Representing logic as data in JSON

Question

For business reasons we need to externalize some conditional logic into external files: preferably JSON.

A simple filter-by scenario could be handled by adding a node as follows:

"filter": [   {     "criteria": "status",     "value": "open",     "condition": "=="   } ] 

Multiple conditions could be handled by additional values in the array.

"filter": [   {     "criteria": "status",     "value": "open",     "condition": "=="   },   {     "criteria": "condition2",     "value": "value2",     "condition": "=="   } ] 

However, it gets a little confusing when we have handle complex conditions involving ANDs or ORs.

Question: is there a standardized (or even widely accepted) format for representing such logic within JSONs? How would you do it if it were up to you?

NOTE: The first answer has been made an editable wiki so it can be improved by anyone who feels it can be.

Answer 1

If you must implement this using standard JSON, i'd recommend something akin to Lisp's "S-expressions". A condition could be either a plain object, or an array whose first entry is the logical operation that joins them.

For example:

["AND",     {"var1" : "value1"},     ["OR",         { "var2" : "value2" },         { "var3" : "value3" }     ] ] 

would represent var1 == value1 AND (var2 == value2 OR var3 == value3).

If you prefer brevity over consistency, you could also allow an object to have multiple properties, which would implicitly be joined by an AND. For example, { "a": "b", "c": "d" } would be equivalent to ["AND", { "a": "b" }, { "c": "d" }]. But there are cases (like the example) where the former syntax can not faithfully represent the condition as written; you'd need additional trickery like translating the condition or using dummy property names. The latter syntax should always work.