Database Management 414

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Relationship Cardinality

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the relationship of one data table with respect to another (1 to Many).

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Schema

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defines the tables, the fields in each table, the relationships between fields and tables, and the grouping of objects within the database.

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Attribute Domains

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define what values are allowed in a field in a feature class or nonspatial attribute table

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Subtypes

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a subset of features in a feature class or objects in a table that share the same attributes.

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Ranks

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A method of assigning an accuracy value to feature classes to avoid having vertices from a feature class collected with a high level of accuracy being snapped to vertices from a less accurate feature class.

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What is a complex edge?

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A complex edge is always connected to at least two junction features at its endpoints. It can also be connected to additional junction features along its length.

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Displacement Links

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the links that describe the translation that needs to occur. Created to define the source and destination coordinates for a spatial adjustment.

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Identity Links

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the points that show the editing tool what not to change.

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Rubber Sheeting

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A procedure for adjusting the coordinates of all the data points in a dataset to allow a more accurate match between known locations and a few data points within the dataset. Rubber sheeting preserves the interconnectivity between points and objects through stretching, shrinking, or reorienting their interconnecting lines.

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5 key parts of schema representation

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1. Datasets- specify feature class, raster catalog, or attribute tables. Defines the columns in each table.

2. Domains- list range of valid values for specific columns. The DBMS will enforce these domains.

3. Relationships-define how rows in one table relate to rows in other tables (cardinality).

4. Spatial Rules- define how features share geometry.

5. Map Layers- define how layers are to be rendered .

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Is there a unique method of defining spatial indexes?

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Yes- Several methods include Grid-Based, B-tree, and R-tree.

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What type of spatial indexing approach does ArcGIS use?

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Grid-Based

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What are dirty areas?

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Dirty areas allow you to see where edits to source features have been made since the last time the network dataset was built. They are rectangles that highlight portions of the dataset that are out of date due to edits.

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What are the fields required in a polygon coverage?

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1. Area

2. Perimeter

3. Cover ID

4. User ID

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What are the three required files need to create a “shape” file?

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1. Shp file

2. Shx file

3. Dbf file

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what does a Shp file contain?

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the geographic coordinates

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what does a Shx file contain?

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an index that indicates where in the shapefile each record starts

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What does a Dbf file contain?

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the attributes in a one- to- one relationship with the shapes

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In database theory, what is meant by first normal form?

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1. There’s no top-to-bottom ordering of rows.

2. There’s no left-to-right ordering of columns.

3. There are no duplicate rows.

4. Every row-and-column intersection cell contains only one value (“atomic”- simplest form).

5. All columns are regular (no hidden components such as row IDS, object IDS, or hidden timestamps).

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What types of anomalies can occur if a database is not properly normalized?

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1. Update anomalies

2. Deletion anomalies

3. Insertion anomalies

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What is a DBMS?

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Database Management System- it is a collection software that manages the database structure and controls access to data stored in the database.

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What does a DBMS facilitate?

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1. Defining a database

2. Constructing the database

3. Manipulating the database

4. Querying the database

5. Updating the database

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What does data independence mean?

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Users can access data without regard to how the data is stored

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What are SADTs?

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Spatial Abstract Data Types- Domain specific storage types that have their own rules for validation and methods of manipulation.The SADTs should define not only their storage structure, but also the operations that can be performed on them.

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What are some advantages of geodatabases over other spatial data storage methods?

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1. Multiple users

2. Can handle large amounts of data

3. Create subtypes

4. Create validation rules

5. Create custom relationships

6.Versioning

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Feature dataset

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a collection of feature classes stored together that share the same spatial reference

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Feature Class

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a collection of geographic features with the same geometry type (such as point, line, or polygon), the same attributes, and the same spatial reference

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Relationship Class

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an item in the geodatabase that stores information about a relationship

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How many coordinate systems can be used in a single feature dataset?

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One

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What are the three strategies for storing raster data in a geodatabase?

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1. Raster datasets- Any valid raster format organized into one or more bands

2. Mosaic datasets - Collection of raster datasets (images) stored as a catalog and viewed as a mosaicked image.

3. Raster catalogs - Collection of raster datasets defined a table format with each row representing an individual raster dataset

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What are some advantages of mosaic datasets over raster datasets?

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1. Uses overviews for fast display

2. Can define processing for individual raster datasets

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Which type of dataset is recommended by ESRI (unless the number of rasters is very large)?

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Mosaic Datasets

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Lossy comression

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pixel values are changed by the algorithm

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Lossless compression

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all original values are maintained in the result (no loss, lossless)

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What type of compression should you use for sharp data images?

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lossless

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Which type of compression should you use for continuous rasters like elevation data?

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lossy

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Which type of compression should you use for discrete rasters like land use?

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lossless

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Versioned editing

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stores edits without affecting the original. Can manage/ maintain multiple states, records the states of individual features, enables multiple users, and queries to view individual users' edits.

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Non-Versioned editing

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standard edit session, single use only. Does not stores data in tables. Short transaction performance is better. Can edit simple features, can't edit feature classes.

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Is a version a copy of the geodatabase?

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NO

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What are the pros of non-versioned editing?

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1. Does not store changes in other tables (smaller storage and easier management).

2. Changes saved immediately on dataset.

3. Can edit simple feature classes in a topology, network dataset, or geometric network.

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What are the cons of non-versioned editing?

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1. Single user only – dataset is locked for editing by others.

2. Can’t edit feature classes in a topology, network dataset, or geometric network.

3. Other users might be editing another part of the network or topology in a way that conflicts with your edit.

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What is meant by long transactions?

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Extended editing operations, which may involve many short transactions with multiple database editors

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What are A and D tables?

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All edits to a feature class or table are stored in delta tables. It does not matter in which version the edits were made, they are all stored together.For each table or feature class that has been versioned, two new delta tables, an Adds and a Deletes table, are created.

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Lineage

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Lineage - A sequence of states that leads to the current state of a version

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States

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A unit of work. A number per edit, made up of multiple transactions on the DB level.To keep track of which rows go with which version, a state ID is created for each row.States define a tree structure. Maintains a list of all database states. Each state has a creation time, closing time, parent state, and owner.

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Merging Changes- post

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synchronized current edit session with target version. Modifications saved to target; two versions now identical.Must be done in an edit session. Performed after reconciling with another version.Cannot be undone - applying changes to target version

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Merging changes- reconcile

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There may be times when an editor wants to see what edits have already been incorporated into the parent version.

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Types of version permissions

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Private, protected, public.

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Version permissions- private

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Only the owner can see and edit

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Version permissions: protected

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Anyone can view, only the owner can edit.

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Version permissions: public

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Anyone who has permissions can view or edit. For example, street editors can edit the edits version but street readers can only view.

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In a GDB, at what level are users and roles defined?

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The database level.

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If a user has read access to a versioned database, can she create a new version that she owns?

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No, a user needs edit access to create new versions

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Who can assign or change privileges?

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A DBO or table owner

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What happens to non-posted edits when a database is unregistered as versioned?

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They are lost unless they are posted to the archival database

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Who may register or unregister a feature class or table as versioned?

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Database Owner

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How does database archiving support keeping track of editing histories (what key time related values exist in the archive?)

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Allows you to automatically save earlier states of the database as changes are saved.

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What types of queries do these key values facilitate?

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1. Moment in Time query (what did the database look like on this date?) - Can think of it like Bookmark when working on a map.

2. Temporal Range query (all records for these features between these dates)

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What is the difference between valid time and transaction time?

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1. Valid time- when the change occurred.

2. Transaction time - when the change was recorded in the database.

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Which is used in an archive database, valid time or transaction time?

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transaction time

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When a geodatabase is registered as archived, an archive ID is added. What other two fields are added?

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gdb_from_date, gdb_to_date

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What are the three types (or “directions”) of geodatabase replication.

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1. One way

2. Two way

3. Checkout

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What is One Way geodatabase replication?

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the only option available is to send changes from the parent replica to the child replica

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What is Two Way geodatabase replication?

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allows you to choose the direction in which you would like to send changes.

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What is Checkout geodatabase replication?

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the only option available is to send changes from the child replica to parent replica.

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Does replication require versioning to work?

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Yes

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Why is replication better than copying a geodatabase?

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1. All or part of your dataset can be copied to a replica in the database

2. A pair of that replica is distributed to a different database

3. These two replicas are synchronized to match each other

4. Built on top of versioning environment and can support topologies, networks, terrains, relationships

5. Can work with file geodatabases or enterprise geodatabase

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What is a feature service and how is it different from other kinds of ArcGIS Server/ArcGIS Online web services?

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1. Unlike map services and mobile services, can be edited

2. Can be hosted on ArcGIS online or via ArcGIS server

3. Allows download of selected data, disconnected editing, and sync with server data

4. Can host replica to manage workflow to default geodatabase

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What is VGI?

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Volunteer Geographic Information

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What are some examples of how VGI can be used?

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1. Reporting of events (e.g. Fires, Road Hazards [like the Waze app])

2. Weather

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What are the 7 "game changers" with respect to data collection?

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1. People are used to seeing things mapped- Google Maps, Google Earth

2. Low cost GPS

3. Government removed “selective availability errors”

4. GPS in mobile devices

5. Geo-tagging and GeoRSS- Can lead to “subconscious digitizing”

6. Web services for storing data and hosting services

7. Faster internet connections

8. Persistent digitization

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What are the "3 Vs" of Big Data?

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1. Volume - (‘Zettabytes’ – 1,000,000,000,000,000,000,000) – too large for relational databases or other traditional analysis

2. Variety – Text, photos, videos, binary data, unstructured, etc. from sensors, cameras, GPSs, cars, personal fitness devices, web enabled appliances (internet of things).

3. Velocity – Processing needs accelerated from batch, to periodic to near real time, to real time.

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How was the location quotient used to map racist tweets after the 2008 election?

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Location quotient = (# of hate tweets in state/ # of hate tweets in USA) / (# of all tweets in state/ # of All tweets in USA).

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What is Ushahidi platform?

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Ushahidi, Inc. is a non-profit software company that develops free and open-source software (LGPL) for information collection, visualisation, and interactive mapping. Developed to map records of violence in Kenya.

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Traditional GIS compared to Neogeography

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1. more formal

2. used by academia, gov't, businesses

3. analytical, quantitative

4. data-driven

5. Costly, complex, and expensive tools

6. Ex. ESRI software

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Neogeography compared to Traditional GIS

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1. less formal

2. Used by people, groups, and communities

3. interactivity, qualitative

4. people-driven/social

5. affordable and accessible tools

6. Ex. floatingsheep.org

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What are some issues with VGI?

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1. Data Quality

2. Fear of the “great unwashed” non-geographers, non-professionals

3. Can VGI be used for immoral or illegal purposes?

4. Can VGI be manipulated by governments or political activists?

5. OpenStreetMap and fake streets

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SQL INSERT

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Inserts new records into a table

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SQL UPDATE

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Update records to a table

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SQL LIKE

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used in a WHERE clause to search for a specific pattern in a column

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SQL DISTINCT

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returns only different values

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SQL ONLY

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Limits return to a certain number of record EX: FETCH FIRST 10 RECORDS ONLY

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SQL INNER JOIN

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selects all rows from both tables as long as there is a match between the columns in both tables

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SQL LEFT JOIN

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returns all rows from the left table with matching rows from the right

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SQL RIGHT JOIN

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returns all rows from the right table with matching rows from the left

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SQL SELECT

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selects data from a database

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What is a spatial query?

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1. A query that is supported by geodatabases and spatial databases.

2. Selects geographic features based on location or spatial relationship

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What do the STArea() and STIntersection() functions do?

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1. STAREA() - Returns the total surface area of a feature

2. STINTERSECTION() - shows where the instance of geography intersects with other instance of geography. (Which features fall within the boundaries of another feature)

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What does ST stand for?

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Spatial Type

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What does FOSS stand for?

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Free and Open Source Software

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What does FOSS4G stand for?

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Free and Open Source Software for Geospatial

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What does OSGeo stand for?

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Open Source Geospatial foundation

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What does GDAL stand for?

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Geospatial Data Abstraction Library

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Does ArcGIS contain any free and open source software?

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Yes- GDAL

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What are some of the advantages of commercial vs. FOSS?

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1. ArcGIS has better UI

2. Bridging Software to stitch components together

3. In FOSS, the user has to build their own stack connectors

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Stack Levels ESRI

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1. Desktop- Arcmap

2. Data management- ArcCatalog

3. Web Server- ArcServer

4. API for Web- JavaScript API for ArcServer

5. Use of Enterprise Database- ArcSDE with SQL server

6. Extensions- Various types

7. Toolbars

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Stack Levels FOSS

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1. Desktop- QGIS

2. Data Management- GeoServer, QGIS Browser

3. Webserver- Geoserver

4. API for Web- OpenLayers

5. Use of Enterprise Database- PostgreSQL with PostGIS

6. Extensions- pgRouting, several QGIS plugins

7. Links to other packages, such as R