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Re: [LDM #DJB-370769]: New LDM feedtype for SPG Level II



Thanks Steve. There are a couple of reasons why we'd rather avoid using EXP. I'm not a networking, data distribution or LDM expert, but the people who are tell me that it will cause confusion for externally distributed products (the TDWR data is going out to the public) and is problematic for our internal tools as well.

You said that the identifiers are pretty much spoken for, does that mean that there might be an option for assigning a new type? This is an impactful data set from a large observation network (as I'm sure all the others are as well). Any chance we can reclassify or rename an existing one that's no longer in use?

If you're around next week, maybe it would be easier to have a quick call to talk further. Thanks.

Blake

PS - I'd prefer this not be published to the web.

On Thu, Dec 13, 2018 at 12:24 PM Unidata LDM Support <address@hidden> wrote:
Hi Blake,

I moved your inquiry into our support-email tracking system. It won't be publicly visible, however.

> Hope all is well. I'm with the NWS Radar Operations Center in Norman, and
> we're working a project to publish Level II data from the FAA's TDWR/NWS
> Supplemental Product Generator (SPG) system. The data distribution will be
> via LDM, but to my knowledge, there's no established feedtype.
>
> Are you familiar with the process for creating a new feedtype? If not,
> could you point me in the right direction? Thanks.

Once upon a time, when computers were much slower, having an integer feedtype was a good idea. Now, with much faster computers and with the 32 bits of the feedtype pretty much spoken for, not so much.

Consequently, we recommend using the EXP feedtype but **making sure** that the LDM product-identifier (the string in the data-product header that identifies the product) 1) uniquely identifies the product; and 2) is **easy to match for a particular class of products**. For example, your identifiers could be something like

    FAA/TDWR/SPG/...

where the "..." would be unique to that particular data-product. You might choose a different prefix. The point is that the prefix should provide an quick and easy way to distinguish this class of products.

The above allows a site that's interested in these products to have REQUEST entry like

    REQUEST EXP ^FAA/TDWR/SPG some.host.somewhere

and a pqact(1) entry like

    EXP<tab>^FAA/TDWR/SPG<tab>PIPE<tab>...

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: DJB-370769
Department: Support LDM
Priority: Normal
Status: Closed
===================
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--
Blake McGuire
Engineering Special Projects Team Lead
Radar Operations Center
405-573-3378