Internet Engineering Task Force A. Boronine, Ed. Internet-Draft Intended status: Informational December 5, 2014 Expires: June 8, 2015 Minimal JSON Type System draft-boronine-teleport-02 Abstract Teleport is a minimal type system designed as an extension of JSON. It comes with 10 types sufficient for basic use and provides two patterns for extending it with new types. Teleport's type definitions are JSON values, for example, an array of strings is defined as {"Array": "String"}. Teleport implementations can be used for data serialization, input validation, for documenting JSON APIs and for building API clients. This document provides the mathematical basis for Teleport and can be used for implementing libraries. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 8, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Boronine Expires June 8, 2015 [Page 1] Internet-Draft Abbreviated Title December 2014 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Type Patterns . . . . . . . . . . . . . . . . . . . . . . . . 3 4. JSON Schemas . . . . . . . . . . . . . . . . . . . . . . . . 3 5. Mathematical Basis . . . . . . . . . . . . . . . . . . . . . 4 5.1. Concrete Types . . . . . . . . . . . . . . . . . . . . . 4 5.2. Generic Types . . . . . . . . . . . . . . . . . . . . . . 4 6. Built-in Concrete Types . . . . . . . . . . . . . . . . . . . 4 7. Built-in Generic Types . . . . . . . . . . . . . . . . . . . 5 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 10.2. Informative References . . . . . . . . . . . . . . . . . 6 Appendix A. Mailing List . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction In Teleport, a type is a relation between a type definition and a value space. For example: t("Integer") = {0, -1, 1, -2, 2, -3, 3, ...} Here "Integer" is a type definition and t("Integer") is the set of all values this type can take. The t function is used to represent this relationship. Because Teleport is based on JSON, all value spaces are sets of JSON values. More interestingly, type definitions are JSON values too, which makes it trivial to share them with other programs. Teleport's design goals is to be a natural extension of JSON, be extremely lightweight, and extendable not only with rich types but with high-level type system concepts. Boronine Expires June 8, 2015 [Page 2] Internet-Draft Abbreviated Title December 2014 2. Conventions and Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. The terms "JSON", "JSON text", "JSON value", "member", "element", "object", "array", "number", "string", "boolean", "true", "false", and "null" in this document are to be interpreted as defined in RFC 4627 [RFC4627]. 2.1. Syntax Throughout this document, an extended JSON syntax is used. Unquoted strings are symbols representing JSON values, sets and functions. Also, the following set theory syntax is used: a :: A Set A contains element a. D -> C The set of functions that map values from set D to values from set C. 3. Type Patterns Types defined simply by a string, like "Integer" above, are called concrete. Teleport ships with 7 concrete types. A generic type maps a set of schemas to a set of value spaces. Each pair in the mapping is called an instance. For example, {"Array": "Integer"} is an instance of the Array type. Three generic types are provided: Array, Map and Struct. Their precise definition is provided in the following sections, but these examples should be enough to understand how they work: ["foo", "bar"] :: t({"Array": "String"}) {"a": 1, "b": 2} :: t({"Map": "Integer"}) {"name": "Alexei"} :: t({"Struct": { "required": {"name": "String"}, "optional": {"age": "Integer"}}) 4. JSON Schemas Schema, one of the build-in concrete types, is made possible by the fact that type definitions are JSON values. The Schema type is Boronine Expires June 8, 2015 [Page 3] Internet-Draft Abbreviated Title December 2014 useful to specify APIs. For example, to describe a function you can use this: t({"Struct": { "optional": {}, "required": { "input": "Schema", "output": "Schema"}}} 5. Mathematical Basis The set of all JSON values is called V. A subset of V is called a value space and the set of all value spaces is called S. V = {null, true, false, 0, 1, 2, 3, 4, ...} S = {{}, {null}, {null, true}, {null, ...}, ...} There is a certain function t that maps JSON values to value spaces. t :: (V -> S) This document does not give a full definition of the t function, it merely provides some instances of its inputs and outputs. Expanding the definition of the t function is the basis for extending Teleport. 5.1. Concrete Types x is of concrete type c if and only if 1. c is a string 2. x :: t(c). 5.2. Generic Types x is of generic type g if and only if 1. g is a string 2. x :: t({g: p}) for some p 6. Built-in Concrete Types JSON t("JSON") is the set of all JSON values. This type can be used as a wildcard for type-checking or as a noop for composable serialization. Boronine Expires June 8, 2015 [Page 4] Internet-Draft Abbreviated Title December 2014 Schema t("Schema") is the set of all type definitions, including all strings representing concrete types as well as every instance of every generic type. Decimal t("Decimal") is the set of all numbers. This type represents real numbers and arbitrary-precision approximations of real numbers. Integer t("Integer") is the set of all numbers that don't have a fractional or exponent part. String t("String") is the set of all strings. Note that JSON strings are sequences of Unicode characters. Boolean t("Boolean") is a set containing the JSON values true and false. DateTime t("DateTime") is the set of all strings that are valid according to RFC 3339 [RFC3339]. This type represents typestamps with optional timezone data. 7. Built-in Generic Types x :: t({"Array": p}) if and only if x is an array e :: t(p) for every element e in x x :: t({"Map": p}) if and only if x is an object v :: t(p) for every pair (k, v) in x x :: t({"Struct": p}) if and only if p is an object with at least two members: required and optional. Both are objects and their names are disjoint, that is, they don't have a pair of members with the same name. x is an object. The name of every member of p.required is also the name of a member of x. For every pair (k, v) in x, there is a pair (k, s) in either p.required or p.optional such that v :: t(s). Boronine Expires June 8, 2015 [Page 5] Internet-Draft Abbreviated Title December 2014 NOTE: the definition of Struct implies that its parameter p can contain arbitrary metadata in the form of other object members. 8. IANA Considerations This memo includes no request to IANA. 9. Security Considerations All drafts are required to have a security considerations section. See RFC 3552 [RFC3552] for a guide. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, July 2002. [RFC4627] Crockford, D., "The application/json Media Type for JavaScript Object Notation (JSON)", RFC 4627, July 2006. 10.2. Informative References [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on Security Considerations", BCP 72, RFC 3552, July 2003. Appendix A. Mailing List Comments are solicited and should be addressed to the working group's mailing list at teleport-json@googlegroups.com and/or the author. Author's Address Alexei Boronine (editor) Email: alexei@boronine.com Boronine Expires June 8, 2015 [Page 6]