[Xastir-Dev] proposed method of doing canoncial shapefile DBF attributes support

[Gerry Creager (N5JXS)]

Woohoo!  Metadata!  In a consistent fashion!

There are standards we can tap for metadata, including GML instead of 
awk syntax, which are reasonably mature and don't require defining our own.

If there's interest, I can get the OGC GML references and making them 
available; they're on the OpenGIS.org site, too.

One thing I'd love to see is Xastir-2 OGC compliant for Location-Based 
Services, among other areas.

gerry

Alan Crosswell wrote:
> OK, so I guess attachments get broken.  Here it is inline:
> 
> Use a metadata file for each map that translates map-specific fields into
> canonical fields.  When the metadata file is missing, guess at which one
> of several pre-defined metadata definitions to use based on the dbf
> "signature" (as the code does currently).
> 
> Let's try a sample file (use Tiger/line since they are the most 
> complicated):
> 
> Use awk subset syntax.  Implement patterns using the pcre(3) library.
> pattern { action}
> 
> Action grammar is:
> <attr> := "width" | "color" | "name" | "filled" | "pattern"
>           | "display_level" | "label_level"
> <attr_set> := <attr> "=" value
> <op>   := "next"   # like awk, to end pattern search
> <stmt> := <attr_set> | <op>
> <stmt_list> := <stmt_list> ";" <stmt> | <stmt>
> <action> := <stmt_list>
> 
> Read DBF fields and pass them to this function as
> <field>=value
> 
> Sample file for Tiger/Line:
> # see tig2aprs.c cfccrange() for related examples.  See Tiger/Line
> # technical documentation for complete list of codes.
> # set defaults:  empty pattern matches everything.
> {key=""; width=1; color=black; name=""; filled=0; pattern=solid;
>  display_level=8192; label_level=32}
> # set the search key to be the Tiger/Line ID.  Not currently used.
> /^TLID=\(.*\)$/ {key=$1}
> # set the label to be the Feature Name
> /^FENAME=United States Highway\(.*\)$/ {label="US $1"};
> /^FENAME=State Highway\(.*\)$/ {label="State $1"};
> /^FENAME=State Route\(.*\)$/ {label="SR $1"};
> /^FENAME=\(.*\)$/ {label=$1}
> # Census Feature Class Code
> # A: roads
> /^CFCC=A1/ {lanes=4; color=brown}
> /^CFCC=A2/ {lanes=3; color=black}
> /^CFCC=A3[1-6]/ {display_level=256; next}
> /^CFCC=A3[7-8]/ {display_level=128; next}
> /^CFCC=A3/ {lanes=2; color=black}
> /^CFCC=A4/ {display_level=96; label_level=16; color=gray35; lanes=1}
> /^CFCC=A5/ {lanes=2; color=gray35; display_level=64}
> /^CFCC=A65/ {lanes=2, color=black, pattern=dashed; next}
> /^CFCC=A6[^5]/ {color=gray35; display_level=64; next}
> /^CFCC=A7[12]/ {lanes=1; color=red; pattern=dashed; display_level=64; next}
> /^CFCC=A7[03-9]/ {lanes=1; color=gray35; pattern=dashed; 
> display_level=64; next}
> # need to implement these:
> # B: railroads
> # C: transmission lines
> # D: landmarks
> # E: physical featuers
> # F: county boundaries
> # (G not used by census;  tig2aprs uses for special maps)
> # H: hydrography
> /^CFCC=H0/ {lanes=0; color=Steelblue;}
> /^CFCC=H02/ {pattern=dashed; next}
> /^CFCC=H[1-6]2/ {lanes=1; pattern=dashed; next}
> /^CFCC=H[1-6][013-9] {lanes=1; next}
> /^CFCC=H7/ {display_level=0; label_level=0; next}
> /^CFCC=H8/ {color=steelblue; lanes=1}
> /^CFCC=H81/ {color=white; next}
> 
> 
> Alan Crosswell wrote:
> 
>> What do you think:
>>
>>
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Network Engineering -- AATLT, Texas A&M University
Office: 979.458.4020  FAX: 979.847.8578
Cell: 979.229.5301    Pager: 979.228.0173