edit language to make more precise.

schema.md

@@ -5,7 +5,6 @@ title: Common Core Metadata Schema
 permalink: /schema/
 filename: schema.md
 id: schema
-
 ---
 
 This section contains guidance to support the use of the common core metadata to list agency datasets and application programming interfaces (APIs) as hosted at agency.gov/data.
@@ -14,16 +13,18 @@ Updates to the metadata schema can be found in the [changelog](/metadata-changel
 
 Standard Metadata Vocabulary
 ----------------------------
-Metadata are selected fields or elements which describe data. The challenge is to define the standard metadata fields and the names of those fields so that the consumer of the data has sufficient information to process and understand the data. The more information that can be conveyed in a standardized regular format, the more valuable data becomes. Metadata can range from basic to advanced, from allowing one to discover the mere fact that a certain data asset exists and is about a general subject all the way to providing detailed semantic information that enables a high degree of machine readability. Making the metadata machine readable greatly increases its openness and utility.
+Metadata is structured information that describes, explains, locates, or otherwise makes it easier to retrieve, use, or manage an information resource (NISO 2004, ISBN: 1-880124-62-9).  The challenge is to define and name standard metadata fields so that a data consumer has sufficient information to process and understand the described data. The more information that can be conveyed in a standardized regular format, the more valuable data becomes. Metadata can range from basic to advanced, from allowing one to discover the mere fact that a certain data asset exists and is about a general subject all the way to providing detailed information documenting the structure, processing history, quality, relationships, and other properties of a dataset. Making metadata machine readable greatly increases its utility, but requires more detailed standardization, defining not only field names, but how information is encoded in the metadata fields.
 
-Establishing a common vocabulary is the key to any communication, including communication between machines.  [DCAT](http://www.w3.org/TR/vocab-dcat/) is a hierarchical vocabulary specific to datasets that serves as the basis for the **common core metadata** required in this memorandum. The standard consists of a number of schemas (hierarchical vocabulary terms) that represent things that are most often looked for on the web, with [mappings](http://project-open-data.github.io/metadata-resources/#common_core_required_fields_equivalents) to their equivalents in other standards.  
+Establishing a common vocabulary is the key to communication. The **common core metadata** specified in this memorandum is based on [DCAT](http://www.w3.org/TR/vocab-dcat/), a hierarchical vocabulary specific to datasets. This specification defines three levels of metadata elements: Required, Required-if (conditionally required), and Expanded fields.  These elements were selected to represent information that is most often looked for on the web. To assist users of other metadata standards, [mappings](http://project-open-data.github.io/metadata-resources/#common_core_required_fields_equivalents) to equivalent elements in other standards are provided.  
 
-What to Document -- Datasets and APIs
+What to Document -- Datasets and Web APIs
 -------------------------------------
 
-APIs allow developers (both internal to the agency and the public) to dynamically query a dataset. For example, a dataset [of farmers markets](https://explore.data.gov/Agriculture/Farmers-Markets-Geographic-Data/wfna-38ey) may be made available for download as a single file (e.g., a CSV), or may be made available to developers as an API, such that a developer could provide the agency with a ZIP Code, and retrieve a list of farmers markets in that area.
+A dataset is an identifiable collection of structured data objects unified by some criteria (authorship, subject, scope, spatial or temporal extent...). A catalog is a collection of descriptions of datasets; each description is a metadata record. The intention of a data catalog is to facilitate data access by users who are first interested in a particular kind of data, and upon finding a fit-for-purpose dataset, will next want to know how to get the data.
+
+A Web API (**A**pplication **P**rogramming **I**nterface) allows computer programs to dynamically query a dataset using the World Wide Web. For example, a dataset [of farmers markets](https://explore.data.gov/Agriculture/Farmers-Markets-Geographic-Data/wfna-38ey) may be made available for download as a single file (e.g., a CSV), or may be made available to developers through a Web API, such that a computer program could use a ZIP Code to retrieve a list of farmers markets in the ZIP Code area.
 
-The catalog file should list all of an agency's datasets that can be made public, regardless of form -- this includes raw datasets and APIs.  Use **Endpoint** to indicate which datasets offer dynamic APIs (see below for more information on Common Core and Extensional metadata elements).
+The catalog file for each agency should list all of the agency's datasets that can be made public, regardless of whether they are distributed by a file download or through a Web API.  The **Endpoint** data element is used to indicate which datasets offer Web APIs (see below for more information on Common Core and Extended metadata elements).
 
 
 Metadata File Format --  JSON
@@ -390,5 +391,4 @@ Additional Information
 * [Schema.org](http://schema.org)
 * [DCAT](http://www.w3.org/TR/vocab-dcat/)
 * [Vocab.Data.gov](http://vocab.data.gov)
-* [Template and Sample Files (CSV and JSON format)](/metadata-resources/)
-
+* [Template and Sample Files (CSV and JSON format)](/metadata-resources/)