How should a Rebol-structured data file (which contains no code) be written and read? - reflection

Question

If you build up a block structure, convert it to a string with MOLD, and write it to a file like this:
>> write %datafile.dat mold [
[{Release} 12-Dec-2012]
[{Conference} [12-Jul-2013 .. 14-Jul-2013]]
]
You can LOAD it back in later. But what about headers? If a file contains code, it is supposed to start with a header like:
rebol [
title: "Local Area Defringer"
date: 1-Jun-1957
file: %defringe.r
purpose: {
Stabilize the wide area ignition transcriber
using a double ganged defringing algorithm.
}
]
If you are just writing out data and reading it back in, are you expected to have a rebol [] header, and extend it with any properties you want to add? Should you come up with your own myformat [] header concept with your own properties?
Also, given that LOAD does binding, does it make sense to use it for data or is there a different operation?

Answer 1

Rebol data doesn't have to have a header, but is best practice to include one (even if it's just data).
Some notes:
SAVE is your best bet for serializing to file! or port! and has a mechanism for including a header.
MOLD and SAVE both have an /ALL refinement that corresponds to LOAD (without /ALL, some data from MOLD and SAVE cannot be reliably recovered, including Object, Logic and None values).
LOAD discards the header, though you can load it using the /HEADER refinement.
Putting this together:
save/all/header %datafile.dat reduce [next "some" 'data][
title: "Some Data"
]
header: take data: load/header %datafile.dat
To use a header other than Rebol [], you'd need to devise a separate loader/saver.

Answer 2

For the case of reading, construct works very well alongside load to prevent evaluation (of code as opposed to data):
prefs: construct/with load %options.reb default-prefs
It is:
Similar to context
obj: [
name: "Fred"
age: 27
city: "Ukiah"
]
obj-context: context obj
obj-construct: construct obj
In this case, the same:
>> obj-context = obj-construct
== true
Different
when it comes to evaluating code:
obj-eval: [
name: uppercase "Fred"
age: 20 + 7
time: now/time
]
obj-eval-context: context obj-eval
obj-eval-construct: construct obj-eval
This time parsing differently:
>> obj-eval-context = obj-eval-construct
false
>> ?? obj-eval-construct
obj-eval-construct: make object! [
name: 'uppercase
age: 20
time: now/time
]
Aside:
This is the point I realize the following code wasn't behaving as I expected:
obj-eval: [
title: uppercase "Fred"
age: 20 + 7
city: "Ukiah"
time: now/time
]
gives in red (and by extension, rebol2):
>> obj-eval-construct: construct obj-eval
== make object! [
title: 'uppercase
age: 20
city: "Ukiah"
time: now/time
]
lit-word! and lit-path! is different.
TODO: question
It has also
Useful refinement /with
Which can be used for defaults, similar to make