Stemnode Diagrams

About

Stemnode diagrams is in alpha which means you should expect bugs and some difficulty in using. Stemnode diagrams enable the diagraming of systems of systems, witch each node in the system linking back to the knowledge base within stemnode. If a piece of equipment is made of multiple other pieces of equipment, stemnode can map how a fluid flows through the different elements (e.g. from an HPLC to a detector). Alternatively, methods can be linked to nodes and combined to show how samples are processed through multiple experimental plans.

Elements of a System Map

There are three elements to every system map

1. Nodes - circles and squares

Nodes represent systems that can have subsystems or connect to other systems. Circular nodes represent a system that converts input flows into output flows while a square node represents a storage system where inputs are typically the same as outputs. For example, in a diagram of a car's electrical system an an alternator would be represented with a circle node because it converts mechanical torque into electrical energy, while the car battery would be represented with a square node because it stores energy but has electricity as both an input and output. The use of a square node vs. a circle node in a system diagram is a judgement call because sometimes a system element both stores and converts something; think of which function is more dominant when choosing how to represent the system.

2. Ports - small circles on the edges of nodes (also known as stems).

Ports represent the entry point of a flow into a node.  Typically, ports are named the same as corresponding flows.  Ports are required to connect flows to nodes.

3. Flows - solid and dotted arrows

Flows represent the movement of something in or out of a node; solid arrows represent the flow of something physical while dashed arrows represent the flow of information. For example, the flow of gas out of a gas tank would be represented by a solid line, however the signal to the driver of the level of the gas tank would be represented by dotted line because the signal is primarily of an informational value (despite an actual physical process sending that signal).

Guidelines for Building System Maps

Do's and Don'ts

-Do build generalized system maps that fit a generalized purpose, but do not attempt to represent every potential configuration of that system in a single diagram.  Instead place each practical configuration in a separate node so that others can use that configuration in other systems.

-Do map specific systems; maps of systems that actually exist at a specific location (even if that location may move in time).  These often serve as case studies that others can learn from.

-Do build system maps of theoretical systems that could be possible in the future but are not yet built, as long as they serve a function or improvement for society.

-Do use a node to hold nodes that are all the same type of system, or components in the same category of systems (e.g. Building Scale Wastewater Treatment Systems, Electrical Components), however do not try to connect nodes with flows because you often end up with messy diagrams where many combinations of subsystems are possible.

-It is typically appropriate to name ports the same as the external flow that connects to it.  When two or more different flows connect to it use more generic terminology which describes all the connecting flows succinctly (e.g. if both starch and sucrose are input flows to a port, then "carbohydrates" may be an appropriate name for the port).  Alternatively, use terminology for the connection point itself (e.g. a "terminal" on a battery, or a "Universal Serial Bus (USB)" port on a computing system).

-Do not title flows with verbs or actions.  Names of flows should typically be nouns although adjectives may also be appropriate to include.