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Benefits of XML/XSL rules/templates [message #1717349]

Fri, 11 December 2015 23:33

John Cocula

Messages: 21
Registered: June 2015

Junior Member

I see the nice new rule engine has a preference for JSON encoding, which is undoubtedly valuable (UIs for example), but I think if there were an XML schema and transport for rules, there would be benefits.

Any XML document could be a source to generate rules. Rule templates would be represented as XSL transforms to produce XML documents in the accepted rule schema. Rules could be generated from potentially complex configuration data in XML files, simplifying the process of having rules match the real world configuration.

Of course all of this could be done external to ESH and then converted to JSON as the last step, but it would have value to have a published schema and benefit from XML/XSL transformations.

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Re: Benefits of XML/XSL rules/templates [message #1717535 is a reply to message #1717349]

Mon, 14 December 2015 15:36

Kai Kreuzer

Messages: 673
Registered: December 2011

Senior Member

Hi John,

I think there is a lot of dispute whether or not XML is a superior format over JSON. Smile

We have decided to go for JSON as a parser implementation, because this is what we needed for the REST API anyhow.
Note that we created an architecture that allows for other serialization formats as well - all you would have to do is to implement an implementation for this interface: https://github.com/eclipse/smarthome/blob/master/bundles/automation/org.eclipse.smarthome.automation.api/src/main/java/org/eclipse/smarthome/automation/parser/Parser.java
So yes, if anybody feels XML is important, PRs for additional parsers are always welcome!

Btw, I think neither JSON nor XML is nice for manually writing it; For authoring rule templates, we should probably rather come up with some DSL or a nice user interface (which then again is likely to directly produce JSON).

Regards,
Kai

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Re: Benefits of XML/XSL rules/templates [message #1717537 is a reply to message #1717349]

Mon, 14 December 2015 15:37

Kai Kreuzer

Messages: 42
Registered: July 2009

Member

Hi John,

I think there is a lot of dispute whether or not XML is a superior format over JSON. :)
We have decided to go for JSON as a parser implementation, because this is what we needed for the REST API anyhow.
Note that we created an architecture that allows for other serialization formats as well - all you would have to do is to implement an implementation for this interface: https://github.com/eclipse/smarthome/blob/master/bundles/automation/org.eclipse.smarthome.automation.api/src/main/java/org/eclipse/smarthome/automation/parser/Parser.java
So yes, if anybody feels XML is important, PRs for additional parsers are always welcome!

Btw, I think neither JSON nor XML is nice for manually writing it; For authoring rule templates, we should probably rather come up with some DSL or a nice user interface (which then again is likely to directly produce JSON).

Regards,
Kai

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Re: Benefits of XML/XSL rules/templates [message #1717548 is a reply to message #1717537]

Mon, 14 December 2015 16:27

John Cocula

Messages: 21
Registered: June 2015

Junior Member

Quote:

I think there is a lot of dispute whether or not XML is a superior format over JSON.

Of course the answer depends on the surrounding components, and for REST and UIs I imagine JSON is just simpler to deal with. And the last thing I want to do is flame about this format vs. that format.

I wanted to draw attention to the rich set of XML tools that have been around longer than JSON for validating and transforming structured information, and why there is value in leveraging those things instead of rolling out a custom templating/transformation engine, or hand-validating structural correctness. One could achieve a lot more openness, I believe, by using these tools instead of hand-rolling domain-specific workalikes.

Quote:

Note that we created an architecture that allows for other serialization formats as well - all you would have to do is to implement an implementation for this interface:
https://github.com/eclipse/smarthome/blob/master/bundles/automation/org.eclipse.smarthome.automation.api/src/main/java/org/eclipse/smarthome/automation/parser/Parser.java

I had read that interface and it seems some what tied to JSON already, in that this line of the interface has a hardcoded "json" constant in it. In other words, there is not full separation of the model from serialization/deserialization methods in the current code.

Quote:

So yes, if anybody feels XML is important, PRs for additional parsers are always welcome!

Btw, I think neither JSON nor XML is nice for manually writing it; For authoring rule templates, we should probably rather come up with some DSL or a nice user interface (which then again is likely to directly produce JSON).

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Re: Benefits of XML/XSL rules/templates [message #1717552 is a reply to message #1717548]

Mon, 14 December 2015 16:42

Kai Kreuzer

Messages: 673
Registered: December 2011

Senior Member

Quote:

in that this line of the interface has a hardcoded "json" constant in it.

Well, this line is exactly there to indicate that there can be others in future Smile

So it is waiting to be accompanied by

public static String FORMAT_XML = "xml";

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Re: Benefits of XML/XSL rules/templates [message #1717555 is a reply to message #1717552]

Mon, 14 December 2015 17:15

John Cocula

Messages: 21
Registered: June 2015

Junior Member

Oh, I see now; I did not expect the interface to hold that sort of information. Thanks for explaining.

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