Metadata-driven Data Access Layer

Returns resampled/aligned timeseries data from Brick queries + UUIDs

Requests look like:

query = {
    "Composition": ["temp"],
    "Selectors": [MEAN],
    "Variables": [
        {"Name": "meter",
         "Definition": "SELECT ?meter_uuid WHERE { ?meter rdf:type/rdfs:subClassOf* brick:Electric_Meter . ?meter bf:uuid ?meter_uuid . };",
         "Units": "kW",
        },
        {"Name": "temp",
         "Definition": "SELECT ?temp_uuid WHERE { ?temp rdf:type/rdfs:subClassOf* brick:Temperature_Sensor . ?temp bf:uuid ?temp_uuid . };",
         "Units": "C",
        },
    ],
    "Time": {
        "T0": "2017-07-21 00:00:00",
        "T1": "2017-08-30 00:00:00",
        "WindowSize": '2h',
        "Aligned": True,
    },
}

• Composition: the order of variables and UUIDs to be included in the response matrix. Variables are defined in Variables key (below) and resolve to a set of UUIDs. UUIDs are the pointers used by the timeseries database and represent a single timeseries sequence
• Selectors: for each timeseries stream, we can get the raw data, or we can get resampled min, mean and/or max (as well as bucket count). Each item in the Composition list has a corresponding selector. This is a set of flags:
  • MEAN: selects the mean stream
  • MAX: selects the max stream
  • MIN: selects the min stream
  • COUNT: selects the count stream (how many readings in each resampled bucket)
  • RAW: selects the raw data. This cannot be resampled and is mutually exclusive with the above flags Combine flags like MEAN|MAX
• Variables: each variable mentioned in Composition has a definition here. Each variable needs the following fields:
  • Name: the name of the variable. Refer to the variable in Composition using this name
  • Definition: the BRICK query that will be resolved to a set of UUIDs. The returned variables need to end in _uuid
  • Units: the desired units for the stream; MDAL will perform the unit conversion if possible
• Time: the temporal parameters of the data query
  • T0: the first half of the range (inclusive)
  • T1: the second half of the range (inclusive). These will be reordered appropriately by MDAL
  • WindowSize: window size as a Go-style duration, e.g. "5m", "1h", "3d".
    • Supported units are: d,h,m,s,us,ms,ns
  • Aligned: if true, then all timesetamps will be the same, else each stream (UUID) will have its own timestamps. Its best to leave this as True
• Params: don't touch this for now

Supported unit conversions (case insensitive):

• w/watt, kw/kilowatt
• wh/watthour, kwh,kilowatthour
• c/celsius,f/fahrenheit,k/kelvin

Python Client

from xbos.services import mdal
client = mdal.BOSSWAVEMDALClient("scratch.ns")
query = {
    "Composition": ["temp"],
    "Selectors": [mdal.MEAN],
    "Variables": [
        {"Name": "temp",
         "Definition": "SELECT ?temp_uuid WHERE { ?temp rdf:type/rdfs:subClassOf* brick:Temperature_Sensor . ?temp bf:uuid ?temp_uuid . };",
         "Units": "C",
        },
    ],
    "Time": {
        "T0": "2017-07-21 00:00:00",
        "T1": "2017-08-21 00:00:00",
        "WindowSize": '30m',
        "Aligned": True,
    },
}
resp = client.do_query(query,timeout=300)
df = resp['df']
print df.describe()