ian, having recently attempted the task of translating seamlessly between XML ->JSON->ruby hashes, i have a very low opinion of this sort of type declaration. it makes moving between representations a bear and most commonly results in eliminating the unit-specifier and normalizing to a known base (see option 4 below). a 3rd option you did not mention is something like this: <memory> <size>2</size> <units>GB</size> </memory> a 4th option, which i rather prefer since the units stuff tends to be relevant to and consumed by humans via UI rather than machines via API, is not to use units at all. <memory>2147483648</memory> either of the above is far easier to transform to and from non-XML representations, in my experience, with the latter being zero effort. a couple extra bytes won't harm us and we adhere to my first engineering rule: the best solution to a problem is not to have it in the first place. b On Tue, May 26, 2009 at 8:56 AM, Ian Stokes-Rees <ijstokes@spmetric.com>wrote:
I finished my PhD thesis on a RESTful model for grid computing a few years ago. I did some work on formalizing XML-based descriptors, including units/scaling. You may find that some of the material in Appendix B and C is useful:
I envisioned two options: i) units were specified in attributes on an element:
<memory type="GB"> 2 </memory>
ii) units were specified in-line and needed to be parsed:
<memory> 2 GB </memory>
At the time I felt that "type" provided a more generic modifier on a value than "units", and would allow things like:
<start type="USDate">5/21/2009</start>
or
<start type="EUDate">21/5/2009</start>
I provide 5 sets of "type" modifiers: time, frequency, metric, binary, transfer. No rocket science, but perhaps providing an cut-down portion of the schemas will be helpful, so I include them below.
Ian
<xs:simpleType name="TimeTypeList"> <xs:enumeration value="fs"/> <xs:enumeration value="ps"/> <xs:enumeration value="ns"/> <xs:enumeration value="us"/> <xs:enumeration value="ms"/> <xs:enumeration value="s"/> <xs:enumeration value="sec"/> <xs:enumeration value="second"/> <xs:enumeration value="min"/> <xs:enumeration value="minute"/> <xs:enumeration value="h"/> <xs:enumeration value="hr"/> <xs:enumeration value="hour"/> <xs:enumeration value="d"/> <xs:enumeration value="day"/> <xs:enumeration value="wk"/> <xs:enumeration value="week"/> <xs:enumeration value="mon"/> <xs:enumeration value="month"/> <xs:enumeration value="yr"/> <xs:enumeration value="year"/>
<xs:simpleType name="MetricTypeList"> <xs:enumeration value="f"/> <xs:enumeration value="p"/> <xs:enumeration value="n"/> <xs:enumeration value="u"/> <xs:enumeration value="m"/> <xs:enumeration value="K"/> <xs:enumeration value="M"/> <xs:enumeration value="G"/> <xs:enumeration value="T"/> <xs:enumeration value="P"/>
<xs:simpleType name="FrequencyTypeList"> <xs:enumeration value="Hz"/> <xs:enumeration value="KHz"/> <xs:enumeration value="MHz"/> <xs:enumeration value="GHz"/> <xs:enumeration value="THz"/>
<xs:simpleType name="BinaryTypeList"> <xs:enumeration value="B"/> <xs:enumeration value="KB"/> <xs:enumeration value="MB"/> <xs:enumeration value="GB"/> <xs:enumeration value="TB"/> <xs:enumeration value="PB"/>
<xs:simpleType name="TransferTypeList"> <xs:enumeration value="Kb/s"/> <xs:enumeration value="Mb/s"/> <xs:enumeration value="Gb/s"/> <xs:enumeration value="Tb/s"/> <xs:enumeration value="Pb/s"/>
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