README: re-phrase text to have the style as vlkb-soda

## vlkb-siav2

is a web-application to discover astronomical data (supports FITS-files) and described in a VO ObsTAP table

(https://ivoa.net/documents/ObsCore).

It implements the SIA version 2, IVOA recommendation (https://ivoa.net/documents/SIA) with optional VLKB-specific features:

is a web-application to discover astronomical data (supports FITS-files) and described in a [VO ObsTAP table](https://ivoa.net/documents/ObsCore).

It implements IVOA recommendation [SIA version 2](https://ivoa.net/documents/SIA) with optional VLKB-specific features:

- provides overlap code

- the filtering paramters (POS, BAND) can be given in GALACTIC and VELO-LSRK-km/s coordinates systems

When used with [**vlkb-soda**](https://ict.inaf.it/gitlab/ViaLactea/vlkb-soda) they provide complete data-discovery and access solution.

## Launching the service

The service consists of **vlkb-siav2** web-application and associated **vlkb-obscore** command line tool to create the ObsTAP table from FITS-files headers.

The vlkb-obscore cli is available from https://ict.inaf.it/gitlab/butora/vlkb-datasets .

Dockerized version of the web-app is available from https://ict.inaf.it/gitlab/butora/vlkb-datasets-docker .

The service may be launched by docker compose with [compose.yaml](./docker/example-compose.yaml). The database service is not needed, running database instance may de set directly by DB_URI parameters. Additionaly choose context root and point to the data access service.

To check the service status access the availability endpoint:

```bash

curl --get http://localhost:8004/vlkb/datasets/availability

```

## Endpoints

- **availability** is a [VOSI](https://ivoa.net/documents/VOSI/20170524/REC-VOSI-1.1.html) end-point and returns information whether the service is active

- **capabilities** is a [VOSI](https://ivoa.net/documents/VOSI/20170524/REC-VOSI-1.1.html) end-point which describes service' functions and paramters

- **siav2** synchronous end-point provides [SIAv2](https://ivoa.net/documents/SIA) service; responds with a [VOTable](https://ivoa.net/documents/VOTable/).

## Docker image

To configure the application choose a context-root where the SIAv2 can be accessed,

provide database URI which points to the ObsTAP table and provide URL for data-access

(typically a SODA service).

Example compose.yaml entry for VLKB-SIAv2:

```yaml

  vlkb-siav2:

    container_name: vlkb-siav2

    image: git.ia2.inaf.it:5050/vialactea/vlkb-siav2/siav2:1.6

    ports:

      - 8080:8080

    environment:

      - DISCOVERY_CONTEXT_ROOT=vlkb#datasets#siav2

      - DB_URI=jdbc:postgresql://vlkb-db:5432/vialactea

      - DB_USERNAME=vialactea

      - DB_PASSWORD=ia2vlkb

      - CUTOUT_SERVICE_URL=http://vlkb-devel.ia2.inaf.it:8004/vlkb/datasets/soda

```

The vlkb-siav2 is available from the gitlab repositary of this project. 

## Installation

Configuration parameters are set by these docker environment variables:

There is a war-package for the search web-application and the package (deb or rpm) with linux

executable for Debian, CentOS and Fedora:

- vlkb-search-X.Y.Z.war

- vlkb-obscore-X.Y.Z.deb|.rpm

| parameter | description  |

|---------|--------------|

| **DISCOVERY_CONTEXT_ROOT** | root of the vlkb-soda end-points |

| **DB_URI** | DB which holds ObsTAP table |

| **DB_USERNAME** | DB user which has access to ObsTAP |

| **DB_PASSWORD** | and user's password |

| **CUTOUT_SERVICE_URL** | URL of a SODA service presented in the response |

To download version X.Y, add one of the above package names to

```bash

curl -O --header "PRIVATE-TOKEN: <security-token>"  "https://ict.inaf.it/gitlab/api/v4/projects/79/packages/generic/vlkb-datasets/X.Y/vlkb-obscore-<version>.{deb|rpm}"

## vlkb-obscore

```

There are binary packages for Debian, CentOS and Fedora. All cli tools are currenlty distributed with the **vlkb-soda** (and not vlkb-siav2) and are hosted in vlkb-soda gitlab repository. The ObsTAP-tool package is:

- vlkb-obscore-X.Y.Z.deb|.rpm