76 lines
2.1 KiB
XML
76 lines
2.1 KiB
XML
= dgtxt file format
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Human readable file format for directed graphs
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== Design goals
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- any valid input to `tsort`, not containing `#`, is always valid dgtxt.
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- removing every occureance of the RegEx `#.*?\n` should produce a valid input to `tsort` (if it doesn't contain cycles of course)
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- easy to generate
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- human readable
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- easy to parse fully
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== Concepts
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=== Node
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Has:
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- incoming edges
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- outgoing edges
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- name
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- key-value attributes
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=== Edge
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Has:
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- source node
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- destination node
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- key-value attributes
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== Syntax
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Note that `{x}` means none or more times.
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```ebnf
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ident char = anything - '\n' - '\r' - ' ' - '#';
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ident = ident char, { ident char };
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node attribute = '##', {spaces},
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ident, {spaces}, (* referred node *)
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ident, {spaces}, (* attribute key *)
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{ not new line } (* attribute value *)
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;
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comment = '#', { note new line };
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edge attribute = '#:', {spaces}, ident, {spaces}, {not new line} ;
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edge = ident, {spaces}, (* source node *)
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ident, {spaces}, (* destination node *)
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{ {spaces}, edge attribute, {spaces} }
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;
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element = edge
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| node attribute
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| comment
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;
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grammar = { spaces, element, spaces };
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```
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== Example
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```
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# comment line (ignored)
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DownloadLinux FlashDrive
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# double hashtass start node attributes:
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## DownloadLinux describtion Attrbiute key/value formats are not standardized her
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FindFlashDrive FlashDrive #: cost 200
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#: another-attr-key another attr value (until end of line)
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DownloadDriveFlashSoftware FlashDrive
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FlashDrive ShutdownWindows
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ShutdownWindows RestartPc
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RestartPc InstallLinux
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```
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== Recommendations
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- tools should prefix attribute names with the tool names, unless they think that other tools might adopt that attribute too.
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- tools that modify graphs should preserve all attributes
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- tools should not error on unknown attributes (or invalid attribute values), as they might be valid in a different tool
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- actual comments should have a space after the `#`, for future proofing
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- node attributes be listed directly after node definitions
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