We’re answering your questions from our “Take your data management to new heights with geodatabases” webinar in a two-part series. In the first part, we covered general geodatabase questions and attribute rules. In this second post, we cover questions about Subtypes and Domains, and Topology.
Attention all geospatial enthusiasts! Are you ready to continue soaring to new heights with geodatabases? During our recent webinar Maggie Samson, one of our Technical Solutions Specialists and I discussed how geodatabases in ArcGIS Pro are essential tools for managing and analyzing geospatial data.
For a recap of what we covered, access the webinar recording and presentation slides.
Maintaining the air force theme we used in the webinar, we'll be answering your top questions on geodatabases to help you become a skilled pilot in your field. Buckle up and get ready to continue learning how geodatabases can take your geospatial projects to new heights!
Subtypes and Domains:
Subtypes and domains are components of feature layers and feature classes which are very commonly used in geodatabases. These will help to maintain consistency within your data and help to prevent false entries/restrictions on data entries. It is important to remember to have our geodatabases set up correctly from the start (Including the setup of your subtypes and domains), to prevent problems from occurring in the future in your data.
Q: Is there a limit to the number of domains that can be applied to geodatabase?
A: This is a very common question as domains are often used in various ways by many organizations. In terms of the number of limit to the number of domains that can be applied to a geodatabase, there is NO limit.
With this said, it is important to remember that the more domains you have, the more important your naming conventions become in order to keep track of what domain does what to avoid confusion. When a domain is created on that geodatabase, it will remain on this database until it is deleted.
In terms of the Enterprise geodatabase, when domains are created, the owner of the domain will be recorded and be associated with this domain. Only the owner of the Enterprise geodatabase or the administrator will now be able to modify or delete these domains.
Q: Do domains function like a look-up table?
A: Domains do function in a similar way to look-up tables, but look up tables are often recognized as an alternative for domains. As mentioned in the webinar, there are two types of domains that can be created: Range domains and Coded domains.
Range domains specify a valid range of numeric values that an attribute can be between where as Coded value domains can apply to any type of attribute such as text, numeric values, dates etc.
Look-up tables are specifically an alternative to Coded domains. They are most commonly used when creating a route using location referencing. In this case, an example would be if we had all the airline routes from Canada to other countries. This could have several hundred potential values in regard to their names or even something like a code for the airlines. This would make this a valid reason to use a look-up table.
Q: Is there a significant difference between when you would use a subtype and when you would use a domain?
A: When comparing the functionality of subtypes and domains, subtypes are typically used to categorize your data, whereas domains are used to constrain input information to help validate data entry. The use case for each of these will completely depend on what you are trying to analyze within your dataset and what type of values you would like to have restricted within your data.
If you would like the option to simply categorize your data within your attribute table in the form of a drop-down menu, then choose to use a subtype. On the other hand, if you simply want to have restrictions within data, you can apply a domain to allow only specific values to be entered and the rest will be restricted. This will help to maintain data integrity.
For example, consider the scenario if you would like to use domains to help restrict what type of roads can actually be selected. In this instance, we can see that a domain was created to classify and help restrict what road segments could be used. According to what is created in this example, only local roads and express roads can be classified.
File Geodatabase can have domains applied to it and this is what It would look like when it is configured.
Following the example for domains, we can also have subtypes that define our data. For this instance, we analyzed bus transit routes and identified that we only wanted highways and local roads to be defined for bus paths that lead to nearby airports. Below you can see that this has been specified in our subtypes menu.
File Geodatabase can have subtypes applied to it and this is what It would look like when it is configured.
For more information on the differences between domains and subtypes, click here.
Q: Can subtypes and domains be combined?
A: Subtypes and domains can be used together but cannot be combined in sense where they are interchanged for one another. As specified previously, your use case will completely be dependent on what you would like to show in your data.
Both of these concepts have their individual uses, and you will use them in different cases (either to restrict fields or categorize your data). You can definitely use them together but cannot interchange one for the other.
Q: Can subtypes be used with hosted data in ArcGIS Online or Enterprise portal for use in applications like field maps?
A: Yes! Both subtypes and domains can be created and applied to a field within a feature class and the published to your organization as a hosted feature layer. Please note that if you would like to have subtypes applied on your hosted feature layers, these have to be configured within ArcGIS Pro and then published as these cannot be defined directly within ArcGIS Online or ArcGIS Enterprise. Domains on the other hand also have the ability to have attributes and ranges created directly within ArcGIS Online or ArcGIS Enterprise.
Overall, working with subtypes and domains can allow you to enhance your geodatabase experience and help you to maintain data integrity. Alongside our questions about subtypes and domains, we also had some questions regarding topology.
When it comes to data integrity, another very valuable tool available within ArcGIS Pro is the ability to apply topology rules on your datasets. Topology rules can allow you to set corresponding attributes to your data to ensure that your data is spatially consistent and consists of no errors. If there are errors, this is not a problem as when these rules are applied, your data will be reviewed by the system and you will then have the opportunity to fix these errors when needed. Here is a video providing a use case of topology in ArcGIS Pro.
After having a better understanding of topology and how it can be applied, here are the answers to some of our most frequently asked questions.
Q: Is there a way to apply topology constraints when users insert a new feature rather than checking for topology errors after the fact?
A: No, there is not a way to apply topology constraints when users insert a new feature. There are two ways that you could proceed with this workflow. You could create topology rules and validate for topology errors after you have inserted the feature to see if it goes against any of your rules. The other way would be to use an attribute rule to define specifically what you would like entered for a specific field while being able to avoid errors when possible.
Q: How do I know whether the network topology is enabled?
A: A network topology is enabled to be able to use network diagrams and to have the ability to perform tracing of network features. When this is enabled, dirty areas will be shown for the areas that have changes/ edits made to them.
To check if this functionality is enabled, you can simply try to see if errors appear and if you are able to validate them after the errors have been generated. If you cannot, you will need to enable this functionality by using the ‘Enable Network Topology’ Geoprocessing tool. Please note that in order to be able to enable this functionality, the utility network dataset must be registered as branch versioned.
When this is confirmed, you will now have access to the network topology functionality. For more information please visit this resource.
Q: Can I create custom topology rules?
A: No. Currently, there is not a way to create your own topology rules. There are many in the software that are currently available for points, lines and polygons.
Q: What are some best practices for using topology effectively?
A: To use topology effectively, there are many things that should be noted as best practices. It is important to remember that you should carefully define your topology rules to match the specific needs of the data being analyzed. You should also be validating your topology frequently to ensure that the errors are being corrected in the process of fixing your data. This will also help to prevent errors from getting too large to a point where they are too difficult to fix.
It is recommended to incorporate topology into a larger data quality management workflow to help ensure ongoing data integrity. Using topology errors layers can help to visualize topology errors in the context of a large dataset to help you determine what errors you think are relevant to your data.
Finally, it would be recommended to do some testing topology validation before on a testing dataset to ensure that the rules you have set are in fact the correct topology rules that you need to fulfill your needs. There are many more tips to recommend regarding best practices. My greatest tip would be to validate consistently.
For more tips regarding topology, please click here.
Q: How many topology rules are there?
A: Within the poster for topology rules found here, there are 32 topology rules that are available currently available to use with your ArcGIS geodatabases. There are more rules that may get added in the future if there is a need for them. Stay updated with the topology posters provided by Esri to see if there are any updates.
This answers some of the most frequently asked questions regarding domains, subtypes and topology. Stay tuned for upcoming webinars.