flow of data or nonmaterial goods (information) as a mailbox. An object is the envelope addressed with control information, while the data are found inside the envelope. A process store in the flow of material goods can be seen as a buffer or transit camp. An object is a crate inscribed with control information, while the goods are found inside the crate.
    A process store stores tasks waiting in line to be processed. The impetus for processing an object is given by an event: a sensor, such as the human eye, registers a state and finds an envelope in the mailbox. Thus, the event is an implicit part of process storage.
  • A rectangle represents a logistics task that may be described in detail within the rec­­tangle. If the effect of a task is the important aspect, the rectangle stands for a function. If procedure according to plan is the focus, the rectangle stands for a me­thod. If the focus is the way of implementation, the well-known value-adding ar­row, which stands for a process, is used in­stead of the rectangle. A task or process can be “nuclear” or com­prise subtasks or subprocesses, which are connected via flows.
  • The rectangle in the shape of an arrow represents a logistics system (LS) in the direction of the temporal axis. The logistics system includes logistics tasks, states, flows, and sublogistics. It has its own order and process management, which is indicated by the doubled top line. As compared to the simple value-adding arrow, a logistics system includes not only the process itself, but also the process store containing the trigger event(s), that is, the impetus to start the process.

Logistics systems are represented in graphic form by using and connecting the symbols. Figure 4.1.2.2 shows the connections used conventionally in MEDILS.

Fig. 4.1.2.2        MEDILS: connecting the symbols.

  • Goods or data along with control information or control informa­tion alone flow from storage into a task or function, or process. Execution of the task, function, or process transforms the goods or data, and they are then moved to new storage points. Multiple flows to a task must be coordinated at the start of the task. Depen­ding upon the context, related flows may be combined in the sense of “and” connections. Flows that need to be separated in the sense of an “or” or “exclusive or” connection are handled separately. Flows leading out from the task are handled analogously.
  • Goods, data, or control flow originate in a task outside the logis­tics system LS into a process store in the LS or from a task within the LS to a process store outside the LS. We can think of this as follows: goods or information in the order processing “train” are transferred to a transport “train” and delivered to another logistics systems “train.” This takes place, for example, when production turns over a completed customer order to distribution.
  • Special brackets stand for sequential or overlapping repetition of (sub)logistics, for as many times as demanded by the situation (even zero times). The flows leading into the brackets must be of the same type as those leading out of the brackets. The contents within the brackets can also be executed selectively, i.e., under conditions.

Small exercise: Logistics systems are represented in graphic form by using and connecting the symbols. The animation shows the connections used conventionally in MEDILS.
Roll over the various elements and see what they signify. By clicking the forward button you can change between three different figures.



Course section 4.1: Subsections and their intended learning outcomes

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