fix: Initial draft of a deep dive into exchaning data between multipl…

…e projects

docs/dataexchange.md

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+# Exchanging Data
+
+Exchanging data between projects has a few issues, namely the ID of
+the user, the project, and the organization are different in the
+different projects. Not all fields are useful cross-project, so some
+but not all of the columns in a database table are exchanged w ith
+other projects. There are other issues to handle, a projet
+manager/admin in Tasking Manager (TM) may only be a a mapper in the
+Field Mapping Tasking Manager (FMTM) project, so the roles change, but
+the rest of the user profile stays the same.
+
+Currently all the database tables have every column used by FMTM or
+TM. Since there are many application specific columns, these are
+simply ignored by the application. While this does make the database
+slightly larger having multiple empty columns, it's a tradeoff between
+database size and simplifying the code base. A future enhancement to
+the YAML config file subsystem will support using a subset of all the
+database columns.
+
+# Identifying Records
+
+Since the ID can't be used between projects, the name or address is
+the only unique field that can be used to identify a user or an
+organization, etc...  For users, the best ID is their OpenStreetMap
+(ODM) ID, as that is unique globally. While some support can be added
+to track unique IDs across multiple projects, this can be cumbersome.
+
+Another way to identify a record is through location. Since both
+projects and tasks have an polygon area of interest, a point within a
+project in one application, can be used to query a remote project to
+find the project or task. For example, if a field mapper finds bad
+data, the location of that data can be used to find the TM project and
+task, so the task can be invalidated.
+
+# Filtering Data
+
+Since not all data fields are needed in each project, the YAML
+configuration file supports a flag for each item in a data structure
+as to whether it should be shared or not. For example, a database
+query might return many columns, but only a few are usefully portable
+across multiple projects.
+
+For instance, Tasking Manager has task boundaries, in FMTM, tasks
+are smaller, because it involves mappers walking. So transferrihng
+exact task boundaries would be meaningless. In this usage case, the
+tasks transfer from TM to FMTM would be a multi-polygon. FMTM would
+create a project AOI based on the outer boundary of all the of the
+tasks, and then recalulate FMTM specific tasks boundaries.
+
+## Data Exchange Schemas
+
+Some fields need to be in any data packet that is intended for
+database queries, since the there needs to be a way to refer to an
+existing record, if it exists. 
+
+### Project Data
+
+A project has a wide definition depending on the type of
+application. Since this module is focused on Tasking Manager style
+applications, all version will have at least a project name and an
+Area of Interest (AOI). In addition, each tracks task usage, so the
+number of tasks mapped, validated, or invalidated exists in all
+tables, but has different data.
+
+#### Field Mapping Tasking Manager
+
+For FMTM, it uses an *odkid* column, which is used to communicate with
+ODK Central. This is an example of needing to store the ID of a remote
+application to exchange data for specific items. How the ID of a
+remote project is stored may change in the future to handle multiple
+remote applications, but for now, it's only the one for ODK Central.
+
+FMTM also uses several columns for working with
+OpenDataKit(ODK). These are the login credentials for an ODK Central
+server, and an XLSForm for the project.
+
+#### Tasking Manager
+
+TM uses a series of columns that are used for editing OSM data. This
+includes presets for several editors. 
+
+### User Data
+
+### Task Data
+
+A task AOI is not usually useful between projects, as a TM task is
+much larger than an FMTM task. For a Drone Tasking Manager (DTM), the
+task size will also be different. Since tasks are not portable across
+projects, each project maintains it's own data on the creation date,
+tasks mapped, validated, invalidated, etc...
+
+### Organization Data
+
+### 
+
+