Adding additional namespaces to a Service Information XML document

[nicholas...@bbc.co.uk]

Hello,

If we were to add additional namespaces/attributes/elements to an otherwise standard ETSI TS 102 818 Service Information file, what is the likelihood of it causing problems for clients?

A partner organisation (you know who you are!) has asked us to provide some additional elements in our SI.xml document and I am not sure if we should create a bespoke response for them, or if it would be acceptable to return the additional elements to all consumers of the Service Information file.

The whole point of XML is it is supposed to be extensible but I am not sure if it will pass validation and/or unexpectedly break clients.

Thanks!

nick.

[zoulou]

Hi Nick,

I would assume a likelihood of near 100% that there are a set of devices out there, which would fail to decode the SI XML document, if it does not meet the schema.

The consequences of a failure to decode are difficult to predict.

Best case, after the decode failure, the SI document is ignored and it is only a loss of functionality of the device, hopefully limited to the list of services that are covered by this SI. End customers may notice this, or not.

Worst case, the device reboots each time it receives such non-standard SI. End customers would definitely notice this.

XML is extensible at design stage of a schema. Not necessarily after the schema was implemented in devices.

Software is written by humans and therefore inherently error prone.

Also don't assume that standard, usually open-source, XML parser libraries are being used in all devices (which would help a bit).

"Small" devices might decode the XML document "by hand", means: self-written parser, only able to decode what the software developer had as examples at the time of writing the software, potentially years ago.

Cheers,

Richard

[James Cridland]

Experience from podcasting, where RSS/XML namespaces are regularly extended, suggests:

a) nothing in my experience ever checks the XMLNS definition files, even validators - I've just noted I'm linking incorrectly to one!

b) The only time it's caused issues is when an existing tag ("enclosure") is placed in a set of new parent tags ("podcast:live") - and it's broken one podcast catcher only, out of the many, many out there. (The podcast catcher was last updated in 2018).

That said, I'd be cautious!

//j

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