Pete,
I have 4 questions about your proposed IPP attributes for Geo Location for
Cloud Printing:
1. The representation of the values of your proposed IPP "size",
"horizontal-precision", and "vertical-precision" attributes are completely
different from the representation of the same attributes in RFC1876.
If this difference is intentional, it would be good to explain the
difference and why and to indicate this intended difference in the spec?
As I read RFC 1876, the representation of the SIZE, HORIZ PRE, and VERT PRE
attributes are all using this funny SIZE representation as a pair of
four-bit unsigned integers, where the most significant 4-bit unsigned
integer represents the base and the second 4-bit integer represents the
power of 10 by which to multiple the base, sort of a compressed floating
point representation, but using power of 10, not power of 2. The reason
give in RFC 1876 is so that the value is more easily human readable. HORIZ
PRE and VERT PRE attributes defined in RFC 1876, say:
expressed using the same representation as SIZE
i.e., using this same 8-bit "floating point" representation.
BTW, the VERT PRE attribute has an ironic Freudian slip typo in RFC 1876,
since I don't find this representation very sane :-(:
expressed using the sane representation as for SIZE
2. The definitions on the <http://pwg-wiki.wikispaces.com/Geolocation>
appear to be part of the PWG Semantic Model:
This page proposes an IPP collection representing the DNS LOC data defined
in RFC 1876 <http://www.rfc-editor.org/rfc/rfc1876.txt> .
printer-geo-location (collection)
The "printer-geo-location" attribute provides the physical location of the
printer. The collection has the following member attributes.
size (integer (0:MAX))
Diameter of enclosing sphere for printer in centimeters. 0 represents any
size less than one centimeter.
horizontal-precision (integer (0:MAX))
The circle of error of the latitude and longitude measurement in
centimeters. 0 represents an error of less than one centimeter.
vertical-precision (integer(0:MAX))
The circle of error of the altitude measurement in centimeters. 0 represents
an error of less than one centimeter.
latitude (integer(-324000000:324000000))
The latitude in thousandths of arc seconds from the equator. 0 represents
the equator, positive values represent locations North of the equator, and
negative values represent locations South of the equator.
longitude (integer(-648000000:648000000))
The longitude in thousandths of arc seconds from the prime meridian. 0
represents the prime meridian, positive values represent locations East of
the meridian, and negative values represent locations West of the meridian.
altitude (integer(-100000:MAX))
The distance in centimeters from the WGS-84 ellipsoid to the center of the
enclosing sphere defined by the "side" member attribute. 0 represents the
WGS-84 ellipsoid height, positive values represent locations above the
ellipsoid, and negative values represent locations below the ellipsoid.
The PWG SM definitions appear to use signed 32-bit integer notation and
description which have the same bit representation as the unsigned 32-bit
integer notation and description in RFC 1876, right? Why change to use the
unsigned integer notation and descriptions, when the rest of the SM and IPP
use signed integer notations and descriptions?
3. What is the relationship between Cloud Printing (which these definitions
are proposed for) and IPP Everywhere?
4. I like the idea used in IPP and the SM to have the data type indicate the
range of values in the definition of the attribute name and attribute
syntax, i.e., latitude (integer(-324000000:324000000)). Why isn't this
technique of specifying the data type and the data type range used in your
proposal for attributes needed for Cloud Printing?
Tom
_____
From: ipp-bounces at pwg.org [mailto:ipp-bounces at pwg.org] On Behalf Of Zehler,
Peter
Sent: Thursday, July 22, 2010 11:48
To: ipp at pwg.org; mfd at pwg.org
Subject: [IPP] Attributes needed for Cloud Printing and definition
inconsistencies
Job Identifiers:
*existing*
job-id (SM: JobId): The identifier for a job with a local scope. That is
the ID is unique within the service. The ID may be reused in other instance
of a Printer (i.e. Print Service) or for jobs in other types of services
(e.g. Copy Service). Datatype: abstract:int32, IPP:integer, SM:xs:int
*new*
job-uuid (SM:JobUuid): The identifier for a job with a global scope. The
identifier is unique for a Job across all service instances of any service
type. The UUID URN namespace is specified in rfc4122. The format used
for "job-uuid" is the string representation of a UUID as a URN. An example
is "urn:uuid:a6b90f34-d0b1-1956 -7dec-009c4386fe3". The version (aka
subtype) used is implementation specific. Version 1 (i.e. time based) is
recommended. Datatype: abstract:char[64], IPP:uri MaxLength=64,
SM:xs:anyURI maxLen=64
Note: I do not believe the IPP attribute "job-uri" is applicable as a
globally unique identifier.
1) RFC2911 states "Since every URL is a specialized form of a URI, even
though the more generic term URI is used throughout the rest of this
document, its usage is intended to cover the more specific notion of URL as
well.". All uses of the uri syntax is really a URL syntax.
2) URL implies not only a specific protocol binding but also a
location.
3) Locations can be specified using an IP address that need not be
locally unique (e.g. 192.168.1.1, localhost)
4) Regarding the "job-uri" RFC2911 further states that "This URI is
then used by clients as the target for subsequent Job operations.". The
globally unique identifier for a job should not specify a transport endpoint
for a specific protocol.
5) The globally unique identifier for a Job, Printer or Service should
be a URN. It should be protocol independent so that a product that supports
multiple protocols should have the same identifiers regardless of the
protocol mapping.
6) The globally unique identifier for a Job, Printer or Service should
require no central authority to administrate them. Generation of a unique
identifier should be simple from an administrative point of view and
preferably automated.
Note: Both the local and global identifiers should be mandated. For legacy
protocol mappings (e.g. IPP 1.1, WS-Print, LPR) the local identifier MUST
still be maintained. It is possible to use the time_low portion of the
Timestamp in the version 1 UUID as the local identifier. The implementation
may then keep only the 128 bit local representation of the UUID and use it
to create the appropriate protocol values.
Printer Identifiers:
*existing (Service Monitoring MIB)*
applIndex (SM: <service>Id i.e. PrinterId): The service identifier with a
local scope. That is the ID is unique across the service instances
collocated on a host. Datatype: abstract:int32, MIB:integer, SM:xs:int
*new*
printer-uuid (SM:ServiceUuid): The identifier for a Printer with a global
scope. The identifier is unique across all service instances of any service
type. The UUID URN namespace is specified in rfc4122. The format used
for "job-uuid" is the string representation of a UUID as a URN. An example
is "urn:uuid:a6b90f34-d0b1-1956 -7dec-009c4386fe3". The version (aka
subtype) used is implementation specific. Version 1 (i.e. time based) is
recommended. Datatype: abstract:char[64], IPP:uri, SM:xs:anyURI maxLen=64
Note: I do not believe the IPP attribute "printer-uri" is applicable as a
globally unique identifier.
1) RFC2911 states "Since every URL is a specialized form of a URI, even
though the more generic term URI is used throughout the rest of this
document, its usage is intended to cover the more specific notion of URL as
well.". All uses of the uri syntax is really a URL syntax.
2) URL implies not only a specific protocol binding but also a
location.
3) Locations can be specified using an IP address that need not be
locally unique (e.g. 192.168.1.1, localhost)
4) The printer may have multiple "printer-uri" values as enumerated in
the "printer-uris-supported" attribute. There should be only a single
identifier for a printer.
5) The globally unique identifier for a Job, Printer or Service should
be a URN. It should be protocol independent so that a product that supports
multiple protocols should have the same identifiers regardless of the
protocol mapping.
6) The globally unique identifier for a Job, Printer or Service should
require no central authority to administrate them. Generation of a unique
identifier should be simple from an administrative point of view and
preferably automated.
Note: The local instance id in the MIB and SM are artifacts of the model's
data binding and are insufficient for use as an identifier. IPP's
printer-uri, the URL for Web Service bindings (e.g. WS-Print) and the IP
address for legacy protocols such as LPR and Port 9100 are also
insufficient. They need not be globally unique. Nonroutable IP addresses
may be used.
Printer Location:
*existing*
printer-location (SM: ServiceLocation): Identifies the location of the
device that this Printer represents. (Example: Pete's Office) This is
helpful for a human but is pretty much useless for geolocation since the
content is implementation specific. Datatype: abstract:char[127],
IPP:string MaxLength=127, SM:xs:int
*new*
printer-geo-location (SM:ServiceGeoLocation): This identifies the location
of the associated device using the World Geodetic System 1984(WGS84). The
means for expressing the location information is the same as used in DNS
(rfc1876) Datatype: abstract:class, IPP:collection, SM:sequence
*new*
size (SM:Size): Diameter of the bounding sphere containing the device
expressed in centimeters. Datatype: abstract: int32, IPP:integer,
SM:xs:int
*new*
horizontal-precision (SM: HorizontalPrecision): The horizontal precision
expressed as the diameter of the "circle of error" (i.e. twice the +- error
value) The units are centimeters. Datatype: abstract: int32,
IPP:integer, SM:xs:int
*new*
vertical-precision (SM: VerticalPrecision): The vertical precision
expressed as the diameter of the "circle of error" (i.e. twice the +- error
value) The units are centimeters. Datatype: abstract:integer, IPP:
int32, SM:xs:int
*new*
latitude (SM:Latitude): The latitude of the center of the sphere described
by the size attribute. Expressed in thousandths of a second of arc. The
value 2147483648 (231) represents the equator. Values above that are north
and below are south. Datatype: abstract: int32, IPP:integer, SM:xs:int
*new*
longitude (SM:Latitude): The longitude of the center of the sphere
described by the size attribute. Expressed in thousandths of a second of
arc. The value 2147483648 (231) represents the prime meridian. Values
above that are east and below are south. The value is rounded away from the
prime meridian Datatype: abstract: int32, IPP:integer, SM:xs:int
*new*
altitude (SM:Altitude): The altitude of the center of the sphere described
by the size attribute. Expressed in centimeters from a base of 100,000m
below the reference spheroid used by GPS [WGS 84]. Altitude above (or
below) sea level may be used as an approximation of altitude relative to the
[WGS 84] spheroid, though due to the Earth's surface not being a perfect
spheroid, there will be differences. Datatype: abstract: int32,
IPP:integer, SM:xs:int
Note: There is disagreement on the semantics for all the attributes between
what is posted on <http://pwg-wiki.wikispaces.com/Geolocation> and what I
have in the definition above. I took the definition directly from rfc1876
(I think). See included text from rfc1876 and the location example below.
Peter Zehler
Xerox Research Center Webster
Email: <mailto:Peter.Zehler at Xerox.com> Peter.Zehler at Xerox.com
Voice: (585) 265-8755
FAX: (585) 265-7441
US Mail: Peter Zehler
Xerox Corp.
800 Phillips Rd.
M/S 128-25E
Webster NY, 14580-9701
>From rfc1876 section 2 <http://www.rfc-editor.org/rfc/rfc1876.txt>
SIZE The diameter of a sphere enclosing the described entity, in
centimeters, expressed as a pair of four-bit unsigned
integers, each ranging from zero to nine, with the most
significant four bits representing the base and the second
number representing the power of ten by which to multiply
the base. This allows sizes from 0e0 (<1cm) to 9e9
(90,000km) to be expressed. This representation was chosen
such that the hexadecimal representation can be read by
eye; 0x15 = 1e5. Four-bit values greater than 9 are
undefined, as are values with a base of zero and a non-zero
exponent.
Since 20000000m (represented by the value 0x29) is greater
than the equatorial diameter of the WGS 84 ellipsoid
(12756274m), it is therefore suitable for use as a
"worldwide" size.
HORIZ PRE The horizontal precision of the data, in centimeters,
expressed using the same representation as SIZE. This is
the diameter of the horizontal "circle of error", rather
than a "plus or minus" value. (This was chosen to match
the interpretation of SIZE; to get a "plus or minus" value,
divide by 2.)
VERT PRE The vertical precision of the data, in centimeters,
expressed using the sane representation as for SIZE. This
is the total potential vertical error, rather than a "plus
or minus" value. (This was chosen to match the
interpretation of SIZE; to get a "plus or minus" value,
divide by 2.) Note that if altitude above or below sea
level is used as an approximation for altitude relative to
the [WGS 84] ellipsoid, the precision value should be
adjusted.
LATITUDE The latitude of the center of the sphere described by the
SIZE field, expressed as a 32-bit integer, most significant
octet first (network standard byte order), in thousandths
of a second of arc. 2^31 represents the equator; numbers
above that are north latitude.
LONGITUDE The longitude of the center of the sphere described by the
SIZE field, expressed as a 32-bit integer, most significant
octet first (network standard byte order), in thousandths
of a second of arc, rounded away from the prime meridian.
2^31 represents the prime meridian; numbers above that are
east longitude.
ALTITUDE The altitude of the center of the sphere described by the
SIZE field, expressed as a 32-bit integer, most significant
octet first (network standard byte order), in centimeters,
from a base of 100,000m below the [WGS 84] reference
spheroid used by GPS (semimajor axis a=6378137.0,
reciprocal flattening rf=298.257223563). Altitude above
(or below) sea level may be used as an approximation of
altitude relative to the the [WGS 84] spheroid, though due
to the Earth's surface not being a perfect spheroid, there
will be differences. (For example, the geoid (which sea
level approximates) for the continental US ranges from 10
meters to 50 meters below the [WGS 84] spheroid.
Adjustments to ALTITUDE and/or VERT PRE will be necessary
in most cases. The Defense Mapping Agency publishes geoid
height values relative to the [WGS 84] ellipsoid.
2-Dimmensional Location of my office printer
Google Map URL:
http://maps.google.com/maps?f=q
<http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=800+phillips+rd
+webster+ny+14580&sll=37.0625,-95.677068&sspn=62.226996,106.962891&ie=UTF8&h
q=&hnear=800+Phillips+Rd,+Webster,+Monroe,+New+York+14580&ll=43.220973,-77.4
17162&spn=0.001781,0.003264&t=h&z=19>
&source=s_q&hl=en&geocode=&q=800+phillips+rd+webster+ny+14580&sll=37.0625,-9
5.677068&sspn=62.226996,106.962891&ie=UTF8&hq=&hnear=800+Phillips+Rd,+Webste
r,+Monroe,+New+York+14580&ll=43.220973,-77.417162&spn=0.001781,0.003264&t=h&
z=19
Location representations:
Decimal Degrees (WGS84)
Latitude Longitude
43.220973 -77.417162
Degrees, Minutes & Seconds
Latitude Longitude
N43 13 15 W77 25 01
GPS
Latitude Longitude
N 43 13.258 W 77 25.030
UTM
X Y
18N 303685 4788191
My office elevation:
12800 centimeters (419 feet) above sea level
Size of Printer:
91 centimeter (3 feet)
Margin of error
183 centimeter (6 feet)
PrinterGeoLocation (RFC1876)
Size = 258 (0x0102) (encoded centimeter)
HorizontalPrecision = 514 (0x0202) (encoded centimeter)
VerticalPrecision = 514 (0x0202) (encoded centimeter)
Latitude = 2303079151 (thousandths of a second of arc, 231 represent
equater) ( (DecimalDegreeLatitude*60*60*1000)+2147483648 )
Longitude = 1868781865 (thousandths of a second of arc, 231 represent prime
meridian) ( 2147483648-(DecimalDegreeLongitude*60*60*1000) )
Altitude = 10012800 (centimeter) (OfficeElevation+10000000)
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