Every object in the Udanax Green backend has a unique global address that functions as the object's identifier. This chapter identifies the objects that can be addressed in the backend, and describes the generation of their addresses.
All addresses in Udanax Green are tumblers. Tumblers are multi-part ordinal numbers similar to Dewey Decimal numbers. For example, 2.4.23 and 45.6.72 are both tumblers. Each period separated number is called a tumbler digit. The digits of a tumbler (leftmost first) exactly describe the path to a specific point in a tree. Udanax Green address tumblers use the zero tumbler digit only to separate concatenated fields within the tumbler. This will be shown below.
Each running backend is called a node in anticipation of an interconnected network of Udanax Green backends. Each node has a unique tumbler that positions it in an abstract global address space called the docuverse. Since node addresses are tumblers, any node could give addresses to new nodes by appending another tumbler digit to its own tumbler address. For example, node 23.4 could create nodes 23.4.1, 23.4.2, 23.4.3, etc.
Each node has accounts for any number of users. Each account on a single node is identified by a tumbler. Udanax Green currently makes no use of the potential hierarchy of accounts. The global address of an account is the concatenation of the node's address, the tumbler separator, and the account's tumbler. The separator allows any number of tumbler digits for the node address.
Accounts contain any number of documents. New documents are numbered sequentially for each account. Addresses for versions get allocated like addresses for nodes: the first new version adds a tumbler digit. Each successive version increments the last digit. Each of these new versions can create versions of their own by adding more digits. The global address of any document is created by concatenating the global address of the document's account, the zero tumbler, and the document's address relative to its account.
Data-Bytes and Links
The final level of addressing is for the contents of documents. Documents have two spaces, the data space for storing raw data such as text and pictures, and the link space for storing document interconnections. Characters and links are addressed within a document by a two digit tumbler. The first digit identifies the space (data=1, links=2); the second identifies the position within that space. Thus, the thirty-ninth character has address 1.39 whereas the fourth link has the address 2.4. As above, global addresses for characters and links are made by appending (with a separator) their addresses to the global address of their home document - the document in which they were created. The home document is unique, even though edit operations and versioning can copy a link to many documents.
All addresses used in the FeBe Protocol are global except addresses used in some commands that stay within the bounds of a single document. These addresses, called vaddresses, are relative to the document, and so have only two digits. The containing document is supplied as a separate argument. For historical reasons, document relative terms are annotated with 'v'.
Groups of Udanax Green Objects
Groups of objects can be referred to with spans, vspans, and spec-sets. A span represents a range of global tumbler addresses. A vspan is a range of addresses relative to a single document. A spec-set is a list of spans or vspans (with an associated document identifier). Spec-sets allow specification of an arbitrarily complex set of Udanax Green objects.
Spans are represented with a start tumbler and a width tumbler. The start tumbler is the address of the first thing in the span. The start tumbler plus the width tumbler (see "Tumbler Arithmetic") is the address of the first thing not included in the span.
Vspans are built from document relative tumblers (vaddresses). Thus, the entire data space of a document is in the vspan with a start of 1.1 and a width of 1 . This vspan covers from the first data-byte data up to but not including the first link.
Tumblers are ordered similar to real number fractions. For example, 4 < 4.23 < 4.23.7 < 4.24 < 5. Thus, a single span could cover all the documents for a given account, all the accounts (and their documents) for a given node, all the versions of a particular document, etc. Because addresses at every level of the hierarchy are just tumblers, spans can cover characters, links, documents, versions, or any other Udanax Green entities, including the entire docuverse.