Diagram Elements
This section describes the elements of the diagramming notation, including their shape/style and colour if applicable.
Concepts
Concepts are represented by a rectangle, containing the name of the concept as shown below:
Optionally the definition status of a concept may be represented. Concepts that are fully defined may be represented using a double line border as shown below:
Concrete Values
A concrete value is represented by a rectangle with diagonal lines in the corners. The value itself is added to the rectangle as text, with numeric values (i.e. integers and decimals) preceded by a '#', string values enclosed in double quotes, and boolean values represented as "true" or "false" with no adornment.
Number
String
Attributes
Relationships, or attributes, are represented using a rectangle with rounded ends and a double line border, as shown below:
"Is A" Arrows
"Is a" (subtype) relationships are highlighted by using an open-headed arrow as shown below:
Attribute Groups
Attribute groups are represented with a circle:
Conjunction
A conjunction is represented with a black "dot" (black filled small circle). It is only necessary when two or more attributes are being joined in a diagram. It is optional when attaching a single attribute.
Relational Operators
Relational operators may be represented between expressions using the notation shown in the table below:
Symbol
Character
≣
⊑
⊒
Unicode Character
Unicode: U+2263
UTF-8: E2 89 A3
Unicode: U+2291
UTF-8: E2 8A 91
Unicode: U+2292
UTF-8: E2 8A 92
The characters ≣, ⊑ and ⊒ are only present in fonts that support the full set of Unicode characters. For example users of Microsoft tools will find these characters in the font called "Arial Unicode MS".
Arrow
An arrow as shown below is used to connect related elements where the connection is unidirectional:
Line
Similar to the Arrow above, the Line shown below is used to connect elements in the diagram where the connection is bi-directional.
Names and Element Sizes
Each element contains a name as specified. The diagram elements may be resized and/or the text of the name given to the element may be wrapped as needed to achieve readability. When resizing it is highly recommended that concept and attribute elements remain rectangular and wider than they are tall where possible.
Names chosen must be fully specified names or (usually preferred) synonyms as stated, however a single diagram must consistently use either fully specified names or synonyms for all diagram elements.
It is highly recommended that an element's name be preceded by its concept identifier. This is to eliminate any potential ambiguity.
Colour
Diagrams may be produced in black and white, or colour may be added to aid readability.
In order to provide consistency the following sections specify the colours to be used for each type of element. Specified colours are websafe, do not affect black and white printing and are generally perceptible by most common colour blindness.
Concepts
Primitive concepts are coloured with RGB 99CCFF (decimal 153, 204, 255) as shown below.
Attributes
Attributes are coloured with RGB FFFFCC (decimal 255, 255, 204) as shown below.
Concrete Values
Concrete values are coloured with RGB A5E0B6 (decimal 165, 224, 182) as shown below.
Attribute groups
Attribute groups are not coloured, and are always presented as a circle with a white interior.
Conjunctions
Conjunctions are not coloured, and are always presented as a black dot as shown in Conjunction.
Relational Operators
Relational operators are not coloured and are always represented as shown in Relational Operators
Gradients, Blends and Opacity
Graded shading provided by modern diagramming tools is NOT permitted, as they
Can vary substantially in style
May reduce readability and consistency.
For example, the following are not acceptable.
Fonts
For consistency, all text within diagram elements is to use a sans-serif font such as "" and font size is to be consistent across all elements within a single diagram.
Authors are also strongly encouraged to keep the apparent size of the text in the final image close to that of the surrounding text (usually 8-12 points).
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