Data
You keep using that word...
Avishai Ish-Shalom (@nukemberg)
Define "Data"
My definition of Data
A Representation of information in a computer storable form
Data is
- Bounded, finite
- Discrete (resolution)
- Structured
- Has known format
Data is a snapshot of information
How does information become data?
Data Modeling
Data modeling
The process of defining how to extract data from real world information
Data modeling is lossy
What do we lose?
- Everything we didn't collect
- Accuracy
- Context
Data modeling is biased
-
We select a subset of information
-
The conversion is also biased
Formats matter
Let me tell you a story
Oops
Let's model a person
Names
- First name, last name
- Middle name?
- How long?
Longest name in Africa
Uvuvwevwevwe onyetenvewve ugwemubwem ossas
Longest name in the world
Adolph Blaine Charles David Earl Frederick Gerald Hubert Irvin John Kenneth Lloyd Martin Nero Oliver Paul Quincy Randolph Sherman Thomas Uncas Victor William Xerxes Yancy Zeus Wolfeschlegelsteinhausenbergerdorffwelchevoralternwarengewissenhaftschaferswessenschafewarenwohlgepflegeundsorgfaltigkeitbeschutzenvorangreifendurchihrraubgierigfeindewelchevoralternzwolfhunderttausendjahresvorandieerscheinenvonderersteerdemenschderraumschiffgenachtmittungsteinundsiebeniridiumelektrischmotorsgebrauchlichtalsseinursprungvonkraftgestartseinlangefahrthinzwischensternartigraumaufdersuchennachbarschaftdersternwelchegehabtbewohnbarplanetenkreisedrehensichundwohinderneuerassevonverstandigmenschlichkeitkonntefortpflanzenundsicherfreuenanlebenslanglichfreudeundruhemitnichteinfurchtvorangreifenvorandererintelligentgeschopfsvonhinzwischensternartigraum, Senior.
Mr. Kim
Mr. Un
Or
?
Names are hard
- Cultural differences
- Can change
- Not unicode
- Min length? max length?
Age?
- Changes every year
- Unless it's a dead person
- Min? Max?
- Why int?
Gender?
- Physiological
- Social
- Legal
- Definitely not binary
Adresses?
- Does everyone have one?
- Zip codes
- Can change
- Very quirky
Country?
- When?
- Depends who you ask...
Identity?
Dates
Calendars
- Civil
- Gregorian
- Jewish
- Muslim
- etc
Timezones
- Start/end changes
- Zones change
- Can geographically overlap
- Some dates don't exist
UTC?
- Day or night?
- What day was it?
When Time itself goes wrong
- 24 hours in a day (daylight savings)
- 365 days in a year (leap year)
- 60 seconds in a minute (leap second)
- Infinite (Y2K anyone?)
- Monotonic (clock sync)
Numbers
- Integers/Floats
- Signed/Unsigned
- Resolution
- Bounds
Integers
scala> n.getClass
res3: Class[Int] = int
scala> n > 0
res4: Boolean = true
scala> n + 1 > 0
res5: Boolean = falseFloats
scala> 0.1 + 0.2
res0: Double = 0.30000000000000004
Money
- Should never overflow
- Should not have rounding errors
- But things that convert to money can be float
Data Modeling like a boss
Store facts
- Absolute
- Do not change with time
- New facts can be added
- E.g. Date of birth vs Age
Extensible formats/data types
- Data models evolve
- Some data maybe missing
- Express missing data
Store meta data
- When (date/version)
- Where (location/system)
- How (collection/conversion method)
- Who (system/person)
1. Predefine intended usage
- What do we need the data for?
- How are we going to use it?
- Multiple versions for multiple use cases
2. Select needed subset of information
- Think what you need and what you don't
- Document why
3. Define constraints
- Resolution
- Bounds
- Type
4. Define collection method
- Analog to Digital
- Digital converters
- Lossy/non-lossy
- Possible artifacts
- Versioned
5. Select compatible data type
- Universal/specific
- Secondary formats
- Possible artifacts
- Versioned
Let's model a person
For an HR system
Data
- Surname, full legal name
- Date of Birth (ISO8601)
- Government ID number
- OR independent unique ID
- Facial photo, jpg
- Address - free text (1000 chars), zip code alphanumeric (10 chars)
- Bank account
Meta data
- Collection date
- Collection system
- Collection SW version
- User ID
Thanks! Questions?
